A MANUAL 
OF 
DENTAL PROSTHETICS 
BY / 
GEORGE HENRY WILSON. D.D.S. 
PROFESSOR EMERITUS OF PROSTHESIS AND METALLURGY IN THE DENTAL 
DEPARTMENT OF WESTERN RESERVE UNIVERSITY, CLEVELAND, OHIO; SPECIAL 
PROFESSOR OF PROSTHESIS IN THE DENTAL DEPARTMENT OF THE 
UNIVERSITY OF SOUTHERN CALIFORNIA, LOS ANGELES, CAL. 
FOURTH AND REVISED EDITION 
Illustrated with 451 ^Engravings 
LEA & FEBIGER 
PHILADELPHIA AND NEW YORK 
192 0 Copyright 
LEA & FEBIGER 
1920 THIS VOLUME 
IS DEDICATED TO THE MEMORY OF THE LATE 
JONATHAN TAFT, D.D.S., M.D. 
AS A TOKEN OF RESPECT AND ADMIRATION FOR THE LIFE AND 
WORK OF THE EMINENT TEACHER, PROFESSIONAL 
MAN, AND CHRISTIAN GENTLEMAN 
THE AUTHOR PREFACE TO FOURTH EDITION. 
The author is grateful for the kindly reception of the 
former editions of this book, the many expressions of apprecia- 
tion, and the reviews accorded them on both sides of the 
Atlantic. 
The author is convinced that a New School of Dental 
Prosthetics is rapidly developing, and in this edition has given 
the present status of the New School, while in no way cur- 
tailing the generally accepted teaching of the Bonwill School. 
Chapter I has been extended to give the physics of the 
muscles and ligaments of mastication, thus laying a broad 
foundation for the New School. 
Dr. Hall's theories have been revised by him. 
Casting methods have been much enlarged, and it is 
believed presented in a logical, up-to-date, but conservative 
manner. 
Roofless Dentures are treated in a trenchant, but practical 
way. 
The investigations of Dr. Geo. B. Snow on shrinkage in 
vulcanization, and scientific vulcanization are given in this 
edition. 
The motive of this book is: much in few words. The 
purpose is to give the technic clearly once, and to elaborate 
the underlying principle as much as may seem necessary. 
Therefore if a portion of the book seems to be devoid of 
technical descriptions it is because the text being read is an 
V VI 
PREFACE TO FOURTH EDITION 
elaboration of a principle, a suitable technic for which will 
be found previously stated, but in sequential order. 
The book is designed for both the busy student and prac- 
titioner; therefore in addition to the standard instruction 
in methods and materials the recent methods and materials 
are presented and discussed, but without prolixity. 
The author wishes to express his thanks to Drs. George B. 
Snow and Rupert E. Hall for permission to present their 
valuable work; also to his publishers for their always cour- 
teous and helpful attitude. 
George II. Wilson. 
Cleveland, Ohio, 1920. CONTENTS. 
CHAPTER I. 
The Mouth 17 
CHAPTER II. 
Impressions 63 
CHAPTER HI. 
Casts 136 
CHAPTER IV. 
Occlusion and Contour Models 151 
CHAPTER V. 
Articulators and Antagonizors 176 
CHAPTER VI. 
Rubber and Vulcanite 190 
CHAPTER VII. 
Principles of Retention of Artificial Dentures . . . 318 VIII 
CONTENTS 
CHAPTER VIII. 
Porcelain Teeth 369 
CHAPTER IX. 
Double Vulcanization Method 391 
CHAPTER X. 
Aluminum Base-plate 402 
CHAPTER XI. 
Gold Base-plate 426 
CHAPTER XII. 
Tin Base-plate 489 
CHAPTER XIII. 
Continuous Gum Dentures 492 
CHAPTER XIV. 
Interdental Splines 507 
CHAPTER XV. 
Cleft-palate Appliances 512 
CHAPTER XVI. 
Esthetics 540 PROSTHETIC DENTISTRY. 
CHAPTER I. 
THE MOUTH. 
The mouth, from an anatomical point of view, is the 
entrance to the alimentary canal; and primarily is for re- 
ceiving and preparing the food for deglutition. In mankind 
there is a secondary use, that is, to aid in speech and expres- 
sion. In this chapter the mouth will be considered only in its 
primary relationship; its secondary function will be treated 
in the chapters on Cleft-palate and Esthetics. 
The face is divided into three portions, known as the first 
portion or upper third, second portion or middle third, and 
third portion or lower third (Fig. 1). These thirds are indi- 
cated by four imaginary and approximately parallel lines- 
the first at the top of the forehead, or normal hair line; the 
second at the junction of the forehead and nose, or a line 
ANATOMY.1 
1 It is not within the province of this monograph to treat in detail either 
general or dental anatomy; it considers only their practical application. 
It is assumed that the student has some knowledge of the tissues and organs 
under consideration; and it is hoped that the practically applied anatomical 
science will create a desire for an intimate acquaintance with the subject. 
The student is referred to his text-books on general and dental anatomy, 
and especially to the excellent article, "The Human Dental Mechanism: 
Its Structure, Functions, and Relations," by Charles R. Turner, M.D., 
D.D.S., in the third and fourth editions of the American Text-book of 
Prosthetic Dentistry. 
For convenience of expression, the singular form of the names of bones 
and muscles is used, although, with few exceptions, they are in pairs. One 
side of the cranium is a counterpart of the other. 
17 18 
THE MOUTH 
drawn at the lower border of the crest of the supraorbital 
ridges; the third at the base of the nose and extending from 
the anterior spine of the maxilla to the lower border of the 
external auditory meatus; the fourth line at the lower 
border of the chin. In passing it may be noted that in the 
ideal Greek face these thirds are of equal length, but in 
Fig. 1 
nature they vary greatly. These lines, however, are very 
important in the study of the face, for they determine the 
proportions-whether or not the face is well balanced. 
Plane of the Teeth.-The third line (Camper's line), or the 
naso-auditory meatus line, is of importance in marking or 
indicating the plane of the upper twelve anterior teeth (Figs. A NA TOM Y 
19 
1 and 2). It should be noticed that the teeth plane is a 
straight plane extending from the mesial angle of the upper 
central incisor to the distobuccal cusp of the first molar; also 
that the teeth plane indicates approximately one-third of the 
distance from the third to the fourth face line. The teeth 
plane may be extended backward and it will be seen that the 
Fig. 2 
second and third molars are progressively stepped upward. 
Attention has but recently been called to this fact, so, to 
satisfy himself of the truth of the statement, the student 
should not only notice the fewr illustrations given (Figs. 1 to 
6), but he should observe every normal or nearly normal skull 
and plaster cast of teeth that opportunity may present. The 
straight line from the crest of the cusp of the upper cuspid 20 
THE MOUTH 
tooth to the crest of the distobuccal cusp of the first molar 
is assumed by the author to be the foundation of the forma- 
tion of the dental arch; and the other teeth in the arch are 
in compensating positions. The four teeth-cuspid, first 
and second bicuspids, and first molar-of an artificial denture 
Fig. 3 
may always be placed in this straight line and be considered 
anatomically normal and mechanically correct. 
There is a reason for these four teeth being in a straight 
line and considered as the foundation of the dental arch. By 
referring to Fig. 1 it will be seen that the portion of the 
Fig. 4 
maxilla in which these four teeth are located has a massive 
cubical block formation, and that the remaining teeth are 
in extensions of this cubical block. The cubical block is 
outlined by the frontonasal column A B, the zygomatic 
column C G D, the infraorbital arch B F D, and the molar ANATOMY 
21 
arch A C. The incisors are in the lower nasal arch A E, a 
forward extension of the cubical block; and the second and 
third molars are in a tuberosity extending backward from 
the cubical block. (A cube has the strongest formation 
and the greatest resistance to force because its dimensions 
Fig. 5 
are equal in each direction.) This formation is suggestive 
that the force of mastication should be upon the area of this 
cube, and that the straight formation has the greatest resist- 
ance to a displacing force applied to an artificial denture. 
The scheme presented in this book for antagonizing com- 
plete dentures is based upon this fundamental principle. 
Fig. 6 
Curve of Spee.-The curve of Spee should be located and 
thoroughly understood. The curve of Spee is an imaginary 
one, and is described as a segment of a circle which begins 
with the incisal edges of the lower incisors, passes over the 
crest of the buccal cusps of the lower bicuspids and molars, 22 
THE MOUTH 
and ends in the anterior border of the condyloid process 
(Fig. 71). The degree of curvature of this curve of Spee will 
depend upon the angle of inclination of the articular tubercle 
(Fig. 2, G). For some years writers and teachers have 
made this curve of Spee (theoretically) the fundamental 
principle in the anatomical arrangement of the teeth; and a 
very elaborate and complicated system of "articulation" has 
been evolved from it. 
Compensating Plane.2-This term has been used as synony- 
mous with the curve of Spee. It should not be so used, 
for the curve of Spee belongs entirely to the mandible, and 
Fio. 7 
is anatomical; while the compensating plane is mechanical. 
The compensating plane (as produced for mechanical reasons) 
is rarely ever found in nature; but may be used in complete 
artificial dentures. The compensating plane is that arrange- 
ment of the teeth whereby the so-called three-point contact is 
established between the upper and lower artificial dentures. 
If this plane is to be of any practical value, it must be in 
harmony with the excursions of the condyle. If the articu- 
1 Fig. 7 from a photograph of a specimen in the Wistar Institute of 
Anatomy. 
2 Dr. Amoedo, Emeritus Professor of the Dental School of Paris, proposes 
the term compensating plane in place of compensating curve. It seems to 
the writer to be a much better term. ANATOMY 
23 
lating surface of the articular tubercle is horizontal, the 
condyle moves straight forward in its excursions, and no 
compensating plane to the teeth plane is required; but if this 
articulating surface is oblique the condyle must also descend 
when it moves forward. However, it should be noted that 
the beginning of the downward inclination of the tubercle 
is gradual, and that the upper incisors overlap the lower 
incisors one-third the length of the crown of the tooth, and 
that the one-third overlap represents a segment of a circle 
of 3 degrees. As the head of the condyle will travel forward 
in a straight line approximately 4 mm., therefore the straight 
condyle path of the Bonwill, Snow and Hall antagonizers are 
anatomically correct, and no measurement or special mechan- 
ism is required; however, if for esthetic reasons the upper 
incisors are to be protruded beyond the lower more than 
4 mm. then the inclination of the articular tubercle must be 
taken into consideration. This can best be done in the 
mouth while the artificial teeth are attached with wax. 
Temporomandibular Articulation.-This is a condylar- 
throidal joint, the structures taking part in it being the 
mandibular fossa of the temporal bone and the condyle of the 
mandible, together with the ligaments and the tissues inter- 
posed between the bones. 
The mandibular fossa (Fig. 2, F) is an oblong cavity on the 
under surface of the squamous portion of the temporal bone, 
its concavity being directed downward. It is bounded 
anteriorly by the articular tubercle, externally by the middle 
root of the zygoma and the auditory process and posteriorly 
by the tympanic plate of the petrous portion of this bone. 
The anterior two-thirds of this fossa is smooth, and covered, 
in the recent state, with a dense fibrous tissue, and receives 
the condyle of the mandible. Of the articular portion of the 
fossa the distal part is the most concave, and is also the 
most elevated. From this point it slopes downward and 
forward to the crest of the articular tubercle, furnishing a 
surface over which the condyle glides in the forward excur- 
sions of the mandible. The shape of the cavity varies with 
different nationalities, with different individuals, and some- 
times with the opposite side of the same individual. 24 
THE MOUTH 
The principal variations are, in size and general concavity, 
in correspondence with the shape of the condyle, in extent 
of the surface from the most concave portion of the articular 
tubercle, and in the inclination. The outlines in Fig. 81 
show the curve of its cavity obtained from skulls after the 
method of Tomes and Dolamore. The fossa alters fre- 
quently in old age, from the pull of the muscles upon the 
mandible in trying to bring into occlusion teeth that may be 
widely separated in location. 
Fig. 8.-Outlines of mandibular fossae obtained by the method of Tomesand 
Dolamore. The heavy base line is parallel to a line drawn from the anterior 
nasal spine to the floor of the external auditory meatus. All the fossae out- 
lines were on the left side of the skull: A, from skulls with typical dentures; 
B and C, from skulls with several teeth missing; D and E, from edentulous 
skulls. 
The condyle of the mandible (Fig. 2, H) is the distal upper 
extremity of the ramus, which fits into the mandibular fossa. 
The head is an elongated oval body, with its long axis at 
nearly right angles to the ramus. The head of the condyle 
is separated from the ramus by an elongated neck, about 
which strong ligaments are attached, connecting the mandible 
with the temporal bone. The head is separated from the 
1 Turner's American Text-book. ANATOMY 
25 
mandibular fossa by a series of tissues that act both as a 
cushion and a lubricated gliding surface. By this peculiar 
formation various movements are made possible. The man- 
dible may be carried bodily forward by unison in the move- 
ment of the condyle upon either side of the cranium. Whether 
this movement is horizontal or oblique will depend upon 
the formation of the eminentia articularis. If one condyle 
only is moved forward the other will rotate upon its variable 
axis, showing the ball-and-socket formation. Mr. Norman G. 
Bennett, of England, has recently described a third movement 
of the mandible in which it moves bodily laterally. By this 
movement all of the buccal cusps of either side of the mouth 
are brought evenly in contact in the process of mastication. 
It is the action of the powerful muscles of mastication that 
makes it impossible to absolutely reproduce the movements of 
the mandible upon a mechanical frame; nor is this necessary, 
because the joint is a remarkably adaptable one, and, to an 
extent, conforms to the demands made upon it. The move- 
ments of the condyle may be in any direction, but more freely 
in some directions than in others. The forward movement is 
the freest and the important one in prehension (seizing or 
grasping-as of food), but the lateral mandibular movement 
is the important one of mastication. The distal movement of 
the condyle is usually quite restricted, but there are a few 
instances in which the distal movement from the normal rest 
position is excessive and perplexing. 
The Mandible.-This is the preferred name for the lower jaw 
(Fig. 2). It is often called the inferior maxilla, but this 
name is becoming obsolete. The mandible is the largest and 
strongest bone of the face, and serves for the reception of 
the lower teeth. It consists of a curved horizontal portion, 
the body (Fig. 2, J), and two perpendicular portions, the rami 
(Fig. 2, I), which join the back part of the body at nearly 
right angles. The mandible is the movable portion of the 
dental armament, therefore it is of special interest to the 
dental student, because of its use and the changes that take 
place with the loss of the teeth, and, with old age. Because 
of its position it is subject to serious accidents and dis- 
ease, namely, luxations, fractures, and necrosis. The large 
muscles of mastication are principally attached to the rami, 26 
THE MOUTH 
and the condylar articulation is the only attachment of this 
bone with the cranium. It has been considered that the 
mandible is a lever of the third class. This is undoubtedly 
a misinterpretation of the physics involved, and will be 
considered under the heading: Physics of the muscles of 
mastication and the temporomandibular joint. The length 
of the muscles is necessary to permit freedom of movement, 
and their great strength to make possible the easy perform- 
ance of the work for which they are designed. That much 
power is necessary for masticating food can easily be surmised 
by observing the powerful grip of those animals whose dental 
armament is not designed for offence and defence. This is 
well illustrated in the horse, whose small mouth opening 
prevents the grasping of objects between the molar teeth; but 
with its incisors it may, in a fit of rage, grip and shake a large 
man or an animal, weighing two or three hundred pounds, as 
a small terrier would a rat. The power required for man to 
masticate his food has been experimentally measured by both 
Professor Black and Dr. Head. Professor Black found that 
some articles of food require from forty to eighty pounds of 
force to crush them, while the highest figure obtained by Dr. 
Head was forty-three pounds. 
Ligaments.1-The movements of the condyle are limited 
not only by the form of the fossa but by ligaments. There 
are three ligaments-the stylomandibular, sphenomandibular 
and temporomandibular. 
The first two named are long ligaments extending between 
the parts named, and their function is largely suspensory. 
Anatomists have disagreed upon the function of these liga- 
ments of the mandible. It has been considered that in the 
opening movements of the mouth the mandible rotated 
from the insertion of these ligaments, that is, about the man- 
dibular foramina, and some of the anatomical antagonizors 
have been constructed upon this supposition; fortunately 
this supposition made no practical difference. That the 
mandible rotates from the insertion of these ligaments is 
questioned; for the stylomandibular ligament extends down- 
ward and forward from the styloid process to the angle 
1 See Figs. 309, 310 and 311, Gray's Anatomy, 20th ed. ANATOMY 
27 
of the mandible, and if it were taut enough so that the con- 
dyle could rotate forward and down the articular tubercle 
the ligament would be so taut that the mandible could not 
move bodily forward as it is evident it does when the lower 
incisors are placed in front of the upper ones. 
The capsular ligament is composed of short fibers extending 
from the periphery of the mandibular fossa to the cervix of the 
condyle. It is taught that the external lateral (or the temporo- 
mandibular) ligament is the thickest, strongest and most im- 
portant portion of the capsular ligament. That it has a broad 
attachment to the zygoma and extends obliquely downward and 
backward to the neck of the condyle. That it permits consider- 
able lateral movement of the condyle, but in the opening move- 
ment of the mouth the fibers will, when the teeth are a short 
distance apart, be made taut, and then the cervical attach- 
ment must act as a fulcrum over which the head of the con- 
dyle is thrown forward and downward upon the articular 
tubercle. Therefore the pivotal center of the opening move- 
ment of the mouth, after the first one-fourth inch space 
movement, is at the cervix of the condyle. Furthermore, 
the pivotal center of the first one-fourth inch opening move- 
ment and the last one-fourth inch in closing is at the center 
of the head of the condyle. Hence it is a logical conclusion 
that the pivotal center of the condyle only is of importance 
in mounting artificial teeth because no movements of the 
mandible can influence antagonization of the teeth until at 
least two opposing cusps touch, and no two cusps can occlude 
when the external lateral ligament (temporomandibular) is 
acting as a fulcrum. 
The preceding paragraphs present two interpretations of 
the functions of the temporomandibular ligaments. The 
writer has been convinced by his study of the work of Prof. 
H. J. Prentiss, of the University of Iowa, and of Prof. 
Edmond Souchon, of Tulone University, New Orleans, that 
the temporomandibular ligament, as so clearly shown in 
most of the standard text-books of anatomy, rarely, if ever, 
exists in nature; therefore, is of no importance. 
The whole head of the condyle is free to move in any di- 
rection limited only by the walls of its fossa and capsular 28 
THE MOVTH 
ligament. Its movement is further enhanced by the inter- 
fibrocartilage (articular disk) and two bursae. 
Muscles.-Muscles are bands or bundles of contracting 
fibers with two or more attachments. At least one of these 
attachments may be considered as fixed or stationary. The 
function of a muscle is to produce motion. The motion is 
produced by the contracting fibers drawing its movable 
attachment toward its fixation. As the direction of the 
force of a muscle is always between its attachments, it 
must have a counter, because a muscle fiber can produce 
but one action. Its power is in its contraction. There is 
no active power in the relaxing of the contracted muscle 
fiber. There are several groups of muscles attached to the 
mandible, namely, muscles of mastication, auxiliary muscles 
of mastication, and muscles of expression. 
The temporal, masseter, external and internal pterygoid 
are classed as the muscles of mastication. They are arranged 
in symmetrical pairs, and usually operate simultaneously in 
the movements of the mandible, although each is capable 
and are the powerful elevators of the mandible. It is through 
the various inclinations of these muscles, acting in various 
combinations, that the mandible is protruded, retruded, and 
rotated. The depression of the mandible is by a different 
and a much less powerful set of muscles. The depressors of 
the mandible are the platysma myoides, digastric, mylohyoid, 
and geniohyoid muscles. 
The auxiliary muscles of mastication consist of the bucci- 
nator and the composite muscle-the tongue. So far as the 
functions of these muscles concern the act of mastication, 
they are auxiliary to the muscles of mastication, and their 
use is to keep the bolus of food between the teeth. The 
buccinator (bugle blower) muscle should be given careful 
consideration, because its origin and insertion are such that 
it may seriously interfere with the stability of artificial 
dentures. Its origin is at the union of the alveolar process 
with the body of the maxilla. It begins in the proximity of 
the cuspid (canine) fossa and extends backward to the maxil- 
lary tuberosity. It is inserted in the corresponding portion 
of the mandible, or along the external oblique line. When the 
teeth have been lost and there is excessive resorption of the ANATOMY 
29 
alveolar processes, the attachments of this muscle may be 
very close to the crest of these resorbed processes. In such a 
case the contraction of the muscle in placing the bolus of food 
between the teeth tends to causing irritation of the soft 
tissues, especially if the buccal flanges of the base-plates are 
too deep. Sometimes, through carelessness or at least acci- 
dents in extracting, and through improper or no after-treat- 
ment, false attachments of the muscles are formed upon the 
process. These cases require that the flanges of the base- 
plate shall be cut away so as not to impinge, otherwise the 
false attachment must be surgically removed. 
While the function of the tongue, as an auxiliary masti- 
cating muscle, is to keep the bolus of food between the teeth, 
there are a few of its component muscles that need con- 
sideration. The mylohyoid is attached to the whole length 
of the internal oblique line, and forms the floor of the mouth. 
Sometimes, through excessive resorption, the attachment 
of this muscle and the crest of the alveolar ridge are in such 
close proximity that there can be almost no lingual flange to 
the base-plate of an artificial denture, while with other condi- 
tions an extensive lingual flange may be used advantageously. 
The geniohyoglossi are attached to the genial tubercles 
upon either side of the median line. These muscles form 
not only an important part of the tongue, but their genial 
attachment, in excessive resorption of the process, forms a 
serious obstacle to the stability of a lower artificial denture. 
The union of the anterior borders of these muscles, with its 
mucous membrane covering, forms the frenum lingua?. In 
no case should an impingement of the lingual flange of the 
base-plate upon the frenum be permitted. Upon the end 
of the body of the mandible, that is, at the union of the body 
with the ramus, is found the mandibular attachments of the 
superior constrictor of the pharynx. This, and the distal 
border of the buccinator muscle, in conjunction with the 
tubercle formed as the result of the resorption of the alveolar 
process, indicate the extent to which a lower denture may be 
worn distally. The distal border of the buccinator not only 
passes between the maxilla and mandible, but also sends 
some fibers to the pterygomaxillary ligaments. It is these 
fibers, with their mucous membrane covering, that form the 30 
THE MOUTH 
cord-like tissue extending posteriorly from the hamulus of 
the pterygoid process of the sphenoid and the corresponding 
location on the mandible, posterior end of the mylohyoid 
line of the mandible. The base-plates must be properly 
adjusted to this tissue, as it may dislodge the artificial den- 
tures, and also may become very sore. 
The muscles attached to the anterior external surface of 
the mandible are muscles of expression. Their location 
may affect the retention of an artificial denture, therefore 
we will now consider them from this view-point. Beginning 
on either side of the symphysis and extending outward, 
there are the three muscles, levator labii inferioris, depres- 
sor labii inferioris, and depressor anguli oris. These muscles 
arise at and below the union of the alveolar process with the 
body of the mandible. In excessive resorption of the process 
these attachments are so near the crest of the alveolar ridge 
that very little surface is afforded as a seat for a base- 
plate. However, the base-plate must be so formed as to 
cover as large a surface as possible, yet not be displaced by 
the action of these muscles. At the symphysis is the frenum 
labii inferioris, formed by the blending of a few fibers from 
each of the levator labii inferioris and the covering of mucous 
membrane. Sometimes another frenum is formed just distal 
to the lower cuspid eminence. This buccal frenum should, 
when existent, be provided for in the periphery of the base- 
plate. 
Muscles of the Maxilla.-There are few muscles of the 
maxilla other than the buccinator that interfere with the 
retention of the artificial upper denture. The depressor alee 
nasi and compressor naris have their origin in the incisive 
fossa and require attention because of their influence upon 
facial cosmetics. When the alveolar process is largely re- 
sorbed the attachments, of these muscles are sometimes in 
close proximity to the alveolar crest. The tendency seems 
to be for the prosthetist to pad out or bolster up these muscles 
with the idea of restoring the expression. By studying the 
origin, insertion, and action of these muscles it will be seen 
that the desired result cannot be obtained. The endeavor 
should be not to exaggerate the deformity. The depressor ANATOMY 
31 
ate nasi has two fasciculi, the one going to the wing and 
septum of the nose and the other forming the depressor of the 
upper lip. These few fibers, in conjunction with a like 
portion from the other depressor ate nasi and a well-marked 
fold of mucous membrane, constitute the frenum labii 
superioris. When it is recognized that the function of this 
muscle is to draw in or depress the upper lip and the tip of 
the nose, and that the receding process carries the origin 
of this muscle farther back than normal, it will readily be 
seen that any crowding upward of this muscle tends to still 
further curl inward the upper lip and the tip of the nose. 
Therefore it is necessary that the base-plate shall be well 
cut away to permit free play of the frenum, and that the 
flange of the base-plate passing over the incisive fossa shall 
be well depressed. Otherwise there will be a pouched-out 
effect of the lip just under the nose. The buccal frenum over 
the upper first bicuspid must not be impinged upon by the 
base-plate. 
The Soft Palate.-The soft palate (velum palati) is the 
curtain between the vault of the mouth and the pharynx, and 
is composed of six pairs of small muscles, each having one 
of their attachments upon the palate bones. In some cases 
these muscular attachments will extend farther forward than 
usual, and in such cases may interfere with the retention of an 
artificial denture if the base-plate is improperly adjusted to 
them. This same improper adaptation may not only cause 
loosening of the artificial denture, but also nausea. However, 
the base-plate, for best retention, must extend in every di- 
rection as far as the muscles will permit, because, other con- 
ditions being equal, the retention of artificial dentures is in 
direct ratio to the area covered. 
The above paragraph has expressed the teaching of the 
profession until quite recently, but now it is known that the 
principle herein taught is only in part true, for there are a large 
number of cases in which the best results are obtained by extend- 
ing the palatal border of the artificial denture well upon the 
yieldable soft tissue. This new thought will be discussed in 
the chapter on Retention. 32 
THE MOUTH 
PHYSICS OF THE MUSCLES OF MASTICATION AND 
TEMPOROMANDIBULAR JOINT. 
Gray says (page 298, 20th edition): "The movements 
permitted in this articulation are extensive. Thus, the 
mandible may be depressed or elevated, or carried forward 
or backward; a slight amount of side-to-side movement is 
also permitted. It must be borne in mind that there are two 
distinct joints in this articulation-one between the condyle 
and the articular disk, and another between the disk and 
the mandibular fossa. When the mouth is slightly opened, 
as during ordinary conversation, the movement is confined 
to the lower of the two joints. On the other hand, when the 
mouth is opened more widely, both joints are concerned in 
the movement; in the lower joint the movement is of a hinge- 
like character, the condyle moves around a transverse axis 
on the disk, while in the upper joint the movement is of a 
gliding character, the disk together with the condyle, gliding 
forward on the articular tubercle, around an axis which passes 
through the mandibular foramina. These two movements 
take place simultaneously, the condyle and disk moving 
forward on the eminence, and at the same time the condyle 
revolves on the disk. In shutting the mouth the reverse 
action takes place; the disk glides back, carrying the condyle 
with it, and this at the same time moves back to its former 
position. When the mandible is carried horizontally forward, 
as in protruding the lower incisor teeth in front of the upper, 
the movement takes place principally in the upper joint, the 
disk and condyle gliding forward in the mandibular fossa and 
on the articular tubercle. The grinding or chewing move- 
ment is produced by one condyle, with its disk, gliding alter- 
nately forward and backward, while the other condyle moves 
simultaneously in the opposite direction; at the same time 
the condyle undergoes a vertical rotation on the disk. One 
condyle advances and rotates, the other condyle recedes and 
rotates, in alternate succession. 
"The mandible is depressed by its own weight, assisted by 
the platysma, the digastricus, the mylohyoideus and the 
geniohyoideus. It is elevated by the masseter, pterygoideus MASTICATION AND TEMPOROMANDIBULAR JOINT 
33 
internus and the anterior part of the temporalis. It is drawn 
forward by the simultaneous action of the pterygoideus 
internus and externus, the superficial fibers of the masseter 
and the anterior fibers of the temporalis; and backward by 
the deep fibers of the masseter and the posterior fibers of the 
temporalis. The grinding movement is caused by the alter- 
nate action pf the pterygoidei of either side." 
This statement is concise and probably is the latest 
accepted description by anatomists of the composition and 
action of the temporomandibular joint. A study of the 
physics of the individual muscles, and of their combined 
action, will help to develop an understanding of the function 
of the masticatory apparatus. 
The function of a muscle fiber is to draw its inserted end 
toward its origin in a straight line. Two or more muscles 
that are not parallel but acting simultaneously will produce 
a resultant action. The resultant action is influenced by the 
ratio of the power of the muscles involved as well as by the 
direction of their individual activities. It is by the result of 
the combined action of the muscles that their function is 
determined. Therefore, the parallelogram of forces will 
demonstrate the physics of mastication and the principle 
included. 
The superficial portion of the masseter, and the internal 
pterygoid muscles act in conjunction with each other in a 
direct thrust, and in a vertical and forward direction, at 
approximately an angle of 25 degrees from the perpendicular. 
The posterior portion of the temporal muscle acts also in 
the direct closing thrust of the mandible; however, its line 
of force is upward, and about 45 degrees from the perpen- 
dicular backward. Illustrated by the solid arrows in Fig. 9. 
As the power of the combined action of the masseter and the 
internal pterygoid is two to three times as great as that of the 
temporal muscle, the parallel lines of the parallelogram repre- 
senting the thrust of these muscles must be two to three 
times as long as the parallel lines representing the thrust of 
the temporal muscle; therefore, the diagonal line of an oblique 
parallelogram will represent the resultant of the action of 
these three muscles. As the resultant is at right angles to the 34 
THE MOUTH 
occlusal plane, it is evident that the whole force of these 
muscles is expended upon the bolus of food and not any 
portion of it upon the condyle. Therefore the condyle is not 
a fulcrum and the mandible is not a lever of the third class. 
Fig. 9 
This diagram is the true physical demonstration of the 
action of these muscles; however, a variation of the demon- 
stration may be more easily comprehended. As force acts 
in a straight line, and a force acting upon a solid body acts 
upon every portion of that solid body in parallel lines; there- 
fore the action of the temporal muscle attached to the 
coronoid process is just the same as if the attachment were MASTICATION AND TEMPOROMANDIBULAR JOINT 
35 
carried forward to the apices of the incisor teeth. By con- 
structing the parallelogram below, and to this extended line, 
it may be easier to conceive of the resultant force being at 
right angles to the occlusal plane. (See lower parallelogram, 
Fig. 9.) 
A further proof that the mandible is not a lever of the third 
class is found in the parallelogram of forces (see broken lines, 
Fig. 9) constructed upon the lines of force of the deep portion 
of the masseter which draws the mandible upward and back- 
ward; and the anterior portion of the temporal muscle which 
draws the mandible upward and forward. The resultant 
force of these minor portions is in the same direction as the 
resultant force of the major portions of these muscles; how- 
ever, they act as a stabilizer, and make more positive the 
intent of the action of these muscles. 
Another positive evidence that the mandible is not a lever 
of the third class is found in the action of the external ptery- 
goid muscle. This muscle is inserted into the neck of the 
condyloid process of the mandible, and into the articular 
disk. The function of this muscle is to draw the mandible 
and articular disk forward and inward. This results in draw- 
ing the condyle and articular disk, with its lubricating sacks, 
on to the articular tubercle. Therefore, if the mandible is a 
lever of the third class, then the fulcrum consists of a lubri- 
cated inclined plane, a mechanical construction unthinkable 
of our conception of the Omnipotent Architect. Hence, if the 
articular tubercle does not function as a fulcrum, the man- 
dible does not function as a lever of the third class. 
Another very strong evidence that the mandible is not 
primarily a lever of the third class was presented by H. J. 
Prentiss, M.D., Professor of Anatomy at the University of 
Iowa, in a paper published in the Dental Cosmos, June, 1918. 
This is an exceedingly interesting article and can be read 
with profit by every member of the dental profession. The 
paper is based entirely upon laboratory investigations of 
various joints. He considers the histology of the knee-joint 
from early embryonic to adult life. He says: "We see, there- 
fore, in the knee-joint a retrograde absorption of the meniscus 
(articular disk) which is necessary to a normal function of 36 
THE MOUTH 
the joint. The sequence of events just followed in this joint 
(knee) may be traced to the mandibular joint, only here it 
becomes pathological with the loss of the teeth." 
This is positive evidence that the action of the mandible 
is not primarily a lever of the third class, and that when it 
does become such, as the sequence of the loss of the teeth, 
then it results in a greater or less destruction of the articular 
disk. 
These four evidences show conclusively that nature did 
not design the mandible as a lever, but as the moving part of 
a mill. 
Consider the masticatory apparatus of man as a mill. 
This can best be done by inverting the head, when the max- 
illae become the nether millstone and the mandible the upper 
and movable millstone; the maxillary molars and bicuspids 
represent the convex surface, and the molars and bicuspids 
of the mandible represent the concave rotating or triturating 
surface; the rami are balancing arms supported by ball-and- 
socket joints, the movements of these joints are limited in 
scope by the ligaments; and the milling power is furnished 
by the muscles. 
This arrangement would result in the loss of gravitation 
and require more power in separating the millstones for the 
insertion of the grist, and would place more pressure upon 
the articular disk causing the perforation of the articular disk 
to become a physiological process, which is not the intent of 
nature. Nature reversed this order and suspended the mov- 
able millstone, thus conserving energy, reducing friction and 
preserving tissue. This suggests the function of the ligaments 
and fasciae (suspensors). This principle of suspension in 
mechanics is used in some of the greatest engineering schemes 
of man. For instance, the electric power plant at Niagara 
Falls, where the generating pow'er consists of a column of 
water falling 185 feet and entering the turbine wheel from 
beneath, thereby reducing friction to a minimum and pro- 
viding a maximum of energy. 
The last of the assemblage of factors to be presented as 
proof that the mandible is not primarily a lever of the third 
class is the purpose and action of the ligaments. The purpose MASTICATION AND TEMPOROMANDIBULAR JOINT 
37 
of ligaments is to act in the capacity of a rope. They are 
flexible, but neither elastic nor contractile; they act to sus- 
pend and to restrict. The action of the temporomandibular 
ligament should be elucidated. The quotation from Gray's 
Anatomy, previously given, states: "In the upper joint the 
movement is of a gliding character, the disk, together with 
the condyle, gliding forward on to the articular tubercle, 
around an axis which passes through the mandibular foramina." 
The location of this axis is an error, which is based upon 
the supposition that the stylomandibular ligament and the 
sphenomandibular ligament are the fixation forming this axis. 
Such an action is an impossibility, for if this rope-like 
attachment existed the mandible could not be protruded. 
It is the temporomandibular (external oblique) ligament 
that performs the function of the axis of rotation of the upper 
joint. In opening the mouth the head of the condyle first 
rotates on an axis on the under surface of the articular disk, 
as stated by Gray, when the temporomandibular ligament is 
made taut, its insertion at the neck of the condyle becomes 
the axis of rotation, and the head of the condyle and articular 
disk travel forward on to the articular eminence. As this 
ligament passes from the zygomatic process of the temporal 
bone downward and backward to the neck of the condyle its 
pendulous nature permits protrusion of the mandible, whereas 
the fibers of the stylomandibular, sphenomandibular liga- 
ments pass downward and forward and cannot act as the 
axis of rotation and permit protrusion. Therefore, as it 
permits protrusion it is not the axis of rotation. 
The stylomandibular and sphenomandibular ligaments are 
long thickened bands of fascia colli (deep cervical fascia) 
and function as pendulous suspensors. Incidentally these 
ligaments, with the other temporomandibular ligaments, 
may aid the mandible in acting as a lever of the second class 
(as a nutcracker), just as certain conditions may arise so as 
to cause the mandible to act as a lever of the third class; but 
these are not the primary or normal functions. Therefore, 
the temporomandibular joint is a compensating joint, and 
designed to aid the various factors in the masticatory appa- 
ratus in conforming to requirements. 38 
THE MOUTH 
This evidence and reasoning should and does establish 
the soundness of the statement that the "mandible is not a 
lever of the third class." 
The Teeth.-In the human family the teeth are the hard, 
flint-like, symmetrical formations placed within the mouth for 
the purpose of preparing the food for deglutition. They serve 
also as an aid in speech, but this is a secondary function, 
and an esthetic rather than an anatomical subject. 
It is necessary to study the general characteristics of the 
natural teeth that we may have a comprehensive apprecia- 
tion of the demands made upon artificial substitutes. 
As the teeth of a skull are viewed in mass they are seen to 
be in two parabolic rows (Figs. 3 to 6). The upper row is 
fixed or stationary, while the lower one is attached by a 
hinge (mandible), which carries them into intimate relation 
with the upper. As these two rows of teeth are held firmly 
together there is seen to be a method in their form, grouping, 
and arrangement. Proceeding from the median line in 
either direction, in the upper jaw, the first two teeth pre§ent 
a straight edge, the next three a single point, and the last 
three two points each. It is seen also that the upper teeth 
overlap the lower, and that the mass of teeth viewed as a 
column has the general form of a truncated cone. The 
straight-edged teeth are for cutting the food, and are called 
incisors, central and lateral. The group of three, with one 
point each exposed when the upper and lower rows are in 
occlusion, will be found to differ in form when the rows are 
separated and they are viewed upon their ends (Figs. 10 and 
11). It will be found that the anterior one only has but one 
point or cusp, and hence is called the cuspid. The remaining 
two teeth of this group have two points, one terminating the 
outer or buccal surface, and the other terminating the inner 
or lingual surface. These teeth are called first and second 
bicuspid (bi, two, and cusp, point; two-pointed, bicuspid). 
The remaining three teeth at the end of the parabolic row 
will be found, when viewed upon their ends, to have from 
three to five points, usually four; these teeth are called molars 
-first, second, and third molars. (Molar is from molaris, 
belonging, to a mill, derived from mola, millstone; molo, MASTICATION AND TEMPOROMANDIBULAR JOINT 
39 
grind.) The teeth are, in order, named: central incisor, lateral 
incisor, cuspid, first bicuspid, second bicuspid, first molar, 
second molar, and third molar. The names of the teeth are 
preceded by adjectives denoting location, as right or left and 
upper or lower. Thus, to indicate a certain tooth, it should 
be described as right upper central incisor, left lower first 
molar; that is, first indicate the side of the body, second the 
jaw, and third the distinctive tooth. 
There is another classification that, because of its origin, 
needs consideration. The Basle Anatomical Nomenclature 
(BNA) has the highest endorsement of anatomists and bi- 
ologists. It is in correct Latin and is designed to do away 
with duplicate anatomical terms. To have one definite 
name for an anatomical object is most desirable; but for a 
body of general students to elect terms for the specialist 
student is apt to be quite unsatisfactory. The author of 
this book is of the opinion that the specialist student should 
not acquiesce until his claims have been carefully con- 
sidered. When brevity and simplicity are the cardinal points 
of a scheme, it is certainly illogical to adopt the more cumber- 
some and less significant classification. This is the relation 
of the BNA tooth classification as compared with the tooth 
classification of the dental profession. The following is the 
BNA tooth classification with the English interpretation, 
as given by Dr. Barker, in brackets: Dentes incisivi (incisor 
teeth); dentes canini (canine teeth); dentes prsemolares 
(premolar teeth [O. T., bicuspids]); dentes molares (molar 
teeth); dens serotinus (late tooth [O. T., wisdom tooth]). 
There is no good reason for placing the third molar in a 
class by itself, and the term serotinus (late) is as obnoxious 
as the obsolete term, wisdom tooth. Premolar is no shorter 
than bicuspid, does not describe the tooth as well, and has 
the disadvantage of having been used by some writers to 
indicate the deciduous molars. Canine (dog) has no scientific 
significance. As both classifications will confront the student, 
he should know the writer's authority and reason for each. 
This book gives preference to the former rather than the latter 
classification. 
Returning to our observation of the teeth in the skull 40 
THE MOUTH 
(Figs. 10 and 11) it is seen that the upper central incisor is 
wider than the upper lateral incisor, that the lower central 
incisor is slightly narrower than the lower lateral incisor, 
and that the upper incisors taken together are much wider 
Fig. 10 
Fig. 11 
than the lower incisors. Dr. Black gives the average width 
(in millimeters) of the crowns of the teeth as follows: 
Central incisor Lower' 5 4 Lateral incisor ■'g Cuspid (gg First bicuspid | g' g 
{6 R (10 7 ( Q O ( Q A 
y j First molar Second molar jg y Third molar yg y MASTICATION AND TEMPOROMANDIBULAR JOINT 
41 
This formation permits all of the lower central incisor 
and half of the lower lateral incisor to occlude with the upper 
central incisor (Figs. 3 to 6), the lower lateral incisor to 
occlude with the upper central and lateral incisors, and the 
lower cuspid to occlude with the upper lateral incisor and 
cuspid. This arrangement continues throughout the line 
of teeth. In other words, each tooth, excepting the lower 
central incisor and upper third molar, occludes with two 
teeth. This arrangement necessarily places each tooth of 
the lower row, excepting the central incisor, half of its width 
(approximately) in advance of its fellow of the upper row. 
The fact just stated is fundamental, and should be fixed 
in the student's mind as a landmark. For emphasis, the 
proposition is restated. Excepting the central incisor, each 
lower tooth is approximately half its width in advance of its 
fellow in the upper parabolic curve. In arranging the teeth 
of a complete artificial denture this interlocking of the 
teeth should always be produced. The teeth should not 
be arranged end to end, but interlocked one against two. 
Farther on the mechanical reasons for this interlocking will 
be developed. 
Parabolic Curve.-A parabola is a section of a cone cut 
parallel with one of its sides. This will form a figure with a 
half-circle at one end, a straight line at the other, and the 
ends of the half-circle and straight line joined by diverging 
straight lines. If a skull with typically arranged teeth is 
held in the hand so as to secure a direct view of the morsal 
ends of the upper teeth, it will be seen that the teeth 
describe nearly a perfect parabola (Fig. 10). Dr. Bon will 
demonstrated that the segment of the circle described by 
the six anterior teeth has a radius equal to a line drawn from 
the mesial incisal angle of the central incisor to the distal 
incisal angle of the cuspid. The student should appreciate 
that to study any subject pertaining to nature it is neces- 
sary to have an ideal-a type as a standard for comparison. 
It is an axiom that Nature never exactly reproduces herself, 
therefore science groups the easily recognized modifications 
of the type into classes. 
In studying a large number of human mouths it will be 42 
THE MOUTH 
observed that in many cases the segment of the circle will 
have somewhat of a square form, in others it will be somewhat 
V-shaped (with apex to the front), and in others a flattened 
round. Three types will be further considered in the chapter 
on Esthetics. When the teeth are all in situ the radius of 
the circle may be easily obtained with a pair of dividers, but 
when the maxilla is edentulous it is another proposition. 
The next observation is to determine how to secure this 
radius in an edentulous subject. Upon the skull may be 
observed an elevated ridge, cuspid (canine) eminence, over 
the root of the cuspid tooth. This eminence terminates 
just external to the outer corner of the anterior nares. The 
student may place his finger upon his own lip over the cuspid 
eminence and it may easily be felt. By moving the finger 
upward it will be found that this crest terminates within 
the triangle formed by the upper border of the lip, the wing 
of the nose, and the linea nasolabialis. This point indi- 
cates the termination of the influence of the cuspid root. 
Thus, a point of the dividers placed at the center of the base of 
this triangle and the other point of the instrument placed 
in the median line just below the crest of the anterior nasal 
spine will indicate the length of space to be occupied by the 
central, lateral, and mesial half of the cuspid tooth. With 
the dividers so set, and teeth selected to conform with the 
space indicated, the radius of the required circle can be 
obtained by extending the dividers to cover the distal angle 
of the cuspid. In practice it is unnecessary to use the instru- 
ment for this purpose, for the wax occlusion model should 
be so constructed that the cuspid eminence is established 
by the mouth. The student should remember that this 
cuspid eminence entirely disappears with the resorption of 
the alveolar process; so that the labio-naso-buccal triangle 
is his one guide in determining the width of the anterior 
teeth; also the radius of the dental circle. (Some operators 
consider that the angle of the mouth indicates the distance 
to which the anterior teeth should extend. This is, however, 
a very unreliable guide by which to determine the width of 
the anterior teeth, because of its instability and the seeming 
lack of uniform conformity between the slit of the mouth MASTICATION AND TEMPOROMANDIBULAR JOINT 
43 
and the other features of the face.) The prosthetist should 
establish a mental vision of the segment of the circle de- 
scribed by the anterior teeth and use it as an outline 
by which to arrange the artificial teeth in each individual 
case. He should also keep in mind the parallelogram de- 
scribed by the suture of the maxilla and the cuspid emi- 
nence. By continuing the segment of the dental circle it is 
seen that the line not only passes along the incisal edge of the 
incisors and cusp of the cuspid, but also through the buccal 
cusp of the first bicuspid; and then obliquely across the 
sulcus of the second bicuspid, and across the mesiolingual 
cusp of the first molar (Fig. 10). In viewing the morsal 
surface of the upper denture, it will be seen that if a straight 
line is drawn from the summit of the cusp of the cuspid to the 
summit of the distobuccal cusp of the second molar, the 
line will fall across all the intervening buccal cusps. The 
third molar is usually deflected either lingually or buccally 
from the buccal cusp line. This buccal cusp line always 
diverges, to a greater or less extent, from the median line 
of the skull. A view should now be taken of the side eleva- 
tion of the skull, and it will be seen that the teeth plane is 
identical with the diverging cusp line. Again, attention is 
called to the short compensating plane formed only by the 
elevation of the second and third molars. (Other writers 
describe a longer compensating plane which includes the 
elevation of the distal cusp of the first molar, and often of 
the entire tooth.) Dr. Bonwill and his successors have erred 
in considering the curve of Spee and the teeth plane equiva- 
lent one to the other. 
Truncated Cone.-In viewing the occluded teeth, as a mass, 
it will be seen that they present the form of a truncated cone. 
This is necessarily so because the crest of the alveolar process 
of the mandible describes a larger circle than the crest of the 
alveolar process of the maxilla. This arrangement favors 
concentrating the bolus of food, by giving a lateral incli- 
nation to the grinding teeth, the lowers being inclined inward 
(Fig. 121) and the uppers being inclined outward. Usually 
1 Fig. 12 from photograph of specimen in the Wistar Institute of Anatomy. 44 
THE MOUTH 
the incisors, both upper and lower, incline somewhat outward. 
In some cases the lower incisors incline inward, and in a few 
instances the upper incisors incline inward, giving a snake- 
like appearance to the mouth. It is quite probable that 
this unsightly appearance is the result of the unfortunate 
loss of the permanent first molars in youth. Too often the 
dentist gives this unnatural inclination to artificial dentures. 
It is rarely, if ever, justifiable. 
Fig. 12 
There is usually an inclination of all the teeth toward the 
median line of the skull. This is partly due to the conforma- 
tion of the individual tooth and partly to the tilting of the 
teeth bodily in that direction. As age and especially as 
certain diseased conditions progress this mesial inclination 
prevails. 
Function of the Teeth.-In mastication there are three 
functions of the teeth, namely-prehensile, tactile and com- 
minution. Prehension is a very primitive function and in 
the primate man is nearly extinct. The tactile sense in man 
is quite specialized, it serves to guide the teeth into proper 
relation with each other, and to protect the teeth against 
excessive stress. The sense of touch is transmitted through 
the teeth to the nerve filaments of the peridental membrane. 
The touch sense seems to be most highly developed in the 
cuspid teeth. When the teeth are lost this touch sense seems MASTICATION AND TEMPOROMANDIBULAR JOINT 
45 
to be lost and the individual seems to revert to the primitive 
prehensile function. However, when the lost dental organs 
are replaced with artificial dentures the touch sense is soon 
restored by educating the mucous membrane covering the 
alveolar process which is in contact with the restoration. 
It is very evident that the tactile or touch sense is not in 
the temporomandibular joint. The function of comminution 
is as an aid to insalivation of the food. 
Eruption of the Teeth.-Nature seems to have an admi- 
rably adapted plan for the erupting of the permanent teeth. 
This function begins with the lower first molar, upon each side 
of the mandible, at about six and one-half years of age. This 
tooth erupts in the angle formed by the body and ramus 
of the mandible. It is a wise provision of Nature, as it is the 
most fixed portion of either parabolic curve, and becomes 
the guide to the eruption and development of the entire 
dental armament. It is supported by the coronoid column 
of the ramus and causes the forward development of the 
alveolar process. As this tooth is in a fixed and fortified 
position, it directs and sustains the upper first molar through 
their interlocking cusps. These two teeth upon each side 
of the mouth being established, the other teeth must assume 
their normal position and usefulness unless interfered with 
by abnormal conditions. The dental student cannot too 
early become imbued with the importance and necessity 
of preserving throughout life the first permanent molars. 
The lower teeth are all erupted in advance of their corre- 
spondents in the upper dental curve (arch). For this reason 
some dentists have argued that the lower artificial denture 
should be set up first, and the upper arranged to the lower. 
This argument is not tenable, because the reason for the 
order in which nature places the teeth is entirely different 
from those confronting the dentist. Nature's foundation 
principle is to develop the jaws, while the dentist is required 
to secure mechanical leverage for retention of the artificial 
substitute. As the maxilla acts as a fulcrum, the upper teeth 
must be properly and securely placed. The second reason is 
cosmetic. The upper anterior teeth have much the larger 
part in establishing the contour and expression, while the 46 
THE MOUTH 
arrangement of the lower teeth is little more than me- 
chanical. 
The Alveolar Processes.-The alveolar processes are the 
portions both of the maxilla and mandible that support 
the teeth. They develop with the teeth and disappear with 
their loss. The alveolar processes are removed by resorp- 
tion. The process of removal is quite active for six months, 
after which it is much slower for six to twelve months longer, 
when it is spoken of as a settled or a permanent process upon 
which an artificial denture may be placed which is designed 
to be worn for a few years. It is the changing relation of the 
processes of the two jaws that makes the wearing of artificial 
dentures so difficult for some people. If measurements 
were tp be made of the crest of the alveolar ridges of the 
Fig. 13 
maxilla and mandible soon after the removal of the teeth, it 
would be found that the radius of the summit curve would 
be greater in the mandible than in the maxilla. This is 
evident because of the truncated cone formation of the 
dental armament. As the long axis of a cross-section of the 
body of the mandible is divergent from above downward, 
it is apparent that the radius of its summit curve must 
increase with its summit recession. While the radius of the 
summit curve of the mandible is constantly increasing with 
resorption, the radius of the summit curve of the maxilla is 
constantly decreasing, therefore increasing the difficulties 
inherent in wearing artificial dentures. As the palatal 
processes are the least changeable of any portion of the 
maxilla, the schematic drawing (Fig. 13) will explain why MASTICATION AND TEMPOROMANDIBULAR JOINT 
47 
the crest of the maxillary process recedes so rapidly inward 
as well as upward. The two views of the edentulous skull 
show the result of resorption (Figs. 14 and 151). It is cus- 
Fig. 14 
Fig. 15 
1 Figs. 14 and 15 from photographs of a specimen in the collection of 
Dr. M. H. Cryer. 48 
THE MOUTH 
tomary to say that where resorption has continued for twelve 
to eighteen months they are in a permanent condition. 
This is only relatively so, for the processes may slowly 
continue to resorb for many years, not only until the sur- 
faces occupied by the alveolar processes are perfectly flat, 
but until there is an extensive concavity. This is especially 
true of the mandible. The author, in his practice, has con- 
structed two lower dentures in which a portion of mandibu- 
lar surface of the base-plate of the artificial denture was 
convex to the extent of nearly half a circle. This condition 
does not imply added difficulties in the retention of the 
denture, but it does imply decreased substance in the man- 
dible and increased danger of fracture. 
THE USE OF THE MOUTH. 
Mastication.-As the first essential for a man is his life, 
so the first and most important use of the mouth is to pre- 
pare the materials of sustenance for deglutition and assimila- 
tion. The teeth are most important organs in this operation. 
The incisors cut off morsels of food of sufficient size for com- 
minuting between the grinding teeth. The bicuspids are 
designed especially to lacerate fibrous food, while the molars 
are designed to pulverize and triturate the food with the 
fluids of the mouth. It is the importance of these organs 
in preparing the food for its onward movement that creates 
the dental profession for their preservation, and restoration 
when lost. The physiology of mastication is beyond the 
scope of this book, but its importance is so great that the 
dental student should familiarize himself with the subject 
to a greater extent, if possible, than the medical student. 
In fact, the dental student should consider that he is intrusted 
with the comfort and preservation of the most vital organs 
of the human economy. It is a lamentable fact that the 
profession has not yet arrived at that stage of proficiency by 
which the organs of mastication, in all cases, can be pre- 
served for use and comfort; therefore the dental prosthetist 
is necessary to provide a substitute for the lost dental 
organs, The dentist should appreciate that this office is THE USE OF THE MOUTH 
49 
very important and not one to be thoughtlessly turned over 
to incompetent hands. The student of prosthetics should 
delve thoroughly and earnestly into the art, science, and 
esthetics of restoration that he may properly serve those 
needing his services. 
Speech.-Articulate speech is the means by which man 
communicates his thoughts. The sounds forming speech 
are produced by air passing over the vocal cords aided by 
the resonant chambers of the chest and head. The mouth 
with the tongue is the most important aid to the vocal cords. 
The teeth are important factors of the mouth in vocalization, 
as they give support and shape to the side walls (cheeks) 
and tongue. When the teeth are lost, certain muscles must 
be developed and a greater effort is required on the part of 
the speaker. With the loss of the teeth there is a permanent 
loss of certain qualities of resonance and clearness of enun- 
ciation that cannot be reacquired by developing the soft 
tissues. However, by the aid of artificial dentures the original 
conditions can be so nearly restored that a defect in speech 
can only be detected by the trained ear. Indeed, in some 
cases of natural defects and deficiencies of the mouth great 
improvement of the speech may be made possible by properly 
constructed artificial dentures and appliances. Artificial 
dentures may be an impediment to speech, by the base-plate 
not conforming to the parts upon which they are supposed 
to rest, thus acting as an edge to split the expelled air of 
vocalization; or the artificial appliance may be so cumber- 
some that it fills space required by other factors of enunci- 
ation. However, all deficiencies of speech observed in 
people wearing artificial dentures are not due to improperly 
constructed substitutes. The personal equation is an 
important factor. Thus, lisping and whistling are often 
entirely unnecessary, being faulty conformation of the 
tongue. Where the prosthetist has satisfied himself that 
the base-plate is properly fitted and retained, and that there 
is no unnecessary incumbrance to the movement of the 
tongue, he should explain and perhaps demonstrate to the 
patient that the defect in speech is due to the faulty use 
of the tongue. The proper contour and conformation of 50 
THE MOUTH 
artificial dentures will be considered with the technic of 
construction, and on pages 530 to 537. The object sought 
at this time is to establish the fact that artificial dentures 
are an important factor in both restoring and impeding 
speech. 
RESULTS OF LOSING THE TEETH. 
Importance.-The importance of the teeth cannot be ques- 
tioned. Their eruption and retention develop the lower third 
of the face, and have much to do with cosmetics. They are 
useful in the formation of speech, and, above all, they are 
necessary in preparing the intake of food. 
Results of Loss.-The loss of one or more teeth in youth will 
prevent the full development of the face and seriously inter- 
fere with the usefulness of the remaining ones. The loss of 
one or more teeth in adult life weakens the mesiodistal sup- 
port of the dental armament and exposes a portion of the 
gum to injury during mastication. The loss of the entire 
dentures makes impossible the mastication of food. There 
are a few exceptions to this statement, as there are cases in 
which the opposing jaws may be brought in contact, and, 
by use, the gum tissue becomes so toughened that the food 
can be mashed and insalivated. It is a safe statement to 
make that the loss of all the natural teeth adds ten to fifteen 
years to the apparent age of the patient, and it quite likely 
cuts off as many years of his natural life. It is the province 
of the operative dentist to prevent these calamities, and the 
duty of the prosthetist to supply substitutes for the losses 
sustained by accident, ignorance, or necessity. 
The statement is often made that a patient can only use 
about one-fourth as much force with artificial dentures 
resting upon soft tissues as could be used with healthful 
natural teeth. This is probably true, but it should not be 
assumed that artificial dentures are only one-fourth as effec- 
tual as natural ones; because in no case does a patient 
anywhere near use the maximum of his power in preparing 
and masticating the food. However, there can be no question 
but that more time is required to properly insalivate the food 
with artificial substitutes than with healthful natural ones; EXAMINATION OF THE MOUTH 
51 
and there is undoubtedly more temptation to bolt the food. 
The loss of the natural teeth should be considered a calamity, 
but in such a misfortune one should be grateful for the 
services of the prosthetist. 
A word as to the time of removing the natural teeth and 
replacing them with artificial substitutes. It should be 
established as a fact that the removal of the natural teeth 
at any time is more or less a shock and a strain upon the 
nervous system, and especially so if the patient is in an 
exhausted or a debilitated condition. Under such conditions 
no more teeth should be removed than is necessary to give 
relief from pain and remove danger of septic infection. The 
dentist should be very cautious about attempting to con- 
struct and insert artificial dentures while he patient is much 
below par in physical vigor. It is not an uncommon incident 
or the dentist to be told that "father or mother must have 
some new teeth, as he or she is failing rapidly." In these 
cases the dentist should satisfy himself that there is a lack 
of adaptation of the artificial dentures being worn, and that 
the unsatisfactory condition is not due to a lack of tone of 
the tissue, in which latter extremity he cannot successfully 
insert new dentures. 
EXAMINATION OF THE MOUTH. 
Seating and Protecting the Patient.-The patient should 
be seated in a dentist's operating chair, facing a good light. 
The chair should be adjusted to the comfort of the patient, 
and tilted slightly backward. A napkin should be fastened 
about the neck of the patient as a protection to the clothing. 
If, after examination, an operation is to be performed that 
may soil the patient's clothing, a further suitable covering 
for protection should be provided. The mouth mirror and 
all instruments used about the mouth should be scrupulously 
clean. 
Cleansing the Hands.-Special emphasis is placed upon the 
cleansing of the hands. Surgical cleansing is not necessary, 
but mechanical cleansing is imperative. It is not sufficient 
that the hands have been thoroughly cleansed just before the 52 
THE MOUTH 
patient enters the office, bnt the patient should be conscious 
that the hands have been laved either just before or just 
after he or she is seated in the operating chair. The impres- 
sion produced is most beneficial. The attention given the 
hands will cause the patient to unconsciously, perhaps, con- 
clude that the instruments are not only apparently clean, 
but are clean. The dentist should establish a regular course 
of procedure. His manner should be positive but gentle. 
These attentions and methods will have much to do with 
securing the confidence of the patient. 
Method of Examination.-A mouth mirror, an examining 
point, a pair of cotton tweezers, possibly a blunt probe, 
absorbent cotton, a supply of aseptic mouth napkins, and 
a water syringe should be accessible. A compressed-air 
spray is often convenient, but is not a necessity in examina- 
tions, for the water syringe will take its place. The operator 
should stand at the right and slightly back of the patient. 
This position will give a good view of the mouth, and the 
person of the operator will not obstruct the light. This 
position is advantageous for manipulation. 
The first glance should observe any inflammatory (sore) 
conditions of the lips, and then of the interior of the mouth, 
when, if such exists, the operator should endeavor to cause 
the patient as little discomfort as possible, yet be thorough. 
Should there be any suspicion of an infectious condition, 
the operator should use every precaution to protect himself, 
and after the patient is dismissed every instrument used 
about the patient's mouth should be sterilized. (Steriliza- 
tion is taught by another chair; however, when not contra- 
indicated, keeping the instruments submerged for thirty 
minutes in boiling water will be very effectual.) 
With the mouth mirror in the right hand and the assistance 
of the fingers of his left hand, every portion of the mouth 
cavern should be brought, in turn, under inspection and 
investigation. Should the operator observe that there is 
resistance on the part of the patient, such as moving the 
head or contracting the lips, he should instantly cast about 
for an explanation. He should satisfy himself that there 
is no evidence of filth about his hands or instruments, or EXAMINATION OF THE MOUTH 
53 
that he is not unconsciously pulling the patient's hair, 
pressing a cuff-button into the ear, handling the mouth in 
an awkward manner, or causing unnecessary pain. These 
possibilities of discomfort should in an instant be detected 
by thought and a glance. Having satisfied himself that 
he is not at fault, but that the patient is fearful or over- 
sensitive, he should endeavor to overcome these conditions 
by his gentle manner and kindly speech. Often the simple 
request to relax the mouth, expressed in a gentlemanly 
manner, will be all that is necessary. At other times an 
assurance that the work in hand does not necessitate pain, 
an explanation of what is desired, or of the condition found, 
will place the patient at ease through the confidence gained. 
What to Look For.-The things to be observed in the 
mouth are: Remaining teeth and roots, shape of arches and 
vault, size of maxillary and mandibular surfaces, extent 
and condition of the alveolar processes, muscular attachments 
and glandular tissue, mucous and submucous tissues, and 
fluids of the mouth. We will consider each of these in the 
order named. 
Teeth and Roots.-A good rule for the dentist to establish 
is: The difficulties of inserting, and often in using, artificial 
teeth are in the ratio to the number required. While there 
are many exceptions to this rule, it is a safe one when con- 
sidering the advisability of extracting teeth. Another rule 
is: A base-plate should not be placed over a root unless the 
root is used as a means for support of the artificial denture. 
Unused roots are a source of irritation, and usually add to 
the instability of the artificial denture. However, if the 
root can be placed in a healthy condition and crowned, 
or used as an attachment for the artificial appliance, it may 
be very valuable. The advisability of retaining the cuspid 
roots as an aid to expression is very questionable, unless 
they are used for the retention of the artificial denture. In 
practice, when preparing the mouth for artificial dentures, 
the operator must often determine whether he will or will 
not retain one or more sound and firm teeth. In no case 
should such teeth be removed until their usefulness as a means 
of retaining the artificial ones has been carefully considered. 54 
THE MOUTH 
Sometimes a single tooth is of great value in supporting 
an artificial denture; especially is this true in the mandible. 
A single tooth in the maxilla may be of great value when the 
conditions are unfavorable for the usual methods of retaining 
full dentures. Two teeth in either the maxilla or mandible, 
if properly located, may furnish the best possible means of 
securing the artificial denture. However, a tooth or two 
may be so located that their retention will be a positive 
detriment to the wearing of artificial dentures. 
It often happens that the patient places much value upon 
the few remaining teeth, either for their use or cosmetics. 
If there are two teeth, one in each jaw, opposing each other, 
it is always doubtful wisdom to remove such; though they 
may, as they doubtless will, interfere with the retention of 
artificial dentures. In advising the patient, the dentist must 
take into consideration that the personal equation is an 
important factor; that the patient may be one who will never 
make a success of wearing artificial teeth. However, one 
factor that the patient should be apprised of regarding the 
retention of one or more incisors only is that if any move- 
ment of the artificial teeth occurs, it is made conspicuous by 
reason of the stationary condition of the remaining ones. 
The chapter on Retention of Artificial Dentures will consider 
the relative value of individual teeth. 
Arches and Vaults.-The student should have a clear 
understanding of these terms. In common parlance an 
arch is an upright structure spanning an opening, but this 
does not apply to the dental arches. The dental arch has 
reference to the parabolic curve only of the teeth. It is 
often erroneously used to designate the curve of the roof of 
the mouth. Such use either shows ignorance or carelessness 
in the use of accepted dental terms. Vault is the term 
used to designate the roof of the mouth, the more or less 
curved span over the tongue. The dental arches are the 
curved lines described by the teeth of both the maxilla 
and mandible, while the vault is the curved line extending 
from side to side of the mouth, over the tongue. 
The shape of the arches and vault will be similar in any 
given case. Thus, if the upper dental arch is V-shaped, the EXAMINATION OF THE MOUTH 
55 
vault will tend toward the same conformation. This is 
easily explainable. If in infancy and childhood some influ- 
ence is brought to bear upon the outer surfaces of the 
biscupids and molars (that is, the diverging straght lines of 
the parabolic curve), so as to compress them, it will also 
force the suture of the palatal processes of the maxillae 
upward, giving the V-shape to the vault. Any continuous 
pressure upon the plastic osseous structure of youth will 
have its beneficial or detrimental effect. Thus, the shape 
of the dental arches and vault are similar unless they are 
acted upon by two or more opposing forces. While the shape 
of the arches and vault are supposed to harmonize with the 
"temperament" of the individual, they may be indicative 
only of abnormalities. The curve of the edentulous alveolar 
processes and the vault will indicate the curve of the teeth 
produced through nature, but that is no assurance that the 
natural teeth were in harmony with the rest of the physical 
organization. Consequently the curves of the alveolar 
processes and vault are of much interest, both directly and 
indirectly, to the prosthetist. The work being done by the 
orthodontists in bringing the teeth of youth into occlusion 
is of importance throughout life. It not only helps to pre- 
serve the teeth, at least to make them useful while they are 
retained, but it puts the mouth in the best possible shape 
for the retention of complete artificial dentures when such 
may be required. Some persons may foolishly have sound 
natural teeth removed because of their unsightly irregu- 
larity, and with the intent of having "beautiful" artificial 
ones inserted. If possible, before the teeth are extracted, 
the patient should be informed that the conditions of the 
mouth accompanying the mal-aligned teeth may add to the 
difficulties of using artificial dentures. 
The maxillary suture or raphe requires special attention. 
This is part of the median line noticed in many portions of 
the body. Usually it is little more than a slight ridge or fold 
of mucosa; however, it may develop to the extent of an 
obstructive osseous tumor the size of a man's thumb. The 
author's belief (based on experience only) is that these 
osseous enlargements of the raphe are much more common 56 
THE MOUTH 
in the mouths of females than of males. If possible, the 
palatal border of the base-plate should pass about and not 
over these excessive enlargements; at least the pressure 
must be relieved the entire length of the base-plate; that is, 
even the posterior edge must be relieved. A vacuum chamber 
over any portion of this tumorous surface is more than useless. 
It only tends to concentrate the pressure upon the remaining 
portion of the tumor covered. Dr. L. P. Haskell states that 
95 per cent, of all cases requiring artificial dentures need the 
pressure of the base-plate relieved over this portion of the 
vault. 
Size of the Maxillary and Mandibular Surfaces.-The 
size of these surfaces is not always in harmony with the 
size of the individual. Sometimes a very large maxilla is 
associated with a small physical organization and mouth 
orifice; at other times the reverse occurs, and occasionally 
one is large and the other small. These varying conditions 
will influence the construction and wearing of artificial 
dentures. These conditions should be well noted in examining 
the mouth. The size of the maxilla and mandible is an impor- 
tant factor in retaining artificial dentures; other conditions 
(shape, soft tissues, tone, and fluids of the mouth) being 
equal, the amount of retention will be in the ratio to the 
flat surface (base-plane) covered. In estimating the amount 
of retention surface that may be of value in retaining a 
base-plate, only that portion through which direct pressure 
is brought to bear upon the maxilla or mandible should be 
considered. In those cases where the maxillary alveolus 
flares outward the crest of the alveolus should define the 
border of the base-plane. The buccal surface of this class 
of alveolar process will only serve to prevent lateral move- 
ment of the base-plate covering it, which, aided by the soft 
tissues, will exclude the air, and thus be of value in reten- 
tion. The diagrams (Fig. 16) representing cross-sections of 
maxillee will make clear this idea. The arrow points indicate 
the distance to which direct pressure may be applied, and 
the dotted lines indicate the relative base-planes. As the 
base-plates rest upon the soft tissue, it is obvious that 
pressure brought to bear upon it in the proximity of one arrow EXAMINATION OF THE MOUTH 
57 
only will be concentrated, and tend not only to dislodge 
the base-plate, but to bruise the supporting soft tissue; 
while pressure applied at any point approaching the median 
line will be more diffused over the base-plate, and conse- 
quently present greater resistance and better retention. 
This demonstration shows that the common statement that 
a flat vault is unfavorable for retaining artificial dentures 
is not well founded. The poor retention often observed 
in such cases is due to other causes and often to faulty 
technic only. 
Alveolar Processes.-An earlier section of this chapter 
treats of the applied anatomy of the alveolar processes; this 
section will treat of them as supports for artificial dentures. 
Fig. 16 
When a number of teeth have been recently extracted, in 
common parlance the gums are spoken of as fresh gums, and 
when resorption has taken place they are called permanent 
gums. In a few days (seven to twenty-one) after the teeth 
have been extracted the gums will have closed over the 
alveoli, but the gums are not in a condition to withstand 
much pressure, yet they are in shape for temporary artificial 
dentures. No matter of what material the base-plate is 
constructed, when it has been constructed for fresh gums, 
the artificial denture should be considered as temporary. 
As the alveolar process recedes it ceases to properly support 
the artificial denture. The denture may become very 
insecure, and often irritates the tissues severely. During 
this process of resorption the base-plate may require refitting 
once or twice; however, when the artificial denture has been 
worn from twelve to eighteen months a new one should be 58 
THE MOUTH 
constructed. This is necessary to secure proper adaptation 
of the base-plate and for restoring the contour of the soft 
tissues. 
As the soft tissues (after extraction) close over the alveoli 
a very irregular surface may present, from portions of the 
process having been sprung out of position, or possibly 
fractured to the extent of separation. In such mishaps the 
loose pieces should be removed at the time of extracting 
the teeth, or as soon thereafter as discovered; because the 
detached portion will not be resorbed by the physiological 
process, but assumes a pathological import. So long as the 
displaced portion of process is vitally connected with the 
bone structure, the physiological action will dispose of it. 
Meanwhile the pressure of a base-plate may be a source of 
much irritation, and will necessitate cutting away sufficient 
of the base-plate for relief. However, much of this discomfort 
for the patient and annoyance for the prosthetist can be 
avoided by treatment properly administered by the exodon- 
tist. The extraction of the teeth should not be considered 
the end of the responsibility of the extractor. Modern 
surgery requires that mutilated tissue shall be consistently 
dressed. Obviously much improvement can be made, over 
the negligence of past times. 
Alveolectomy is a modern operation and it will require 
time to determine the extent to which it should be practised. 
Nevertheless it is a progressive step in oral restorations and 
will eventually be appraised at its true worth. 
A well-retained artificial denture must have its greatest 
bearing as near the periphery of its inclosed base-plane as 
possible. 
When the process of resorption is practically complete, 
several conditions may be present that should be observed. 
The process may be very prominent, so that the lip is full 
enough, and the absence of the teeth not noticeable when 
the patient is not speaking. In such a case, when laughing, 
the edentulous subject may show from a line to a quarter 
of an inch or more of the natural gum. Cases of this kind 
need no artificial gum to restore sunken lip and cheeks. 
Indeed, they probably present, when not speaking, a much EXAMINATION OF THE MOUTH 
59 
improved appearance from that possessed with the natural 
teeth. The artificial denture should be constructed without 
a gum portion as far back as the individual case shall require. 
This may require no artificial gum over the two central 
incisors, the four incisors, the incisors and cuspids, or, in 
extreme cases, no gum portion may be tolerated anterior 
to the first molars. The artificial teeth in these cases must 
be ground to set closely against the gum, indeed, press into 
and apparently grow from the gum. They may be placed 
with their labial surfaces in line with the crest of the process, 
or they may be carried outward and lap well over the process. 
The diagrammatic sketch (Fig. 17) illustrates these con- 
ditions. 
Fig. 17 
The vast majority of cases may be classed as regular, and 
present no complications. 
The resorption may continue until the process is almost 
extinct, when it is classed as flat. The methods of handling 
these cases will be discussed in technic methods, especially 
the technic of impressions. 
The process when receded may be broad or narrow. The 
broad alveolar ridge is ordinary, and the thin (knife-edged) 
ridge is only too common. They are a constant source of 
annoyance. In time the thin alveolar process disappears, 
leaving^ a pendulous, flabby gum. The base-plate should 
not be permitted to rest upon the sharp edge. 60 
THE MOUTH 
Sharp ridges may appear upon any portion of the process, 
especially upon the lingual aspect of the mandible. They 
will not tolerate the pressure of a close-fitting base-plate. 
Nodules from the size of a millet seed to a lima bean, or 
larger, may appear on any portion of the maxilla or mandible. 
If they are to be covered with a base-plate the pressure must 
be removed from their entire extent. This can be done with 
one or more layers of No. 60 tinfoil. 
Firm or pendulous: The firm gum consisting of an even 
layer of soft tissue is the desirable condition, but the pendu- 
lous and spongy gums indicate complications, and the extent 
of such complications must be ascertained. 
Muscular Attachments and Glandular Tissues.-These may 
be observed and their obstructiveness may be judged by 
distending the cheeks and lips, and having the patient raise 
the tongue to the roof of the mouth. The sublingual and 
especially the submaxillary glands may interfere with ob- 
taining a perfect impression of this portion of the mandible. 
The submaxillary gland may entirely cover the bicuspid and 
first molar portion of the mandible. The impression must 
be obtained of the surface upon which the gland rests and not 
of the gland. The method of doing this will be considered 
in the chapter on Impressions. The muscles and freme 
attached to the maxilla and mandible have already been 
considered, but on examining the mouth the location of their 
attachments and any obstruction they may present should 
be carefully observed. 
Mucous and Submucous Tissues.-The mucous membrane 
covers the entire surface of the mouth. It is underlaid with 
more or less submucous tissue. The condition of these tissues 
is an important factor in retaining artificial dentures, and 
requires observation. While all the preceding organs and 
tissues which we have mentioned for investigation in examin- 
ing the mouth are inspected by vision, and in a few instances 
by touch (either finger or instrument), the tissues (mucous 
and submucous) under consideration can be determined 
only by the sense of touch. It will be found that in some 
mouths the mucous membrane is very firm and tense over 
the whole surface upon which artificial dentures may be EXAMINATION OF THE MOUTH 
61 
worn; in others, that this membrane is largely underlaid 
with submucous tissue of more or less thickness. It is this 
class of cases that afford the greatest retention provided 
other conditions are favorable, and the submucous tissue is 
not excessive. A third class consists of those cases in which 
a portion of the surface is covered with tense mucous mem- 
brane and other portions are underlaid with submucous 
tissue. These three classes play an important role in the 
method of taking impressions and the method of securing 
the retention of the base-plate. They should be carefully 
examined. 
Fluids.-The fluids of the mouth consist of a mixture of 
the saliva and mucous secretion. They may be in moderate 
amount, or they may be excessive; they may be thin, or 
thick and ropy. The thin, watery fluid and in moderate 
amount is the most favorable for good retention of artificial 
dentures. When the fluid of the mouth is excessive and 
strings from the mouth as an impression tray or an artificial 
denture is removed, it may be considered as an unfavorable 
factor. The thick secretion prevents that close adaptation 
necessary for the strongest retention. 
Recapitulation.-Having a definite knowledge of what 
conditions may be found in the mouth, the examination is 
simple and expeditious. Ordinarily no record is made of the 
examination; however, much valuable information could in 
time be acquired if blanks were used for systematic work. 
When the prosthetist examines the mouth he desires to know 
the conditions presenting, so that he may determine at once 
whether it is an ordinary or a complicated case. The patient 
being comfortably seated, and facing good light, the operator 
makes a momentary visual and digital examination. By 
this preliminary examination he determines whether there is 
anything out of the ordinary that may complicate the work; 
if so, it must be given careful consideration. If he sees no 
complications, such as inflammatory conditions (sores), unde- 
sirable teeth or roots, ill-shaped arches or vault, disproportion 
between the maxilla and mandible, unfavorable muscle or 
frense attachments or gland complication, and no mucous 
and submucous tissue or fluid complications, he diagnos- 62 
THE MOUTH 
ticates the case as ordinary or simple, with success contin- 
gent only upon his technic and the personal equation of 
the patient. The prosthetist then determines the kind of 
restoration indicated, whether a bridge or an artificial 
denture, and the variety of either desirable or permissible. 
If there are complicating conditions present, he determines 
whether they are corrective or not, and, if not, how best to 
circumvent the difficulty. Having a clear conception of the 
requirements of the case, the prosthetist consults with the 
patient, as the involved expense may be prohibitive. An 
artificial denture supported upon a base-plate having been 
determined upon, the next step will be to take a suitable 
impression. CHAPTER II. 
IMPRESSIONS. 
Definition.-An impression is a negative likeness of an 
object or part taken in a plastic material, form which a 
cast or positive likeness may be produced. 
Scheme.-When the prosthetist determines to construct 
a base-plate artificial denture, he at once decides upon its 
general form and extent of surface to be covered with the 
base-plate. He also forms a tentative plan for retaining the 
artificial denture. This plan for retention may be altered or 
abandoned, as a result of a future critical study of the case; 
nevertheless, a definite scheme must be in mind before taking 
the impression, because an impression suitable for the con- 
templated appliance should be obtained. An impression 
that is most desirable for orthodontia may be entirely inade- 
quate for prosthesis; and certainly an impression that is 
desired by either the orthodontist or the prosthetist may be 
distorted for the other. This statement is made to impress 
the student with the fact that an impression is not necessarily 
an exact negative likeness of a part, but it must be perfect 
in its suitableness for the work in hand. The soft tissue 
is the factor that creates the variableness in impressions. 
Rarely is an impression perfect for its intended use unless 
the soft tissues are, to a greater or lesser extent, distorted; 
nevertheless, this distortion must be suitable for its intended 
purpose. The methods herein detailed are for base-plate 
work. However, there is much in common in impression 
taking for all specialists. The extent of the impression 
should be governed by the kind of an artificial denture 
required, whether a partial or full, a saddle or adhesion 
base-plate. The impression should extend a little farther in 
every direction than the contemplated base-plate; but any 
63 64 
IMPRESSIONS 
excessive extension causes unnecessary discomfort to the 
patient, and indicates indifference or thoughtlessness on the 
part of the prosthetist. Therefore a definite scheme or 
plan of procedure should be devised for the case in hand, and 
good workmanship requires that every step shall be neatly 
and accurately performed. This is a fundamental principle 
of mechanics, and, as a profession is superior to a trade, the 
prosthetist should show superior manipulation. Another 
thought for the young student of dentistry is this: There is 
no legerdemain associated with prosthesis, the profession 
being only an expression of cause and effect; therefore it 
behooves one to cultivate thoughtfulness and thoroughness 
in manipulation. 
New Scheme.1-Modern ideas of impression taking are 
undergoing a radical change, or rather, there is a radical 
change in the appreciation of some old ideas. The new 
appreciation is that: With full dentures-that as large an area 
as possible must be covered, that the periphery of the denture 
must extend upon yieldable tissue sufficient to form a valve-like 
1 Great credit should be given the late Dr. J. W. Greene and Mr. Samuel 
G. Supplee for their improvements in materials and technic, also for the 
strenuous work they have done in teaching their improved methods to the 
profession. The underlying principles are not new. However, these men 
have devised an improved technic by which they used modelling com- 
pound in such a -way as to emphasize the illy understood fundamental 
principles of retention. These men are entitled to much credit for the 
stupendous work they have done in arousing the profession to the possi- 
bilities of retention for full dentures. Nevertheless it is regrettable that 
they did not comprehend and with their splendid energy teach the under- 
lying principles of retention and impression taking, in place of devoting their 
efforts to the technic of a material. Unfortunately the material with 
which they have labored, although it has much value as an aid to the pros- 
thetist, is the most difficult to manipulate, and is also deceptive in the results 
obtained. It is the desire of the writer of this book to present the physics 
and technic of both retention and impression taking, in such a manner, 
that the reader may have a comprehensive and discriminating understand- 
ing of the relative value of the various materials and methods. 
Again, the writer of this book wishes to emphatically express and acknowl- 
edge his obligation to these men as his teachers; but he feels it a duty to 
correct gross errors in their teachings. His contention is for truth, but he is 
not in any way opposing men. 
Bryant has well said: 
"Truth crushed to earth shall rise again; 
The eternal years of God are hers." MATERIALS 
65 
contact, and that there must be contact with the entire area covered 
by the base-plate. 
The technic of the methods involved with these modern 
methods will be presented in this chapter, and the philosophy 
of the methods will be discussed in the chapter on Retention. 
MATERIALS. 
The materials used for taking impressions, making casts, 
and occlusion and contour models need careful consideration 
that they may be intelligently manipulated, thereby securing 
the best results. 
There are two classes of material used for taking impres- 
sions : First, those substances made pliable by heat and that 
harden on cooling; and second, materials made plastic with 
water and that harden by crystallization. Wax, modelling 
compound, and gutta-percha are the materials of the first 
class, while plaster of Paris is the one material of the second 
class. 
Wax.-Wax is a general term applied to a solid fatty sub- 
stance obtained from all three of the kingdoms of matter. 
The general properties of the various substances called wax 
may be stated thus: They are solid or semisolid substances; 
are easily broken when cold, but at a moderate heat are 
soft and pliable, and fuse at a temperature below 212° F. 
They have a peculiar glistening appearance, are lighter than 
water, are insoluble in that fluid and in cold alcohol, but 
dissolve readily in ether; they are combustible, burning with 
an illuminating flame, and are non-volatile. 
Beeswax.-Beeswax is an animal secretion formed by 
bees from sugar, and is the material of which the honey- 
comb is formed. It is obtained by expressing the honey and 
fusing the residue in water. In this state it is of a yellowish 
color (Cera flava). It may be bleached, so as to form white 
wax (Cera alba), by being exposed in thin slices to the action 
of solar light. The yellow wax is firm, breaking with a gran- 
ular fracture, yellowish, having an agreeable honey-like 
odor; not unctuous to the touch; melts at about 175° F.; 
is insoluble in alcohol, but dissolves in oil of turpentine, 66 
IMPRESSIONS 
ether, and chloroform. It is of a complex formation, and a 
number of derivatives are obtained from it. C48H92O2 is 
considered as its general composition. 
Vegetable Wax.-These waxes may be obtained from several 
varieties of plants. They are of no value to the dentist. 
Mineral Wax.-This is a natural material known as ozo- 
cerite, and is a waxy translucent mixture of the paraffins 
of coal formations. The paraffins have a chemical formula 
of CnH2n + 2- The natural mineral wax (earth wax) may be 
used, but the manufactured mineral wax (paraffin, a by- 
product of the distillation of coal and petroleum) is exten- 
sively used in the dental laboratory. It is used in sheet form 
as base-plate wax, also combined with beeswax. 
Wax is softened for use by heating in hot water or a flame, 
and kneading with the fingers. If the wax is to be softened 
in water, small lumps should be placed in a dish containing 
a quart or two of cold water, then as the water is heated 
the heat will penetrate the wax and not melt the surface 
only, as would be the case if the lumps of wax were placed 
in hot water. As the wax softens it is removed from the 
water, dried upon a cloth and kneaded between the fingers 
until it is smoothly plastic. Should the softened wax 
become too hard for its intended use it may be again warmed 
in the water or passed a few times through a smokeless 
flame. The dry-heat method of working wax consists in 
having the wax from to | inch thick and passing it re- 
peatedly through the Bunsen flame and kneading between 
the fingers. It is reheated and kneaded until it is of the 
proper plasticity. Should it be overheated upon the surface 
it will appear crumbly, but soon becomes smoothly plastic 
by kneading. Beeswax adulterated with tallow may be 
detected by the odor and greasy feeling. Such wax is not 
desirable for dental purposes. 
Wax may be easily made into sheets of any thickness by 
the dipping method. The wax is melted over water in a 
double pan (that is, one pan set in a larger pan containing 
water, thus lessening the danger of ignition); when it is 
thoroughly melted and any dirt it may have contained has 
settled, a flat quart bottle containing cold water is dipped MATERIALS 
67 
into it and instantly removed. When the layer of wax upon 
the surface of the bottle has chilled, it should be slit upon the 
sides and at the edge of the bottom of the bottle, when it 
can be stripped from the glass. Sheets of varying thickness 
may be made by dipping repeatedly. 
Modelling Compound.-This material is a composition of a 
resinous gum, as copal, dammar, etc., with stearin and French 
chalk, colored and flavored. 
In the Zahnarztliche Rundschau, Berlin, January, 1913, 
Dr. F. Schoenbeck, of Leipzig, says: 
"The plastic impression materials used in dentistry are 
composed chiefly of resin and stearin, to which, for the 
sake of obtaining a certain consistence, fillers, such as talcum, 
are added. Some dyestuff and a few drops of an ethereal 
oil improve appearance and taste. Under a low-power 
microscope these materials present the picture of a uniform 
surface, permeated with fatty acid needles, particles of 
coloring matter and grains of the filler employed. Besides 
these we observe more or less dissolved resin particles, 
which are easily recognized by their yellow color. The size 
of these resin particles directly influences the plasticity of 
the material, which should possess the following properties: 
It should soften at a temperature higher than that of the 
mouth, should possess great plasticity, uniform structure, 
should give a sharp impression, should not stick, should 
harden quickly in the mouth, and should not contract or 
expand to any great extent, though a slight expansion is 
not detrimental. The temperatures at which the various 
impression materials tested became soft and workable 
varied between 41° and 45° C. The size of the grain of the 
filler employed greatly influences the plasticity of the ma- 
terial. The amount of contraction in an impression com- 
pound can be determined: First (and unsatisfactorily), by 
a ruler and calipers; second, by the micrometer. The tests 
carried out by the writer with the micrometer method 
showed, in the various brands examined, a variation [in 
contraction of from 0.005 to 0.035 mm. For very delicate 
measurements he uses a telescope, the lens of which is 
provided with a micrometer scale, 68 
IMPRESSIONS 
"On the whole, the volumetric changes in impression 
materials do not differ very widely, since a difference in 
temperature of only about 20° is to be reckoned with, the 
various materials being workable at from about 40° to 60° C. 
"If placed in boiling water, the composition of modelling 
compound is altered entirely. Fatty acids and resin particles 
are dissolved or melted out, and the change in the quanti- 
tative ratio of the materials contained in the compound 
naturally alters the physical behavior of the mass. 
"In order to obtain a homogeneous, plastic mass, the 
softened compound should be kneaded thoroughly, micro- 
scopic examination showing a much more uniform dis- 
tribution of the filler in the kneaded mass. Kneading also 
discloses any large particles of resin which may be imbedded 
in the compound, and which can be easily removed before 
taking an impression." 
A formula and instruction for compounding, attributed 
to Mr. E. Lloyd Williams, of London, England, is as follows: 
French chalk, 1| parts; kauri, 1 part; stearin, 1| parts. 
Melt the stearin in an enamelled pan and stir in the gum. 
When these are thoroughly incorporated stir in the chalk. 
This material will be of a yellowish-white color. It may be 
colored with carmine and flavored as desired. Modelling 
compound is much used in taking impressions, for trial 
base-plates, and occlusion and contour models. 
Modelling compound is softened in water after the manner 
described as the wet method for softening wax. The surface 
of the compound, just before placing in the mouth, should be 
passed over a flame. As the softened modelling compound 
is liable to adhere to the bottom of the pan, it is a good plan 
to place one end of a strip of white paper in the pan for the 
compound to rest upon. The other end is a convenient 
means for withdrawing the compound from the hot water. 
Gutta-percha (gatah, gum; percha, the tree from which it is 
obtained).-The gum is in many respects similar to caout- 
chouc. The former is only slightly elastic, while the latter 
has almost perfect elasticity. Gutta-percha is the dried 
milky juice of a tree, Isonandra gutta, growing in the Ma- 
layan Archipelago. The material may be had at the dental MATERIALS 
69 
supply houses in sheet form. It is considerably used for 
trial base-plates, and formerly was much used for taking 
impressions. Its use for this purpose has been, of late years, 
superseded by modelling compound, a superior material. 
Plaster of Paris.1-Plaster of Paris is made from the mineral 
called gypsum. This mineral is found in various forms, as 
massive or rock gypsum; alabaster, a pure white, fine-grained 
massive gypsum; and selenite, a crystalline, almost trans- 
parent gypsum. The chemical composition of pure gypsum 
is CaSO4+2II2O. Therefore pure gypsum is a hydrous 
sulphate of lime, made up of one molecule of calcium sulphate 
combined with two molecules of water. This, when reduced 
to percentages of weight, corresponds to the following: 
Gypsum (CaSCh+2ELO) 
' Lime sulphate (CaSOi) 79.1 per cent. 
k Water (H2O) 20.9 per cent. 
Lime sulphate 
Lime (CaO) 
Sulphur trioxide (SOa) 
Gypsum is rarely found chemically pure. The usual im- 
purities are silica, alumina, iron oxide, calcium carbonate, 
and magnesium carbonate. Usually these impurities do not 
attain a volume of 3 per cent., and are often less than 1 per 
cent. Gypsum is prepared for the market by grinding and 
burning, and mixing with accelerators and retarders. The 
products of manufacture are designed for a definite purpose, 
and cannot be interchanged advantageously. The dentist 
should have a general knowledge of the various gypsum 
products, so as to select his plasters intelligently. 
Classification of Plaster.-"A. Produced by incomplete 
dehydration of gypsum, the calcining being carried on at a 
temperature not exceeding 400° F. 
" 1. Produced by the calcining of a pure gypsum, no foreign 
material being added either during or after calcining. Plaster 
of Paris. 
1 The authorities for this general sketch of plaster of Paris are: Cements 
and Plasters, by Edwin C. Eckel, C.E., published by John Wiley & Sons, 
New York, 1907: Calcareous Cements, by Gilbert R. Redgrave and Charles 
Spackman, published by Charles Griffin & Co., London, 1905. 70 
IMPRESSIONS 
"2. Produced by the calcining of a gypsum containing 
certain natural impurities, or by the addition to a calcined 
pure gypsum of certain materials which serve to retard the 
set of product. Cement plaster. 
" B. Produced by the complete dehydration of gypsum, 
the calcination being carried on at a temperature exceeding 
400° 
"3. Produced by the calcination of a pure gypsum. 
Flooring plaster. 
"4. Produced by the calcination, at a red heat or over, of 
gypsum to which certain substances (usually alum or borax) 
have been added. I lard-finish plaster." 
In the trade these names are used extensively, but at times 
in a careless and indefinite fashion. Calcined plaster com- 
monly means a burned plaster to which no retarder has been 
added. It may be either plaster of Paris or cement plaster. 
Stucco plaster is less finely ground than plaster of Paris, and 
usually is not made of as pure a quality of gypsum. Wall 
plasters are made by adding not only a retarder, but some 
kind of fiber, to calcined plaster. Keene's, Martin's, and 
Mack's cements are hard-finish plasters variously treated with 
such substances as alum, borax, borax and cream of tartar, 
potassium carbonate, and potassium or sodium sulphate. 
Chemistry of Gypsum Burning.-If pure crude gypsum is 
heated to a temperature of more than 212° F., and less than 
400° F., a certain definite portion of the water of crystalliza- 
tion will be driven off, and the gypsum thus partially dehy- 
drated will be plaster of Paris. Plaster of Paris has the for- 
mula CaSCh+jlKO, which equals calcium sulphate (CaSO4), 
93.8 per cent., and water (H2O), 6.2 per cent. Dehydration 
to this extent can be accomplished at any temperature 
between 212° F. and 400° F., but for economy of fuel and 
time it is usually carried on at the highest allowable tempera- 
ture ; and 330° to 395° may be regarded as the usual limiting 
temperature for plaster manufacture. The late Prof. Essig 
stated that "the highest-grade dental plaster is calcined 
at about 261° F." The writer has been unable to confirm 
this statement, for the manufacturers refuse to give this 
information, saying that the temperature used is their MATERIALS 
71 
trade secret. Several of the manufacturers state that their 
dental plasters are calcined from the purest selected rock 
obtainable, and that no accelerator nor retarder is added. 
It is quite probable that the difference in the various dental 
plasters upon the market is largely physical and not chemi- 
cal; and are dependent upon: (1) degree of dehydration; 
(2) degree of pulverization, and (3) blending plasters of 
various degree of dehydration and pulverization. About 
400° F. is a critical temperature, for if gypsum be heated 
much above this it loses all of its water of crystallization, 
becoming an anhydrous sulphate of lime, and useless as a 
normal plaster. Under certain conditions, however, "dead- 
burned" gypsum gains certain properties, and forms flooring 
and hard-finish plasters. Partially dehydrated gypsum has 
the property of taking up the lost water of crystallization 
and setting or recrystallizing. If the gypsum is pure and 
unmixed with retarder, the setting of the plaster will be 
complete in a few moments, while dead-burned plaster, as 
such, is spoken of as non-setting; however, it does set, 
but requires hours for the initial set and weeks for complete 
hydration. 
There are three methods of calcining gypsum, known as 
the kettle, oven, and rotary-cylinder processes. So far as 
the writer has been able to learn, the kettle process only 
is used in America for manufacturing dental plasters; but 
the rotary cylinder is extensively used for building plasters. 
It is reported that the oven and kiln are in vogue in Europe 
and England. The rotary-cylinder process is an improved 
method of recent years. 
Grinding of Gypsum Products.-Grinding is an important 
factor in the manufacture of gypsum products. In the kettle 
process the rock is first ground and then roasted, while in 
the oven and the rotary-cylinder processes the rock is 
broken into convenient-size masses, roasted, and then ground. 
The use for which the plaster is designed will determine its 
fineness. However, it is a factor only, as the finest plasters 
to be obtained are much slower setting than some coarser- 
ground ones. Eckels states that: "A dust chamber located 
above the rotary calciner catches the most finely ground 72 
IMPRESSIONS 
plaster, which is marketed for dental plaster and other 
special purposes." 
The Theory for the Setting of Plaster.-M. Le Chatelier has 
formulated a new theory, based upon the phenomena of super- 
saturation investigated by Marignac. This observer has 
shown that: "Hydrated calcium sulphate with half an 
equivalent of water, which remains undecomposed at a tem- 
perature of about 310° F., dissolves freely when shaken up 
with water, but that after a short interval the solution 
becomes turbid. This is due to the formation of a crystal- 
line precipitate of the common hydrate with two equivalents 
of water, which has the formula of gypsum. The solution 
formed in the first case is five times as concentrated as that 
made from the less completely hydrated sulphate. It would 
appear from this that the most important agent in the 
accomplishment of the setting process is the relatively 
soluble hydrate, namely, that with a small percentage of 
water. This hydrate is at once dissolved, and then gives 
rise to the formation of the other hydrate, with the full 
equivalent of water. The latter compound decreases the 
solubility of the mixture, and the water becomes super- 
saturated with the CaSO42H2O hydrate, which crystallizes 
out. This process continues so long as there remains any 
of the soluble hydrate [2 (CaSO4)H2O] to fortify the solution. 
" The set of plaster is thus the result of two distinct series 
of operations, which take place simultaneously: First, the 
particles of calcium sulphate in the act of hydration are 
dissolved in the water used to gauge them, and produce a 
supersaturated solution; the solution thus formed deposits 
crystals of the hydrated sulphate. These crystals gradually 
increase in size, and form a compact mass in the same way 
as do all similar crystals deposited slowly from a saline 
solution, and this process is continued as long as any of the 
more anhydrous sulphate remains available to become 
dissolved and to keep the solution supersaturated." 
Properties of Dental Plaster.-Gypsum products, to be 
suitable for dental purposes, should possess certain properties, 
and a special brand is of value only as it meets the require- 
ments. It should be free of all foreign substances (as dirt MATERIALS 
73 
and fibrous matter), sufficiently ground to form a smooth 
mix, quick setting, generate but little heat, minimum of 
change of form while crystallizing, and sufficiently resisting 
to any stress to which it may be subjected. 
There are three different requirements of practice that 
make a demand for as many classes of plaster: (1) for 
impressions the plaster should be quick setting, expand but 
little (not contract), and easily broken; (2) for casts the 
plaster should be as little changeable while crystallizing 
and under stress as possible; and (3) for flasking and luting 
a medium between the preceding two is required. However, 
the first class of plaster may well, and can, be dispensed 
with by adding a chemical substance to a well-chosen third- 
class plaster, and is used for impressions. 
In fact, a strictly impression plaster is a dangerous article 
in the laboratory, as it is unfit for casts and flasking and 
is too apt to be improperly used. The addition of sodium 
chloride or potassium sulphate to a high-grade suitable 
plaster for flasking answers well for impressions. 
See pages 74, 76, 77, and 78 for two tabulations designed 
to illustrate the physical and working properties of, as it is 
believed, the leading brands of dental plaster used in America, 
England, and Europe: 
The first table has to do with the amount of moisture 
absorbed from the atmosphere after calcining and the 
percentage of the degrees of fineness of the product. Fifty 
grams of plaster is dried and weighed to ascertain the per- 
centage of moisture that has been absorbed. It is then 
placed in a tier of sieves and racked for five minutes, when 
each portion is weighed and expressed in percentage. The 
plaster is permitted to stand exposed to the atmosphere 
of the room, when it is again weighed, and the loss represents 
the amount of moisture not reabsorbed, and the loss of 
material in handling, which is the larger part of the loss. 
The last column indicates time in hours. The first line of 
data may be read: French's impression plaster (White's is 
the same), dried for two and one-half hours at a temperature 
varying from 220° to 240° F., lost 3.7 per cent, (moisture), 
and after sieving there remained 5.68 per cent, of plaster 74 
IMPRESSIONS 
upon the 50-mesh, 21.80 on the 100-mesh, 46.07 on the 150- 
mesh, 24.77 on the 200-mesh, and 1.11 on the bottom. 
Table I. 
Degree of pulverization. 
Dried degrees F. 
Time in hours. 
Per cent, of dehydration. 
Top 50-mesh, per cent. 
Top 100-mesh, per cent. 
Top 150-mesh, per cent. 
Top 200-mesh, per cent. 
Bottom, per cent. 
Loss of material. 
Time of last weighing. 
French's Impression 
White's Impression .... 
220 
245 
3.70 
5.68 
21.80 
46.07 
24.77 
1.11 
1.48 
24 
French's Regular .... 
White's Cast 
-i 
220 
245 
3.30 
7.83 
34.45 
45.17 
12.28 
0.25 
1.18 
18 
French's Slow 
2 
240 
264 
3.32 
7.29 
31.60 
52.67 
7.14 
1.26 
1.60 
15 
Spence Plaster Compound . . 
2 
216 
222 
3i 
260 
3.04 
16.35 
49.60 
26.05 
6.34 
1.44 
1.80 
48 
Newburg Green Star . . . 
6.50 
3.10 
10.24 
34.73 
34.90 
17.27 
1.66 
40 
King's 
220 
230 
3.40 
1.05 
22.64 
43.19 
23.38 
9.71 
1.56 
30 
Keystone Impression . . . 
3 
260 
6.30 
0.21 
2.18 
19.73 
27.81 
49.81 
1.68 
27 
Keystone Cast 
2 
300 
5.16 
1.23 
8.78 
41.75 
38.53 
9.68 
1.88 
48 
Nephi, Utah 
3 
220 
2.00 
3.69 
14.27 
21.64 
24.07 
36.32 
0.90 
23 
Demare, Chartier & Co., France, 
Impression and Cast . . 
2 
200 
240 
2.86 
4.72 
57.22 
35.63 
6.22 
2.19 
3.26 
12 
Rapp & Reitenbach, France, 
Casts 
3 
230 
240 
4.38 
5.28 
35.61 
42.87 
12.90 
3.31 
4.66 
1 
The Gips-Union, Zurich Casts 
3 
220 
5.06 
0.42 
21.22 
44.88 
22.66 
10.85 
5.76 
1 
Stolnbrock, Germany, Casts . 
245 
4 
220 
0.50 
2.81 
16.15 
27.87 
23.61 
29.56 
0.60 
1 
Alabaster Gips, Germany . . 
240 
5 
220 
2.73 
7.02 
52.57 
36.70 
3.11 
0.57 
0.48 
48 
Mountain & Son, Leeds, Eng- 
240 
4 
230 
6.50 
16.80 
53.77 
19.58 
4.65 
4.96 
3.46 
22 
land, Casts 
Bellman, Joey & Carter, Lon- 
2J 
200 
3.04 
15.65 
58.16 
23.63 
2.60 
0.35 
2.06 
18 
don, Impression .... 
240 
3 
Twenty-four hours later there was a loss of 1.48 per cent, 
of the original 50 grams of plaster. MATERIALS 
75 
The second table records experiments in setting, con- 
traction and expansion, and compression. The first column 
indicates the brand of plaster, the ratio of water to plaster, 
and, if an accelerator is added, the number of grains (Troy) 
to the ounce (weight) of water. The second and third 
columns indicate the number of minutes for initial and hard 
set respectively. The upper figure in the fourth column is 
the number of points (0.0001 of an inch) contraction to the 
lineal inch, and the lower figure the number of minutes in 
which contraction took place. The fifth column is the num- 
ber of minutes elapsing between placing the plaster in the 
instrument and the beginning of expansion; the following 
three columns, the number of points of expansion to the 
lineal inch in fifteen, thirty, and sixty minutes respectively. 
In the next column the upper number indicates the points 
of expansion attained in the time (hours) expressed in the 
lower number. The following four columns give the amount 
of compression in twenty minutes, thirty minutes, one hour, 
and twenty-four hours after mixing, upon a confined mass 
of plaster approximately nine-tenths inch thick. The upper 
figures indicate the number of pounds pressure applied to a 
circular surface one-half inch in diameter, and the lower 
figures the percentage of compression. In the remaining 
two columns the figures indicate weight, percentage of 
compression and time. The setting time was ascertained 
by aid of the Gilmore needles. When the setting plaster 
will sustain, without indentation, a needle weighing | 
pound upon a point inch diameter it is said to have 
attained initial set; and when it will sustain the needle of 
1 pound weight upon a point of inch diameter it indicates 
hard set. The instruments for measurements of contrac- 
tion, expansion, and compression are well made and reason- 
ably accurate; certainly the resulting figures are equitable 
for comparison, subject to the personal equation of the 
operator only, which was the writer. The figures under the 
name of the brand of plaster indicate the ratio of water 
and plaster by weight, as water 1 part and plaster from 1| 
to 4 parts as indicated. The amount of accelerator indi- 
cates the number of grains to the ounce (Troy) of water. 76 
IMPRESSIONS 
Initial set, minutes. 
Hard set, minutes. 
Contraction. 
Points and minutes. 
Expansion began in minutes 
from mixing. 
Expansion 15 minutes from 
mixing. 
Expansion 30 minutes. 
Expansion 1 hour. 
Expansion. Points, hours. 
Compression 20 minutes. 
Weight and per cent. 
Compression 30 minutes. 
Weight and per cent. 
our. 
r cent. 
Compression 24 hours. 
Weight and per oent. 
and hours. 
ompression i m 
Weight and pe 
ompression. 
reight, per oent. 
O 
French's Impression, 1 to 1J .• . . . 
4 
8 
4 
6 
14 
19 
20 
20 
500 
500 
500 
500 
1000 
ii 
3 
3.39 
2.39 
2.61 
4.61 
30.86 
24 
French's Impression, 1 to lj and 5 grs. 
500 
500 
500 
500 
NaCl 
3 
6 
2 
15 
■15 
15 
14.64 
15.03 
9.24 
18.16 
French's Impression, 1 to 1} and 3 grs. 
12 
500 
500 
500 
500 
K2SO< 
2* 
4 
li 
9 
9 
9 
24 
11.27 
8.41 
11 30 
11.86 
French's Regular 1 to 2 
7i 
16 
7 
71 
6 
23 
26 
28 
500 
500 
1000 
1000 
2000 
2| 
24 
10.40 
0.22 
6.06 
4.69 
35.97 
24 
French's Regular 1 to 2 and 5 grs. NaCl 
3 
8 
2 
4 
22 
25 
26 
500 
500 
1000 
2000 
1 
0.55 
0.44 
11.12 
37.00 
24 
French's Regular, 1 to 2 and 3 grs. K2SO< 
3 
7 
1 
4 
18 
18 
18 
23 
500 
500 
1000 
2000 
1 
24 
0.53 
1.12 
8.81 
39.81 
24 
French's Regular, 1 to H 
10 
18 
4 
101 
2 
14 
16 
22 
500 
500 
500 
1000 
2 
24 
15.00 
9.27 
9.08 
34.72 
French's Regular, 1 to 1J and 5 grs. NaCl 
7 
12 
41 
12 
12 
12 
10 
500 
500 
500 
1000 
500 
24 
9.68 
11.89 
8.74 
43.18 
9.48 
24 
French's Regular, 1 to lj and 3 grs. K2SO< 
5 
8 
41 
8 
8 
8 
500 
500 
500 
1000 
500 
10.99 
10.56 
9.52 
44.05 
7.82 
24 
French's Slow Set, 1 to 2 
17* 
311 
1000 
10.64 
3i 
French's Slow Set, 1 to 2 and 5 grs. NaCl 
9 
16 
2 
3 
6 
17 
18 
18 
1000 
1000 
1000 
1000 
2 
3 
6.31 
8.20 
7.88 
10.27 
French's Slow Set, 1 to 2 and 3 grs. K2SO4 
6 
Hi 
1000 
1000 
1000 
8.24 
8.39 
8.39 
Table II. MATERIALS 
77 
Spenoe Plaster Compound, 1 to 3j . . . 
15 
29 
5 
30 
3 
3J 
500 
1000 
2000 
2000 
4i. 
2j 
13.14 
0.43 
8.67 
5.92 
Spenoe Plaster Compound, 1 to 4 . . . 
11 
7 
30 
4 
71 
500 
1000 
2000 
18 
17 
0.36 
1.34 
0.60 
Newburg Green Star, 1 to 2 .... 
21 
21 
11 
25 
40 
Newburg Green Star, 1 to 2 and 5 grs. 
25 
500 
1000 
NaCl 
4 
6 
25 
24 
0.53 
26.62 
Newburg Green Star, 1 to 2j . . . . 
5 
is 
8 
6 
24 
30 
34 
500 
1000 
24 
0.35 
1.48 
Newburg Green Star, excess water poured 
1'000 
1000 
1000 
off of mixture 
22.03 
23.27 
27.87 
King's Knickerbocker, 1 to 2 . . . . 
18 
31 
7 
29 
2 
13 
20 
1000 
1500 
13 
12.03 
35.96 
King's Knickerbocker, 1 to 2 and 5 grs. 
1000 
1000 
NaCl 
8 
16 
12.58 
13.47 
King's Knickerbocker, 1 to 2 and 3 grs. 
1000 
1000 
K2SO4 
12 
16 
17.37 
17.73 
18 
King's Knickerbocker 1 to 2i . . . . 
15 
29 
7 
21 
5 
20 
44 
1000 
1000 
19 
18 
5.61 
5.02 
18 
Keystone Impression, 1 to 1| . . . . 
7 
12i 
4 
13 
15 
15 
500 
500 
500 
23.92 
21.42 
36.68 
Keystone Impression, 1 to 1J and 5 grs. 
500 
500 
NaCl 
5i 
8i 
5 
23 
23 
22.56 
29.19 
Keystone Impression, 1 to 1J and 3 grs. 
500 
500 
K2SO4 
4 
11 
8 
16 
16 
23.59 
24.36 
Keystone Cast, 1 to 2 
9 
21 
13 
21 
6 
28 
37 
1000 
1000 
1000 
18 
24 
29.65 
24.80 
15.43 
Keystone Cast, 1 to 2j 
8 
15 
7 
14 
11 
22 
30 
1000 
1000 
1000 
2000 
8 
24 
10.01 
5.35 
2.30 
29.16 
24 
Nephi Dental 1 to 1J 
8 
15 
1 
6J 
15 
34 
39 
500 
1000 
1000 
1000 
1 
0.28 
10.76 
17.62 
13.60 
Nephi Dental, 1 to If and 5 grs. NaCl 
4 
8 
3 
26 
28 
500 
500 
1000 
1000 
0.99 
0.76 
15.96 
21.46 
Nephi Dental, 1 to 11 and 3 grs. K2SO4 . 
4 
6 
20 
19 
500 
500 
1000 
1000 
0.84 
0.52 
18.13 
19.20 
Demare, Chartier & Co., France, Impres- 
7 
16 
0 
7 
22 
30 
35 
500 
500 
1000 
sion and Casts, 1 to 2 
12 
0.96 
1.12 
12.39 78 
IMPRESSIONS 
Initial set, minutes. 
Hard set, minutes. 
Contraction. 
Points and minutes. 
Expansion began in minutes 
from mixing. 
Expansion 15 minutes from 
mixing. 
Expansion 30 minutes. 
Expansion 1 hour. 
Expansion. Points, hours. 
Compression 20 minutes. 
Weight and per cent. 
Compression 30 minutes. 
Weight and per cent. 
Compression 1 hour. 
Weight and per cent. 
Compression 24 hours. 
Weight and per cent. 
Compression. 
Weight, percent, and hours. 
Compression. 
Weight, per cent, and hours. 
Rapp & Reitenbach, Franoe, Cast, 1 to 2 
16j 
26 
2 
23 
2 
17 
25 
1000 
1000 
20 
24 
17.08 
20.56 
Rapp & Reitenbach, France, Cast, 1 to 2| 
14 
23 
14 
23 
1 
20 
244 
1000 
1000 
22 
24 
1.00 
1.13 
Gips Union, Zurich, Cast, 1 to 2 . . . 
94 
174 
500 
1000 
18 
0.60 
24.55 
Gips Union, Zurich, Cast, 1 to 2 and 3 grs. 
K,SO< 
114 
13 
18 
24 
Gips Union, Zurich, Cast, 1 to 2} . . . 
5 
84 
6 
8 
20 
27 
500 
1000 
1000 
0.44 
2.70 
2.15 
Stolnbrock, Berlin, Cast, 1 to 34 . . . 
30 
2000 
1000 
2000 
1.30 
0.31 
2.36 
13 
13 
Stolnbrook, Berlin, Cast, 1 to 34 and 5 grs. 
2000 
1000 
NaCl 
29 
2.26 
0.75 
24 
Stolnbrock, Berlin, Cast, 1 to 34 and 3 grs. 
35 
13 
500 
2000 
k2so« 
28 
60 
60 
24 
No 
0.68 
resist. 
Alabaster Gips, Berlin, 1 to 2 . . . . 
7 
12 
0 
14 
28 
32 
44 
1000 
1000 
24 
8.12 
6.63 
Alabaster Gips, Berlin, 1 to 2 and 3 grs. 
27 
500 
500 
500 
K2SO4 
34 
6 
0 
20 
24 
24 
24 
2.02 
1 21 
2.30 
Alabaster Gips, Berlin, 1 to 21 . . . . 
44 
74 
3 
5 
24 
35 
38 
5057 
500 
1000 
1000 
1000 
44 
2442 
0.20 
2.73 
3.34 
1.40 
Mountain & Son, Leeds, Cast, 1 to 24 . . 
74 
114 
0 
12 
32 
42 
51 
1000 
1000 
1000 
24 
13.78 
12.45 
9.37 
Bellman, Joey & Carter, London, 1 to 2 . 
84 
154 
2 
8 
8 
17 
24 
40 
500 
500 
1000 
7 
20 
1.03 
0.46 
11.07 
Bellman, Joey & Carter, London, 1 to 2 
8 
500 
500 
and 5 grs. NaCl 
44 
7 
5 
20 
24 
0.72 
0.57 
Table II-Concluded. MATERIALS 
79 
The method of mixing consisted of placing the weighed 
water (and accelerator when used) in the bowl into which 
the entire amount of plaster to be used for the mix is placed 
and quickly agitated with a spatula until smoothly mixed; 
however, avoiding excessive stirring. The impression plasters 
are treated only with a mix of 1 of water to 1| of plaster, 
as this is the best consistency for impression taking. For 
all other uses (than impressions) plaster should be mixed 
thicker, and when but one mix of a brand of plaster is tested 
it is the one the writer believes is the best for the brand. 
In studying this chart it is well to keep in mind that the 
lower the contraction and expansion the better for all uses; 
but in strength (as indicated by compression), a weak plaster 
is desired for impressions, and for all other purposes the 
stronger the plaster the more desirable. (Notice that the 
strength of the plaster decreases with the increased percentage 
of compression.) It is obvious, from this chart, that the 
larger the ratio of plaster to water the quicker setting and 
greater strength; also, unfortunately, the greater expansion. 
Also, that the addition of sodium chloride hastens the setting 
and reduces the strength, and that potassium sulphate 
hastens the setting and reduces the expansion and strength. 
The plasters manufactured by the S. II. French & Co. are 
extensively used by the profession in America, therefore 
careful study should be given them. The impression plaster 
without an accelerator is quick setting and unnecessarily 
strong for impression, but too weak for any other purpose. 
It is very much improved by the addition of accelerator, 
but is entirely unfit for any purpose other than impressions. 
The "Regular Dental Plaster" with an accelerator and 
mixed thin is a very good substitute for the impression 
plaster. However, it does not set quite so quickly and is a 
trifle stronger than necessary; nevertheless, it expands less. 
The slow-setting plaster is a delusion and has nothing to 
commend it. It is made to comply with certain ideas enter- 
tained by the profession in that a slow-setting plaster is 
stronger and better for casts. It is true it is stronger than 
the regular dental plaster, but because of its slowness of 
set the workman is liable to work upon it before it has 80 
IMPRESSIONS 
attained the strength the regular plaster would have; 
further, it contracts and expands more than the regular, 
and cannot compare with the Spence Plaster Compounds 
for casts. 
The Spence Plaster Compound changes form less than 
any of the pure plasters and attains its maximum strength 
in one hour; however, it is much stronger in thirty minutes 
than a pure plaster. The writer commends French's Regular 
Dental Plaster for all purposes except casts, and without 
exception Spence Plaster Compound for casts. However, 
by consulting the table it will be seen that there is very 
little difference between French's Regular Plaster and 
several other good brands for general purposes. Hence, 
if an operator is obtaining satisfactory results with any 
good brand it is unnecessary, and may be unwise, to change. 
For casts and casts only, no other plaster in the table com- 
pares with the Spence Plaster Compound. 
Another interesting experiment is in connection with 
the hydration of plaster. Gypsum contains 20.9 per cent, 
of water of crystallization; when partially dehydrated for 
dental plaster it contains 6.2 per cent, of water. The table 
shows that French's Regular Dental Plaster loses approxi- 
mately 3.5 per cent, of its weight (abnormal moisture) when 
subjected to a "temperature" not exceeding 240° F., thus 
showing that the plaster ready for the dentist's use con- 
tains 9.7 per cent, of water, therefore 9.7 substracted from 
20.9 would leave 11.2 per cent., the amount necessary 
for complete hydration. However, if the quantity of 
water representing the 11.2 per cent, is placed in a beaker 
and the requisite amount of dental plaster is added to it 
without agitation it will eventually be found that there is a 
small portion in the bottom of the beaker perfectly crystal- 
lized, another portion partially crystallized, and the top 
portion apparently unaffected. If a block is made containing 
by weight one ounce of water and two ounces of French's 
Regular Dental Plaster and left exposed until it ceases to 
lose weight (about twenty-five hours), it will be found that 
it has lost approximately 22 per cent, of its entire weight. 
As the loss is water the 22 per cent, deducted from the one- IMPRESSION TRAYS 
81 
third (33.33 per cent.) water would show that approximately 
11.3 per cent, had combined permanently with the plaster. 
The practical points to be derived from these hydration 
experiments are: that it is impossible to mix dental plaster 
without an excess of water, that the larger the excess of 
water* the less dense and weaker the plaster, and that the 
smaller the excess of water the denser and stronger the 
plaster. Conclusion: that plaster should be hydrated to 
meet the requirements of the operation. 
A New Impression Plaster.1-Nielsin.-A compound of 
plaster of Paris and starch. The advantage claimed for this 
is that the impression may be removed from the cast by 
boiling in water. This phenomenon is explained by the 
well-known property of starches, that is, that they are 
insoluble in cold water, but soluble in hot water. The 
material is used the same as ordinary impression plaster. 
The subsequent technic is the same as for plaster except 
the separation of the cast from the impression-which is 
as before stated. 
IMPRESSION TRAYS. 
Definition.-A dentist's tray or cup used for holding the 
impression material while taking an impression of the 
mouth or teeth. Tray is the better term to use, as it conveys 
an idea of a utensil having flanges and a capacity to hold 
and carry, while cup conveys the idea of symmetry of form 
with a base on which to stand, and holding capacity. Trays 
are made of various materials and sizes. 
Tray Material.-The materials of which trays are made 
are block tin or alloyed tin, cast and pressed aluminum, 
German silver, and porcelain. Each material has its advan- 
tages and disadvantages, hence for special purposes the tray 
should be constructed of the material best adapted. While 
porcelain is the most cleanly material, it is not practical 
because its form cannot be changed, and it is easily broken. 
Block tin (or some of its alloys) is most commonly used. 
1 "Byrites" is an imitation of "Nielsin." 82 
IMPRESSIONS 
The trays made of this material may be readily changed in 
form, by cutting and bending, which is an essential property. 
Tray Nomenclature.-A tray has a body and a handle. 
The body consists of a floor and flanges, and those designed 
for the upper jaws have a vault portion. There are two types 
of floors-oval, for edentulous jaws, and/Zaf, for accommodat- 
ing remaining teeth. The flanges are called outer and inner. 
The outer flange has two portions, the anterior or labial, 
and the posterior or buccal. The dividing line is the prox- 
imity of the distal surface of the cuspid tooth. The inner 
flange is also called the lingual flange. The surfaces of the 
tray are named for the surfaces they approximate, as maxil- 
lary, labial, buccal, and lingual. (These terms are used also 
in base-plate nomenclature.) The term palatal surface is 
used indiscriminately, meaning either the maxillary or lingual 
surface. The term is confusing, and should be avoided. 
The vault portion spans the space described by the curve 
of the lingual flange of the upper tray. 
The handle is an extension from the union of the floor 
and the anterior flange. The handle is designed to be used 
while carrying the tray into the mouth; also for removing the 
tray and impression from the mouth. The handle should 
never be used for holding the tray while the impression is 
hardening, as it acts as a lever, and it is almost impossible 
to avoid enlarging the intaglio of the impression. 
Tray Forms.-The form of the tray should be such as to 
approximate the form of the part of which the impression 
is to be taken. This would require a great variety of trays, 
therefore it is desirable to have the trays constructed of a 
material that can be readily adapted to the individual case. 
These changes are made by cutting away the undesired 
portion, or by bending in or out the portion not properly 
adjusted; or the desired form may be obtained by adding 
some plastic adhesive material, such as wax or modelling 
compound. This added material should not be considered 
as a part of the impression, but as a part of the tray only 
as the surface outline of the built-up tray would be such as 
a specially constructed one should have. In fact, some 
prosthetists have advocated taking a crude impression and IMPRESSION TRAYS 
83 
Fig. 18 
Fig. 19 
Fig. 20 84 
IMPRESSIONS 
making a plaster cast, from which a tray is constructed.1 
This tray would have the advantages of requiring but a 
small amount of impression material, and of carrying it 
accurately into place. Such methods require too much time 
and work, and do not meet the requirements of really diffi- 
cult cases. The metal tray should approach equally all the 
Fig. 21 
surfaces to be impressed. There should be a space of about 
one-eighth of an inch to be occupied by the impression 
material. This will give sufficient body of material for 
strength, and in case of fracture of the impression the 
pieces are thick enough to be readjusted. The exception to 
1 Dr. Bean's method, Turner's American Text-book. IMPRESSION TRAYS 
85 
the one-eighth-inch rule is where compression of the soft 
tissues is required. In such cases no stock tray could answer 
the purpose; but a simple stock tray may be reinforced so as 
to perfectly meet the requirements. It is wise to reject all 
fanciful and complicated trays, depending entirely upon the 
simplest forms. The various forms of stock trays are made 
Fig. 22 
in several sizes. The student or young practitioner should 
select a few sizes of each of the primary forms, and, as 
necessity requires, extra sizes, special forms and duplicates 
may be added to the equipment. The several manufacturers 
offer similar lines of trays, and each may have some special 
and fanciful forms, but these should not interest the student. 86 
IMPRESSIONS 
For the purpose of illustration, the well-known S. S. W. 
trays have been selected. These are made of the best 
quality of Britannia metal, and will meet all ordinary 
requirements. Fig. 18 shows an upper tray of the oval 
floor type. There are eight sizes of this type, numbered 
from 1 (largest) to 8 (smallest). For the first outfit sizes 2, 
Fig. 23 
Fig. 24 
4, and 6 will suffice. Fig. 19 illustrates the lower trays of 
this type. There are seven sizes, of which 1, 3, and 7 are 
good selections. Fig. 20 represents the flat-floor type. 
There are five sizes for the upper jaw, numbered from 12 to 
16. Nos. 12 and 15 should be the first selected. Fig. 21 
shows a lower tray of the flat-floor type. The largest and 
smallest of the sizes, 14 and 16, will well complete the initial TECHNIC FOR FULL UPPER IMPRESSIONS 
87 
collection of trays. While the prosthetist can adapt the ten 
trays recommended to meet every requirement that may 
be present, it is well to have some special trays. The most 
desirable of these are shown in Figs. 22, 23, and 24. The 
first two are designed for the lower jaw only, while the last 
one, because of its swivel joint, may be used in any part of 
the mouth for any small impression. 
Notice.-The following classification and technic for 
taking plaster impressions has in no way been changed 
from the former editions of this book except in the technic 
for the class in which modelling compound was recommended; 
and, modelling compound for impressions has been placed 
in a section by itself. 
However, to derive the greatest benefit from this classi- 
fication and technic the operator must comprehend the 
modern trend of thought, and have a clear understanding 
of the extent to which the impression shall be taken; also, 
that the soft tissues under the entire periphery of the impression 
must be held firmly against its bone foundation. 
The peripheral border of the upper impression under the 
lip and cheeks may be high or low according to the operator's 
conception for esthetics, provided it is sufficiently high 
for the lip and cheeks to seal it against ingress of air. The 
vital point is the palatal border. There must be compression 
of yieldable soft tissue of at least one-fourth-inch width extend- 
ing from the buccal side of one tuberosity to the buccal side 
of the other tuberosity. 
The peripheral border of the lower impression must just 
include the external and internal oblique ridges. 
TECHNIC FOR FULL UPPER IMPRESSIONS. 
Normal. 
High vault. 
Flat vaults 
Enlarged raphe. 
Thin and tense tissues. 
Medium soft tissues. 
Soft and flabby tissues, ropy 
secretions. 
Classification 88 
IMPRESSIONS 
Application.-We will suppose we have an edentulous 
patient in the chair. The patient's comfort having been 
looked after by adjusting the chair, placing suitable pro- 
tection for the clothing, and with a glass of water upon 
the bracket table; the examination of the mouth having 
been made as described in Chapter I, the case being a 
"normal" one in every respect, will indicate that plaster 
impressions are required. The case being of average size 
will require the oval-floor tray No. 4. The tray should be 
tried in the mouth to ascertain if any alteration is required. 
As the aperture of the mouth is less than the width of the 
palatal end of the tray, it will require suitable manipulation 
for its insertion. This is accomplished by the operator 
standing erect, at the right and a little back of the patient; 
the patient's chin should be about on a level with the elbow 
when the chair and patient's head are each slightly tilted 
backward. The patient is instructed to open the mouth 
moderately wide, when the tip of the index finger of the left 
hand is placed in the left angle of the mouth. The tray is 
grasped by its handle between the thumb and first two 
fingers of the right hand. The anterior portion of the right 
buccal flange of the tray is placed in the right angle of the 
mouth, and while distending the lips the tray is swung into 
the oral cavity. The palatal border of the tray is carried 
upward over the tuberosities; at the same time the anterior 
portion of the tray should be depressed sufficiently to permit 
a view of the relation of the palatal border of the tray with 
the tuberosities and vault. 
Adjusting the Tray.-Should the flanges be too close to the 
tuberosities, they may be bent outward by grasping the body 
of the tray in the left hand, and the use of a pair of 4- or 
5-inch smooth-nosed pliers in the right hand. By the same 
means the flanges may be brought nearer to the tuberosities. 
Should the vault portion impinge, it may be depressed by 
striking a few times with a horn mallet. (See Metal Plate- 
work Implements, Chapter XI.) 
Fig. 25 exhibits a tray with an extreme amount of bending 
of the flanges outward, and the vault portion slightly de- 
pressed. In very flat mouths the base-plane may be very TECHNIC FOR FULL UPPER IMPRESSIONS 
89 
broad, when it would be desirable to have the flanges bent 
outward rather than cut away. 
The anterior flange should next be inspected. Should the 
tray impinge upon the fraenum labii, relief should be afforded 
by deepening the notch in the tray by use of a half-round 
file, such as is used in vulcanite work. The flange at either 
side of the median notch may require adjusting, and often 
should be cut away. This flange should not obstruct free 
Fig. 25 
manipulation of the impression material. It would be 
advantageous if this portion of all prosthetic trays were 
largely cut away. The student should keep this axiom in 
mind, that it is better to have the flanges cut away too much 
rather than not enough, for they may be easily reinforced. 
Reinforcing the Tray.-This may be done with either wax 
or modelling compound. The writer much prefers pure 
yellow beeswax. This is done by softening a strip of wax 90 
IMPRESSIONS 
by the dry-heat method and making it into a roll a little 
larger than the shaft of a lead-pencil. The palatal border of 
the tray is slightly warmed in the flame and the roll of soft 
wax is formed upon the maxillary surface, permitting the 
ends of the wax roll to extend around the tuberosities. 
This is placed in the mouth and forced firmly to place. The 
tray is then removed from the mouth, the wax made cold, 
Fig. 26 
and any excess removed with a hot wax spatula or knife. As 
has been stated, this reinforcement of wax is in no sense a 
part of the impression; it should be considered only as an 
integral part of the tray. This peripheral reinforcement 
serves a double purpose: first, it acts as a dam to prevent the 
soft plaster extending too far backward, and second, it acts 
as a compress to prevent the contraction of the palate muscles TECHNIC FOR FULL UPPER IMPRESSIONS 
91 
drawing down or depressing the palatal portion of the 
impression. Inattention to this portion of the impression 
often causes failure in the retention of the denture. Fig. 26 
illustrates the tray with wax reinforcement of the palatal 
border. The reinforcement may extend forward upon the 
buccal flanges to include the malar processes, but it should 
not extend so far forward as to include the buccal frena. 
However, if the reinforcement extends over the malar 
process it should be properly adjusted. This is done as 
follows: When the tray with the peripheral roll has been 
forced into place, the tray is supported by firm pressure of 
the index finger of the left hand placed upon the center of 
the lingual surface of the vault of the tray; when the right 
cheek is grasped and drawn downward by the index finger and 
thumb of the right hand, the cheek is released and instantly 
pressure is made with the fingers upon the cheek over the wax. 
The left index finger is replaced with the right one, when the 
left cheek is manipulated in like manner. This illustration 
shows also the frenal notch sufficiently cut away to prevent 
impingement, and the labial flange properly adjusted. The 
tray is now prepared for the case in hand, and could not be 
improved upon even if a new metal tray were to be made for 
this individual case. 
Changing the Position of the Patient.-The tray being 
properly prepared for the impression, it is well to change the 
position of the patient to an upright position with the head 
slightly inclined forward. This is simply a precaution to 
prevent any plaster falling into the throat. However, an 
experienced operator may keep the patient in the first 
position for his own convenience, and be justified in so doing 
because of his expertness; but not so with the inexperienced 
operator. 
Mixing the Plaster.-One fluidounce of water, of the tem- 
perature of the room or a little warmer, is placed in a rubber 
bowl (Fig. 27) and four or five grains of salt (NaCl) dissolved 
in it. A measure holding 2 fluidounces should be filled with 
regular dental plaster (French's), but not packed; this 
plaster should be shaken or sifted into the salted water and 
gently agitated with the plaster spatula (Fig. 28) until it is 92 
IMPRESSIONS 
smoothly mixed. The object desired is to get the plaster 
cement smoothly mixed, free from confined air, and in the 
mouth as quickly as possible. The time required should 
be but a few seconds. If a special impression plaster is used 
in place of French's regular dental plaster, the salt will 
probably not need to be added, as possibly the manufacturer 
has added an accelerator. Some operators prefer the use of 
potassium sulphate (K2SO4) in place of common table salt 
(NaCl), but either serves an excellent purpose, the NaCI 
having the more agreeable flavor. 
Filling the Tray.-The mixed plaster should be transferred 
from the bowl to the prepared tray as expeditiously as 
possible. The plaster should cover the entire maxillary 
Fig. 27 
surface of the tray; it should be flush with the palatal rein- 
forcement and piled up somewhat at the anterior vault 
portion. 
Inserting and Placing the Filled Tray.-The filled tray should 
be instantly inserted into the oral cavity, using the technic 
previously described in this chapter. While the thumb and 
index finger support the tray, the second finger should be 
carried backward against the vault of the tray. This will 
favor carrying the palatal border of the tray firmly into 
place. While placing the palatal border of the tray the index 
finger of the left hand is slipped forward under the lip, which 
is grasped between the finger and thumb, and the lip dis- 
tended. As the palatal border of the tray is held securely in TECHNIC FOR FULL UPPER IMPRESSIONS 
93 
position, the anterior portion of the tray is carried into place 
by a swinging upward movement of the hand. Instantly the 
Fig. 28 94 
IMPRESSIONS 
median portion of the lip, which is in the grasp of the finger 
and thumb of the left hand, should be drawn downward, thus 
setting the frenum labii in the soft plaster. The finger is 
then slipped backward to the left angle of the mouth, which 
is grasped and drawn downward, marking and placing the 
buccal frenum. Either the first or second or both of these 
fingers of the left hand are placed against the vault of the 
tray, thus releasing the right hand. The right angle of the 
mouth is now drawn downward, thus placing the right 
buccal frenum. While firm pressure is maintained upon the 
vault of the tray, the cheeks and lips are firmly pressed against 
the soft plaster with the thumb and fingers of the right hand. 
By this means the soft tissues of the buccal and labial 
walls of the maxilla are compressed. No effort need be 
made to compress the plaster over the malar processes, as the 
wax reinforcement will provide for this. Furthermore, if 
there is any portion of the periphery of the plate which should 
not press firmly, it is that over the malar processes. The 
fingers of the right hand may now relieve the left hand, which 
is placed upon the top of the patient's head. By pressing 
with both hands, not hard but firmly, the setting plaster is 
held more steadily in place. If the operator removes a little 
of the excess plaster upon a finger of the left hand as he 
removes it from the mouth the last time, he will have a guide 
as to the hardening of the plaster. It should be left in the 
mouth (probably two or three minutes) until it will break 
with a clean fracture, when it is ready to be removed. 
Removing the Impression.-When the plaster breaks with 
a clean fracture and does not crush, the impression should 
be removed by grasping the handle of the tray with the thumb 
and fingers of the right hand, while the left cheek is elevated 
from within with the index finger of the left hand. Pressure 
is made upon the handle in such a manner as to depress the 
palatal border of the impression. If the impression does 
not loosen after a reasonable amount of force has been 
applied in this manner, a slight rocking movement of the 
handle up and down may aid. If the operator has left the 
impression too long in the mouth it may be necessary to 
throw a jet of water, with a water syringe, around the TECHNIC FOR FULL UPPER IMPRESSIONS 
95 
periphery of the impression. This is done by tilting the 
head slightly backward and lifting the lip and cheek upon 
one side, when the crevice between the impression and the 
Fig. 29 
Fig. 30 96 
IMPRESSIONS 
lifted soft tissues is filled with water. The other side of the 
mouth is treated in the same manner, when the handle should 
again be manipulated. If the impression is removed at the 
proper time there will be only moderate adhesion. Strong 
adhesion of a plaster impression is no evidence that it is a 
good one, but it is a positive evidence that the plaster has 
been left so long in the mouth that it has absorbed all the 
Fig. 31 
moisture from the surface of the mucous membrane, thus 
creating a powerful vacuum suction, which upon being 
broken may tear the mucous membrane. With attention 
given to the work in hand there should be no excuse for 
such an accident. 
Fig. 29 shows the maxillary surface of a plaster impression. 
Notice the peripheral outline. Fig. 30 shows the palatal 
border of the impression. Notice the clean cut-off of the TECHNIC FOR FULL UPPER IMPRESSIONS 
97 
plaster by the wax reinforcement. Fig. 31 is another 
plaster impression in which the palatal border reinforcement 
wax has entirely excluded the plaster in places, as can be 
seen by the difference in color. This illustration shows 
also the excess plaster pressed forw'ard upon the handle of 
the tray. The edge of the anterior flange of the tray can be 
seen much below the periphery of the impression, and yet 
Fig. 32 
there is much thickness to the labial wall of plaster. This 
is because the low labial wTall of the tray was reinforced with 
wax, which with the soft plaster was forced against the labial 
wall of the maxilla by the external pressure upon the lip. 
In contrast with this, Fig. 29 shows a thin labial wall of 
plaster, because a higher anterior flange was used with no 
wax reinforcement. Fig. 32 shows a tray with palatal and 98 
IMPRESSIONS 
labial wax reinforcements ready to receive the freshly mixed 
plaster. 
The method detailed will suffice for a very large percentage 
of cases requiring a full upper artificial denture; but there 
are some cases that will require special manipulation in order 
to produce the best results. These may be classified as: 
(1) high vaults, (2) flat vaults, and (3) enlarged raphe. 
Fig. 33 
High Vaults.-The high vault may be oval, square, or an 
inverted V-shape. In either case the wax reinforcement 
should not only be placed along the palatal border, but it 
should be carried forward to fill the entire vault. After 
the wax has cooled, the surface of the anterior portion to 
the thickness of of an inch should be removed with a 
warmed wax knife. The palatal border should be left undis- TECHNIC FOR FULL UPPER IMPRESSIONS 
99 
turbed to the width of | to | of an inch. The object of the 
reinforced vault portion is to insure the plaster being carried 
fully to place, and the use of less plaster. Fig. 33 shows a 
tray prepared for an inverted V-vault. A high vault will 
always require a high labial flange to the tray. It is better 
to use a tray with a narrow labial flange, and then build the 
required flange of wax, thus providing for the compression of 
the soft tissues over the labial wall of the maxilla. The illus- 
tration shows the low metal flange upon the right side and 
the wax restoration upon the left. 
Fig. 34 
Flat Vaults.-These cases will present one of three condi- 
tions of the soft tissues: (1) thin and tense, (2) medium soft, 
or (3) soft and flabby. Fig. 34 is a cast of the second class. 
The impression from which this cast was made was taken 
in the tray shown in Fig. 25. Obviously a case of this kind 
would require that the flanges of the tray should be cut away 
or that they should be bent well over, as shown. The latter 
is to be preferred, as it provides the desired large base-plane. 
(This feature will be further considered under the subject 
Retention of Artificial Dentures.) In both the first and 
second classes the impression is taken in the usual manner. 
It is in these flat cases that the student is tempted to omit 
the palatal border wax reinforcement, but he should remem- 
ber that the rule is universal, and has no exceptions, that to 
omit this reinforcement in any case is to invite failure; 100 
IMPRESSIONS 
however, failure may not come at the bidding. The third 
class of flat vaults requires special consideration and treat- 
ment. 
Difficult Flat Vaults.-The flat vault per se is not neces- 
sarily difficult to cope with, for under favorable conditions 
it provides the strongest retention. However, there are 
such a considerable number of vexatious cases associated 
with flat vaults that they have become the bete noir of the 
dental profession. This is a very unjust condemnation, 
Fig. 35 
because there are other vault forms that present much 
greater difficulties. The trouble is that the dentist fails to 
recognize the conditions, therefore fails to meet the require- 
ments. In the three classes named of conditions of the soft 
tissues, the first class (hard and tense) presents only the 
usual difficulties of impression taking; yet the retention in 
this class is poor. This will be considered in the chapter 
on Retention. The second class (medium soft tissues), 
provided the fluids are normal, is one of the most favorable TECHNIC FOR FULL UPPER IMPRESSIONS 
101 
cases the dentist can have. The third class (soft and flabby) 
is troublesome and requires study, and suitably taken 
impressions. 
Before entering upon the technic of taking impressions 
for this class, it is necessary to refer to another factor some- 
times associated with flat vaults. A thick, ropy secretion is 
always a menace to the retention of artificial dentures. This 
factor is mentioned at this time because one method of 
impression taking is especially designed to offset the viscid 
secretions. In this third class the flabby tissue may be 
evenly distributed over the entire surface to be covered with 
the base-plate, or it may be interspersed with hard tissue. 
Each condition will require a suitable impression. 
Technic for Flabby Gum.-When the soft tissues are 
thick and evenly laid over the surface to be covered with the 
base-plate, a suitable-size, flat, oval-floor tray is selected, a 
roll of soft wax, the size of a lead-pencil, is placed upon the 
maxillary surface at the periphery of the tray, carried into 
the mouth, and placed firmly into place. While holding 
the tray firmly with a finger or two upon the center of the 
vault of the tray, the lip and cheeks are drawn downward and 
then externally pressed inward. The tray is then removed 
from the mouth, and the wax cooled. The space formed by 
the peripheral wax is filled with a soft mix of plaster. The 
technic of inserting the tray into the oral cavity and 
adjusting it is the same as previously described. The object 
sought is to have the soft tissues evenly compressed through- 
out the entire periphery of the base-plate and no compres- 
sion over the inclosed portion. Fig. 35 shows a flat tray with 
peripheral wax. 
Technic for Interspersed Hard and Soft Tissues.-As an 
axiom, it may be stated that increased pressure should not 
be placed upon either hard or soft tissue in the vault of the 
mouth except upon the palatal border; or, conversely stated, 
increased pressure should be made upon the palatal border, 
the alveolar ridge, and external to the alveolar ridge. The 
most common occurrence of the condition under consideration 
is a spongy vault with the alveolar ridge moderately hard 
upon either side as far forward as the location of the cuspids, 
and a flabby condition from cuspid to cuspid location. 102 
IMPRESSIONS 
Fig. 36 is a tray reinforced for such a case. The palatal 
border wax should extend forward to rest upon the malar 
process, only when it is covered with an excessive amount 
of soft tissue. The anterior portion of the tray should have 
a sufficient quantity of wax to cover all of the flabby gum 
tissue. The metal flange should be cut low and replaced 
with a thin piece of yellow wax. As in all cases, the soft wax 
is adjusted to the mouth. The tray is filled (avoid much 
excess) with a moderately thin plaster, inserted, and adjusted 
Fig. 36 
as previously described. Notice! Hard-not firm, but hard, 
continued-pressure is made upon the center of the vault of 
the tray. The lip and cheeks are drawn downward and 
compressed externally as in other cases. The pressure upon 
the tray is continued until the plaster has set. By this 
means a firm foundation will be established for the artificial 
denture. 
Rarely will the buccal portion of the gum tissue be exces- 
sively flabby, but when it is the denture must have a bearing TECHNIC FOR FULL UPPER IMPRESSIONS 
103 
beyond the soft flabby tissue if possible; and the buccal 
flange of the base-plate must extend as far outward as the 
free action of the buccinator muscle will permit. The object 
sought is to have the force of mastication distributed over 
as broad a surface as possible, and thus prevent undue 
pressure upon the palatal processes of the maxilla. 
So far there has been discussed but one method, with its 
modifications, for taking full upper impressions. Plaster of 
Paris with a suitably prepared tray is the best material the 
dental profession of today possesses to meet the requirements 
of all cases. The one serious objection to plaster of Paris is 
that there is no practical test for the perfection of the impres- 
sion. Dependence must be placed upon knowledge and skill; 
knowledge of the requirements of the case and skill in apply- 
ing the knowledge. Should a plaster impression be replaced 
in the mouth, strong adhesion may be induced by its capacity 
to absorb the moisture upon the mucous membrane; but this 
will take place equally as well or better with a poorly adapted 
impression. An inspection of the impression may show a 
perfect imprint of the mucous membrane, but it does not 
differentiate between proper compression and improper 
distortion of the soft tissues. So knowledge and applied 
knowledge (skill) must be arbiters of the perfection of the 
impression. The artificial denture made from an impression 
may be positive evidence that the impression was perfect, but 
it is no evidence that it was not good. 
Mention has been made of ropy or viscid secretions as an 
adverse factor associated with flat and more or less flabby 
vaults. The author is of the opinion that these conditions 
may be best met by the use of modelling compound. Also, 
he believes that no first impression should be taken with 
this material, because the line of demarcation where plaster 
ceases to be the best material and modelling compound 
demanded is so obscure that preference should always be 
given plaster of Paris. Modelling compound is far more 
difficult to handle (properly) than plaster of Paris. The latter 
material is more scientific and requires less skill than the 
former, especially if the case is a difficult one. This last 
statement is contrary to the generally accepted opinion, but 104 
IMPRESSIONS 
nevertheless it is true. The reasons for these statements 
will develop as the methods for the use of the compound 
are described. 
Technic.-The impression for this class is the same as 
for the normal class, except in the palatal reinforcement 
wax. 
The object sought with these enlarged raphe is to have 
contact without pressure. The palatal reinforcement wax is 
adjusted as in all cases, when a layer of the wax covering 
the hard raphe is removed to the extent of of an inch in 
thickness; and the impression and denture must extend back- 
ward beyond the hard area, at least | inch, and better, if 
there is | inch for bearing surface. If there is much thick- 
ness of soft tissue upon each side of the hard raphe, a little 
additional soft wax may be placed over the cold reinforcement 
wax covering the soft tissue of the vault, and readjusted to the 
mouth with moderately firm pressure. Should the anterior 
portion of the raphe touch the tray, it must be relieved by 
depressing the tray (use horn or wooden mallet). The tray 
is filled with soft plaster and placed in the mouth and pressure 
applied back of the middle of the vault of the tray. This 
will compress the soft tissue upon each side of the hard 
raphe. As a space has been made in the wax covering of 
the hard raphe, some of the soft plaster will be forced back- 
ward. This objectionable feature may be controlled by 
having the patient's head inclined forward. 
IMPRESSIONS FOR ENLARGED RAPHE. 
FULL LOWER IMPRESSIONS 
Iligh ridges 
Flat ridges 
Broad. 
Thin. 
Broad buccal and lingual 
flanges. 
Narrow buccal and broad 
lingual flanges. 
Narrow lingual and broad 
buccal flanges. 
Both flanges narrow. 
Classification FULL LOWER IMPRESSIONS 
105 
Technic.-In all lower impressions the controlling factor 
for the width of the flanges of the tray will be the insertion 
of the mylohyoid and the frenum linguae on the lingual and 
the buccinator and labial muscles on the outer flange. A 
rule may be established that in no case shall the flange 
impinge upon a muscle. 
High Ridge.-The only difference required for an impres- 
sion for a broad or thin high ridge is in the wax reinforce- 
ment. With a broad ridge the reinforcement is upon the 
lingual flange only, while for a thin ridge both flanges should 
be reinforced. Fig. 37 illustrates a tray reinforced for a 
broad ridge, and Fig. 38 is prepared for a thin ridge. 
Broad Ridge.^-The operator should assume same position 
in respect to patient as mentioned in technic for upper 
impressions. After the flanges of the tray have been adjusted 
for a broad high ridge, a roll of soft wax, about the size of 
a lead-pencil, is placed upon the warmed mandibular surface 
of the lingual flange, and inserted in the mouth in the same 
manner as described on page 88, except that the floor of the 
tray is upward. As the wax is pressed against the lingual 
wall of the process the patient is requested to raise the tongue 
momentarily to the roof of the mouth. The tray is removed, 
wax chilled, and excess cut away. It is then filled with 
soft mixed plaster and quickly adjusted in the mouth, by 
first adjusting the left side, and then the right side. As the 
left side of the tray is settled into position the finger used to 
distend the left angle of the mouth is carried backward, and 
with the thumb grasps the cheek, drawing it downward 
and outward, thus preventing a portion of soft tissue being 
entrapped under the buccal flange of the tray. The finger is 
then moved forward to the buccal frenum, which is distended, 
and then the labial frenum is drawn into place. The finger 
is removed and the left thumb inserted across the mouth as 
far backward as the angle of the mouth will permit. The 
fingers will be under the mandible, and the thumb resting 
upon both arms of the tray. As the right side of the tray 
is being forced into position, the right index finger having 
been carried into the mouth, the right cheek is grasped and 
drawn out of the way of the buccal flange. Pressure is then 106 
IMPRESSIONS 
Fig. 37 
Fig. 38 FULL LOWER IMPRESSIONS 
107 
made over the border of the buccal and labial flanges with 
the fingers of the right hand. The thumb of the left hand 
is then placed upon the left side of the tray a little back 
of the angle of the mouth, while the right thumb is placed 
in a like position upon the right arm of the tray. As the 
fingers of both hands are pressing firmly against the under 
margin of the mandible the tray is held as in a vise. The 
patient is requested to raise the tongue firmly against the 
roof of the mouth, after which it may rest easily on the floor 
of the mouth. The tray should be held firmly until the 
plaster is set, when it is removed by grasping the handle 
with the right hand and distending the left cheek and lip 
with the index finger of the left hand. 
It is necessary to get the tray and tissues adjusted before 
crystallization of the plaster has much progressed; therefore 
it is desirable to have a definite system, so that no time 
may be lost. Every movement should be positive, but gently 
executed. 
Thin Ridge.-The flanges of the tray having been adjusted, 
a roll of soft wax is placed upon each flange and pressed into 
position. The wax cooled and trimmed is shown in Fig. 
38. The object sought in this impression is to have even 
compression upon the periphery of the base-plate while 
there is but slight pressure upon the crest of the ridge. This 
should relieve one source of pain in artificial dentures; that 
is, undue pressure upon the mucous tissue drawn over a 
sharp crest of bone. If the thin ridge of gum has become 
pendulous, from excessive resorption of the process, it is 
well also to have it relieved of pressure. The plaster should 
not be mixed stiff enough to make pressure in any impression; 
the pressure should be made by the reinforcement wax. The 
plaster is designed for close adaptation. 
Flat Ridges.-For these cases a series of oval-floor trays 
should be prepared as the emergency demands. Two or 
three trays of different sizes prepared for this class of cases 
will probably be sufficient. The tray is prepared by cutting 
off the handle and about one-half of the flanges. They 
should be so trimmed that when they are placed in the mouth 
the muscles of the mandible will not much disturb them. 108 
IMPRESSIONS 
First Subclass.-(See classification for full lower impres- 
sions.) Either the regular oval-floor tray with the flanges 
bent outward, or one of the specially prepared trays should 
be chosen, as best fits the case. 
Second Subclass.-A regular tray with the lingual flanges 
bent inward and the buccal flanges rolled outward and 
upward will probably best meet the requirements. 
Third and Fourth Subclasses will require the specially 
prepared tray. 
The impressions of all of the flat-ridge cases should be 
taken first in wax, or, in modelling compound. If the patient 
can be prevailed upon to aid, the margins should be muscle 
Fig. 39 
trimmed. If the patient has not sufficient control of the 
muscles of the face so he can assist, the operator must hold 
the tray with the thumb of one hand so that the other hand 
is free to work the tissues. The right hand should hold the 
tray while working the tissues upon the left side, and vice 
versa. The patient can at least be prevailed upon to force- 
fully raise the tongue. This wax or modelling compound 
impression should be considered only as a reinforced tray. 
Grooves should be cut in the mandibular surface of the rein- 
forcement when it is covered with soft plaster and inserted 
in the mouth. The buccal tissues must be removed from 
under the buccal flanges of the tray as directed on page 97. PARTIAL UPPER IMPRESSIONS 
109 
The impression should not be removed from the mouth until 
the plaster is thoroughly hard. As the impression is sur- 
rounded by saliva, there will be little danger of excessive 
adhesion. 
Fig. 39 exhibits full upper and lower impressions of the 
broad type. The lower has the lingual flange reinforced 
and the upper has the palatal reinforcement. 
PARTIAL UPPER IMPRESSIONS 
Anterior teeth lost. 
Posterior teeth lost. 
Teeth and spaces alternating. 
Classification 
Fig. 40 
Anterior Teeth Lost.-For all partial cases a flat-floor tray 
of suitable size should be chosen. If three or more teeth 
are lost the vault reinforcement wax of Fig. 40 should be 
extended forward to nearly fill the space occupied by the 110 
IMPRESSIONS 
lost teeth. There should be about | of an inch of space 
between the wax and the remaining teeth, also between the 
wax and gum (Fig. 40). Judgment should be exercised in 
the quantity of plaster used, thus avoiding much excess. As 
partial plaster impressions are almost certain to be broken 
while removing from the mouth, a small tray (lacquer or 
metal) and tweezers should be upon the bracket table, so that 
the pieces may be placed in order as they are removed from 
Fig. 41 
the mouth. Figs. 48-52 illustrate such an arrangement. 
Fig. 41 is a tray properly filled with plaster for taking an 
impression where the four upper incisors are missing. The 
plaster should be mixed just stiff enough so it will not run 
when placed in the tray. This implies that, because of its 
stiffness, the time of setting is shortened, and that it must 
be quickly adjusted. In such a partial case the lingual 
aspect, and possibly the occlusal surface of the teeth, is 
desired. PARTIAL UPPER IMPRESSIONS 
111 
With the loss of any increasing number of teeth backward, 
the reinforcement wax is extended; the technic is the same 
as just described. Fig. 42 illustrates the wax reinforcement 
for the lost ten anterior teeth. 
Posterior Teeth Lost.-This class implies that the remaining 
anterior teeth are in phalanx and that there are distally no 
isolated teeth. In such cases a flat-floor tray should have the 
Fig. 42 
reinforcement wax as in Fig. 43. This prepared tray is for a 
case with the teeth lost distal to the first bicuspids. Fig. 44 
has the plaster suitably placed. 
Teeth and Spaces Alternating.-Fig. 45 is,a tray suitably 
reinforced. In all partial cases, except where wax contact 
is desired, there should be a space for plaster over the wax 
reinforcement of | of an inch or little more. The alternating 112 
IMPRESSIONS 
Fig. 43 
Fig. 44 PARTIAL UPPER IMPRESSIONS 
113 
spaces may be dovetail-shaped. In such cases cores should 
be made of wax to fill them. Fig. 46 is a plaster cast show- 
ing a space between the second bicuspid and second molar 
Fig 45 
Fig. 46 114 
IMPRESSIONS 
requiring a core. In the illustration the core is attached to 
the upper surface of the cast. The core is made by filling 
the space (without drying the teeth) full of soft wax. Most 
of the excess wax may be trimmed away in the mouth. The 
wax is made cold and removed through the wider aspect of 
the space. In this instance it should be pushed inward. 
The wax is then thoroughly chilled and trimmed pyramid- 
shape, with the base resting upon the gum. After it has 
been cooled and trimmed (pyramid-shape) so the plaster 
will draw from it, it is secured in place by slightly pinching 
Fig. 47 
the occlusal end. If there are large spaces, as for the incisor 
teeth, the tray should be reinforced as shown in Fig. 46. 
After the impression has been removed from the mouth, the 
wax core is carefully removed and replaced in the impression. 
Isolated Teeth Methods.-Fig. 47 shows a cast with the two 
cuspids and the left second bicuspid remaining. The teeth 
were short and firmly attached, so there was no danger of 
their extraction in the impression. In this case all the prepa- 
ration nece'ssary was the reinforcement of the tray, as in Fig. 
43. However, if the teeth had been long and bell-shaped, 
and loose, it w'ould then have been necessary to have thor- PARTIAL UPPER IMPRESSIONS 
115 
oughly dried the teeth (one at a time), and to have molded 
a little soft wax about the neck of each tooth as it was 
dried. The plaster impression would either draw away from 
the wax, when it should have been replaced in the impres- 
sion, or the wax would have remained in the impression. 
Had the teeth dragged through the wax no harm would 
have been done other than a slight distortion of the wax. 
Fig. 48 
Fig. 48 is the impression taken for the cast shown in Fig. 47. 
Some of the reinforcement wax is shown; also the fragments 
are placed in order about the main portion of the impres- 
sion. Fig. 49 shows the assembled pieces luted together with 
wax. 
Detachable Tray Method.-In this method no wax rein- 
forcement should be used, except as in Fig. 45; and this 116 
IMPRESSIONS 
should be so trimmed that there are no undercuts. The 
maxillary surface of the tray and reinforcement wax are 
smeared with a thin layer of vaselin. This will permit the 
tray to part from the hardened plaster, which may be 
removed in sections after the manner used by orthodontists. 
The maxillary surface of the tray should be smooth, and 
in no degree dovetail-shaped. If this method is to be used. 
Fig. 49 
the operator should first carefully observe the teeth and 
vacancies, and devise a scheme for notching and breaking 
the plaster in sections. The notching and breaking are done 
with a stout knife, which must be well guarded so the patient 
may not be injured. As the pieces are removed from the 
mouth they are placed in order on the lacquer tray. The 
impression tray may be removed from the mouth and 
notches cut in the plaster, but no attempt should be made PARTIAL LOWER IMPRESSIONS 
117 
to break the plaster away from the teeth until it will make 
a clean break, that is, not crush. The inexperienced student 
should be very cautious of choosing this method, because 
of the danger from the knife. However, the tray may part 
from an impression unexpectedly, when it becomes necessary 
to notch and remove the impression in sections. 
Fig. 50 
PARTIAL LOWER IMPRESSIONS. 
Classification.-The classification used for partial upper 
impressions is applicable for lower ones. The wax reinforce- 
ments are the same except that there is no vault, and in place 
of a palatal-margin reinforcement a lingual-flange reinforce- 
ment is required. Rarely should any lower impression 
(either partial or full) be taken without the lingual flange 
being reinforced. This is necessary to control the folds of 
the soft tissues and the submaxillary and sublingual glands 
that are occasionally very troublesome. In all cases the 
mylohyoid muscle influences the loosely attached mucous 
membrane for a long distance above the origin of the muscle, 
and draws it inward and upward. As a result, if the lingual- 118 
IMPRESSIONS 
Fig. 51 
Fig. 52 Fig. 53 
Fig. 54 120 
IMPRESSIONS 
flange compression wax is not used the lingual flange of the 
completed artificial denture will not lie close to the mandible. 
This is often a source of annoyance to the patient. 
Fig. 50 shows a flat-floor lower tray with reinforcement. 
Fig. 51, with the plaster in place ready for insertion. Fig. 
52 shows the impression with the fragments and a core. 
Fig. 53 is the assembled impression. Fig. 54 is a Weiss tray 
Fig. 55 
(a modification of the type shown in Fig. 23) and fragments. 
This tray requires the lingual-flange reinforcement only. 
Fig. 55 is the assembled impression. 
As Ordinarily Used.-A tray is selected, and the flanges 
adjusted as for a plaster impression. No reinforcement 
MODELLING COMPOUND FOR IMPRESSIONS MODELLING COMPOUND FOR IMPRESSIONS 
121 
is required. A portion or a whole cake of modelling com- 
pound, as the judgment dictates, is softened in water (see 
page 68) and placed in the warmed tray. In manipulating 
the compound all folds should be kept on the under portion, 
so the surface taking the imprint may be smooth and con- 
tinuous. The side of the index finger may be imbedded 
first upon one side and then upon the other, so as to form a 
groove for the alveolar process. The surface is then given 
an extra softening by passing over a smokeless flame. The 
compound filled tray is carried into the mouth and forced 
into place after the manner described for plaster (page 
88). The lip and cheeks are manipulated in the same 
manner as for plaster. The compound is left in the mouth 
until it has hardened. Hardening may be expedited by using 
cold water. A small piece of cloth (an aseptic napkin) is 
saturated with cold water and held against the lingual 
surface of the tray. Some of the cold water may be thrown 
under the lip with a syringe. When the compound has 
become hard it is removed in the same manner as a plaster 
impression, except in no case will it be necessary to use a 
spray of water as an aid to loosen it. 
Advantages and Disadvantages.-The advantages of com- 
pound are claimed to be that it takes a sharp impression, 
does not break upon removal, and compresses the soft 
tissues. The first two claims are true, but the second claim 
of superiority should be classed as a disadvantage, for a 
material that does not break must bend or drag when taken 
from an undercut or dovetail-shaped space. The third 
advantage claimed is very questionable. As ordinarily used 
the compression is not under the control of the operator. 
The material is usually forced so far backward upon the 
soft palate as to produce contraction of that organ, and cause 
depression in place of compression at the palatal border 
of the impression. The soft tissues upon the labial and 
buccal surfaces are usually distorted. Because of this dis- 
tortion many operators find it expedient and useful to 
use a "bead" upon the maxillary surface of labial and 
buccal flanges of an artificial denture. Following a properly 
taken impression, a bead in this position should be unbear- 122 
IMPRESSIONS 
able. One skilled in the use of any material may produce 
excellent results, but that is not evidence that it is scientific 
or the best. The confusion existing in the profession regard- 
ing the various impression materials, is due to a lack of 
comprehension of the underlying principles. 
Technic for Modelling Compound Impression.-A suitable- 
sized oval-floor tray having been selected, the handle and 
most of the labial and buccal flanges are cut away. If an 
unsatisfactory base-plate has been constructed it may be 
converted into an admirable tray by cutting away at least 
one-half of the width of the flanges. About one-third of a 
cake of compound is softened, dried, and spread over the 
warmed maxillary surface of the prepared tray. This is 
carried into the mouth and hard, continued pressure applied 
so as to compress all the tissues over the vault and ridges; at 
the same time the patient should comply with the instruction 
previously given and draw the lip and cheeks downward by 
hard, vigorous muscular action. This, Dr. J. W. Greene, in 
the Greene brothers' method of impression, calls muscle 
trimming. The best position in which the operator may 
stand while taking this form of impression is directly back 
of the patient. The partially taken impression is removed 
from the mouth, thoroughly chilled, and any excess removed. 
The peripheral labial and buccal borders are warmed over a 
small, weak Bunsen flame and quickly returned to place in 
the mouth. It is securely held in place with one hand, and, 
while the patient is muscle trimming, the operator makes 
interrupted compression over the lip and cheeks with the 
disengaged hand. It may be necessary to rewarm and muscle 
trim several times, or an addition of soft dry compound may 
be needed upon portions of the rim of the impressions. This 
addition may be made by ''tracing on" with a stick of com- 
pound. When the operator is satisfied that the rim of the 
impression is perfectly adapted backward to the anterior 
border of the malar processes, the impression is thoroughly 
chilled, dried, and a small roll of soft modelling compound 
placed along the palatal border, upon the maxillary surface, 
and extended around the tuberosities to the malar processes. 
This addition is made quite soft in the small Bunsen flame, MODELLING COMPOUND FOR IMPRESSIONS 
123 
carried into the mouth, and quickly forced into place, 
removed, and dried. If it has not been sufficiently com- 
pressed, it is again softened and pressed in the mouth. The 
impression may now be considered complete. It is placed in 
cold water until thoroughly cold, and without drying it is 
replaced in the mouth and very firm pressure made upon the 
lingual surface of the tray while the lip and cheeks are lifted 
and drawn into position over the rim of the impression. The 
fingers are removed from the mouth and the patient requested 
to remove the impression. If the impression has been 
properly manipulated it may be impossible for an inexperi- 
enced patient to remove it. The patient should be instructed 
to dislodge it by working the lip and cheeks and closing their 
lower teeth upon it in every way possible. Should it prove to 
be insecure at any place it should be corrected, either by 
softening and muscle trimming, or by adding soft compound. 
Rationale.-The reason for this excessively strong adhesion 
is apparent. By this method of taking the impression there 
is absolute contact of the entire periphery of the impression 
except over the malar (zygomatic) processes, where there is an 
automatic valve in the soft tissues of the cheek. As the pe- 
ripheral border is forced into the soft tissues and either cheek 
raised, the moisture and air occupying the free .space within 
the impression is forced out over the malar process; then, as 
the cheek is lowered, it acts as a valve and prevents ingress of 
air. As the pressure is relieved from the lingual surface of 
the tray, the resilience of the soft tissues under the periphery 
of the impression causes a thin vacuum space over nearly 
the whole maxillary surface.1 
This explanation of the strong retention of the impression 
suggests also how to remove the impression, which is done 
by raising the cheek and pulling downward upon the per- 
iphery of the impression at the malar process. As air is 
admitted the impression is loosened. 
The durability of such strong adhesion and its sequence 
are not relevant at this time, but will be discussed in the 
chapter on Retention. 
1 This description is but a slight modification of the Greene brothers' 
method. 124 
IMPRESSIONS 
Fig. 56 is a modelling compound impression taken in an 
inefficient cast aluminum base-plate. A close inspection 
will show the muscle trimming, lines showing addition to 
the anterior flange, and a well-marked line showing the 
compressing portion added to the palatal border and tuber- 
osities. That the student may appreciate the painstaking 
exactness such an impression requires, it is well to state that 
this individual impression was adjusted to the mouth 
probably fifteen times, but the final result was good. 
Fig. 56 
THE GREENE-SUPPLEE METHODS FOR MODELLING 
COMPOUND IMPRESSIONS. 
Mr. S. G. Supplee, of New York City, has formulated and 
introduced a system for taking impressions, based upon the 
methods taught by the late Dr. J. W. Greene, which has both 
merit and fallacies. 
It would not be time well spent to try and differentiate the 
methods employed so as to give credit to each man, nor, is it 
at all likely that either man has made a new discovery; but 
great credit is due both of them for creating a new apprecia- 
tion of old though illy understood truths. They have both 
done meritorious work in developing an improved technic and 
apparatus for convenience. Unfortunately they were both MODELLING COMPOUND IMPRESSIONS 
125 
imbued with the commercial spirit and devoted to creating 
something to sell rather than in discovering the underlying 
principles. Nor could more be expected, for neither of them 
was grounded in anatomy and physics, but both have given 
freely of their inspiration. It remains for the profession to 
convert their veiled teachings into concrete and classified 
knowledge. These men have done a great work in awaking 
the profession to the possibilities of impression taking in this 
dawn of a new era in dental prosthesis. 
"Muscle trimming" and "closed-mouth methods" are fal- 
lacies. The results obtained were due to clever manipula- 
tion notwithstanding the fallacious methods used. The 
secret of the success of the methods taught by these men was 
entirely due to the palatal adaptation and extension. The 
two methods will be discussed in the chapter on Retention. 
Requirements for impression taking with modelling com- 
pound : 
1. Fine quality low heat compound. 
2. A large and small Bunsen flame. 
3. Hot water of a definite temperature. 
4. Cold water or compressed air. 
5. Trays to suit the fancy of the operator. 
6. A technic. 
The quality of compound should be carefully selected for 
fineness, smoothness, and low heat properties. These prop- 
erties are easily ruined by overheating and repeated use 
which is also unsanitary. 
The ordinary Bunsen flame used in the laboratory will 
suffice for the large, but a small weak gas flame or an alcohol 
lamp is necessary for the small flame. 
Fig. 57 shows Mr. Supplee's hot-water heater for working 
modelling compound. It is excellent for its purpose. The 
upper stratum of water should be kept at 160° to 170° F., 
while the water at the bottom of the pan will be approximately 
20 degrees cooler. The bottom keeps the stock compound in 
condition for first adaptation, the upper stratum is the suit- 
able temperature for immersion of compound after heating in 
the Bunsen flame and just before inserting in the mouth. 126 
IMPRESSIONS 
Cold water or compressed air is an absolute necessity for 
setting the compound just before removing from the mouth. 
The essential qualities for the trays are, low flanges and 
ease of adaptation. Each of these men has provided a 
patented set, yes sets, that expressed their conception at the 
time of invention, for the necessary attributes for trays. 
Others, notably Dr. W. A. Giffin, prefer to swage a tray, for 
each case, of English dental tin. However, any tray will 
suffice that will support the compound and permit manipula- 
tion of the periphery of the impression. 
Fig. 57 
The technic varies with the individuality of the demon- 
strator. The writer has never seen a demonstrator of strong 
personality that exactly followed his instructor. Ue usually 
insists that certain modifications are essential for "per- 
fection." However, the underlying principles of all the 
various methods may be summed up in three statements: 
1. Areal contact. 
2. Peripheral bearing with freedom of muscle action. 
3. Extension for retention. THE HALL METHOD FOR IMPRESSIONS 
127 
On page 120 is a general description for the technic of the 
various methods. 
Partial Cases.-Impressions for partial cases without 
undercuts are taken the same as though no teeth were 
present. All partial cases with dovetailed spaces may be 
taken in a tray with little or no labial and buccal flanges. 
First take the impression of the lingual and occlusal surfaces 
of teeth and the required portion of the gum only. This 
portion may be removed, trimmed and readjusted as many 
times as necessary. The edentulous spaces are taken one- 
half through. With this portion of the impression held in 
place an impression is taken of the labial and buccal surfaces. 
This second portion of the impression necessarily overlaps the 
first portion, so that the two portions may be accurately 
adjusted out of the mouth. The labial and buccal compound 
may be supported by a strip of sheet tin or aluminum. 
THE HALL METHOD FOR IMPRESSIONS. 
Dr. Rupert E. Hall,1 of Houston,Texas, has devised a method 
for plaster impressions designed to utilize the modelling com- 
pound principles advocated by the late Dr. J. W. Greene. He 
uses a specially prepared hard black tray compound (The 
S. S. White Dental Mfg. Co., maker) for making a suitable 
tray for each case, and a very thin mix of impression plaster, 
which is built up in layers as required. 
The Hall method is especially adapted to difficult full cases. 
It is not recommended for partial cases. This plaster method 
is superior to the modelling compound methods in that the 
soft mix of plaster is far more delicate and adaptable than 
the compound, and when set it is not distorted by subse- 
quent treatment. 
With a few minor changes the following description is in the 
words of Dr. Hall and as such is commended for careful 
consideration. 
The Individual Tray.-The first, or basal essential in the 
taking of a perfect impression is a tray suited to the case; 
in other words, a tray that fits. You see this in the changes 
xNow of Chicago. 128 
IMPRESSIONS 
the prosthetist makes in his metal trays-bending and cut- 
ting them to secure better adaptation. From the very nature 
of the work a special tray is necessary to get perfect results. 
The black impression-tray compound was devised for the 
particular purpose of making these individual trays quickly 
and economically. It is somewhat of the nature of a model- 
ling composition, but with differences that adapt it specially 
to the making of trays. It is jet black in color to make it 
readily distinguishable; has a high melting-point to assure 
ample rigidity when set or hardened and trimmed to a thin 
edge; and is readily cut as may be desirable in shaping it. 
The Impression Material.-The second essential to the mak- 
ing of a perfect impression is a material of a consistence that 
will yield to the delicate soft tissues of the mouth when it is 
applied, without offering the slightest resistance; and then 
set or harden quickly into a rigid non-elastic mass bearing 
the perfect impress of every detail of the surface with which 
it has been brought into contact. Thin-mixed plaster-so 
thin that it flows-is the ideal material for taking impressions. 
The superiority of plaster as an impression material has al- 
ways been recognized. The method described below shows 
the way to utilize it to get the ideal results that have been the 
aim and the despair of prosthetists from time immemorial. 
Making a Tray.-It is necessary in employing the black 
impression-tray compound to have a few regular metal trays 
of suitable forms and sizes. (S. S. White britannia-metal 
upper trays Nos. 1, 2 and 3, and lower trays Nos. 1, 2, 3, 18 
and 19, are most desirable for this method. In taking lower 
impressions, the Nos. 18 and 19 should be employed whenever 
the conformation of the tissue permits their use.) Take a 
metal tray of the proper shape for the case, but somewhat 
larger than you would ordinarily use. Fill it with the com- 
pound, softening in hot water-a higher heat will be required 
than in softening ordinary modelling composition. Pass it 
over a Bunsen or alcohol flame to soften and remove inequal- 
ities in the surface and give it a glaze. Plunge quickly into 
hot water to wet the surface and prevent sticking to the 
tissues, and as soon as it cools to a bearable degree insert in 
the mouth and secure an impression in the regular way. In THE HALL METHOD FOR IMPRESSIONS 
129 
a short time it can be removed from the mouth and placed in 
cold water to harden. 
Remove the compound impression from the metal tray, 
trim away the compound until you have a thin tray form; 
the inner surface of the periphery should also be trimmed to 
allow plenty of room for the plaster to escape freely to prevent 
compression of the tissues. Do not trim the tray too short, 
as otherwise the plaster when applied in the tray may not be 
carried to place; or if it is, it will break off because of the 
unsupported overhang. If you should happen to trim the 
tray too short, or need to add to it, the difficulty can be reme- 
Fig. 58.-Palatal view of finished individual tray after trimming 
and scoring. 
died by fusing more of the compound to the form wherever 
desired, inserting in the mouth while soft, and allowing the 
tissues of the mouth to properly shape the tray outline, which 
can then be cut down a little to allow for the plaster. Finally, 
score the maxillary surface to give the plaster a firm hold. 
(Fig. 58.) 
You now have a tray that perfectly conforms to and fits 
the individual case, with no bulky projections or protruding 
edges to impinge upon and distort the soft tissues or push 
them from their normal positions. 
Plaster and Its Manipulation.-Mix clean, fine, quick-setting 
impression plaster very thin. The plaster should be sifted 130 
IMPRESSIONS 
thoroughly at the time it is used, to be sure that it is freed 
from'any lumps caused by dehydration, as commonly found in 
plaster. French's Impression Plaster (cans or buckets only) 
should be used; never bulk plaster. 
Mixing the plaster homogeneously of the proper consist- 
ence is difficult and extremely uncertain by hit-or-miss 
methods, but by following the plan here outlined the homo- 
geneity and consistence of the mix can be perfectly controlled 
Fig. 59.-Dipper sieve for sifting plaster. It is used by holding it over 
the plaster bowl, and tapping the rim with the spatula, which assures the 
plaster reaching the water in a finely divided condition, free from lumps and 
debris. 
and standardized: Place the proper quantity of plaster in a 
dipper sieve of a size that will work inside the plaster bowl 
(Fig. 59); provide an excess of water in the bowl and sift the 
plaster into the water as fast as it will sink. When sufficient 
plaster has dropped to the bottom of the bowl pour off the 
free water-down to the plaster-and you have the correct 
proportions of plaster and water to make the proper mix. THE HALL METHOD FOR IMPRESSIONS 
131 
Little spatulating is necessary-just enough to assure a 
uniform consistence. You will then have a plaster mix of 
cream-like character much thinner than is ordinarily used 
in impression taking-thin enough, in fact, to flow readily 
around and over the soft tissues without disturbing them. 
Because of this thinness it is obvious that the plaster must 
set as quickly as possible after it is inserted in the mouth and 
flowed about the tissues; as otherwise the influx of the secre- 
tions will wash away the plaster before crystallization, thus 
preventing the close contact with the tissue that is necessary. 
No fixed rule for the setting time can be made. Grades of 
plaster vary in setting time; climatic conditions, room tem- 
peratures, the temperature of the water, individually or in 
combination, are all factors that affect the mixing and man- 
ipulation of plaster. However, as the best results demand 
quick setting the plaster should be so mixed and manipulated 
with regard to varying conditions as to effect the result. 
Upper Impressions.-The taking of upper impressions re- 
quires a series of applications of plaster, the first of which is 
only to determine the approximate position of the delicate 
tissues and muscles and to indicate points where the tray 
must be trimmed away. 
Have the patient sit erect in a normal position. This 
closes the fauces and prevents the plaster passing down the 
throat. Fill the tray, insert in the mouth and proceed with 
a wiggling motion to carry the tray to place, being careful to 
use no more force than is absolutely necessary, while the 
patient slowly closes the mouth. 
To expedite and insure a safe removal of the impression 
have the patient close the lips and fill the mouth with air, dis- 
tending the cheeks and lips, which breaks the adhesion (Fig. 
60). All interfering parts of the tray showing compression of 
the tissues and muscles are cut away and all excess plaster 
removed. A second application of plaster or as many as are 
necessary to correct any imperfections are made until a perfect 
counter-reproduction of the tissues or impression is obtained. 
The average case requires two applications of plaster. 
This method properly carried out will produce a perfect 
impression from which a plate can be made that, because of its 132 
IMPRESSIONS 
accurate adaptation, dispenses with the need of air-chambers, 
suction devices and the like (Fig. 61). 
Fig. 60.-First trial plaster impression. Note imperfections that make 
a second application of plaster necessary. 
Fig. 61.-Second trial, producing a perfect plaster impression, bringing 
out every detail of the palatal surface and peripheral margin with normal 
muscle relations. 
For Lower Impressions.-In taking a lower impression we 
have the help of gravity in carrying the plaster to place. THE HALL METHOD FOR IMPRESSIONS 
133 
Because of this only one mix of plaster and one trial are 
necessary instead of two or three; but to carry out the work 
correctly and to get the perfect result possible with this 
method it is important that the tray fit as accurately as pos- 
sible; that is, all long interfering edges must be relieved. 
The most delicate or gentle pressure possible should be em- 
ployed in bringing the plaster into contact at every point 
without' compressing the soft parts. A small handle (that 
will not interfere with the lip) made from the tray compound 
or wax attached to the tray with a hot spatula greatly facili- 
tates the manipulation of the tray. The tray should never 
be forced against the tissues; but after being inserted prop- 
erly should be gently "wiggled" to allow the plaster to drop 
in place. 
After the tray carrying the plaster has been inserted, have 
the patient raise the tongue as high as may be, pointing it 
forward; then after the tray is adjusted, drop the tongue to 
rest. This procedure allows the thin plaster to run into every 
space, extending under the tongue wherever there is room. 
Do not trim this off, but preserve it carefully, remembering 
that wherever the plaster runs rubber may be substituted, 
because it can be depended upon that plaster used as here 
described-very thin-will not compress or displace the 
tissues. The flanges (when extending under the tongue) so 
provided give the plate a larger bearing surface, assure the 
help of the tongue in holding it in place, and diminish the 
opportunities for food to get under the denture. 
This method properly carried out may be depended upon 
to produce lower dentures which, because of their perfect 
adaptation, will have suction, a condition heretofore unknown 
except in rare cases; proving beyond doubt the accuracy of 
the method and its superiority over any other procedure yet 
devised. 
Relieving the Hard Spots.-After the impressions are made, 
try the upper in the mouth and test for fit. Put pressure 
upon one side and the other, as would be exerted in masticat- 
ing upon the finished denture. If it rocks, you have evidence 
of a hard area or areas in the palate. Remove the impression, 
locate the hard areas, outline them upon the maxillary side, 134 
IMPRESSIONS 
cut away (with sandpaper-the knife will cause chipping of 
the layers) the plaster at the places indicated until you have 
relieved all pressure or contact between it and the hard areas 
of the palate, and you can no longer rock and dislodge the 
impression. Sometimes hard areas will be found which are 
not extensive enough to noticeably affect the fit. They 
should always be outlined and relieved upon the impression, 
or upon the cast with tinfoil at the time of vulcanization, 
because after the denture is worn for a time it may settle and 
ultimately bear upon the hard areas and develop rocking. 
The work is done under normal temperatures-there is no 
distortion through engorgement of the tissues by a high heat. 
The plaster because of its thinness flows naturally into under- 
cuts and spaces, assuring a perfect reproduction of all parts- 
soft and hard-in repose, and all surplus escapes. 
IMPRESSION APHORISMS. 
1. An impression constitutes the foundation upon which 
the success of an artificial denture depends. 
2. A suitable impression can be obtained only by studying 
the case and devising a definite scheme of procedure. 
3. A stock tray should be adapted to the individual case, 
by bending, trimming, and the addition of reinforcement. 
4. Compression should be made through a properly 
formed tray by means of reinforcements. No impression 
material has discriminating power, hence cannot be depended 
upon to make suitable compression. 
5. Plaster of Paris is the best impression material because 
of its plasticity, adaptability, rigidity, friability, and con- 
trollability. 
6. Modelling compound is valuable in specific cases 
because of its rigidity and workableness. It is very delusive 
because of its toughness. 
7. An impression material is of value only as it is intelli- 
gently and skilfully worked. 
8. Plaster of Paris is aseptic because it can be used but 
once. Modelling compound is dangerous because it may IMPRESSION APHORISMS 
135 
be used repeatedly and cannot be sterilized by heat without 
destroying its working properties. 
9. Small simple impressions may be taken either in plaster 
of Paris, modelling compound, or wax. The accuracy will 
be in the order named. 
10. The more difficult the case the more essential is the 
plaster-of-Paris impression. CHAPTER III 
CASTS. 
Definition.-A cast is a reproduction in plaster of Paris, 
its compounds, or some plastic material, of an object or part, 
made from an impression or mold. Casts are used to give 
their negative likeness to an artificial denture. 
Unfortunately there is much confusion in dental nomen- 
clature in the use of the term cast and model. There is no 
authority outside of the dental profession for calling a cast 
a model, as is too commonly done in vulcanite nomenclature; 
and such indifference in the use of technical terms can only 
lower one in the estimation of learned people. "Cast" is 
from kasta, throw, and is used in the sense of throwing, 
pouring, or forming a plastic material in a mold or impression. 
The term "cast" is applied to objects made of plaster of 
Paris, wax, and similar substances, while the term casting is 
usually applied to metallic objects formed in molds. 
Model is from modus, measure, and is defined as an object 
representing accurately something to be made or already 
existing; a material pattern of natural, heroic, or diminutive 
size. Model is differentiated from pattern in that a pattern 
is usually flat, while a model has material contour. 
In sculpture the model is the plaster or clay original of 
the work to be executed in stone or metal; a person who 
does duty as a copy for painters or sculptors. 
A sculptor may idealize his living model; but his workman 
must exactly copy the clay model made for him. 
Even the dressmaking trade uses the term model correctly. 
They use a model to give its form to the human body, also 
to the external surface of the garment. It is only an incident 
that the garment is made over the model, for the object 
sought is to give form to the outer surface of the garment. 
The photographer speaks of his negative, not of his pattern 
or model. If he uses the term model, he uses it correctly 
136 MATERIALS FOR CASTS 
137 
and applies it to his subject, not to the intermediate, the 
negative. 
A dentist uses casts, castings, and models, and he should, 
if he is a member of a learned profession, differentiate and 
use his terms intelligently and correctly. A cast is anything 
formed, while in a plastic state, in a mold or impression; 
casting (noun) is a term applied to metal casts; and model is 
an object to be copied, but it is a positive, not a negative 
copy. Of all the arts, sciences, and crafts, dentistry alone 
uses the term in both a positive and negative sense. Such 
use is entirely inexcusable, because it leads to confusion of 
thought; besides there is no dearth of correct terms in 
common use. 
It is interesting to note the origin of this use of the term 
model in dentistry. At the time of the introduction of vul- 
canite, during the fifties of the last century, plaster models 
were in constant use for constructing dies for metal base- 
plates. As vulcanite work is constructed upon the plaster 
form in place of a metal form, it was only natural that the 
familiar term model should be retained for the new use. 
Unfortunately, the teachers and writers of text-books at the 
time of the introduction of vulcanite did not give sufficient 
thought to the philology of the glossary required for the new 
art; hence some of the terms that have come down, even to 
this day, are not scientific. 
A plaster model is never used in vulcanite work as ordi- 
narily constructed. Plaster casts are used. A plaster cast 
gives its negative likeness only to the inner surface of a 
vulcanite denture, therefore cannot correctly be called a 
model. Orthodontists make plaster casts of cases as records 
of progress and completion. A plaster cast becomes a model 
only when it is used for duplication. The patient's jaws are 
the models, not their plaster reproduction. 
Uses for Casts.-There are two general uses for casts in 
dentistry: (1) as a form over which something is constructed; 
(2) as a model or copy. 
Materials for Casts.-The material for casts must be 
chosen with regard to the process to be employed. The 
materials may be classified as: (1) plaster of Paris; (2) 138 
CASTS 
Spence plaster compound; (3) plaster compounds known as 
"investment compounds;" (4) wax and its compounds as 
models for metal castings; (5) new compounds. 
Plaster for Casts.-From the study of the expansion, con- 
traction, and compressibility of plaster, it is obvious that its 
use is limited, and that dental operations often require 
casts that are less subject to change by heat and pressure. 
While some operators are accustomed to use building plasters 
for certain purposes, it is better to select from the various 
compounds of plaster for dental use the one designed for the 
work at hand. Failures and imperfections due to the use of 
unsuitable material may thus be avoided. For all purposes, 
when little heat or pressure is to be used, French's regular 
dental plaster serves an excellent purpose. This plaster is 
found in all well-stocked dental supply houses, and is the 
only plaster carried by many of them. 
Spence Plaster Compound.-This is an excellent prepara- 
tion of plaster of Paris, Portland cement, and chemicals to 
control its setting and expansion properties. This material 
has four times the strength of dental plaster, and the expan- 
sion is nearly at zero. As the material is now placed upon 
the market, if properly worked, its setting time is about 
the same as slow-setting dental plaster. Dr. Stewart J. 
Spence, of Chattanooga, Tenn., has certainly produced a 
very valuable material for casts which are to be subjected 
to moderate heat and considerable pressure. It is especially 
adapted for casts for vulcanite work. 
It may be well at this time to consider tersely the important 
addition to plaster in the production of this compound. The 
student should not consider that any mixture of cement 
purchased upon the market and plaster will answer the same 
purpose as that bearing the name of Spence, because the 
Spence compound is the result of much study and experi- 
mentation. 
Portland Cement.-This term was first used in 1824, and 
was given to a patented cement manufactured at Leeds, 
England. It is made by calcining and grinding a suitable 
mixture of lime and clay. It may be considered as a silicate 
of lime and alumina. There is a greater variety of cements WAX AND COMPOUNDS 
139 
grouped under the general heading of Portland cement than 
there is of plasters under the general term of plaster. 
Working Spence Plaster Compound.-The mixing of this 
compound with water is much more laborious than mixing 
plaster of Paris. The ratio of water to the compound, as 
now placed upon the market, is one to four. For a cast a 
fluidounce of water is placed in the plaster bowl, and three 
measured ounces of the compound are added and thoroughly 
spatulated with a very stiff spatula until it becomes soft and 
plastic, after which a half-ounce more maybe thoroughly 
incorporated. The remaining half-ounce may be better 
added one-half at a time. It must be spatulated and kneaded 
in a bowl until the mass is putty-like in consistency, and if 
on continued working it becomes too soft, more of the com- 
pound should be added. When properly mixed it can be 
handled with the fingers and requires to be well-packed and 
jarred in filling the impression. 
Investment Compound Casts.-This class of casts is designed 
to stand high heat, and must be made of a material suitable 
for its intended use. The supply houses furnish many of 
these compounds, which answer a good purpose. They con- 
sist largely of plaster of Paris for a bond to combine the 
material and such materials as will well withstand high heat, 
either singly or in combination. Of the materials used may 
be named: Sand (silica), clay, lime, asbestos, pulverized cal- 
cined fireclay, Portland cement, oxide of iron, pumice stone, 
chalk, etc. 
Working Investment Compound Materials.-These materials 
are worked at about the consistency of plaster of Paris. 
Owing to the small quantity of plaster they contain, they will 
require much less water than pure plaster; usually one 
measure of water to three or four of investment compound. 
Wax and Compounds.-There are a variety of preparations 
in the dental supply houses composed of wax, paraffin, gum, 
and terpene. They are formed in a mold or impression, 
and then the wax cast is used as a model for producing a 
metal casting. This material is often carved into form for a 
model. Such a model cannot be spoken of as a cast because 
it was not formed in a cavity. 140 
CASTS 
Weinstein's Cast Compound.1-This is a calcium, barium 
silicate compound. It is a fine grained, hard and strong 
material. It is slow setting, requiring several hours for 
its maximum hardness. The claim is made for it that it 
neither expands nor shrinks. 
This is a new material with which the writer has had little 
experience. However, any material offered to the profession 
by Mr. L. J. Weinstein is worthy of confidence. Nevertheless 
with the slight experience of the writer he cannot see that he 
would be benefited by substituting it for Spence Plaster 
Compound. 
Magnesium Oxychloride.-Professor J. II. Prothero of the 
Northwestern University Dental School has experimented 
with and used this material, for casts upon which to vulcanize, 
for some years. His recent work, Prosthetic Dentistry 
(1916), gives a full description of the material and its use. 
He says: "The powder is the heavy oxide of magnesium 
(commercial) and the liquid is the supersaturated solution of 
the chloride of magnesium (commercial). The powder can to 
advantage be mixed with clean sand. Sand 50 to 80 parts 
magnesium oxide 50 to 20 parts. It requires about twelve 
hours to harden." 
He further says : " The principal advantages of oxychloride 
of magnesium for casts in vulcanite work are these: hardness, 
density, smoothness of surface and extremely low expansion 
index, less than one-fourth that of the best grades of plaster. 
It is sufficiently impervious to moisture and heat to maintain 
its form without crushing, even under high pressure. 
"Rubber of any shade vulcanized in contact with oxy- 
chloride of magnesium is hard, dense, elastic, capable of 
taking a high polish, and on account of the density of the 
cast is free from nodules." 
CASTS FOR ARTIFICIAL DENTURES. 
The construction of plaster casts only will be further con- 
sidered in this chapter, but in discussing each variety of 
1 Peeso's Crown and Bridge-work, page 120. CASTS FOR ARTIFICIAL DENTURES 
141 
artificial denture the cast suitable for the work will be 
described. 
Use of Impressions.-The preceding chapter treated of im- 
pressions and how to obtain them. This chapter treats of 
the use of the impression. All base plate artificial dentures 
are constructed over either a cast or casting, therefore for 
each artificial denture it is necessary to obtain a suitable 
impression from which a cast is obtained. This implies 
that there is a technic for preparing the impression and 
making the cast. 
Preparing the Impression.-A plaster impression is often 
broken in removing it from the mouth. Indeed, often a 
plaster impression can be removed only by fracturing The 
property of being easily broken is one of the valuable features 
of plaster of Paris. This insures its removal and the accuracy 
of imprint when the fragments are assembled. The impres- 
sion having been removed (if broken, the fragments arranged 
in order upon a small tray), it is permitted to dry for a few 
minutes (five to thirty), when, any small particles of plaster 
having' been removed with an ox-hair brush, or a pointed 
instrument if necessary, the fragments are accurately read- 
justed in the impression tray and secured with melted 
wax (Figs. 48-52). If any carving is to be done upon the 
impression, it should be done at this stage of the procedure. 
However, as any carving must be done for a specific pur- 
pose, instruction as to where and how to do it can be given 
only in describing the work requiring such treatment. The 
impression is next treated with a separating fluid to facilitate 
the removal of the impression from the cast. 
Separating Fluids -The object of the separating fluid is 
to so treat the surface of the impression that a perfect coun- 
terpart of the intaglio may be formed of plaster or its com- 
pounds, and the two easily separated. This is accomplished 
by flowing over the surface of the impression some material 
that will prevent adhesion of the added plaster. The 
desirable properties for a separating medium are as follows: 
(1) It should add as little substance as possible to the surface 
of the impression; (2) it should provide a line of demarcation 
with a distinct penetration of the impression; (3) it should 142 
CASTS 
not cause chemical changes and injurious effects upon either 
the surface of the cast or the denture to be constructed over 
it; and (4) it should give a smooth glazed surface to the cast. 
There are a great variety of materials recommended and used 
for this purpose, but few are extensively used. They may be 
classified as: Alcoholic solutions: (a) shellac, (6) sandarac, 
and (c) other gums and terpenes added to these foundation 
solutions. Aqueous solutions: (a) liquid silex (silicate of 
soda), (6) soap, (c) borax and shellac, (d) ammonia or other 
alkaline substances and shellac. Oils, as sperm, lard, sweet, 
Fig. 62 
or vaselin; and ethereal solutions: (a) of soap and (b) collo- 
dion. The aniline dyes are used as coloring matter for some 
of these preparations. Many of these preparations are kept 
in stock by the supply houses, and some of them under 
fanciful names. 
Perhaps the best and most commonly used method is to 
first saturate the surface of the impression with a thin 
alcoholic solution of shellac, and, when dry, to apply one or 
more coats of alcoholic solution of sandarac. These varnishes 
are made by dissolving one ounce of either gum in 4 ounces 
of alcohol. The solution is greatly facilitated by heating the CASTS FOR ARTIFICIAL DENTURES 
143 
uncorked bottle, containing the gum and alcohol, in simmer- 
ing water for a half-hour or until dissolved. The stock bottle 
should be kept well corked. If either varnish becomes too 
thick (by evaporation), it should be thinned with cold 
alcohol. The varnishes are applied to the impression with 
a camel-hair brush. Each coat should be permitted to dry 
before applying another. The shellac varnish will penetrate 
and give a yellowish color to the plaster of the impression 
for °f an inch, which is a warning of the approach to the 
cast when cutting away the plaster impression. This may be 
seen in Fig. 62. If the plaster is not well colored, it should 
be given another coat of shellac, after which it is given one 
or more coats of sandarac varnish. The shellac penetrates 
and gives depth of color line, and the sandarac remains upon 
the surface and forms a glaze. 
Pouring the Impression.-This is a common term used for 
filling the impression. The term is slightly misleading in 
that it implies that the plaster mix is poured into the impres- 
sion. The plaster batter should be a little thicker than for 
an impression and a trifle too thick to pour. However, it 
must not be so stiff that it. will not flow perfectly over the 
surface of the impression when jarred by rapping the tray 
lightly upon the table. The same rule (as to the ratio of 
water and plaster) is used for casts as for impressions-that 
is, one measure of water and two measures of regular dental 
plaster. If the mix seems too thin, more dry plaster should 
be added until the mix will stand as placed. However, it 
must have a pronounced glossy or watery appearance, and 
when this characteristic diminishes it is evidence that either 
too much plaster has been added or that crystallization has 
commenced. The surface of the impression should be thor- 
oughly covered before this deadened appearance begins. 
The student should observe carefully the appearance of his 
plaster mixes, because the quality of the cast depends much 
upon the manipulation. An excessive amount of plaster 
added to the water or overspatulation interferes with the 
process of crystallization, thus causing increased expansion 
and reduced strength of the cast. 144 
CASTS 
Technic for Filling the Impression-The surface of the 
impression having been properly varnished while dry, it 
should then be immersed in water until bubbles cease to 
form, the plaster gauged, and smoothly and quickly mixed; a 
portion of the mix (about a teaspoonful) is placed upon the 
higher central portion of the impression and caused to flow 
into the lower portions of the intaglio by rapping the tray 
three or four times upon the plaster bench. Portion after 
portion of the mix is added and jarred into position until the 
intaglio of the impression is full, when the jarring ceases and 
the remainder of the mix is piled on and spread with the 
spatula until the plaster forming the cast is about one-half 
inch thick over the highest portion of the vault. 
Shape for a Plaster Cast.-For the sake of convenience it 
is well to adopt such a form as will be best adapted to the 
various uses to which a cast may be put. A suitable form 
not only favors and expedites future operations, but in some 
cases it affords additional strength. The form affording the 
greatest usefulness is the truncated cone. This form is 
easily given to the cast by inverting the tray while the 
plaster is somewhat soft and gently pressing it down upon 
any smooth surface, as a slab of marble, glass, or metal. If 
the base of the cast is formed upon any rigid material, the 
surface should be slightly oiled, to facilitate the removal 
of the plaster. (A convenient arrangement is to have a 
6-inch square block of wood covered with sheet zinc. This 
will need no oiling, for the sheet metal is flexible and will 
yield to pressure applied at the sides of the cast.) After 
the filled tray is inverted upon the smooth surface the plaster 
spatula should be passed about it, producing a smooth and 
symmetrical outline. The truncated cone form of an upper 
cast will not be a symmetrical truncated cone, for its base 
will be a parabola; and the lower one will be horseshoe- 
shape. Instructors are accustomed to direct that the base 
of a lower cast should be made solid (for strength) in place 
of a horseshoe-shape. It is better to sacrifice a portion of 
the strength of the lower cast for the convenience obtained 
in antagonization of the teeth. Fig. 63 illustrates properly 
formed upper and lower casts, CASTS FOR ARTIFICIAL DENTURES 
145 
Separating Cast from Impression.-There are three steps to 
this operation: (a) removing any plaster overhanging the 
edge of the tray, (6) removing the tray from the impression, 
and (c) removing the impression from the cast. 
A sharp plaster knife is used to cut away any overhanging 
plaster so that the outer edge of the tray is visible. 
Fig. 63 
If the impression is either wax or plaster, the outer surface 
of the tray should be slightly warmed over a Bunsen flame. 
The heat applied to the tray will soften the wax in contact 
with the tray, and the two may be easily parted. The plaster 
impression is as easily removed from the tray as a wax one, 
provided heat sufficient to soften wax is passed through the 
tray (Fig. 64). This is probably accomplished by slightly 146 
CASTS 
expanding the metal of the tray, and also by generating a 
small amount of steam between the tray and plaster, or at 
least the expansion of the moisture upon the surface of the 
impression next to the tray. A modelling compound impres- 
sion can be readily removed by rapping upon the outer sur- 
face of the tray. If the tray is of such shape that the two 
are dovetailed together, the rapping method may not suffice, 
and heat should be applied. This can be best done by 
placing it in a dish of cold water and applying slow heat. 
Care must be exercised not to apply too much heat or the 
modelling compound will be made very adhesive and will 
adhere both to the tray and cast. 
Fig. 64 
Separating the impression from the cast can be neatly 
done by the exercise of care. Wax should be slowly warmed 
over a soft flame, and modelling compound in water. Either 
material should be removed from the cast by lifting the outer 
portions and turning them over upon the central mass, when 
it is easily removed. While a separating fluid is not neces- 
sarily applied to wax and modelling compound impressions, 
nevertheless, if a thin coat of sandarac is dried upon either 
impression before filling, it does facilitate the removal of the 
impression material, provided it has been slightly overheated. CASTS FOR ARTIFICIAL DENTURES 
147 
Plaster impressions may be grouped into two classes to 
conform to as many procedures for separating them from 
their casts: (1) Flat impressions without undercuts. It is 
not necessary to remove these impressions from the tray, 
but by holding them with the cast downward and gently 
rapping upon the tray they will drop from the impression. 
(2) Prominent flaring processes. The plaster impression 
should be carefully pared away, with a sharp plaster knife, 
over the crest of the alveolar process, until the shellac line 
of demarcation is visible. The outer flange of the impression 
may then be flaked away. The remaining central portion, 
provided it is not keyed into place, may be lifted out. by 
inserting the point of the knife or a wax spatula under any 
convenient edge of the impression. Should the central 
portion not yield to reasonable force, it must be carefully 
notched along the median line, when first one-half and then 
the other may be pushed inward. 
Casts of Partial Cases.-The principle of construction of 
partial cases is the same as for full cases, but the technic 
varies to suit the conditions. Care must be exercised, in 
applying the separating fluid to the imprint of the teeth, that 
every portion may be thoroughly covered. This may be 
facilitated by applying an excessive amount of fluid, and 
using a rotary movement of the brush, or it may be applied 
with a pledget of cotton held in a pair of tweezers. While 
drying, the impression should be inverted so that any excess 
may not settle into the depressions of the impression. If 
the impression has been standing for a half-hour it should 
be dipped in water and the excess water shaken out just 
before filling. If the impression has been standing for sev- 
eral hours it should stand in water for three or four minutes 
before filling. This will aid the flow of the plaster and help 
to prevent air bubbles forming in the plaster of the cast. 
The filling plaster should be caused to flow down one side 
of the deep depressions (as the intaglio of the teeth), thus 
permitting the air to escape from the other. It is well also 
to have a tamping stick to press into the imprints of the 
teeth. (A small riveting hammer handle with the head cut off 
at the smallest part of the neck is an excellent tamper. Use 148 
CASTS 
either end as convenience requires.) Each added portion 
of plaster should be jarred into place. An excellent way 
used by many for strengthening isolated plaster teeth of a 
cast is, as soon as the intaglio of the tooth is filled with soft 
Fig 65 
Fig. 66 
plaster, to force into the center of each tooth, for its entire 
length, a pin or a small diameter |-inch wire brad. Much 
care is required in removing the impression from the cast. 
It must first be carved down to the shellac line of demar- 
cation before any attempt is made at breaking away the CASTS FOR ARTIFICIAL DENTURES 
149 
impression. Fig. 62 shows a plaster cast with the plaster 
about the isolated teeth carved ready for breaking away the 
impression. Fig. 47 shows the cast. 
Repairing Broken Casts.-Plaster casts may be broken 
accidentally. These may be nicely and strongly mended by 
uniting the sections with moderately thin, well-spatulated 
Fig. 67 
oxy phosphate of zinc cement. The sections should be 
supported until the cement has set sufficiently to be un- 
yielding to their weight. The cast should then be undis- 
turbed for at least a half-hour. If the cement is properly 
mixed and the portions of the cast are well pressed together 
the resulting union should be very strong. 150 
CASTS 
Base-plate Outline.-With a soft lead-pencil the outline 
of the periphery of the denture is traced upon the cast. 
Figs. 65 and 66 show the base-plate outlines for an upper 
and lower denture. 
These outlines represent average cases. In upper cases, 
difficult of retention, the palatal border should extend one- 
fourth inch or more backward; provided the impression is 
taken in such a manner that the soft tissues are held firmly 
against its bone foundation. The lower base-plate should 
always extend to approximately the external and internal 
(mylohyoid) oblique ridges; and in flat cases may extend 
slightly beyond these ridges, provided the edges are turned 
slightly upward. 
However, with the modern trend in the technic of im- 
pression taking and cast forming a definite outline is estab- 
lished, thereby dispensing with the pencil traced outline. 
Fig. 67 illustrates knives for cutting plaster. A is a com- 
mon form; B is a Wilson knife having a 2f-inch draw blade 
and a If-inch push blade; C is a saddler's knife. The sad- 
dler's knife is a powerful tool for trimming the base of casts 
only. It is used with a rocking motion. All plaster knives 
need frequent grinding, as plaster, and especially Spence 
compound, quickly blunts the edge. CHAPTER IV. 
OCCLUSION AND CONTOUR MODELS. 
Use.-Occlude, to strike against or close. This term is used 
to represent the teeth closed in their natural position of ease 
and rest. In this state the condyles of the mandible are in 
their normal retruded position in their glenoid mandibular 
fossae, except in a few cases of acquired abnormal condyle 
articulation. It is apparent that to construct an artificial 
denture much data, other than a cast of the jaw upon which a 
base-plate is to be worn, is necessary, in securing which the 
occlusion model is an important factor. This occlusion model 
is a mass of material roughly outlined, and indicating the 
normal (probably the natural) relation of the teeth and jaws 
while at rest. The term "contour" is added to the title to 
imply that the mass of material has been molded or carved 
to such a form as will give the desired contour to the external 
soft tissues of the lower third of the face. Therefore if this 
mass of material which we call the occlusion and contour 
model is truly a model pattern it must be accurately repro- 
duced in the essentials which it represents. However, this 
does not mean that the forms of the teeth should be carved 
in these models because the teeth are not to be made by the 
prosthetist (they may be obtained of the trade in much 
better form and strength than would be possible to produce 
in the dental laboratory); but it does mean that the lines 
indicated by the occlusion and contour models are to be 
permanently retained. This implies that thought and 
technic are to be employed in constructing these models. 
The student should have fixed in his mind the idea that the 
two primary objects of these models are to establish the 
position of the artificial teeth when at rest, and to give 
harmonious contour to the soft tissues covering the artificial 
dentures. In addition to these primary factors they are 
151 152 
OCCLUSION AND CONTOUR MODELS 
used to record other important data, such as the high and 
low lip lines, also the median line and the slit of the lips. 
Materials Used.-Wax and its combinations, modelling 
compound, resinous preparations, gutta-percha, and possibly 
plaster of Paris, may be named as the materials of which 
occlusion and contour models are made. These materials are 
used by the profession in the order named. The materials 
are attached to a base-plate, either a temporary one or 
the base-plate upon which the teeth are to be permanently 
mounted. 
Wax is most commonly used as well as most misused for 
the purpose under consideration. 
THE BITE. 
This term is generally used in connection with the use of 
wax for obtaining the relation between the jaws and teeth. 
The word bite is of Anglo-Saxon origin, and means "split;" 
hence it is used in the sense of cut, lacerate, take severe hold 
of, and similar ideas. As applied to dental technology, it 
means to cut into a mass of soft wax with the teeth or bare 
gums. The term is inelegant and unscientific, and except for 
a very limited use it is non-expressive and associated with 
pernicious methods. The term should never be applied to 
occlusion and contour models. The term wax-bite is known 
by several other inelegant terms, as mush-bite, quash-bite, 
hunk-bite, and like terms. They all refer to the common 
practice of placing a mass of wax in the mouth and requiring 
the patient to bite into it. To bite, cut: As in 95 per cent, 
of cases the upper incisors overlap the lower incisors, to bite 
or cut means to bring the lower incisors forward and in 
contact with the upper incisors, thus inviting the patient 
to do the thing that is the bete noir of the dentist in mount- 
ing artificial teeth. The first requirement in obtaining 
the desired relation between the jaws and teeth is that the 
mandible shall be in its most retruded position. There is 
but one class of cases where the prosthetist should ever use 
the quash-bite, and that is where there are two or more 
natural teeth that have the required occlusion, but not THE BITE 
153 
enough points of contact to support the casts while being 
attached to the articulated frames. If contour and other 
data provided by occlusion and contour models are not 
desired, then, and then only, may the quash-bite be used 
advantageously. As an illustration of an appropriate place 
to use a quash-bite, an imaginary case may be considered, 
consisting of a full lower natural denture and the six anterior, 
right first bicuspid and left second molar remaining in the 
upper jaw, the bicuspid and molar only in occlusion. Such 
a case would be the most favorable imaginable for casts 
with only two points of contact being self-sustained; and it 
is surprising to the student, no matter how he may have 
bolstered the casts with pieces of wax before mounting on 
the articulated frames, to find how much the finished den- 
tures may be off from perfect occlusion. This is easily 
understood when consideration is given to the points of 
contact as fulcra and the distant positions for the left first 
bicuspid and right second molar as ends of a lever. A very 
slight movement at the fulcra will mean relatively a large 
amount at the ends of the lever. A modification of this 
supposed case would be having the retained second molar 
upon the right side; it would then be evident that some 
means of establishing the relationship of the left side would 
be necessary. As a result of the consideration of these 
imaginary cases this rule may be established: All partial 
cases, unless they have three or more widely separated 
points of occlusal contact, require occlusion guides. Quash- 
bites may serve an excellent purpose as occlusion guides. A 
suitable quash-bite for the case just considered would be to 
form a crescent-shaped mass of soft wax of a little greater 
thickness than the space between the teeth of the lower 
jaw and the gum of the upper jaw, and having imbedded in 
it a 14-gauge soft-iron wire stiffener. This prepared mass of 
wax is placed just inside the anterior teeth, with the ends 
occupying the edentulous spaces. The patient is then in- 
structed to close and hold the teeth together firmly. The 
operator should press against the extruding wax, molding 
it firmly against the buccal surfaces of the teeth and gums. 
The patient is then instructed to open the mouth moderately 154 
OCCLUSION AND CONTOUR MODELS 
wide, when the operator should remove the wax with as 
little distortion as possible. It should then be made hard 
by placing in cold water, after which it is dried, trimmed 
of excess wax, and a small roll of soft wax placed in the 
imprint of the gums. It is then readjusted in the mouth 
and the mouth firmly closed upon it. This will correct any 
imperfections caused by manipulating the soft mass of wax. 
In using this wax occlusion guide care should be exercised 
to see that excessive portions of plaster or wax do not prevent 
the plaster casts going fully to place. Usually the casts or 
wax guides will require considerable trimming to permit of 
adjustment. 
Occlusion models require a well-adjusted base-plate. The 
base-plate of the artificial denture being permanently con- 
structed is the very best that can be provided for occlusion 
models. In fact, the best results can only be obtained in 
artificial dentures by first constructing the base-plate. This 
statement will invite disagreement, nevertheless the state- 
ment is tenable and will be demonstrated. However, where 
the single vulcanization method is to be employed in making 
an artificial denture, a temporary base-plate will necessarily 
be constructed for the occlusion model. There are several 
materials used for this purpose, as j^-inch thick sheets of 
wax, paraffin, modelling compound, gutta-percha and 
"ideal base-plate," and similar preparations obtainable at 
the supply houses. These preparations are composed of 
shellac or a similar substance. 
Methods for forming a base-plate of tin are used by a few 
operators, as swaging a base-plate of sheet block tin, and 
by burnishing tinfoil over the cast. Excellent results by 
the burnishing method may be obtained by the following 
technic: Adapt a sheet of No. 20 tinfoil to the plaster cast 
with the fingers and thumbs; the surplus is cut away with 
scissors, after which the tin is burnished with a steel or 
agate burnisher. Care should be exercised not to use suffi- 
cient force to mar the face of the cast. A second sheet is 
adapted to the burnished sheet by the fingers and thumbs, 
removed, and trimmed. A small dab of thick sandarac var- 
nish is placed upon the center of the burnished sheet when THE BITE 
155 
the second sheet is readjusted and burnished, beginning at 
the center and working outward. Layer after layer is thus 
added until the required thickness is obtained. After the 
first sheet of No. 20 is adjusted a heavier foil may be used 
if preferred. 
Paraffin Base-plate.-Paraffin is found in the supply houses 
in the form of thin sheets put up in half-pound boxes. It is 
usually called pink wax because of the color the manu- 
facturers have given it. This material is used by slightly 
warming it over a smokeless flame and adapting it to the 
plaster cast. The excess base-plate wax is trimmed away 
with a warm wax spatula at the indicated peripheral outline 
of the artificial denture. An excellent addition may be made 
to this paraffin base-plate by first adapting a sheet of tinfoil 
to the cast. This will prevent the paraffin, if overheated, 
from adhering to the cast, and also add some rigidity to the 
base-plate. The principal objection to wax or paraffin as a 
base-plate is that it is not rigid enough to retain its form 
while adjusting the occlusal model, and later the mounted 
teeth, to the mouth. For this reason some operators make 
this temporary base-plate of modelling compound, gutta- 
percha, or of the various resinous preparations offered for 
sale. The temporary base-plate having been formed over the 
cast, it is well to try it in the mouth and prove the correct- 
ness of its adaptation and peripheral outline. This is not 
very satisfactorily done with the less rigid base-plate, but 
with the permanent base-plates of vulcanite or metal it is 
a most important step in the procedure. Mention is made 
of this fact to impress the idea that the most commonly 
used method is the most unsatisfactory and unreliable one. 
The base-plate (when adjusted) is removed from the mouth, 
dried, and replaced upon the cast, a roll of softened pure 
yellow wax is molded over the ridge of the base-plate to the 
estimated length and fulness of the lip, when it is tried in 
the mouth and manipulated to the required contour. (The 
full details of contouring the occlusion model can only be 
properly considered under the subject of Esthetics, Chapter 
XVI.) The edge of the wax rim should come to, and thus 
indicate, the lip line. If the occlusion model is an upper one 156 
OCCLUSION AND CONTOUR MODELS 
to be adapted to a full lower artificial or natural denture, 
the occlusal border of the wax rim must be trimmed to 
evenly press upon the opposing denture. It is not necessary 
to trim so as to have perfect contact of the occlusal border, 
but there must be at least four well-spaced points of con- 
tact, then a small flattened roll of soft wax placed along 
the occlusal border and closed upon will make perfect con- 
tact. If the occlusion models are being formed for an upper 
and lower edentulous case, the occlusal border should 
represent the plane of the teeth (see Chapter I). This is 
accomplished by having the occlusal border of the upper 
model exactly at the slit of the lips and extending straight 
backward parallel with the imaginary line drawn from the 
base of the nose to the lower border of the external auditory 
meatus (Camper's line) or the line dividing the middle and 
lower thirds of the face (Fig. 1). 
Modelling Compound Technic.-The following description 
is a quotation from Dr. Charles R. Turner, in the American 
Text-book of Prosthetic Dentistry: 
"For the Upper Jaw.-To construct a bite-plate of modelling 
composition for the upper jaw, the cast should be placed 
upon its base on the work-bench with the distal portion 
toward the operator. The method of making the bite-plate 
in one piece proposed by Dr. W. W. Evans is to be recom- 
mended. Three-fourths of a cake of modelling composition 
is softened in warm water, kneaded in the hands until homo- 
geneous, and rolled into an ellipsoid about two inches long. 
One side of this should be thinned out by pressure between 
the fingers, and the mass so placed upon the cast that the 
thinned portion projects slightly beyond the posterior margin 
of the plate outline. By manipulation with the thumbs the 
remainder of the compound is gradually worked forward so 
that the vault of the cast is covered by it to the thickness 
of about of an inch. The thickness of this may be readily 
gauged, for the cast chills the material as it comes in contact 
with it, thus hardening it, while the overlying soft portion 
may be pushed forward. When the top of the alveolar ridge 
has been reached, the compound should be carried over it 
and slightly beyond the plate outline, along the labial and THE BITE 
157 
buccal surfaces, the most of the mass, however, remaining 
upon the ridge and being shaped to represent the occlusal 
portion of the bite-plate. The probable relation of this part 
of the artificial denture to the alveolar ridge and the prob- 
able fulness of the buccal and labial portions should be borne 
in mind and the compound disposed accordingly, since the 
bite-plate when completed should be a rough model for the 
denture in these particulars. It should be taken from the 
cast and its margin brought into close contact therewith 
around the plate outline. This is to insure firm retention 
of the plate in the mouth, which is of the greatest importance, 
and should be secured, even if it be necessary to make at this 
time the changes in the surface of the cast which provide for 
the adhesion of the future denture. The form of the bite- 
plate at this time is largely tentative, as it is purposed to 
complete its modelling when the bite is taken, in accordance 
with the requirements which shall then be indicated. During 
the process of forming the plate, to prevent adhesion, the 
hands should be wet and the compound occasionally taken 
off the cast to break up its adhesion while it is soft, and then 
replaced, but under no circumstances must the cast be wet, 
as this will injure it for subsequent use. Rubbing its surface 
with soapstone or talcum powder will effectually prevent the 
adhesion of the compound. 
" It is possible to construct the plate in two portions, that in 
contact with the mucous membrane being made of one piece 
of modelling compound rolled into a thin sheet and adapted 
to the cast, that representing the occlusal portion being 
formed of a roll bent to the shape of the alveolar ridge, and 
made to adhere by dry heat. The occlusal portion is made 
of wax by some practitioners because of the greater ease with 
which it may be carved, but its softness and tendency to 
yield under pressure make it less safe than modelling com- 
pound in preserving a fixed distance between the jaws. 
"The Lower Bite-plate.-The lower bite-plate is more easily 
made than the upper. With the cast face up on the work- 
bench, a piece of compound equal to about one-half of a 
sheet is softened and worked into a long uniform roll, bent 
to the shape of the alveolar process, and placed upon its 158 
OCCLUSION AND CONTOUR MODELS 
summit. With the thumbs and fingers it is worked down 
the lingual and labial sides to a point slightly beyond the 
plate outline, that portion over the ridge being shaped to 
represent this part of the future lower plate and made to 
correspond in outline to the arch of the upper bite-plate. It 
is removed and trimmed to the plate outline like the upper, 
its occlusal surface being left rough. If the lower plate must 
be very thin, it may be strengthened by imbedding in it a 
piece of iron or brass wire shaped to conform to the alveolar 
outline." 
Modelling Compound Base-plate.-The preceding method, 
as described by Dr. Turner, consists of forming the base- 
plate and occlusion model of one piece. Another method is 
to form the base-plate of a thin sheet of modelling compound 
and building up the occlusion and contour portion with 
yellow or pink wax. 
Technic.-The plaster cast is covered with a sheet of tin- 
foil or pattern tin, by adjusting the tin with the thumb and 
finger. It is not necessary to adjust the foil accurately, for 
the following step of adapting the modelling compound will 
perfectly adjust the foil. The modelling compound should 
be rolled or pressed into a sheet jV to of an inch thick. 
The sheet may be formed by rolling with a moistened wooden 
roller or pressing it with the fingers upon a warm plate 
of glass. The glass slab should be slightly lubricated with 
vaselin, or moistened with water, to prevent adhesion. The 
warm and pliable sheet of modelling compound is quickly 
and accurately adjusted to the plaster cast over the tinfoil, 
and trimmed to the peripheral outline of the desired plate. 
The tinfoil serves a double purpose; it renders easy the 
removal of the base-plate from the cast, and prevents soiling 
of the cast should the compound be overheated in any sub- 
sequent operation. Any portion of the modelling compound 
base-plate that may not be perfectly adjusted may be per- 
fected by passing repeatedly over the Bunsen flame and 
conforming with the fingers slightly moistened. 
Gutta-percha and the Resinoid Preparations.-These are 
obtained at the supply houses in sheets about /g of an inch 
thick. They are both manipulated in the same manner as THE BITE 
159 
the thin sheets of modelling compound, and will not need 
further description. 
Vulcanite Base-plate.-This form of base-plate is applicable 
only where there is considerable recession of the alveoli. 
It is apparent that a vulcanite base-plate must have con- 
siderable thickness for strength and rigidity; and admit of 
sufficient added material to attach the teeth and to give the 
indicated restoration without overdistending the supported 
soft tissues. 
The advantages of a vulcanite base-plate are: (1) It detects 
a faulty impression before much work has been done. (2) It 
permits study of the retention of the artificial denture. If 
it is evident that the impression was defective, or that the 
devised scheme for retention is insufficient, a new impression 
may be taken and the mistakes corrected without much loss 
of time and labor. (3) It gives stability and proper support 
to the subsequent operation of construction. 
The only disadvantage in the vulcanite base-plate, where 
it is indicated, is that the finished artificial denture has a 
portion of its substance vulcanized a second time. As rubber 
contracts every time it is vulcanized the revulcanized base- 
plate does necessarily slightly change form; however, it 
would be illogical to condemn the method for this reason 
unless repairing is unallowable. Some have thought that 
the re vulcanization of a portion of the denture weakened it. 
This cannot be, as the revulcanized portion is next to the 
fulcrum (gum) and the fracture must begin in the surface 
farthest from the fulcrum, that is, in the portion but once 
vulcanized. Further, the base-plate being re vulcanized is 
harder, more rigid and less flexible, hence is a firmer support 
for the superstructure. However, the student should know 
that it is essential that the heavy bearings of the base-plate 
upon the tissues must be properly located, and that there is 
danger of warping in the second vulcanization. This phase 
of the subject will be considered in the technic of double 
vulcanization. 
Vulcanite Base-plate Technic.-A suitably prepared cast 
of plaster of Paris or Spence plaster compound having been 
obtained, it is preferably (though not necessarily) overlaid 160 
OCCLUSION AND CONTOUR MODELS 
with a sheet of thin tinfoil, after which a sheet of slightly 
softened paraffin (pink wax) is accurately adjusted to the 
cast over the tin protection. The excess wax and tin are 
cut away at the previously indicated peripheral outline for 
the base-plate. A roll of yellow wax | inch diameter (made 
by rolling between two flat surfaces) is adapted by finger 
pressure to the labial and buccal periphery including the tub- 
erosities in the upper, but also extending the entire length of 
lingual periphery in the lower base-plate. The wax rim is 
pressed into place with the finger, but it is luted and carved 
with a warmed wax spatula and knife. This additional is not 
shown in Fig. 68, but the result is shown in Fig. 70. The technic 
of this wax rim is further described in the chapter on Alumi- 
num Base-plate (X). The advantages of the peripheral addi- 
tions are rigidity of base-plate, and a finish margin. The 
edge of the wax base-plate is then carefully sealed to the cast 
with a hot wax spatula. 
Fig. 68 
The cast and model base-plate is flashed in a Star or Snow 
flask, the flask opened, model base-plate removed, surface 
of the cast finished (either silex or tin), packed with rubber, 
flask closed, and the case vulcanized. After the vulcanization 
is complete and the vulcanizer cold, the base-plate is removed 
from the flask, cleaned of plaster, the edges filed, and the 
outer surface scraped to give a suitable surface for the attach- 
ment of the rubber at the time of second vulcanization. 
The inner surface, or the surface to rest upon the soft tissues 
should not be changed except to remove any excrescences 
produced by defects on the surface of the cast. Fig. 68 
shows a vulcanite base-plate. 
This outline sketch has introduced several laboratory 
processes, which will be discussed in their proper place. THE BITE 
161 
Metal Base-plates.-When an artificial denture is to be 
constructed upon a metal base, the base-plate is formed 
either by the casting or swaging method. It is obvious 
that the base-plate constructed as a component part of the 
finished artificial denture is the very best base-plate for the 
occlusion and contour models. Therefore the vulcanite and 
metal base-plates are to be much preferred to the temporary 
base-plates formed of wax or of the gum or resinous prepara- 
tions. 
The base-plate, of whatever material, having been adjusted 
to the mouth, the walls of the model are to be built up of 
either pure yellow beeswax, white wax, pink wax (paraffin), or 
modelling compound. Their rigidity is in the inverse order 
as named: The ease of manipulation is in the order given. 
The yellow wax is the least rigid, but because of its ease 
of manipulation it is most commonly used for building up 
the occlusion walls. The student should constantly bear in 
mind this one deficiency of yellow wax, although the material 
is commended to him because of its desirable properties for 
subsequent procedures. No matter, at this time, which 
material is selected, the material will be manipulated in the 
same manner, so far as construction is concerned. Having 
placed the base-plate on the cast, a cylindrical roll of the 
softened material of sufficient length to cover the crest of the 
alveolar ridge, and in diameter varying from | to f of an 
inch, according to the amount of space to be filled, is con- 
formed by manipulating with the fingers and thumbs to the 
ridge portion of the base-plate. The plastic material is luted 
to the base-plate by the use of a hot spatula. The labial and 
buccal surfaces are added to or carved away as may be 
necessary to give the required contour for the support of the 
lip and cheeks. This first shaping is entirely by guesswork; 
however, this is only to give it general form for trying in 
the mouth. 
The esthetic manipulation of the plastic material to the 
mouth will be treated of in the chapter on Esthetics. The 
occlusal surface of the plastic rim must be a perfectly flat 
surface, and as this edge forms the occlusal plane or teeth 
plane, it must be correctly located. The perpendicular 162 
OCCLUSION AND CONTOUR MODELS 
length of the plastic rim is indicated by the length of the 
lip, and is located by the slit of the mouth when the lips are 
perfectly relaxed and at rest. The slit of the lip marks the 
anterior border of the plastic rim, but from that point back- 
ward the length is indicated only by the naso-auditory- 
meatus line (see Chapter I, Fig. 1). The occlusal surface is 
carved from or added to until the required plane is obtained. 
The method of testing this wax plane is to place the occlu- 
sion model in the mouth, and a straight edge placed against 
the occlusal surface and extending 4 inches from the mouth 
Fig. 69 
will indicate whether the occlusal surface of the occlusion 
model is parallel with the naso-auditory-meatus line or not 
(Fig. 69). Should the student have trouble in carrying this 
naso-auditory-meatus line with his eye, he can stretch a 
string so as to include the two points named, thus ascer- 
taining whether the string and straight edge are parallel 
or not. A suitable straight edge may be formed of a thin 
sheet of metal, horn, or vulcanite. It should be 2 inches 
wide at one end and 6 inches long. After the correct occlusal 
plane has been established and any deficiencies noticed THE BITE 
163 
filled in, the occlusion model is pressed upon a flat surface 
with sufficient force to give a true even plane to the occlusal 
surface of the model. At all times, in using any force 
upon a base-plate, it should be upon the plaster cast, thus 
avoiding any possibility of warping. Prevention is always 
better than remedying. 
The upper occlusion model having been perfected, it is 
removed from the mouth and placed in cold water. 
The lower model is built up in the same manner as the 
upper and then adjusted to the upper in the mouth. The 
upper model is kept in cold water except during the few 
moments at a time that it is needed in the mouth while 
adjusting the lower. By keeping the upper model cold and 
rigid, all change resulting from closing the mouth will be in 
the softer, lower model. The lower model must be manipu- 
lated until it has a suitable vertical length, contour, and an 
even pressure upon the occlusal surface of the upper model. 
The occlusion models having been satisfactorily adjusted, 
they are removed and placed in cold water to thoroughly 
chill. 
The patient should be instructed regarding the next step 
of the operation, that is, retruding and protruding the chin. 
Often it will require considerable time and patience to 
educate the patient in placing the chin as requested. It is 
not necessary; in fact, it is better that the patient should 
not place the chin in the extreme protruded position. It 
should be placed in the extreme retruded position and be 
protruded at least one-fourth of an inch. A hand mirror is 
often an aid to the patient in learning to protrude and 
retrude the chin. If the patient does not readily do as 
requested, the operator may demonstrate with his own 
mouth the desired movements. The patient having become 
proficient in the exercise, the occlusion models are adjusted 
in the mouth. Should either of the models be refractory and 
not keep its place, it may be temporarily "glued" into place 
by sprinkling the inner surface with powdered gum traga- 
canth. 
The patient is requested to retrude the mandible and close 
the jaws; then to protrude and close. These instructions 164 
OCCLUSION AND CONTOUR MODELS 
being satisfactorily obeyed, the patient is requested to 
retrude the mandible, close the jaws, and hold the occlusion 
models firmly together. The head is then moderately tilted 
backward. The patient is requested to swallow. The act of 
deglutition necessarily places the mandible in the retruded 
position. 
As a further test that the condyle is at its normal retruded 
position the operator may place his fingers upon the anterior 
portion of the temporal muscles and request the patient to 
moderately pinch the wax occlusion models together three or 
four times. If there is distinct contraction of the anterior 
portion of the temporal muscle the condyles are in their 
normal rest position; but if the mandible is protruded there 
Fig. 70 
will be hardly a perceptible contraction of the muscle. The 
student may study the value of this diagnostic sign in his 
own person by noting the contraction when he compresses 
the molars and none when the incisors are in contact and 
compressed. 
While the occlusion models are thus firmly occluded, the 
lips are parted and the median line of the face is marked upon 
both models with a sharp instrument. 
The patient is requested to raise the upper lip as high 
as possible by muscular action. Then a horizontal line is 
made indicating the highest point at which the lip can be 
raised. The lower lip is depressed and the low lip line 
traced. The cheeks are distended and two perpendicular 
lines are drawn upon each buccal surface. These buccal THE BITE 
165 
lines must extend into both the upper and lower models 
and are used as location marks only (Fig. 70). There are 
now registered upon the occlusion models the length of the 
lips, the median line of the face, and the high and low lip 
lines. Besides these lines used in mounting the teeth, there 
are four buccal lines used in conjunction with the median 
line to properly assemble the models when out of the mouth. 
Condyle Path.-The next record to be made by means of 
the occluding models is the condyle path. By reference to 
Figs. 2 and 8, and Chapter I, it will be seen that there is a 
great variation of the condyle path, that the principal portion 
of the path is a straight and more or less oblique line, but 
if the mandible is protruded to its extreme position the con- 
dyle has described a " straightened out" letter S rather than 
a nearly straight line; therefore in taking this measurement 
the extreme protrusion is not desired, but one-fourth of an 
Fig. 71 
inch or a little more will include the portion required. It 
is obvious that if the condyle moves forward and glides down 
the eminentia articularis (articular tubercle), and the incisal 
portions of the occlusion models are brought together, the 
distal or molar portion of the occlusion models cannot be in 
contact; also that if a measure is taken of the forward move- 
ment of the mandible and of the separation of the distal 
portion of the models, sufficient data is obtained to reproduce 
the condyle path. These measurements are easily obtained 
with Dr. Snow's "bite gauges" (Fig. 71). The bite gauges 
consist of a small plate of metal with the under side so formed 
as to be easily attached to the occlusal surface of the lower 
wax model; the upper surface of the bite gauge carries a blunt 
metal spud. A bite gauge is mounted near each end of the 
lower model by wetting the metal and pressing it, flush into 
the occlusal surface of the model. The patients are told that 
when the lower model is replaced they are to protrude the 166 
OCCLUSION AND CONTOUR MODELS 
mandible and close the jaws until the incisal portion of the 
models are in contact. By this means the spud on top of the 
bite gauge will be forced part way into the occlusal surface of 
the upper model, thus in one operation marking the forward 
position of the mandible and the distal separation of the occlu- 
sion models. The lower model is removed from the mouth and 
the bite gauges carefully removed so as not to distort the 
marks made by them. At a future time these bite gauges 
will be returned to their place in the occlusion models and 
establish the condyle path. 
Fig. 72 
Snow Face Bow.-The remaining data to be obtained is the 
relation of the alveolar process of the maxilla to the condyles. 
This measurement is obtained by the Snow face bow, an 
invention of Dr. George B. Snow, of Buffalo, N. Y. The 
instrument consists of a bow-shaped bar of metal with a 
sliding condyle bar at each end, and at the center carrying a 
universal clamp and fork for holding the occlusion model. 
A and B are two forms of the fork or mouth piece (Fig. 72). 
Before attempting to use the face bow the outer tubercle 
of the condyle should be accurately located. By referring THE BITE 
167 
to the skull (Fig. 2, Chapter I), it will be seen that the man- 
dibular fossa in which the condyle rests is just in front of 
the external auditory meatus, that it is inclosed by the 
auditory process at the back, the distal end of the zygoma 
above, and the tubercle of the zygoma or articular tubercle 
in front. This fossa may be located by pressing with the 
finger upon the face of the patient about one-half inch in 
front of the tragus of the ear, and at the same time requesting 
the patient to widely open the mouth. The outline of the 
depression or fossa should be accurately located. By again 
referring to Fig. 2 it will be seen that the crest of the tubercle 
of the condyle, when in the retruded position, is a little in 
front of the center of the glenoid fossa. As the mouth is 
closed the tubercle of the condyle may be easily felt in a 
spare patient, but with much difficulty in a very fleshy 
patient. However, the fossa can always be detected and the 
location of the tubercle of the condyle closely estimated. 
It may be well to mark the location of the tubercle of the con- 
dyle upon both sides of the face. This may be done with a 
very soft-lead pencil or a small piece of court plaster. 
Face-bow Technic.-The fork of the face bow is removed 
from the clamp and the prongs of the fork sufficiently 
warmed to permit of their being inserted into the body of the 
upper occlusion model. The tail of the fork should be in the 
median line of the face and parallel with the imaginary 
extension of the occlusal surface of the model. A slight 
variation from the indicated location of the fork will be of 
no consequence, as the universal joint will accommodate itself 
to this. The face bow is adjusted to the face by sliding the 
condyle bars in so that an equal length of each is on the inside 
of the bow (the notched rings are a means for measuring), 
and the head of the condyle bars will rest firmly upon the 
tubercles of the heads of the condyles. There is sufficient 
spring in the face bow to aid in adjusting and supporting it. 
The condyle bars should be securely clamped in their adjusted 
position. The wax occlusion models are placed in the mouth 
in their normal retruded position, the universal clamp of the 
face bow is loosely placed over the tail of the fork, and the 
heads of the condyle bars are swung and sprung into position 168 
OCCLUSION AND CONTOUR MODELS 
upon the tubercles of the condyles. The bow is held in 
position by the left hand while the right hand fastens the 
universalelamp securely. The condyle bars should again be 
universal clamp securely (Fig. 73.) The condyle bars should 
again be inspected to see that they are properly located. 
Fig. 73 
While the patient is firmly holding the occlusion models, the 
lips are parted and if the models are properly occluded, as 
indicated by the median and four buccal lines, the models may 
be securely united by inserting Dr. Snow's (Fig. 74) four- 
Fig. 74 
Fig. 75 
pronged staple upon each side; or, steel belt lacings (Fig. 75) 
may be used. The condyle bars are drawn away from the 
face, the mouth opened, and the united models attached to 
the face bow removed. 
The order of the measurements just given is such as to THE BITE 
169 
economize the time of the patient; however, by reversing 
the order of measurements, a slight change of technic and 
detaining the patient longer will assure greater accuracy. 
The face-bow measurement is first obtained and the casts 
and wax occlusion models mounted upon the antagonizer. 
This procedure may be much expedited without detriment 
by adding an accelerator to the luting plaster. The wax 
occlusion models are then returned to the mouth with the 
bite gauges in place and the protruded or forward position 
of the condyle marked. 
The Christensen method of recording the condyle path 
consists of placing a small mass of softened wax at the ends 
of the lower occlusion model, in place of the Snow bite 
gauges. With either method the occlusion models are 
united with the four-pronged staples. The occlusion models 
are then returned to the antagonizer and it adjusted. 
Attention.-With either method for obtaining the condyle 
path equal pressure must be obtained at the regions of the 
molars and incisors. The danger is, that excessive pressure 
will be made at the molar region, and that the incisal por- 
tion of the lower occlusion model will be lifted from the 
gum, thereby recording a steep condyle when only a slight 
one exists. Test the relationship with aflat spatula. 
Resume and Observation.-The object of this chapter has 
been to differentiate between the wax-bite and the occlu- 
sion and contour models; also to teach their use and how to 
construct them. 
It should be observed that the wax-bite (often called the 
quash-bite) is very limited in its usefulness, that it is very 
inadequate for any purpose except as location guides for 
partial cases. The quash-bite used for constructing com- 
plete artificial dentures belongs to that class of short-cut 
procedures essayed by charlatans and ignorant persons. 
No operator with an intelligent conception of the anatomy 
and physics of mastication can place any confidence in such 
methods. It is true that the quash-bite has been very 
largely used in the past and is too much used today; never- 
theless it is an empirical method, and can never be asso- 
ciated with successful prosthesis. 170 
OCCLUSION AND CONTOUR MODELS 
It is apparent that the occlusion and contour models are 
the scientific and only practical method of gaining the 
necessary data for constructing useful artificial dentures; 
also that measuring instruments are necessary for obtaining 
data that can be acquired in no other way. In preceding 
sections of this chapter the Snow face bow for obtaining 
the relation of the alveolar processes of the maxilla to the 
condyle, and the bite gauges, for recording two points in 
the movement of the condyle in its path, have been pre- 
sented. Other important instruments are those of Prof. 
Gysi. 
GYSI MEASURING INSTRUMENTS. 
Prof. Alfred Gysi, of Zurich, Switzerland, gives a very 
lucid description of his instruments for measuring the con- 
dyle path,. the retruded position of the condyle, and the 
rotation points of the condyles, beginning with the January, 
1910, number of the Dental Cosmos. Since that time Prof. 
Gysi has extensively revised his theories and instruments. 
His latest work appeared in the 1913 Digest and through 
courtesy we are permitted to present the revisions. 
Fig. 76 shows the various instruments in knock-down, 
and the parts named. 
Fig. 77 shows the condyle path register attached to the 
lower wax occlusion model by means of the horseshoe plate, 
and the method of making the measurement. 
Figs. 78 and 79 show the method of completing the meas- 
urements of the vertical or condyle path. 
Fig. 80 shows the method of holding and using the lateral 
path register. With ground glass resting upon the vertical 
lead-pencils, the register is moved laterally to mark the 
starting- or resting-points. The patient is then requested to 
move the mandible repeatedly right and left. 
Fig. 81 and legend shows how to obtain the angle from the 
tracing on the ground-glass plate. 
Fig. 82 shows the incisor path register in place upon the 
upper wax occlusion model. 
Fig. 83 shows the tracings made of the incisal path upon 
the horseshoe plate. GYSI MEASURING INSTRUMENTS 
171 
Fig. 76.-The Tarts are as follows: Nos. 1-2, upper and lower parts of articular frame which carry the upper 
and lower model bows; Nos. 1 A and 2 A, upper and lower model bows; Nos. 3-3, straight incisor guide pin 
and curved incisor guide pin. The curved pin is used only when mounting models or setting anteriors; No. 3 A, 
small pin for all set screws; Nos. framework of condyle path register; Nos. 4 A-J^ A, pencil holders 
and pencils of condyle path register; Nos. 5-5, lateral path register; Nos. 6-6 A, stand and gooseneck for 
holding condyle path register and models; No. 7, horseshoe plate; No. 8, degree plate for measuring inclinations of 
paths; No. 9, incisor path register. 172 
OCCLUSION AND CONTOUR MODELS 
Fig 77.-The forward and downward movements of the condyles are 
recorded by the horizontal pencils of the condyle path register. The ends of 
the pencils are placed opposite the' condyle heads, a card is held against the 
face with its lower edge parallel with the broad plate of the register, and the 
mandible is caused to exercise its different movements. The movements 
of one condyle at a time are thus recorded. 
Fig. 78.-Shows the mode of measuring the angle formed by the condyle 
path and the lower border of the recording card. Fig. 79.-Shows the completed measurements of the condyle path 
Fig. 80 174 
OCCLUSION AND CONTOUR MODELS 
Fig. 81.-Lateral condyle paths recorded and strengthened. Line 
drawn from "resting point" in one path to "resting point" in the other, 
and perpendiculars erected at these points. Angles may be measured with 
the little plate used for measuring forward paths. 
Fig. 82 
Fig. 83 GYSI MEASURING INSTRUMENTS 
175 
Fig. 84 shows the horseshoe plate, with its tracing of the 
incisor path register in black wax, mounted upon the lower 
wax occlusion model, and their assemblage for obtaining the 
tracings. 
Fig. 84 
The casts, occlusion models, and measurements are now 
ready for their respective antagonizors. CHAPTER V. 
ARTICULATORS AND ANTAGONIZORS. 
Definition.-Articulator is a name applied to apparatus 
of many designs. Of these many designs it may truly be 
said that a few are good, that a few others are bad, but that 
the most of them are indifferent. Unfortunately the name 
is a misnomer, but it is so universally used that it seems a 
useless expenditure of time to more than explain the anomaly. 
The term is used in the anatomical sense, and means "a 
joint," hence the instrument can only rightly be termed an 
articulator because of its hinge joint, not because of the 
operation for which it is designed. The instrument is used 
to assemble artificial teeth in occlusion, and they should be 
in antagonization. The operation for which the instrument 
is intended is to occlude and antagonize the teeth and not 
to articulate the teeth, as is usually stated, for teeth, both 
natural and artificial, can articulate only upon their proxi- 
mate mesial and distal surfaces; but not upon their occlusal 
surfaces. The name "articulation" for assemblage of the 
teeth is a misnomer, therefore it is absurd to name the instru- 
ment in conformity with the misnamed operation. 
Under the general term " articulator" two distinct types of 
instruments are included, the simple hinge-joint class called 
articulator (Fig. 85), and the class which make a pretense 
of imitating the temporomandibular articulation called 
anatomical articulator. Hereafter in this book when the 
hinge-joint type is referred to it will be called occlusion 
frame, and when the other type is meant it will be called 
the antagonizor. 
Occlusion Frame.-An occlusion frame is a dentist's 
apparatus to secure the open and shut arrangement of 
artificial teeth. 
176 HISTORY 
177 
Antagonizor.-An antagonizor is a dentist's apparatus to 
secure anatomical and mechanical arrangement of artificial 
teeth. 
History.-Guerini gives credit for the original invention 
of this device to J. B. Gariot, about 1805. Many forms of 
the apparatus have since been devised, a few of which are of 
historical interest because they denote professional thought 
and endeavor. 
Fig. 85 
August 28, 1840, Daniel T. Evans, of Philadelphia, 
obtained a patent for an apparatus having slot and pin 
joints, by means of which, as he expressed it in his speci- 
fications, "the lower plate is allowed a motion at the joints 
similar to that which is admitted by the condyloid processes 
of the living subject" (Fig. 86). 
In 1858 Dr. W. G. A. Bonwill, of Philadelphia, invented 
his instrument. He presented the instrument and his 
studies of anatomical antagonization before the American 
Dental Association at Niagara Falls, N. Y., in 1864. Dr. 
Bonwill may be justly called the father of anatomical antago- 178 
ARTICULATORS AND ANTAGONIZORS 
nization and antagonizors because of the volume of research 
work and writing he did upon the subject. Undoubtedly 
his genius has inspired all later work in this field of endeavor 
(Fig. 87). 
In 1889 Dr. Richmond S. Hayes, of East Bloomfield, N. Y., 
received a patent for an antagonizor which embodied at 
least one new feature. He probably was the first to attempt 
to reproduce the downward motion of the condyle. Prof. 
Fig. 86 
Gysi says, speaking of the "forward and downward slope": 
"This fact had previously been noted by two anatomists- 
Luce, of Boston (1889), and Count Spee (1890)-but their 
work remained unknown to dentists for some years." It 
will be noticed that the earlier date given by Prof. Gysi is 
the same as of the patent paper of Dr. Hayes. 
The Walker antagonizor (Fig. 88): Dr. George B. Snow, 
of Buffalo, in his paper published in the Dentist's Magazine, HISTORY 
179 
July, 1907, says: "In 1896 Dr. W. E. Walker, then of Pass 
Christian, Miss., now of New Orleans, obtained a patent upon 
an antagonizor constructed in much the same manner as the 
Bonwill, but with adjustable joints for imitating the direction 
of the condyle path. Dr. Walker is the first one who clearly 
recognized the fact that there was a considerable variation 
in the inclination of movements of the condyle upon the 
Fig. 87 
articular tubercle. He obtained another patent upon 
an instrument by which the inclination of the condyle path 
could be ascertained. This he called a 'facial clinometer.' 
But he also lost sight of the second condition of the problem, 
the correct location of the casts in the antagonizor. Dr. 
Walker made a close study of his subject, and his papers, 
published in the Cosmos for 1896 and 1897, are well worth 
reading. They are, in fact, nearly exhaustive so far as they 180 
ARTICULATORS AND ANT AGON 1ZORS 
go, and he is entitled to great credit, much more than he has 
received for their presentation." 
In 1899 Dr. A. De Witt Gritman, then of Buffalo, but now 
of Philadelphia, and Dr. George B. Snow introduced the 
Gritman antagonizor and the Snow face bow. 
In 1901, in Ash's Quarterly, and the Cosmos for October, 
1905, Prof. Carl Chistensen describes his antagonizor. In 
the paper previously referred to, Dr. Snow says: "He 
Fig. 88 
(Prof. Christensen) showed at that time his simple and prac- 
tical method of ascertaining the inclination of the condyle 
path, and transferring it to the antagonizor, thus taking the 
last step necessary for the full solution of the problem of the 
correct antagonization of full dentures. But he did not 
recognize the importance of correctly locating the casts in the 
antagonizor, and in the one which he constructed, which 
much resembles that of Dr. Walker, he unfortunately HISTORY 
181 
designed it so that the casts cannot be placed near enough 
to the joints." 
In the Transactions of the Odontological Society of Great 
Britain, 1903, J. B. Parfitt described his antagonizor with 
its curved condyle path constructed for each case. This 
instrument required that the ascertained condyle path for 
each individual case be cut out of a sheet of metal and 
clamped to the jaw of the antagonizor. 
In 1907 Dr. George B. Snow introduced the New Century 
Antagonizor (Fig. 89). This instrument is built upon the 
lines of the Gritman. The frame is higher arched and 
therefore more open at the back than its predecessor. It 
Fig. 89 
has each bow secured with two set screws. The instrument 
is provided with an extra pair of bows, the lower of which 
is extra long and the upper bayonet-shaped, thus accommo- 
dating any thickness of casts. The straight upper bow has 
a sleeve for marking its position, so that it may be removed 
and returned at will. The position of the lower bow is 
registered by the plaster securing the lower cast. It has 
straight-slotted adjustable condyle paths, and metal spuds 
for obtaining the inclination of the paths. The central 
spiral clamping spring is effectual and convenient. There is 
an extension of the slot pin for supporting the face bow. 
The face bow accessory of this instrument has been described 
(Chapter IV). It is a simple, well-constructed, and effectual 182 
ARTICULATORS AND ANTAGONIZORS 
instrument. It reproduces most of the essential movements 
of the mandible. 
Fig. 90 is the Gysi adaptable antagonizor assembled and 
each part named. 
When the antagonizor is used without the help of the 
measuring instruments it is important to place all casts 
so that the occlusal plane is exactly parallel to the table on 
which the antagonizor stands, as the degree scales are 
Fig. 90 
founded on a corresponding horizontal plane. It is also 
important to have the front of the casts at an equal distance 
of 10 cm. from the rear supporting pins, thus forming a 
Bonwill triangle. 
Fig. 91 is the Gysi Simplex, which is a simplified form 
of the Adaptable Antagonizor. 
Fig. 92 is the improved form of the Snow New Century 
Antagonizor. It is designated the "Acme." This instru- 
ment is provided with the Bennett lateral mandibular move- HISTORY 
183 
ment; also, it has the incisal guide pin, a very valuable 
attachment upon any antagonizor. 
Fig. 91 
Fig. 92 184 
ARTICULATORS AND ANTAGONIZORS 
Fig. 93 is the new Hall Antagonizor. It is constructed 
upon an entirely different principle than any other instru- 
ment herein shown. 
Fig. 93 
MOUNTING 
How Mounted.-The two types of instruments under con- 
sideration are for distinct operations. The antagonizors may 
be used as an occlusion frame, but the occlusion frame 
cannot be used as an antagonizor. The operation of occlusion 
is a simple one, while that of antagonization is complex, 
and includes occlusion as one of its factors. 
The occlusion frames are designed to hold the plaster casts 
in a fixed position, but for convenience of mounting the 
teeth upon either cast, the other should be removed suffi- 
ciently to give finger room for manipulation; hence the 
instrument is provided with a hinge joint, thus permitting MOUNTING 
185 
removal without loss of relationship. As the instrument is 
designed to hold the casts in a fixed position, it can make 
no difference in what position the casts are mounted in the 
frames, so long as the position is convenient for manipulation. 
Usually the incisor section of the casts are placed at the 
front, but in some partial casts it may convenience the work- 
man to place the bicuspid section to the front; the relation- 
ship of the casts, however, will be the same. 
The antagonizors being designed to hold the casts and 
mounted teeth in many positions, it is necessary that the 
casts shall be definitely and accurately located; therefore 
specific instruction is required for occlusion frames as a 
class, and each antagonizor; however, of the antagonizors the 
Snow and Gysi only will be further considered in this chapter. 
Mounting upon Occlusion Frames.-The plaster casts and 
wax-bite, or occlusion and contour models, as may be had, 
are assembled and united with a little melted wax. These 
are placed upon the lower part of the occlusion frame, the 
upper part is adjusted with the set screw so that it will be 
just free of the upper cast, and the set screw is fixed with 
the jam nut (Fig. 85). The casts are united to the frame 
with a soft mix of plaster; however, if the plaster casts have 
been standing a few hours so as to become dry, they should 
be saturated with water just before mixing the attaching 
plaster. Some of the soft-mixed plaster is placed upon a 
slightly oiled surface; any convenient substance, as glass, 
marble, metal, wood, a piece of paper, or, sheet celluloid (best), 
may be placed upon the work bench and the plaster placed 
upon it. The occlusion frame containing the casts is placed 
on the soft plaster and firmly pressed into place. The upper 
portion of the occlusion frame is raised, soft plaster placed 
upon the upper cast, and the raised portion of the frame 
pressed firmly into it. The soft plaster may be smoothed by 
trowelling with the plaster spatula (Fig. 28). If the casts 
have been made unnecessarily thick it may be necessary to 
trim them down, otherwise it may be difficult to adjust them 
in the occlusion frames. 
Mounting upon the Snow Antagonizor.-The antagonizor 
is prepared for the case by adjusting the set screw and 186 
ARTICULATORS AND ANTAGONIZORS 
making firm its jam nut, so that the bows are parallel to 
each other. The bows are then adjusted to give the necessary 
space to insert the assembled casts and models. This is 
accomplished by sliding the lower bow either up or down and 
using either the straight or bayonet-shaped upper bow, as 
may be required to accommodate the case. The lower cast 
should be so trimmed that the occlusal surfaces of the wax 
models shall be parallel with the lower bow. The case being 
mounted without the face bow, the assembled casts and 
models should be centrally located, with the portion repre- 
senting the mesial incisal angle of the lower central incisor 
teeth four inches from either condyle joint. The assemblage 
is then united with plaster as described for occlusion frames. 
Mounting with the Face Bow.-The set screw with its jam 
nut having been fixed as described in the preceding paragraph, 
assembled casts, occlusion and contour models, and face 
bow, as described in Chapter IV, are ready for mounting 
in the antagonizor. The condyle bars of the face bow are 
pushed in to their limit and made fast with their jam nuts. 
The head of each condyle bar has a depression which fits 
over the extended slot pin. The heads of the condyle bars 
are adjusted to the antagonizor by springing the face bow 
sufficient to permit the heads to slip over the slot pins. The 
lower cast rests on the lower bow; however, the cast must 
not be attached to the lower bow until the occlusal surface 
of the occlusion model is parallel with the horizontal portion 
of the lower bow. This relationship of cast and bow may be 
secured either by trimming the cast (which is rarely neces- 
sary), or by pushing in or pulling out the lower bow. The 
lower bow being adjusted, it is secured with its set screws. 
Either the straight or bayonet-shaped upper bow is adjusted 
as may be necessary to clear the upper cast. The casts 
are then made fast to the bows with plaster as previously 
described (Fig. 94). The plaster luting having thoroughly 
hardened, the face bow is removed. The remaining step 
is to secure the inclination of the condyle path. Loosen the 
condyle clamps so the slotted condyle bars may move freely, 
unhook the spiral spring, readjust the bite gauges. (See 
Chapter IV.) The bite gauges being adjusted in both wax MOUNTING 
187 
Fig. 94 
Fig. 95 
Fig. 96 188 
ARTICULATORS AND ANTAGONIZORS 
Fig. 97 MOUNTING 
189 
models and the incisal portion of the wax models in contact, 
the slotted condyle bars must assume their respective posi- 
tions, when they are firmly clamped (Fig. 95). The bite 
gauges are removed and the spiral spring attached (Fig. 96). 
A modification of this method consists in first mounting 
the casts and wax occlusion models upon the antagonizor 
with the face bow, then returning the wax occlusion models, 
mounted with the bite gauges (or small balls of soft wax- 
Christensen method) to the mouth and obtaining the meas- 
urements of the condyle paths. The retention spring of the 
antagonizor is released and the condyle path clamps loosened 
when the wax occlusion models are returned and the condyle 
paths adjusted. 
Mounting upon the Gysi Antagonizor.-Fig. 97 shows the 
Adaptable Antagonizor with the condyle path register used 
as a face bow, mounted upon the stand with the goose- 
neck, ready for attaching the cast to the upper "model 
bow" with plaster. The illustration is self-explanatory. 
Mounting upon the Hall Antagonizor.-The method of 
mounting the casts, occlusion and contour models upon the 
Hall Antagonizor is described in Chapter VI in the portion 
devoted to the Hall instrument and method. (See Figs. 142, 
143 and 144.) CHAPTER VI. 
RUBBER AND VULCANITE.1 
Rubber.-India rubber, or caoutchouc. 
Vulcanite.-A chemical compound of caoutchouc and 
sulphur. 
CAOUTCHOUC. 
History.-Caoutchouc is a native Indian name. India 
rubber is a name given the material because its early use 
in Europe was to remove black-lead pencil marks from paper. 
Dr. Priestley, the distinguished discoverer of oxygen, men- 
tions this use in a publication of 1770. Caoutchouc must 
have been known in America at a very early period, because 
balls made from the gum of a tree, lighter and bounding 
better than the wind-balls of Castile, are mentioned by 
Herrera when speaking of the amusements of the natives 
of Haiti, in his account of the second voyage of Columbus. 
In a book published in Madrid, 1615, Juan de Torquemada 
mentions a tree which yields it in Mexico, describes the 
mode of collecting the gum, and states that it was made 
into shoes. More exact information was furnished by a 
French Academician, who visited South America in 1735. 
While the Indians used it more than three hundred years 
ago for water bottles and gum shoes, it was only used in 
the United States and Europe for erasing pencil marks, 
until about 1820, when it was applied to water-proofing 
cloth. As caoutchouc became hard and brittle in cold 
weather and sticky in hot weather, many experiments were 
made to overcome this objectionable quality, which resulted 
in the discovery of vulcanite in 1843. 
1 The history, physical and chemical properties of rubber and vulcanite 
are taken from the author's chapter in Turner's American Text-book of 
Prosthetic Dentistry; however, much enlarged upon in this edition. 
190 CAOUTCHOUC 
191 
Physical Properties.-Caoutchouc is a hydrocarbon pre- 
pared from a watery milky emulsion called "Latex," which is 
procured from the bark of many tropical and semi-tropical 
trees. In a few instances the latex is in the wood as well as 
in the bark. 
Scientists are not certain of the physiological function of the 
latex, but it has been suggested that it may be a reserve food 
material, to provide a protection against bark injury, or it 
may be a waste product of plant metabolism. 
The latex, which is obtained by making incisions in the 
bark, consists of an emulsion of rubber globules in a watery 
fluid. The size of the globule or caoutchouc cell varies from 
0.5 to 3 microns. The cell has very much the appearance 
of an ameba; is mobile and moves with considerable rapidity 
in its watery medium. 
The rubber cells are coagulated by heat and smoke (the 
native Para method); boiling; natural drying; diluting with 
water; and treating with acids. The acid treatment (acetic 
and citric) is in general use in plantation rubbers. 
Porritt1 states that the method of coagulation and the 
quantity of reagent appear to be important factors in deter- 
mining the quality of the resultant rubber. He also states 
that " It is a remarkable fact that Para rubber, produced by 
a primitive process in the Amazon Valley, should be superior 
to that prepared under careful scientific control and super- 
vision from the same species of tree in Asia." It is also note- 
worthy that the best quality of Para gum may be kept for 
years without "perishing" (a technical term denoting oxida- 
tion). This keeping property is undoubtedly much favored 
by the creosote in the smoke used in coagulating the gum 
from the latex. Gums coagulated by other processes may 
spoil in a few months, owing probably to the action of both 
bacteria and oxidation. Some of the vulcanized rubbers 
behave in a similar manner, that is, perish with age. Here 
the problem without doubt is further complicated by the 
1 Chemistry of Rubber, by B. D. Porritt, B.Sc. (Lond.), F.I.C. Pub- 
lished by D. Van Nostrand Company, New York, 1913. 192 
RUBBER AND VULCANITE 
filling agents used, also by the method and degree of vulcani- 
zation. 
In the Amazon Valley there are over three hundred varie- 
ties of rubber-yielding trees, shrubs, vines and plants. The 
most highly valued latex producers are the Heveas of the 
Amazon Valley. There are thirty or more varieties of the 
Heveas, and "Hevea Braziliensis" is considered the finest 
quality. The term Para rubber is a commercial term, and is 
applied to the best grades of the Amazon Valley gum. Other 
commercial terms are Plantation; Ceara Scrap; Java; Amazon 
Ball; Para Negrohead; Assare Scrap; etc. Para is the port 
on the Amazon River from which the gum is exported. The 
name "Plantation" designates the rubber procured from 
cultivated gum trees. The other names refer to locality and 
peculiarities of the gum. The crude gum as it is found upon 
the market is not a pure article, but contains from 2 to 60 
per cent, of the following ingredients: (1) resins; (2) nitrog- 
enous bodies, proteins, peptones; (3) carbohydrates; (4) 
inorganic matter. They may contain also dirt, bark, sand, 
introduced mineral matter, moisture, and free acid. The 
removal of the impurities and the resultant loss of weight 
is a very important commercial item. The plantation gum 
has the lowest percentage of loss in purification, therefore is 
the more profitable to the manufacturer. 
The pure caoutchouc is a colorless transparent substance. 
It has no definite melting-point, but from 150° to 200° C. it 
becomes a viscous liquid which does not solidify again. At 
approximately 126° C. it goes into a viscoid state which 
hardens again on cooling; this temperature is usually spoken 
of as its fusing-point. It is a typical member of a class of 
bodies called colloids. Its density has been given as 0.900. 
Another series of samples of plantation rubber yielded values 
varying from 0.9097 to 0.9261. The gum is insoluble in water 
or alcohol, and is not acted upon by alkalies or acids, except 
when the latter are concentrated and heat is applied. It is 
soluble in ether, chloroform, bisulphide of carbon, naphtha, 
petroleum, benzol, and the essential oils, and in many of the 
fixed oils by the aid of heat. CAOUTCHOUC 
193 
Porritt gives the following list of mixing materials as in 
common use: 
Accelerators of Vulcanization.-Litharge; calcium hydrate; 
magnesium oxide or carbonate. 
Colored Fillings.-Antimony; arsenic or mercuric sulphides; 
lead peroxides; ferric oxide; chromic oxide; lead chromate 
(cold cure); ultramarine; Prussian blue (cold cure); graphite 
and lamp-black. 
Colorless Fillings.-Whiting; barium sulphate; lithophour; 
French chalk and zinc oxide. 
Organic Fillers.-Paraffin wax; pitch; rosin; tar; old vul- 
canite (as crumb and dust). 
Porritt further states that there are but three explanations 
of the union of caoutchouc and sulphur: 
(a) A solidified solution of one substance in another. 
(6) An absorption of one material by another. 
(c) Chemical union. 
The theory of solidified solution is entirely discredited. 
The absorption theory by Ostwald, published in 1910, has 
not been substantiated; while the chemical theory of C. Otto 
Weber, published in 1903, has, according to Porritt writing 
in 1913, the preponderance of evidence in its favor. 
Purifying.-In the manufacture of India rubber the first 
operation is the purification of the crude material. The 
impure rubber is cut into minute shreds and is washed by 
powerful machinery immersed in water, which releases the 
solid impurities. The washed gum is then placed on iron 
trays and dried in a room heated by steam. The material 
then undergoes a process of kneading under very heavy rollers 
which causes the adhesion of its various pieces to each other 
and ultimately yields a mass or block of India rubber so com- 
pact that all air-holes, other cells, and interstices disappear. 
Chemistry of Caoutchouc.1-India rubber, as is well-known, 
is the product of the coagulation of the milky juice of a 
large number of trees, creepers, and shrubs. The com- 
1 The writer uses as his authority for this paragraph and the subsequent 
ones upon the Chemistry of Vulcanite, "The Chemistry of India Rubber," 
by Carl Otto Weber, Ph.D., published by Charles'Griffin & Co., Limited, 
London; J. B. Lippincott Company, Philadelphia, 1903. 194 
RUBBER AND VULCANITE 
mercial article can hardly be expected to be homogeneous, 
and still less a pure product in the chemical sense. Besides 
accidental impurities of sand and fragments, it contains a 
greater or less amount of oily and resinous matter, which 
varies greatly even in the same brand of rubber. Para 
rubber contains from 1 to 2 per cent.; Logus rubber from 
3 to 7 per cent.; Borneo rubber from 6 to 21 per cent.; and 
African flake may contain as high as 64 per cent. Lascelles- 
Scott gives the composition of a brand of unnamed origin: 
Per cent. 
India rubber (gum) 
37.13 
Albumin 
2.71 
Resins 
3.44 
Essential oils 
traces 
Sugar 
4.17 
Mineral matter 
0.23 
Water 
52.32 
The pure Para gum consists of soluble and insoluble 
portions, the latter averaging about 3.5 per cent. The 
soluble portion has a formula of CioHi6, and is the portion 
with which the sulphur combines to form vulcanite. The 
formula for the insoluble portion is CsoIIesOio. 
VULCANITE. 
History.1-Charles Goodyear, of New Haven, Conn., dis- 
covered the process of curing or vulcanizing India rubber 
in 1843. Thomas Hancock, of England, has been credited 
with making this discovery contemporaneously; but his 
own writings state that he had seen small samples of Good- 
year's work, and that after much experimenting he pro- 
duced the same thing; so the priority of the discovery 
undoubtedly belongs to Goodyear. 
On January 30, 1844, a patent was granted to Charles 
Goodyear for making soft or flexible rubber that would resist 
the action of the usual solvents of caoutchouc, and would not 
1 This historical sketch of vulcanite is made up largely from the mono- 
graph, "Instruction in Vulcanite," by Prof. E. Wildman, M.D., D.D.S., 
Philadelphia; Samuel S. White, 1867. VULCANITE 
195 
be affected by cold or heat if the temperature were not raised 
above the vulcanizing-point. The mixture he preferred was 
caoutchouc, 25 parts; sulphur, 5 parts; and white lead, 7 
parts. This produced soft vulcanite. 
The process of making hard rubber was patented by 
Nelson Goodyear May 6, 1851. His formula consisted of 
one-half pound of sulphur to a pound of caoutchouc and 
one-half pound of any one of a long list of earthy substances. 
A patent was granted to Charles Goodyear, Jr., "For 
improvement in plates for artificial teeth," dated March 4, 
1855. He says: "The best compound I believe to be one 
pound of India rubber or gutta-percha (or of the two com- 
bined in suitable proportions) with a half-pound of sulphur, 
together with a suitable quantity of coloring matter. To 
obtain a suitable color, I mix with caoutchouc or gutta- 
percha, vermilion, oxide of zinc, oxide of iron, or any coloring 
substance that will stand the necessary degree of heat with 
the action of sulphur. This compound, after having been 
molded, is subjected to heat for about six hours, and in so 
doing I gradually raise the heat to about 230° F., say in 
half an hour, and then, unless there be a considerable quantity 
of foreign matter present, the heat may be raised, quickly 
as may be, to about 295° F.; otherwise, I raise the heat more 
slowly and keep the compound at about that temperature for 
the remainder of the six hours, and then allow the whole to 
cool down, when the process will be completed." 
A patent was granted in June, 1857, to H. H. Day for 
vulcanizing very thick pieces of rubber. To accomplish this 
he explains that he mixes with the matter prepared for vul- 
canization a substance that will prevent its becoming spongy 
or cellular, by absorbing the sulphur gases as fast as gener- 
ated. The material which he proposed to employ for this 
purpose is ordinary fire clay, but other substances capable 
of absorbing the gas may be employed. 
In Austin G. Day's specification we find some interesting 
remarks upon the nature of rubber compounds. In contra- 
distinction to Nelson Goodyear's hard and inflexible sub- 
stance, he claims his compound to be a hard, but highly 
elastic material obtained by a process differing from that of 196 
RUBBER AND VULCANITE 
N. Goodyear's in the length of time, in the degree of heat, in 
the proportion of the ingredients, and in the mode of equal- 
izing the temperature. 
Day's composition is one pound of purified Para rubber 
and one-half pound of sulphur. 
lie remarks: "In the vulcanizing process there is elimi- 
nated during the whole operation a constant discharge of 
sulphuretted hydrogen and other sulphuretted gases, which 
must have means of escape through the pores of the mass 
while being vulcanized. By my present improved manage- 
ment of the heat in vulcanizing, by raising it very gradually, 
step by step, to the highest point, 1 am enabled to vulcanize 
pieces of an inch or more in thickness with great uniformity 
and perfection. A mixture containing earthy matter may 
be vulcanized in much shorter time than one consisting of 
caoutchouc and sulphur alone, and yet be solid, owing to the 
earthy matter facilitating the escape of the gases generated 
in its substance during the process. At the same time such 
compositions are destitute of elasticity and flexibility. For 
a piece five-eighths of an inch thick, the time required for 
vulcanizing is thirteen and one-half hours: 
It is held at 275° F., for 6 hours 
Then raised to and held at . . . . 280° F., for 3 hours 
Then raised to and held at . . . . 290° F., for 2 hours 
Then raised to and held at . . . . 295° F., for 2 hours 
Then raised to and held at . . . . 300° F., for J hour" 
Composition of Vulcanite for Artificial Dentures.-As the 
formulae of the various makes of rubber are "trade secrets" 
of the manufacturers, our knowledge is limited to the general 
specifications of patent papers and the writings which detail 
the experiments of Prof. Wildman and others. 
Both the soft pliable and the hard flexible vulcanite are 
used in the construction of dentures. The essential com- 
ponents of vulcanite are caoutchouc and sulphur, the ratio 
varying according to the use for which the product is de- 
signed. All other ingredients are for coloring, controls, or to 
cheapen the product. 
The soft pliable variety used in dentistry is known as 
velum rubber, because its most important use is for vela VULCANITE 
197 
for cleft palates. It contains sulphur to the extent of about 
one-fifth of the weight of the gum. Hard vulcanite, some- 
times called ebonite, contains by weight one-half as much 
sulphur as caoutchouc. 
Some of the formulas given by Prof. Wildman are: 
Caoutchouc 48 parts = 66| per cent. 
Sulphur 24 parts = 33 3 " 
Dark Brown. 
Red. 
Caoutchouc 48 parts =44.44 per cent. 
Sulphur 24 parts = 22.22 " 
Vermilion 36 parts =33.33 " 
Caoutchouc 48 parts =42.76 per cent. 
Sulphur 24 parts = 21.38 " 
White oxide of zinc .... 30 parts =26.78 " 
Vermilion 10 parts =8.90 " 
Dark Pink. 
Caoutchouc 48 parts =28.57 per cent. 
Sulphur . 24 parts = 14.28 " 
White oxide of zinc .... 96 parts =57.14 " 
Grayish White. 
Black. 
Caoutchouc 48 parts =50 per ecnt. 
Sulphur 24 parts = 25 
Ivory black, or drop black . . 24 parts =25 
Jet Black. 
Caoutchouc 48 parts =40 percent. 
Sulphur 24 parts =20 " 
Ivory black or drop black ... 48 parts = 40 
The S. S. White Dental Mfg. Co., have standardized their 
rubbers by using the following formulary for all rubber except 
pink and white: Gum, 50 per cent.; sulphur, 16 per cent.; 
dyes and fillers, 34 per cent. This formula provides a ratio of 
three to one of gum and sulphur, and the other formula? 
given have a ratio of two to one. A ratio of gum four parts 
to one of sulphur produces a vulcanite on the border-line 
between hard and soft vulcanite, while the ratio of five of 
gum to one of sulphur is typical soft or velum vulcanite. 
Scientists state that CioIIi6S2, or sulphur 32 per cent., is 198 
RUBBER AND VULCANITE 
the highest combination of caoutchouc and sulphur that has 
been produced; therefore the slight excess of sulphur in the 
two to one mixture, and any sulphur not chemically com- 
bined serves only as a filler. The reduced quantity of sul- 
phur in the S. S. W. new rubbers is the explanation for their 
increased toughness. 
Any dentist can make a comparison of the toughness of 
various brands of rubber by vulcanizing a strip of each of 
the rubbers to be tested under the same conditions, and 
observe the degree of flexion required to break them, also 
note the character of the fracture. 
It is questionable if the usual dental methods for vulcan- 
izing ever combine all of the sulphur in the rubber mixture 
without producing an over hard and brittle vulcanite. 
If pure caoutchouc is burned, there should be but about 
3 per cent, of dark ash remaining. Sulphur and vermilion 
(mercuric sulphide) leave no ash, hence the percentage of 
ash from rubber containing these materials should be less 
than 3 in the ratio of the amount of these materials to 
the caoutchouc. Some rubbers leave as high as 60 per 
cent, of ash. It wrould be reasonable to suppose that the 
strength would be reduced in ratio to the amount of the ash, 
but this is not true, as the pure gum and sulphur produce the 
strongest vulcanite; the red and black are nearly the same 
strength, although the black rubber will leave a much larger 
ash than red, because the coloring matter is animal charcoal 
composed largely of phosphate and carbonate of lime, 
while the mercuric sulphide would be entirely volatilized. 
The oxide of zinc and other earthy matter in the pink and 
white rubbers have a very deleterious effect upon the flexi- 
bility and tenacity of the vulcanized rubber, so much, in fact, 
that these light-colored vulcanites are not one-fourth as 
strong as the brown, red, or black. 
Physical Properties of Vulcanite.-Vulcanite is hard, 
flexible, elastic and horn-like in texture. Dr. George JI. 
Snow gives the specific gravity of a specimen of black vul- 
canite as 1.1974, and that of the same piece before vulcani- 
zing as 1.1333. The specific gravity varies, as it is much VULCANITE 
199 
affected by the coloring matter, and is also increased by 
the temperature and time of vulcanization. Caoutchouc 
expands upon heating. Dr. Snow says: "Rubber expands 
by heat more rapidly than any other solid body. Its rate of 
expansion at ordinary temperature, from 70° to 90° F., is 
over six times that of iron, about five times that of brass, 
and nearly four times that of zinc, which is the most suscep- 
tible to expansion by heat of any of the metals except mercury. 
Its rate of expansion is known to increase as the temperature 
rises, but it has not been definitely determined." In vul- 
canizing soon after chemical action begins (248° F.), expan- 
sion ceases and shrinkage commences, the latter being much 
affected by the contained foreign matter, by a high or low 
temperature, and by a long or short time of vulcanization. 
Its increased specific gravity is due to this shrinkage.1 
The usual solvents of caoutchouc have but little action 
upon vulcanite, and no agent which can be tolerated in the 
mouth has any action upon it. It is susceptible of a high 
polish. It is very opaque, and therefore does not imitate 
well the appearance of the mucous membrane. It is a very 
poor conductor of thermal and electrical changes, in con- 
sequence of which it is not conducive to the health of the 
tissues upon which it is worn. If well vulcanized it is ex- 
ceedingly dense, but may be made porous by careless manip- 
ulation. Great care should be used in vulcanizing rubber 
that is to be worn in the mouth, and the patient should be 
thoroughly instructed in cleansing it. 
New rubber can be added to old vulcanite by reheating; 
hence vulcanite dentures can be easily repaired. It is 
unnecessary to add a solution of rubber to vulcanite to aid 
in its repair, as the solvent has no action upon the vulcanite, 
only leaving a thin layer of soft rubber upon the roughened 
vulcanite; attachment is better accomplished by heat and 
pressure. 
I Dr. Snow has made a very fine and proper distinction in the two words 
-contraction and shrinkage. Contraction is the antonym of expansion; 
and shrinkage is a permanent reduction in form. Shrinkage takes place 
while the rubber is under continued heat and the chemical change is taking 
place; whereas contraction takes place with the cooling process only. 200 
RUBBER AND VULCANITE 
These terse statements of the physical properties of vulcan- 
ite may profitably be amplified. 
Specific Gravity.-The specific gravity of vulcanite varies 
with its composition and method of vulcanization. The 
following table is sufficiently extensive to elucidate these 
facts. Pure Para gum has a specific gravity of 0.915, and 
sulphur a specific gravity of 1.95; therefore velum rubber 
containing 1 of S and 5 of gum should have a specific gravity 
of 1.06; also, hard vulcanizable rubber containing 1 of S and 
2 of gum should have a specific gravity of 1.26. The table on 
page 201 gives four representative dental rubbers, with the 
coloring matter named in the first column and the specific 
gravity of a specimen of each in the second column. The 
third column gives the specific gravity of each vulcanized 
under a Lewis gas regulator set at 320° F. for one hour and 
twenty minutes. The fourth column gives the specific 
gravity of the rubbers vulcanized at the same time as the 
specimens in the third column, but they were not flasked; 
they were wrapped in tinfoil and submerged in the water. 
The second column shows a great variation in the specific 
gravity of unvulcanized rubbers due to the various coloring 
materials; the third column shows a still greater variation 
due to the quantity and conductivity of the coloring material; 
also this column shows the coloring material exerts a direct 
influence upon the denseness of the vulcanite, as shown 
by the increased specific gravity. The pure black vulcanite 
was increased in specific gravity 0.0496, the red vulcanite 
0.0853, and the gold dust 0.0622; therefore gold dust shows 
a condensation over the pure black equivalent to a specific 
gravity of 0.0126, and the red over the black of 0.0357. 
The fourth column shows remarkably the action of the heat 
and its conduction upon the vulcanizing process. The tin 
and water being far better conductors of heat than the 
plaster investment, the red and gold-dust vulcanite show a 
further increase of specific gravity, while the pure black 
shows a decrease of specific gravity to the extent of 0.0008 
less than the unvulcanized rubber. This is explained by the 
poor internal conductivity of the pure black and the rapid 
induration of the surface. VULCANITE 
201 
This increasing condensation suggests the question: Does 
re vulcanization cause shrinkage? It does. This was 
demonstrated by revulcanizing six times (under the con- 
ditions described in the preceding paragraph) a piece of 
red vulcanite 66.3 mm. long. Each time revulcanized it 
was carefully measured and showed an average decrease of 
0.25 mm.; or, approximately, 0.5 per cent, for each vulcani- 
zation, that is, a total of 3.2 per cent, of its length for the 
six revulcanizations. 
Table of specific gravity. 
Coloring 
material. 
Before 
vulcanized. 
After vulcani- 
zation in 
flask. 
Vulcanized 
in tinfoil, not 
flasked. 
Para caoutchouc 
Sulphur 
Mercuric sulphide 
Smoke 
0.915 
1.95+ 
8.2 
Velum rubber (Doherty's) . . 
Smoke 
Less than 
1.0 
Less than 
1.0 
Pure black rubber (Doherty's) 
Drop black 
1.1523 
1.2019 
1.1515 
Bow spring (White's) .... 
HgS 
1.6410 
1.7263 
1.7421 
Gold dust (Traun's) .... 
Aluminum 
powder 
1.1321 
1.1943 
1.1972 
Dr. Snow states graphically the relative expansion of 
vulcanite and certain metals. Other authorities give the 
coefficient of expansion as follows: 
Cast iron - . . . 0.0000055 
Zinc . : . 0.0000140 
Mercury 0.0000998 
Vulcanite 0.0000636 
Thus it is seen the authorities (Heil and Esch and Thorpe) 
for these figures make the expansion of vulcanite more than 
four times as much as for zinc, the most expanding of the 
solid metals. 
Text-books state that rubber expands until vulcanization 
begins and then shrinkage takes place. This is true. The 
author devised a special vulcanizing apparatus for demon- 
strating the expansion and shrinkage of vulcanization. It 
consisted of a brass flask open at the top and a plunger 
cover with a hole through which a thermometer is placed 
in contact with the rubber. The flask is placed in an open 
receptacle filled with glycerin nearly to the top of the flask 202 
RUBBER AND VULCANITE 
A two-pound weight is placed upon the plunger cover, also 
an upright making connection with a recording needle which 
enlarges ten times. Heat is applied by an electric heater. 
Red rubber was placed in the flask and the following record 
obtained: From room temperature to 200° F., one-eighth 
inch, and from 200° to 250° F., one inch. The needle 
remained stationary for a short time, then dropped back 
one-eighth inch and so remained until the end of vulcani- 
zation (320° F., 1 hour), after which it moved back about 
three-sixteenths inch. As both rubber and sulphur melt at 
approximately 250° F. and vulcanization begins at 248° F. it 
is evident that expansion continues until the ingredients are 
melted and union begins, and that the combined shrinkage 
and contraction is greater than the expansion, as shown by the 
increased specific gravity in well-vulcanized rubber. How- 
ever, the improvised recording vulcanizer did not record 
perfectly the shrinkage of vulcanization because the indurat- 
ing rubber had greater resistance than the weight applied. 
The shrinkage took place within, in the direction of least 
resistance, thereby forming several large spaces. There was 
no evidence of gas formation associated with these spaces as 
so evident with porous vulcanite when " something has gone 
wrong." 
A practical application of these physical properties cannot 
be made until after a study is made of the chemistry of 
vulcanization, to which attention is now given. 
Chemistry of Vulcanization.-Vulcanization consists of the 
chemical union of caoutchouc and sulphur, probably pro- 
ducing a series of compounds having the formula CioHi6S2 for 
the highest combination, and CiooHi6OS for the lowest, with 
a series from the lowest to the highest. 
Vulcanization can be brought about either by the cold or 
the hot process, and by using with the latter either the dry 
or the wet method. The essential requisite is to secure the 
union of the sulphur with the polyprene (CioHi6). 
The cold process is by the use of sulphur monochloride, 
and is only suitable for very thin layers of rubber, being, 
therefore, not applicable for dental use. An attempt has 
been made to sell to the profession office rights for the use VULCANITE 
203 
of a porcelain enamel for facing vulcanite dentures. This 
method was based upon the cold vulcanization process. 
While the results were an improvement upon ordinary 
pink rubber, the product lacked the translucent effect of 
fused porcelain, its durability was uncertain, and the process 
was long and tedious. 
Mr. Weber, in the work previously referred to, says: "We 
turn our attention first to the question of the general action 
of sulphur upon India rubber at high temperatures. The 
sulphur bath method might appear from several points of 
view the most suitable method of studying this question, 
but after a number of attempts I abandoned it in favor of 
the method of subjecting carefully prepared homogeneous 
mixtures of Para rubber with a definite amount of sulphur 
to the action of heat. Again, in this case we have the choice 
of several methods of heating, but the one of heating pieces 
of Para mixture of uniform thickness to vulcanizing tem- 
peratures when immersed in water appeared to me the most 
satisfactory, as it involves the minimum of loss of sulphur 
by evaporation. 
"The experiments were carried on with strips cut from a 
calendered sheet, 3 mm. in thickness-a mixture of 100 
parts of Para rubber with 10 parts of pure precipitated 
sulphur. These strips were vulcanized in a phosphor-bronze 
digester. 
" The digester is provided with a thermometer tube 
(thermometer in mercury), a pressure gauge, and a blow-off 
valve. In the digester a porcelain beaker is suspended so 
that it is clear of the bottom. The digester is filled to about 
one-quarter of its capacity with water; the beaker is com- 
pletely charged with water, and a number of the strips to 
be experimented upon immersed in it. The digester is then 
closed, rapidly heated to the required temperature, and 
maintained thereat, either by carefully adjusting the gas 
burner, or by means of some form of thermoregulator. At 
regular intervals one of the strips is withdrawn after blowing 
off steam and rapidly opening the digester, which is then 
immediately closed again to continue the series. The time 
error caused by these successive withdrawals does not 204 
RUBBER AND VULCANITE 
exceed four minutes per sample. Of course the water lost 
by the blow-off steam is from time to time made up with 
boiling water. 
"The strips thus withdrawn are marked, and subsequently 
cut into very fine threads, which are freed from every trace 
of uncombined sulphur by extraction with acetone in a 
Soxhlet extractor. The greatest care was employed to render 
this operation perfect, every sample being subjected to a 
three days' continuous extraction. The extracted samples 
were dried in a current of carbonic acid in the water oven, 
and, until analysis, were preserved in carefully stoppered 
glass tubes. 
Temperature of vulcanization. 
Duration of 
120° C. 
125° C. 
130° C. 
135° C. 
140° C 
vulcanization. 
s.% 
S.% 
S.% 
S.% 
S.% 
30 mins. 
0.71 
0.71 
0.99 
1.76 
60 
1.18 
1.32 
1.44 
2.17 
90 
u 
1.31 
1.67 
2.04 
2.36 
120 
« 
1.62 
1.91 
2.32 
3.92 
5.07 
150 
U 
4.02 
180 
« 
1.78 
2.11 
2.94 
4.18 
6.05 
240 
« 
1.93 
2.22 
5.00 
5.50 
300 
2.25 
2.35 
5.27 
6.74 
360 
« 
2.60 
3.80 
5.82 
6.88 
420 
3.71 
4.04 
6.04 
6.97 
480 
cc 
3.94 
4.31 
6.33 
7.13 
Vulcanization of Para Rubber. 
"About one gram of each of these samples was used for 
analysis. The sulphur determinations were all, without 
exception, carried out by Carius' method, as the results by 
the much simpler and more expeditious method proposed by 
Henriques were found to be liable to an error approaching 
0.1 per cent, in magnitude. In this manner the result 
obtained were as detailed in the table above. 
"These figures amply suffice to demonstrate indisputably 
the fact, even quite recently again denied, that the vulcani- 
zation of India rubber with sulphur involves the chemical 
combination of these two substances, at any rate so far as 
the vulcanization of Para rubber is concerned. 
"That different brands of India rubber behave very 
differently in the vulcanization process is a well-known VULCANITE 
205 
fact, but what we know at this moment respecting the 
composition and chemical relationship of these different 
brands entitles us to assume that, although their behavior 
under vulcanization may not be identical with the Para 
rubber, it will be more or less closely analogous to it." 
Following this, Mr. Weber gives a tabulation of his experi- 
ments with Upper Congo, Beni Uiver, Ceara, and Borneo 
rubber for the same duration of vulcanization and for 125° C. 
and 135° C. He then sums up these experiments thus: 
"The extremely interesting results here tabulated remove 
all doubt that the vulcanization of India rubber is a chemical 
process resulting in the formation of a polyprene sulphide. 
The rate at which the sulphur enters into combination with 
the India rubber hydrocarbon (polyprene) is characteristic 
for each brand of India rubber. Some of the above series 
were repeatedly investigated, always with the same result. 
"There arises now, of course, at once the question as to 
the nature of the process by which sulphur enters into com- 
bination with the polyprene, whether the polyprene sul- 
phide or sulphides formed are addition or substitution 
products. Certainly what we already know respecting the 
chemical nature of India rubber leads us to infer that the 
vulcanization process consists essentially in the formation 
of an addition product of sulphur and polyprene. This 
assumption, however, requires support in view of the fact 
that quite a number of writers, from Payen to most of the 
recent authors, declare that vulcanization is accompanied 
by the evolution of hydrogen sulphide, thereby implying 
that the process is a substitution and not an addition pro- 
cess. Indeed, most of the recent authors on this subject 
state this in so many words. We shall therefore have to 
subject this point to a careful examination. 
" Assuming the compound of polyprene and sulphur, which 
indisputably forms in the vulcanization process, to be a 
substitution product, it follows with absolute necessity 
that for each 32 parts of sulphur combining with the poly- 
prene, we must obtain 34 parts of hydrogen sulphide. Now, 
in the process of vulcanization as practically carried out, we 
obtain on an average a product containing, say, 2.5 per 206 
RUBBER AND VULCANITE 
cent, of combined rubber. Consequently the vulcanization 
of one ton of India rubber, on the above assumption, would 
be bound to yield very nearly 60 pounds of hydrogen sub 
phide, or approximately 18,000 liters. Considering that 
in a number of factories the amount of India rubber vul- 
canized daily largely exceeds one ton in weight, we should 
expect to find the vulcanizing rooms of these factories 
reeking with gas. As a matter of fact, however, there is 
scarcely ever a trace of this gas to be discovered in the 
rubber works' atmosphere, and the very rare cases in which 
its presence becomes noticeable may always be considered 
as an indication of something having gone wrong. 
"In the vulcanization of 'hard rubber' goods (ebonite, 
vulcanite) faint but distinct traces of hydrogen sulphide 
are generally, perhaps always, observable, but they could 
not be ascribed to the vulcanization process proper-the 
combination of polyprene with sulphur-which process, if 
it consisted in the substitution of hydrogen for sulphur, 
should cause a perfectly torrential evolution of hydrogen 
sulphide, seeing that hard rubber contains at least 20 per 
cent, of combined sulphur. 
"It is therefore certain that if hydrogen sulphide forms 
at all in the vulcanizing process, its amount is utterly inade- 
quate to support the assumption that the process of vulcani- 
zation is a substitution process. 
"Laboratory experiments on this question lead to exactly 
the same conclusion. If the experiments are carried out 
with technically pure Para rubber under conditions abso- 
lutely precluding the escape of any gaseous product of the 
reaction, very minute traces of hydrogen sulphide may some- 
times be observed; but in a considerable number of carefully 
devised experiments with highly purified Para rubber no 
hydrogen sulphide at all could be detected. 
" If, on the other hand, the 'insoluble' part of India rubber 
is mixed with sulphur, and this mixture is subjected to a 
vulcanizing temperature, say about 135° C., a considerable 
evolution of hydrogen sulphide takes place, due to the for- 
mation of a substitution product of this insoluble body, 
C3oH680io, with sulphur. This substitution process certainly VULCANITE 
207 
proceeds much slower than the vulcanization process of 
India rubber (polyprene). Under the same conditions of 
temperature and the time under which polyprene forms a 
vulcanization product containing 4 per cent, of sulphur, the 
above-named insoluble constituent forms a substitution 
product containing at most 0.7 per cent, of sulphur. 
"From these facts we are justified in drawing the following 
conclusions: 
"1. The India-rubber hydrocarbon, polyprene (Ci0H16), 
combines with sulphur without evolution of hydrogen 
sulphide. The vulcanization process of India rubber is, 
therefore, an addition process. 
"2. The insoluble constituent of India rubber, which 
forms only an insignificant proportion of the technical prod- 
uct, not exceeding 5 per cent, of the total, combines with 
sulphur under vulcanizing conditions at a very slow rate, 
with evolution of hydrogen sulphide and with the formation 
of a substitution product. 
"The above conclusively settles the question regarding 
the general chemical aspect of the vulcanization process, 
but it confronts us with the further question respecting the 
quantity of sulphur combining with India rubber in this 
process, as well as the more intimate structure of the com- 
pound thus formed." 
Interesting and instructive as the work of Mr. Weber is, 
the limits of this chapter will not permit us to follow him in 
detail, but only to give his conclusions: 
"The process of vulcanization consists in the formation of 
a continuous series of addition products of polyprene and 
sulphur, with probably a polyprene sulphide, CiooHi6OS, as 
the lower, and CiooHi6OS2o as the upper limit of the series. 
Physically this series is characterized by the decrease of 
distensibility, and the increase of rigidity, from the lower 
to the upper limit. Which term of the above series, that is, 
which degree of vulcanization is produced, is in every case 
only a function of temperature, time, and the proportion of 
sulphur present. 
"As a chemical reaction the vulcanization process is not 
influenced by the physical state of the India-rubber colloid; 208 
RUBBER AND VULCANITE 
but the physical state of the India-rubber colloid while 
under vulcanization largely determines the physical con- 
stants of the vulcanization product." 
From the above we conclude that dental vulcanite is 
essentially polyprene disulphide having the symbol CioHi6S2, 
which contains 32 per cent, of combined sulphur. 
How to Vulcanize Rubber.-Having learned that rubber 
expands excessively in heating up to the vulcanizing tem- 
perature and shrinks during vulcanization; also that its in- 
duration is the result of a chemical combination of the poly- 
prene and sulphur, and that a small amount of hydrogen 
sulphide may be formed, but that it is in nowise an essential 
factor of vulcanization; and further, that there is a diversity 
of opinion as to how rubber should be vulcanized, the author 
instituted the following experiments as a means for establish- 
ing a rational method for vulcanization: 
A glass marble 31.5 mm. in diameter wag ground so as to 
form two parallel flat surfaces 25 mm. apart. This was 
used as a model and flashed in a vulcanite flask with French's 
regular dental plaster. Five of these molds were made 
and excess spaces cut approximately three-sixteenths inch 
about the mold, but without gateway connections. No. 1 
was filled with bow-spring (representative of the best rub- 
bers) rubber, the flask closed and held firmly together 
in a Donham clamp (Fig. 102), and vulcanized under the 
Lewis gas regulator set at 320° F. for one hundred minutes. 
It was not removed from the vulcanizer until it normally 
cooled to room temperature. The flask had opened approx- 
imately an eighth of an inch. The specimen was sawed 
through the center of the flat surfaces and disclosed a dense 
rim of approximately 4 mm. thickness, a finely spongy 
interior, and emitted a strong odor of hydrogen sulphide. 
The cross-section measured 28.2 mm., that is, had increased 
in size 3.2 mm. Mold No. 2 was treated in every way the 
same as mold No. 1, except it was vulcanized for three 
hours. It presented the same general aspect except darker 
in color, and measured but 26.6 mm.; a shrinkage of 1.6 
mm. (or one-half the amount of expansion, of No. 1) due to 
the eighty minutes' additional heat. Mold No. 3 was filled VULCANITE 
209 
in like manner, but bolted firmly together with three bolts, 
and subjected to heat the same as No. 1. The flat surfaces 
of Nos. 1 and 2 specimens were not distorted, while No. 3 
was slightly convex. The plaster investment was more or 
less crushed and compressed, as shown by the surface of 
the rubber; the internal appearance was the same, but it 
had expanded to a diameter of 28.6 mm., showing great force 
in the expansion. Mold No. 4 was filled in like manner, 
tightly closed in a Donham clamp and vulcanized slowly; 
that is, the Lewis gas regulator was set at 280° F. for one hour, 
at 290° for forty minutes, and at 300° for two hours. The 
section of this specimen showed evenly dense vulcanization 
throughout its mass, but excessive shrinkage. At the per- 
iphery of the flat surface it measured 23.4 mm., and at the 
center 22.2 mm. Thus showing a difference of 6.4 mm. in 
thickness of the specimens, due to the methods of applying 
heat. Mold No. 5 was filled with two thicknesses of red 
rubber upon one side and the balance filled in with a good 
quality of plain pink rubber. This was placed in the Donham 
clamp and the Lewis regulator set at 320° F., for ninety 
minutes. There was slight excess rubber forced out, but no 
distortion of the flat surfaces. The section measured 25 mm., 
and showed but slight porosity at its center. 
Fig. 98 shows graphically the model and five vulcanite 
specimens. 
Fig. 98 
The rationale of these experiments is arrived at by a study 
of the physical and chemical properties of the ingredients. 210 
RUBBER AND VULCANITE 
The essential constituents of dental rubber are caoutchouc 
and sulphur, both exceedingly poor conductors of Jieat, 
fusing between 239° F. and 250° F., and begins to combine 
chemically at 248° F. Both constituents expand excessively 
by heat, but their mixture begins to shrink with chemical 
union, and continues shrinking indefinitely under vulcan- 
izing heat. 
It is a physical law that: Force of expansion by heat is in 
the ratio to the denseness of the substance. Therefore 
the force of expansion of solids and liquids is very great 
while that of gaseous substances is comparatively small. 
It is evident that the small amount of hydrogen sulphide 
formed in the vulcanization cannot account for the great 
force generated, but that it is due to the expanding dental 
rubber; further, it is evident that it is not the expansion of 
the melted dental rubber, as chemical union and condensation 
begin with liquefaction; therefore perfect vulcanization 
requires a suitable control of the expanding dental rubber 
and the shrinkage in the forming vulcanite. (This cannot 
be accomplished in bolted flasks.) 
The relatively large mass of rubber used in these experi- 
ments introduces no constant, but the magnitude makes 
the phenomena appreciable while a smaller mass would not 
be so readily comprehended. In these experiments (Nos. 
1, 2, and 3) the surface of the rubber was rapidly raised to 
320° F., causing the surface to expand and harden much 
in advance of that within. As the heat advanced more and 
more, expansion was taking place and a thicker and denser 
surface of vulcanite was forming until there was no more 
rubber to expand; and, as the forming vulcanite shrinks 
a vacuum must be created; because the internal melted 
dental rubber must contract in the direction of least resist- 
ance. 
The finely porous condition within is undoubtedly due 
to the formation of II2S. Why hydrogen sulphide should 
be formed is unknown to the writer, but it is quite possible 
the vacuum enabled the heat attained to decompose the 
hydrocarbon and the elements to combine with the sulphur VULCANITE 
211 
to the extent of filling nature's abhorred vacuum. At 
least it is an evidence, as Mr. Weber has said, that something 
has gone wrong. Mr. Weber, as previously quoted, has 
demonstrated that in vulcanizing highly refined rubber 
ingredients, under suitable conditions, no gas is formed. 
Further, the writer has demonstrated this fact by careful 
weighing before and after vulcanization, and found there 
was no loss of weight; whereas if a part of the substance 
had been dissipated as gas there would have been a loss 
of weight. Specimen 4 demonstrates that if the temperature 
is slowly raised to the high vulcanizing-point the resulting 
vulcanite will be dense and perfectly vulcanized through- 
out, but there will be excessive shrinkage. However, 
this does not prevent the expansion due to heating up, as 
both extreme specimens were subjected to the same heat 
during the expanding period. The low temperature of 
280° F. permits but slight hardening of the rubber, and this 
throughout the entire mass, then raising the temperature 
10° F. at a time permits a continuous even vulcanization 
with all the shrinkage toward the center; whereas in rapid 
vulcanization (specimens 1, 2, and 3), the shrinkage is 
toward the indurating peripheral portion. Specimen 5 
introduces another constant, that is, dental rubber heavily 
loaded with oxide of zinc, fuller's earth, or other inert 
material. 
These materials used in dental rubber as a color con- 
stituent act as a control of the properties of expansion, 
shrinkage, and contraction; however, these materials so re- 
duce the strength of dental rubber that such rubber should 
never be used when strength is required. It should be used 
only as a facing and for bulk. 
Summary for Practical Vulcanization.-1. A Spence plaster 
compound cast is necessary. 
2. All wax model dentures should be reduced to the re- 
quired thickness, and preferably encased in tinfoil. 
3. The case should be flasked with a good dental plaster, 
excess space encircling the mold, but no gateways. 
4. The flask being well warmed, but not above 212° F., 212 
RUBBER AND VULCANITE 
is evenly packed with red or black rubber, or a combina- 
tion of the two. In no place should the high-grade rubbers 
be more than 4 mm. in thickness (danger thickness). All 
space not filled with the not to exceed 4 mm. layer of red or 
black rubber is to be filled with pink rubber. A layer of 
pink rubber should be used over the labial and buccal surfaces 
for esthetic purposes. 
5. The flask may be cautiously nearly closed under 
pressure, but the final closure is in the vulcanizer under 
the spring. Bolts and rigid flask presses are dangerous. 
6. A spring should be used that will not permit of a 
pressure exceeding five hundred pounds, and also have a long 
range of resiliency. A volute form is best (Fig. 104). 
7. Vulcanization should be in steam and at high tempera- 
ture and short time, that is, the Lewis gas regulator should 
be set at 320° F. for one hour and twenty minutes. As the 
heating qualities of the gas of various cities fluctuate, the 
time element must be determined by each operator for 
himself. However, sufficient heat should be applied to 
reach the maximum temperature in approximately twenty- 
five minutes, not varying more than five minutes either 
way; then the high heat should be maintained until the 
rubber, where not more than 1 mm. in thickness, is very 
elastic, but hard enough to readily take a high polish. This 
result will be accomplished in many offices in one hour 
and twenty minutes, that is, twenty-five minutes to heat 
up to 320° F. and held at that temperature fifty-five minutes 
which make the one hour and twenty minutes; other labora- 
tories will require a longer or shorter time. 
The reason for the elastic spring and short time method 
of vulcanization is: The expansion cannot be controlled 
as to its amount, because it must reach its maximum of 
expansion before induration can begin. The effect of the 
expansion is influenced by the method of retention by bolts 
or by spring clamps, and whether vents are or are not 
provided. 
The amount of shrinkage is very much influenced by 
time; the longer the time the dental rubber is subjected VULCANITE 
213 
to vulcanizing heat, the greater the amount of shrinkage. 
High heat causes rapid hardening of the surface, and the 
internal pressure during the hardening and shrinking of 
the surface causes a close adaptation of the vulcanite to 
the sides of the mold and teeth; then as the internal shrink- 
age takes place it will be toward the hardened surface. 
By the use of a flexible spring the expansion is controlled 
so that it cannot do harm, and if sufficient expansion has 
taken place to open the flask the spring will permit outflow- 
ing of sufficient rubber to reduce the internal pressure to the 
power of the spring. Whereas if bolts and gateways were 
used the expansion forces out a part of the rubber until there 
is no internal pressure, and when shrinkage takes place there 
cannot be enough material to fill the mold. Therefore rubber 
tightly shut in the flask, with its expansion and shrinkage 
controlled by a suitable spring, and rapid surface hardening, 
due to the high heat (320° F.) at the surface and a decreasing 
degree of heat toward the center of the mass of rubber because 
of its poor conductivity, is the logical and scientific method of 
vulcanizing all dental rubber. However, this method is best 
adapted to comparatively thin masses of rubber; all thick 
places in vulcanite appliances should be filled with an in- 
different material, therefore such places are filled with plain 
pink or white rubber. 
If the flask is to be bolted, then gateways opening into 
vent spaces are imperative. Also the pink rubber is even 
more important than when vulcanizing under a flexible 
spring. If bolts are used the flask should be completely 
closed before the flask is placed in the vulcanizer. This 
closing of the flask is probably more safely done in boiling 
water; whereas by the elastic-spring method it is not neces- 
sary that the flask shall be entirely closed. The plaster 
in the flask should be kept out of water, and therefore will 
have much more resistance to the pressure of the expanding 
rubber and to the force of the spring. There should be from 
two to five ounces of water in the vulcanizer. A support may 
be placed in vulcanizer upon which the flasks rest, or if the 
volute spring is used the spring is placed as shown in Fig. 104. 214 
RUBBER AND VULCANITE 
DR. SNOW'S LATE RESEARCH IN THE SHRINKAGE OF 
RUBBER IN VULCANIZATION. 
A close study of Dr. Snow's experimental work will richly 
repay the student, for a comprehensive knowledge of the 
shrinkage of rubber in vulcanization is most valuable. It 
also suggests the philosophy for the improved method and 
implements for vulcanization to be presented farther over 
in this chapter. 
Fig. 99 is a schematic diagram of the testing vulcanizing 
flask. 
Fig. 99 
Explanations.-All weights in this table are in grams. All 
bulks in cubic centimeters (see p. 216). 
All samples were vulcanized at 75 pounds by the steam 
gauge, it being the same as 300° F. by the mercury bath 
thermometer, or 320° actual temperature. 
Columns 3 and 7 show the weight and also the bulk of 
water equivalent to the respective samples; as a cubic centi- 
meter of water weighs 1 gram. 
All the vulcanizing was done in the same brass mold, 
which was closed by bolts without springs, and had a gateway 
leading to an overflow chamber, which received the rubber 
expelled from the mold as it was heated from 212° F. to the 
vulcanizing point. The capacity of mold at 70° F., 10.710 c.c. 
At 212°, 10.759 c.c. At 320°, (75 pounds pressure) 10.796 c.c. SHRINKAGE OF RUBBER IN VULCANIZATION 
215 
The discrepancies between columns 1 and 5 are due to the 
absorption of a small quantity of water by the rubber when 
vulcanizing; showing that vulcanite is slightly porous. The 
amount of water absorbed is about half a drop for a sheet of 
rubber. Rubber compound does not lose weight by vulcaniz- 
ing. 
Column 11 denotes the weight of rubber expelled from the 
mold as the sample is heated from 212° to the vulcanizing 
point. Column 12 shows the bulk of the same. 
In column 13 the shrinkage, shown in column 9, which is 
the difference between columns 3 and 7, is added to the 
overflow, column 12, and shows the total amount of deficiency 
of vulcanite in the mold when the vulcanizing process was 
completed. Column 14 gives the percentage of this defi- 
ciency. It will be noted that the deficiency is greater in the 
dark-colored rubbers and less in the lighter-colored ones, the 
light rubbers containing more foreign matter in their compo- 
sition. 
Conclusions.-If the flask is bolted and gateways provided 
for the free escape of the rubber as it is heated, the deficien- 
cies shown in columns 13 and 14 are inevitable, and the 
denture will always be defective. 
If spring pressure is applied to close the flask, and the 
rubber is confined so that none of it can escape unless the 
parts of the flask are separated by its expansion, the defi- 
ciency will be less than that shown in columns 13 and 14; 
the amount depending upon the average thickness of rubber 
in the case. 
To produce the best results, spring pressure must be used 
to close the flask, the mold must contain an excess of from 
3 to 5 per cent, of rubber when vulcanizing commences, and 
the flask must, therefore, not be entirely closed at this time. 
Its closing must be effected gradually by spring pressure and 
after the vulcanizing process has progressed far enough to 
cause a partial shrinkage of the rubber. For vulcanizers of 
the ordinary type this may be accomplished by two vul- 
canizations. 216 
RUBBER AND VULCANITE 
> H 0 g 
©Sr QP g^gg- 
p» £.£ §°p2 P2-F . m FPr V 
£" 5* B ^3 3 £3^3 
S 0 ajsg" W^br: WB^ISg' 
g I . a- 2-g • - &• 
o' p" 
. ... ... . . Q . 
PT 
1 
28.247 
11.380 
17.235 
17.321 
18.165 
16.417 
21.595 
15.821 
17.368 
14.545 
11.498 
13.200 
Weight 
unvulcanized. 
2 
17.872 
1.155 
6.965 
7.009 
7.912 
6.091 
11.302 
5.526 
7.162 
4.34 
1.272 
2.730 
Weight in water, 
unvulcanized. 
3 
10.375 
10.225 
10.270 
10.312 
10.253 
10.326 
10.293 
10.295 
10.206 
10.205 
10.226 
10.470 
Displacement in 
grams and cubic 
centimeters. 
4 
2.723 
1.113 
1.678 
1.680 
1.771 
1.589 
2.098 
1.538 
1.702 
1.425 
1.124 
1.261 
Specific gravity, 
un vulcanized. 
5 
28.240 
11.393 
17.263 
17.347 
18.18 
16.437 
21.602 
15.837 
17.379 
14.569 
11.517 
13.220 
Weight 
vulcanized. 
6 
18.197 
1.678 
7.502 
7.478 
8.38 
6.539 
11.725 
6.040 
7.627 
4.864 
1.764 
3.547 
Weight in water, 
vulcanized. 
7 
10.043 
9.715 
9.761 
9.869 
9.8 
9.898 
9.877 
9.797 
9.752 
9.705 
9.753 
9.673 
Displacement in 
grams and cubic 
centimeters. 
8 
2.812 
1.173 
1.768 
1.758 
1.845 
1.66 
2.187 
1.616 
1.782 
1.501 
1.181 
1.366 
Specific gravity, 
vulcanized. 
9 
.332 
.510 
.509 
.443 
.453 
.428 
.416 
.498 
. .454 
.500 
.473 
.797 
Shrinkage, cubic 
centimeters. 
10 
.032 
.050 
.049 
.042 
.044 
.041 
.040 
.048 
.044 
.049 
.046 
.076 
Percentage of 
shrinkage. 
11 
.865 
.625 
.891 
.876 
.708 
.633 
1.036 
.924 
.802 
.792 
.582 
.579 
Overflow, weight. 
12 
.308 
.533 
.503 
.498 
.384 
.381 
.474 
.572 
.450 
.528 
.493 
.424 
Overflow, bulk, 
cubic centimeters. 
13 
.640 
1.043 
1.012 
.941 
.837 
.809 
.890 
1.070 
.904 
1.028 
.966 
1.221 
Deficiency in bulk, 
cubic centimeters. 
14 
.062 
.102 
.099 
.091 
.082 
.078 
.086 
.104 
.089 
.101 
.094 
.117 
Percentage of defi- 
ciency; bulk. 
TABLE SHOWING THE BEHAVIOR OF DIFFERENT RUBBER COMPOUNDS IN VULCANIZING 
BY DR. GEORGE B. SNOW VULCANITE AS A BASE FOR ARTIFICIAL DENTURES 
217 
ADVANTAGES AND DISADVANTAGES OF VULCANITE 
AS A BASE FOR ARTIFICIAL DENTURES. 
Advantages.-1. It is easy of manipulation; it can be 
molded into any form, and it becomes, upon proper vulcani- 
zation, very strong, tough, flexible, and elastic. It is repaired 
with equal ease. 
2. It is the lightest of all substances used in the mouth; 
its specific gravity is from 1.15 to 1.75, while aluminum, the 
lightest metal suitable for use in the mouth, has a specific 
gravity of from 2.5 to 2.7. 
3. It is inexpensive, both as to cost of material and labor 
in construction, thus bringing it within the reach of patients 
unable to afford metal plates. 
4. There is no material with which contours and difficult 
cases can be so easily and perfectly restored. 
Disadvantages.-1. It is a very poor conductor. It pre- 
vents the proper radiation of heat from the mucous mem- 
brane over which it is placed, thereby leading to excessive 
resorption of the hard tissue and lowering the vitality of 
the soft tissue, in consequence of which they are more 
subject to the action of irritants. 
2. The physical property of continued shrinkage under 
vulcanizing heat is certainly a disadvantage, because it 
interferes with perfect adaptation when re vulcanized. 
By some vulcanite is considered as porous. This is 
undoubtedly an error. In 1869 a committee of the Pennsyl- 
vania College of Dental Surgery, consisting of Professors 
Wildman, Buckingham and Truman, were appointed to 
investigate and report upon dental vulcanite. In part the 
report states: "In repeated examinations made to test 
this (porosity), by high power of the microscope, nothing 
resembling pores has ever presented. It has been found 
impossible to procure a section thin enough, to transmit 
light, although ground to extreme tenuity. Examined as 
an opaque object, it presents a homogeneous mass, with no 
appearance of openings for the admission of fluids; nor 
have we ever been able to discover moisture in specimens 
that have been worn. That it is impenetrable to moisture 218 
RUBBER AND VULCANITE 
in the ordinary process of wear, is apparent in the non- 
increase of weight." In correspondence with Professor 
Truman since the first edition of this book, he writes, that 
he has had no evidence to change the conclusion as pre- 
sented in the report published in the Dental Times of July, 
1869. Further than this, the process of manufacture of 
rubber requires compression between very powerful rollers, 
and its physical property of increasing the specific gravity 
by vulcanization would favor great denseness. 
This paragraph is at variance with the recent investiga- 
tions of I )r. Snow. However, it must be recognized that both 
findings were by the highest and most painstaking authorities; 
therefore, it is reasonable to suppose that the difference is in 
the gums or in the dyes and fillers used fifty years ago and 
now. 
Red and pink rubbers are considered injurious because 
of their coloring matter, vermilion (mercuric sulphide). 
This criticism is unjust, because pure mercuric sulphide 
is insoluble in water, alcohol, alkali, and all acids except 
nitrohydrochloric acid, which under no condition should 
come in contact with red or pink vulcanite, as this acid 
converts HgS into HgCl2 (corrosive sublimate). It is 
evident that the heat of the vulcanizer cannot decompose 
vermilion because in its manufacture the ingredients are 
subjected for many hours to a temperature approximating 
1200° F.; therefore it would be unreasonable to expect a 
temperature under 400° F. to undo the work of three times 
as great a heat. However, it is possible that free mercury 
may be in red rubber, but if so it is because it was placed 
there in a poor quality of vermilion; therefore the dentist 
should use only the high-grade rubbers of reliable manu- 
facturers. 
INSTRUMENTS AND APPLIANCES USED IN VULCANITE 
WORK. 
Wax Spatulas.-These are instruments used in manipu- 
lating wax. There are different types of these instruments, 
as carvers, ironers, knives, and spoons. Carvers are small INSTRUMENTS FOR VULCANITE WORK 
219 
knives and scrapers. Nos. 1 and 2 of the Evans set are 
of this class (Fig. 100). (The No. 3 of this set is a bur- 
nisher for tinfoil.) Ironers have sufficient bulk of metal in 
their ends to convey heat to the wax. They are of various 
forms designed to facilitate the work. Fig. 101 shows a 
number of these instruments. Knives are larger than 
the knife-shaped carver and are designed for coarser work. 
Spoons are for melting and carrying wax. These various 
classes are often combined in double-end instruments, 
especially so with the knife and spoon (Fig. 102). 
Flasks.-There are a great many varieties of vulcanite 
flasks upon the market. They are made of iron or brass. 220 
RUBBER AND VULCANITE 
Iron has the greater affinity for oxygen and sulphur in 
vulcanizing, but retain their adjustment and form much 
better than brass. The brass flasks are the more easily 
cleaned. Each time the flasks are used they should be thor- 
oughly cleaned with a stiff brush and sapolio. 
Fig. 101 
The Star flask is one of the oldest forms, and, being rever- 
sible, is probably adapted to more cases than any other 
(Fig. 103). The Wilson flask is characterized by a very 
narrow rim upon the lower section, with a correspondingly INSTRUMENTS FOR VULCANITE WORK 
221 
wide rim in the upper section. It is designed to be used 
for full cases only, and with a clamp and spring (Fig. 104). 
Fig. 104 shows a two-flask Donham clamp with a Wilson 
volute spring1 below and a Wilson flask above. The Whitney 
Fig. 102 
1 The author has perfected a suitable volute spring. It is placed upon 
the market by the Cleveland Dental Mfg. Co. It is not patented and the 
inventor receives no financial benefit from it; therefore address all letters 
of inquiry to the manufacturers. The spring is so formed and tempered 
that each j inch compression produces approximately 100 pounds' pressure. 
The large end should always be placed against the flask. 222 
RUBBER AND VULCANITE 
flask is very much used. There are two sizes, the larger 
being five-sixteenths of an inch deeper than the smaller. 
Fig. 103 INSTRUMENTS FOR VULCANITE WORK 
223 
Fig. 104 
Fig. 105 
Fig. 106 224 
RUBBER AND VULCANITE 
Fig. 105 shows the regular size with springs upon the bolts 
to aid in closing the flask. 
The box flask is designed for interdental splints and any 
extra large pieces of vulcanite. It is made in two sizes, one 
as large as can be used in a two-flask vulcanizer and the 
other for the three-flask vulcanizer (Fig. 106). 
Flask Presses.-The flask press (Fig. 107) is an indis- 
pensable appliance in a well-equipped laboratory, and yet 
probably its improper use has caused more misfit vulcanite 
dentures than all other causes. When the principles involved 
in the flask press and its use are understood, there should be 
no trouble in handling it. 
Fig. 107 
All plasters expand and are compressible, some excessively 
so. French's regular dental plaster is the best and most 
commonly used by the profession; so these statements are 
in connection with this plaster. A molar tooth one-half INSTRUMENTS FOR VULCANITE WORK 
225 
inch in diameter under a thousand pounds' pressure would be 
driven into well-set plaster one-twentieth of an inch. Rubber 
when cold is very tenacious and will resist a very heavy 
pressure for a short time, but will gradually yield. Plaster 
compresses to its full extent in a very few seconds. It is 
easy to comprehend that if an excess of rubber is placed 
over the teeth upon one side, and heavy pressure is applied, 
the teeth will be driven into the plaster encasement and 
consequently the teeth upon that side of the denture will 
be too long. It can also be comprehended that if the cast 
is formed of regular plaster, and excessive rubber and pres- 
sure be applied to the vault of the cast, it will be pressed 
upward and the plate warped. 
We shall now consider the power of the press. The screw 
is a combination of the lever and wedge, and its power is 
calculated by multiplying the circumference described by 
the lever by the pitch of the screw. A press having a handle 
8 inches long would describe a circumference of 25+ inches. 
There are ten threads to the inch, hence a pitch of of an 
inch. An allowance must be made for friction in the screw, 
but | will be very liberal, when we shall have, for every 
pound of force applied at the end of the handle, two hundred 
pounds' pressure under the screw, or a ton for every ten 
pounds of force. If the force is applied nearer the middle of 
the handle it will produce approximately one-half as much 
pressure or a ton for every twenty pounds of force. It is 
now easily understood why plates are warped and these heavy 
malleable-iron presses are sometimes broken. 
At the request of the author the Cleveland Dental Mfg. 
Co. have added a volute spring to their flask press (see 
Fig. 107). This provides an element of safety to this danger- 
ous implement, and creates a follow-up pressure which is 
absent in a rigid press. 
Vulcanizers.-There are in use at the present time many 
forms of vulcanizers. It is unnecessary to enumerate them. 
The description will therefore be confined to one of the 
best examples of the somewhat extensive list. 
The Lewis Cross-bar Vulcanizer (Fig. 108) embodies many 
valuable improvements, and is probably one of the strongest, 226 
RUBBER AND VULCANITE 
safest, and most convenient vulcanizers of the cross-bar 
pattern in use. 
The boiler is hand-made from copper, rolled expressly for 
this form of vulcanizer, and is of unusual thickness. The 
cap is ribbed on the under side to resist any strain which 
may be put upon it. This cap has but two holes drilled 
Fig. 108 
in it: one for the mercury bath, to which the thermometer 
is attached; the other for the "manifold," which carries the 
safety valve, blow-off, gas regulator, or steam gauge (Fig. 
109). The ring surrounding the boiler is of cast steel, and 
is therefore of ample strength. Besides the lugs for taking 
the strain off the cross-bar and bolt, it has a dovetailed 
projection for the insertion of a lifting handle. INSTRUMENTS FOR VULCANITE WORK 
227 
It will be observed that when the cross-bar and cap are 
removed, there are no swinging bolts or attachments to the 
pot. 
The cross-bar is of an improved form, and is made of 
cast steel. One end is at right angles to the main bar, and 
terminates in projections which catch under the lugs on the 
ring. Over the projections is a small rib which prevents 
the bar from dropping out of position. The other end of 
the cross-bar has an enlarged portion for the reception of the 
bolt, and is terminated by a handle. 
Fig. 109 
The vulcanizer is closed by one bolt suspended in a slot 
on the hand-end of the cross-bar. The bolt is squared to 
prevent rotation, and is surrounded by a spring for the pur- 
pose of disengaging it from the lugs when the nut is loosened, 
and for always retaining the bolt perpendicularly and forcing 
it in place automatically. 
The vulcanizer is opened by loosening the nut on the bolt 
by means of the wrench furnished for the purpose. The 
bolt will be forced downward through the action of the 
spring. The handle of the cross-bar is then seized, and with 
the thumb against the nut it is pressed until the bottom of 228 
RUBBER AND VULCANITE 
the bolt is disengaged from the lugs, when the bar may be 
lifted (Fig. 110). 
Fig. 110 
INSTRUCTIONS FOR THE USE OF GAS AND TIME 
REGULATORS. 
"The gas regulator (Fig. Ill) is secured to the cap by 
means of the short iron pipe or coil. This is screwed into a 
hole drilled through the cap of the vulcanizer, and tapped 
with a 'one-eighth gas-pipe tap.' If the vulcanizer has a 
'Lewis manifold' attached to the cap of the vulcanizer, 
remove the screw between the blow-off and safety valve 
and screw the coil pipe in its place. After the gas regulator 
has been properly fitted, place the vulcanizer in the jacket 
and in the position in which it is to be used. Connections 
between the time regulator, gas regulator, and gas burner 
are made by means of rubber tubing. The engraving (Fig. 
112) illustrates the correct method of connecting gas and 
time regulators to vulcanizers. Cut a piece of tubing of INSTRUCTIONS FOR GAS REGULATORS 
229 
sufficient length to reach from the gas-supply tap to the 
time regulator, and qonnect them; cut off another piece to 
reach from the time regulator to the gas regulator, and 
attach to the gas regulator by the upright or straight nipple 
on top of the No. 4 Lewis gas regulator; then connect the 
downward curved tube of the gas regulator to the gas burner 
under the vulcanizer with another piece of rubber tubing. 
Fig. Ill 
"The time regulator is more cohvenient when placed on 
a bracket near the gas-supply pipe. It is then out of the 
way, and not likely to be broken from contact with tools, 
and can also be used as a timepiece. 
"To Set the Time Regulator.-When the valve lever on top 
of the time regulator (Fig. 112) is engaged with the screw 230 
RUBBER AND VULCANITE 
upon the minute arbor on the back of the clock, the valve 
is held open for a length of time depending upon whether 
the lever is engaged with the first, second, or third thread 
Fig. 112 
of the screw; and the lever will be cast off and the valve 
closed when the minute hand reaches the figure XII. When 
the minute hand is at IX the lever will be cast off at the 
end of fifteen minutes, if it is engaged with the first thread INSTRUCTIONS FOR GAS REGULATORS 
231 
of the screw from the end; an hour and a quarter, if engaged 
with the second thread, and so on. A trial should be made, 
and the time ascertained which is necessary for heating 
the vulcanizer to the vulcanizing-point, and this time should 
be added to the proposed time for vulcanizing. We have, 
therefore, the following: 
"Rule.-Turn the minute hand to as many minutes 
before the hour as the number of odd minutes desired; then 
put the end of the lever in the threads of the screw upon 
the minute arbor at the back of the clock. The first thread 
from the end gives the odd minutes to which the clock is 
set; the next and each succeeding thread gives a full hour. 
For example: For an hour and twenty minutes, set the 
minute hand at the figure VIII, and engage the lever in the 
second thread from the end of the screw. At the end of that 
time the lever will disengage and automatically shut off the 
gas from the vulcanizer. If this were to be an hour longer- 
i. e., two hours and twenty minutes-the lever should be 
placed on the third thread of the screw. For three hours, 
set the minute hand at XII and engage the lever in the third 
groove of the screw. 
"Steam Pressure.-Those who use vulcanizers should be 
thoroughly informed as to the nature and properties of 
steam. The fact should be borne in mind that a vulcanizer 
is subject to the same laws and conditions as a steam boiler, 
which it is in fact, and although it is comparatively safe and 
easily operated, it may, by carelessness or ignorance in its 
management, become exceedingly dangerous. 
" The following table of steam pressure will be found con- 
venient for reference, as it has been corrected so that it 
shows the true temperature for any pressure indicated by 
the steam gauge. Fractions are omitted, and the nearest 
whole number is used instead. The French table generally 
used shows 14.7 pounds pressure at 212°, whereas the steam 
gauge at that temperature will indicate 0, unless by the 
expansion of heated air confined in the vulcanizer. The 
gauge is therefore just one atmosphere lower than the French 
table: 232 
RUBBER AND VULCANITE 
Table of the Elastic Force of Steam1 (Corrected to Correspond 
with the Steam Gauge). . 
Degrees of temperature, 
Fahrenheit. 
212 
Elastic force in pounds 
per square inch. - 
0 
220 
2 
230 
6 
240 . 
10 
250 
15 
260 
21 
270 
27 
280 
34 
290 
43 
300 
52 
310 
63 
320 
75 
330 
89 
340 
104 
350 
120 
360 
140 
370 
160 
380 
180 
390 
205 
400 
234 
410 
264 
420 
296 
430 
335 
440 
375 
450 
415 
460 
455 
470 
515 
480 
565 
490 
603 
500 
. . ..... 663 
510 
721 
520 
793 
530 
864 
540 
. 937 
550 
1015 
" It will be noticed that as the temperature rises the 
pressure of steam increases in constantly increasing ratio 
for equal increments of heat, the pressure being nearly 
doubled by the addition of 50° to the temperature. This 
fact will show the necessity of care and watchfulness while 
vulcanizing. 
"The bulb of the thermometer is set in a mercury bath. 
This is the small cup, forming a part of the vulcanizer cap, 
1 General instructions for operating dental vulcanizers, Buffalo Dental 
Manufacturing Co., July, 1898. INSTRUCTIONS FOR GAS REGULATORS 
233 
to which the thermometer case is screwed. This cup should 
contain sufficient mercury to insure its touching the bulb 
of the tube when the thermometer case is screwed down 
properly. This makes a metallic connection between the 
thermometer bulb and the vulcanizer cap, and is absolutely 
necessary for proper indication of heat by the thermometer. 
''Should the mercury column separate, it can usually be 
reunited by removing the tube from the thermometer case, 
holding it perpendicularly, and striking the bulb with some 
force upon the palm of the hand, or by holding the tube 
by the bulb and giving it a sudden flirt. If the vulcanizer 
is used with the thermometer in this condition, it should be 
remembered that it is the whole column that denotes the 
heat, and allowance should be made for the broken part, 
i. e., if there is enough mercury separated to fill the space of 
10°, the remainder of the column should only rise to 10° 
less than the temperature desired. 
"Directions for inserting a new tube in the thermometer 
case will generally be found on the package containing the 
tube and scale. 
"Thermometers are accurately marked, by test instru- 
ments, at the 212° and 320° points, and the scales are 
especially graduated for each tube, as the positions of the 
points above named vary in different tubes. Each tube 
must therefore be used with its own scale, and in fitting it 
to the case care should be taken that the black mark on the 
tube indicating the 320° point is brought exactly opposite 
to the 320° point on the scale. 
"The thermometer does not always give a correct indica- 
tion of the heat of the vulcanizer. It only gives the tem- 
perature of the vulcanizer top, which may not be that of the 
flask. In fact, the indications of the thermometers employed 
on vulcanizers are almost invariably too low, owing to 
imperfect conduction of heat, radiation, etc.; and the vul- 
canization temperature, instead of being 320°, as indicated, 
is more usually 330° to 340°." 
The plan of providing a mercury bath for the reception 
of the bulb is a great improvement over the old way, and 
prevents the fracture of the bulb by the great pressure of 234 
RUBBER AND VULCANITE 
the steam, which was of such frequent occurrence when the 
thermometer was in direct contact with the latter. 
Damage to the glass bulb of the thermometer is manifested 
by a rise in the mercury, which cannot be brought down to 
the usual vulcanizing-point by turning off the flame of the 
burner; consequently the thermometer ceases to correctly 
indicate the degree of heat, and imperfect vulcanization is 
the result. Leakage of steam around the packing of the 
vulcanizer should also be guarded 
against, as in such cases all of the 
water may escape from the appa- 
ratus before the vulcanizing is com- 
plete. Loss of all of the water in 
the vulcanizer may be detected by 
a persistent fall of the mercury, even 
when the gas flame is greatly in- 
creased, and when this phenomenon 
is observed the gas should be turned 
off, the vulcanizer allowed to cool, 
and new packing adjusted. Failure 
to strictly observe this rule has un- 
doubtedly resulted in many serious 
accidents. 
Vulcanizing.-The flask or flasks 
are placed in the vulcanizer and 
filled about 1 inch deep with clean 
water. The packing should be with- 
out a break in its continuity, other- 
wise the steam will escape; the joint 
between the pot and cover must be 
protected from adhesion by slightly 
coating it with black lead or soapstone. The cover is then put 
on, but the valve is not closed until the heated air which pre- 
cedes the generation of steam has escaped; the valve is then 
closed. A close watch must be kept on the thermometer or 
gauge until the vulcanizing point is reached, unless a time 
regulator is used. 
Flask-tongs.-Fig. 113 shows a useful form of flask-tongs 
for lifting flasks from the vulcanizer. They are made of 
Fig. 113 INSTRUCTIONS FOR GAS REGULATORS 
235 
Fig. 114 236 
RUBBER AND VULCANITE 
sufficient length to reach the bottom of a three-case vulcan- 
izer, and will securely grip the flask. 
Files.-Fig. 114 illustrates some excellent forms. 
Vulcanite Trimmers.-There are a great variety of scrapers 
and chisels from which each operator may select such as 
seem best adapted to his hand. The writer's preferences 
are the ones here illustrated (Fig. 115). 
Fig. 115 
GRINDING AND POLISHING. 
In the construction of artificial dentures upon any base, 
grinding and polishing are very important operations and GRINDING AND POLISHING 
237 
require efficient equipment for their accomplishment. For 
this purpose a small lathe of suitable construction is neces- 
sary. These lathes will require approximately one-sixth 
horse-power, which may be provided by either electricity, 
water, steam, or the foot. The desirability of the power 
chosen is in the order named. However, steam is rarely 
used in a dental office because of the expense of installing 
and maintenance. There are many patterns of these imple- 
ments from which the dentist may select. There are two 
general principles involved in all of these appliances: (1) 
the motor and lathe are combined as one implement; (2) the 
motor and lathe are separate and coupled together with a 
band or cord. 
Fig. 116 
The electric current is most convenient and serviceable 
when it can be had in the office. Fig. 116 represents an 
apparatus of the first type, that is, motor and lathe com- 
bined. This electric lathe is admirably adapted to general 
laboratory uses or as an operating-room lathe. Its bearings 
are completely protected from dust. It is noiseless, and is 
constructed with such precision that its motion is hardly 
perceptible. It is adapted to the 110-volt direct current, 
and has sufficient power for all purposes required by the 
dentist. It requires no special table, hence can be placed in 
any position at the convenience of the operator. It has a 
range of speed varying from 1000 to 4000 revolutions per 
minute. The regulation of the speed and starting and 
stopping of the lathe are effected by the milled stud. The 238 
RUBBER AND VULCANITE 
chucks are held upon the shaft of the motor by friction, and 
can be removed while the motor is in motion or stationary by 
turning the milled nuts near the ends of the shaft. These 
motors can be obtained for other voltages and for the alter- 
nating current. 
Fig. 117 is a lathe of the second type, and can be operated 
by any power through a cord. This illustration shows a 
convenient arrangement of lathe and foot power. 
Fig. 117 
These lathes are all provided with various forms of chucks 
for grinding stones, buffers, and polishing brushes. Figs. 116 
and 117 each show a stone-mounted chuck upon one end of 
the shaft, and the tapered-screw-cut spindle for buffers and 
polishing brushes at the other end. 
Most makers of lathes furnish an extra clutch chuck for GRINDING AND POLISHING 
239 
burring engine instruments. Fig. 118 shows an additional 
nut the author has had added to the clutch chuck for his 
Fig. 118 
Fig. 119 
Fig. 120 
lathe. By this means a three by one-half inch carborundum 
stone is mounted. The figure also shows an engine mandrel 
mounted with a small stone in the clutch. The author has 240 
RUBBER AND VULCANITE 
no use for any other stone chuck, and no changes are required 
except in the small stones, burs, and bits used in the chuck. 
Fig. 119 is the "Ideal Emery Cloth Arbor," put upon the 
market by Samuel A. Crocker & Co., Cincinnati. This is an 
especially useful addition to the lathe for vulcanite work. 
The lathe should be kept clean, well oiled, and true running. 
Grinding is a very important accomplishment-indeed, it 
may be called a fine art in mechanical dentistry-and can 
be acquired only by technical training and the use of true- 
running and well-cared-for equipment. Next to the lathe 
running true, the stone must be kept true and sharp; this is 
accomplished by the use of a machinist's emery-stone dresser 
(Fig. 120). This tool is used over a firm support, with a 
moderate pressure, upon the rapidly revolving stone. It 
not only produces a true surface, but a very sharp-cutting 
one. The tool should be applied often. 
Stones.-The stones used in the dental laboratory are 
made of either corundum or carborundum. 
Corundum is a mineral found in Ceylon, and in Pennsyl- 
vania, Georgia, Massachusetts, and North Carolina. It 
occurs in crystals of the form of double six-sided pyramids 
of various sizes, and in some localities in large masses without 
crystalline form. Corundum is an aluminum oxide having 
a formula A12O3. Emery, the use of which preceded corun- 
dum as an abrasive agent in the dental laboratory, is a 
coarse variety of corundum. Corundum is prepared for 
use by crushing in an iron mortar. The required size grit 
is mixed with finely ground shellac in the proportion of 
3 ounces of corundum to 1 of shellac, and formed in iron 
molds by the aid of heat and pressure. The surface shellac 
is dissolved out with alcohol, leaving the abrasive crystals 
exposed. Wheels made of corundum require to be run wet, 
otherwise the frictional heat will draw the softened shellac 
bond to the surface, producing a glaze which is non-abrading 
Carborundum is a manufactured grit; it is harder and 
more brittle than corundum, and is next to the diamond as 
an abradant. Carborundum was made experimentally in 
1893 by Mr. G. E. Acheson, and is now manufactured on an 
extensive scale at Niagara Falls. It is made of a mixture of GRINDING AND POLISHING 
241 
finely divided coke, pure silica sand, sawdust, and salt 
(NaCl). Ten tons of this mixture is placed in a furnace 
16 feet long by 6 feet wide and 8 feet high. Electrodes are 
connected at the center of each end with a core of crushed 
coke. About 1000 horse-power of energy is utilized at an 
average voltage of 185, reaching a temperature approxi- 
mating 7500° F. The salt acts as a flux. The sawdust 
burns out, leaving the mass porous for the escape of gases. 
The current is applied for thirty-six hours; it is then with- 
drawn and the mass given time to cool. About two tons 
Fig. 121 
of crystals are formed about the core, consisting of the 
carbide of silicon (CSi). These crystals are crushed, washed, 
and sieved, mixed with feldspar and clay as a bond, molded 
into shape under heavy pressure, and burned in a kiln for 
several days. Wheels made of carborundum may be run 
either wet or dry. It is claimed for them that they do not 
clog; however, the surface becomes so filled with dust that 
they are not nearly so effective as when tooled as previously 
described. The wheels have a tendency to wear untrue, 
probably due to imperfections in the mixing with the bond 
and burning in the kiln. Frequent tooling overcomes this 242 
RUBBER AND VULCANITE 
defect and keeps them true and sharp until they are worn 
out. 
Buffers.-Buffing wheels and cones are used on the thread- 
cut spindle in finishing the denture; they carry fine abra- 
dants and remove small defects and scratches from the 
surface of the work. They are made of various materials, as 
felt, cotton duck, leather, soft wood, cork, and disks of 
cloth or chamois leather stitched together. Felt is probably 
the best and most commonly used material for dental 
buffers. The wheels are made in various sizes and shapes. 
A wheel two or two and one-half inches in diameter and one- 
half-inch thick is an excellent size. Knife-edge wheels are 
very useful in some places, but they must be properly psed 
or they will quickly cut a groove. They also wear away 
rapidly, thus destroying the knife-edge effect. They require 
frequent tooling with a knife or chisel to keep them turned 
to an edge. 
Brushes.-Brush wheels, both stiff and soft, are used. 
These wheels are made in various forms. Their wooden 
centers, which are straight drilled, should be reamed to a 
taper. Fig. 121 shows a suitable reamer. They are used 
on the threaded taper spindle. The bristles are either 
straight, converging, or diverging. The stiff converging 
wheel is excellent for carrying the abradant between the 
teeth where the felt cannot reach. The soft-bristle brush 
is used to carry the finest abradant and produces the' gloss. 
Finishing Powders for Vulcanite.-Pulverized pumice stone 
for buffing and prepared chalk for glossing are especially 
suited to vulcanite work. 
Pumice stone is volcanic scoria or lava. Chalk is calcium 
carbonate, a soft variety of limestone; it is prepared by 
freeing it from particles of coarser grit. 
Use of Stones.-The stones are used to grind the porcelain 
teeth, sharpen instruments, etc. It is safer to run the stone 
at a low speed. There is danger of chipping and checking 
the porcelain by the pounding of an untrue stone and heat 
produced by a clogged one. If the stone is true and clean, 
and the tooth held with light pressure, it will be rapidly 
cut with hardly perceptible frictional heat, consequently no GRINDING AND POLISHING 
243 
chipping or crazing of the porcelain. By the same care a 
steel instrument may be ground without drawing its temper 
as indicated by the blue color and spoiled cutting edge. A 
higher speed may be used, but greater care is required. 
Buffing.-The buffing is done by first using the large 
felt wheel and pulverized pumice stone. The work, the 
felt, and the pumice must be kept thoroughly wet, other- 
wise sufficient frictional heat may be generated to roughen 
the vulcanite and possibly warp the denture. It should be 
obvious to the student that if the work is held at one 
place against the felt carrying an abradant a depression will 
be cut into its surface. Hence the work while being held 
against the buffer must be kept in constant motion. This 
motion should be a steady systematic procedure, not of a 
jerky, indecisive type. The denture should be finished with 
true symmetrical convex or concave surfaces in keeping 
with the conformation of the part. Facets show either 
inexperienced or careless buffing. The buffer may be run 
at high speed, in which case the work must be held with 
moderate pressure only against the buffer. Usually it is 
safer to use a moderate speed and greater pressure, and in 
some places it is wise to use the lowest speed and light 
pressure. The buffer does not cut of itself, but it carries 
and applies the abradant; therefore the efficiency of the 
buffer is largely due to the manner in which the abradant is 
applied. The abradant, saturated with water to tbe con- 
sistency of soft mud, is applied to the surface to be buffed 
and the farther edge is placed against the well-moistened 
buffer. The buffer engages a small amount of the abradant 
and carries it over the surface of the work. As the buffer 
wheel rises from the surface of the work, it throws off a 
portion of the abradant, but a small portion is imbedded 
in the surface of the buffer to be again carried over the 
surface of the work. As the work is pushed forward, more 
abradant is engaged and made to serve its purpose. The 
work is given a sideways movement as well as a forward 
one until all of the abradant is removed from the surface 
of the work. More abradant is applied and the operation 
repeated until the work is suitably finished. If the buffer 244 
RUBBER AND VULCANITE 
is applied to the nearer edge of the abradant and the work 
drawn forward the buffer will push away the abradant, of 
which only that portion adhering to the buffer and making 
the complete circuit will be effective. This method is waste- 
ful of abradant, time, and energy. 
Glossing.-The glossing is done with the rapidly revolving 
soft-brush wheel and the prepared chalk. The chalk well 
moistened with water or alcohol is applied to the surface of 
the work and held lightly against the brush wheel. As in 
buffing, the work is pushed against the brush. With the 
beginning of glossing the brush wheel is moistened, but 
later is run dry. Alcohol is the preferred moistener for the 
glossing powder because it serves to attach the powder to 
the work and quickly evaporates, leaving the powder in a 
dry condition, best for glossing. 
HEAT. 
In vulcanite work heat is required for warming wax, rubber, 
flasks, and converting the rubber into vulcanite. 
Fig. 122 
Bunsen Burner.-For all these operations the blue or 
Bunsen flame only is suitable. Fig. 122 shows a Bunsen HEAT 
245 
burner designed for the laboratory bench and connected 
to the gas cock with rubber tubing. Fig. 123 shows a 
jeweller s triple burner, one of which is a Bunsen. This 
burner is especially useful because it can be attached to a 
jointed bracket, thus doing away with the gas- 
saturated rubber tubing. One of the other burners 
gives a light flame, and the third burner gives a 
flame suitable for soldering. These extra burners 
are often convenient. The burner in the upright 
position only is in commission, and when any 
one of the burners is turned straight downward 
the gas is cut off from all of them. 
Construction.-The Bunsen burner consists of 
a straight tube with a suitable-size hole near 
the lower end for the admission of air in sufficient 
quantity to produce instant combustion of the 
carbon, thus giving a blue, smokeless flame. 
Nature of the Bunsen Flame.-Fig. 124 is an 
illustration of the Bunsen tube and flame. A 
flame is gaseous matter heated to a state of 
incandescence. The flame has a three-cone struc- 
ture : A shows the mixed gas and air being heated; 
the inner edge of the light cone B indicates that 
the gaseous mixture has reached the state of 
incandescence and has become a flame; the outer 
edge of the light cone B indicates where the 
Fig. 123 
Fig. 124 246 
RUBBER AND VULCANITE 
greatest heat has been attained and that the flame from 
this point outward is cooling until the outer edge of cone 
Fig. 125 
Fig. 126 
Fig. 127 
C is reached. At this point the mixed gases have become 
chemical compounds and cooled below the temperature of 
incandescence, hence the flame ceases to exist. It is evident HEAT 
247 
that the greatest body of heat is between B and C, conse- 
quently this is the portion of the flame in which to quickly 
heat an instrument. 
Fig. 125 is a gas stove of many Bunsen jets, and is suit- 
able when a much greater amount of heat is required than 
can be produced with the small burner. 
Alcohol and Gasolene.-In some of the large office buildings 
in cities, and in many of the small towns, gas is not obtain- 
able as a source of heat; then recourse must be had to either 
alcohol or gasolene. Alcohol is suitable as a substitute for 
Fig. 128 
the Bunsen burner for working wax and resinous compounds; 
it is cleanly, odor not offensive, but the heat is slow. Fig. 
126 shows a good form of waxing lamp. Gasolene is more 
powerful and less expensive, but the odor of the material and 
of the product of its combustion are disagreeable. Fig. 127 
is an excellent Bunsen burner. Fig. 128 is a large heater 
suitable for general heating purposes in the laboratory. 
Petroleum.-Oil seems to be better adapted for the vulcan- 
izer than either alcohol or gasolene. The lamp for using oil 
needs no description, for a suitable oil burner may be had for 
every make of vulcanizer. 248 
RUBBER AND VULCANITE 
TECHNIC OF CONSTRUCTION FOR COMPLETE 
VULCANITE DENTURES. 
Synopsis.-Diagnosis and prognosis; impressions; casts; 
base-plates; occlusion and contour models; mounting on the 
New Century Antagonizor; grinding and setting up the teeth; 
trying in; flasking; packing; vulcanizing, and finishing. 
Diagnosis and Prognosis.-The imaginary patient for whom 
complete artificial dentures are to be constructed is a lady, 
aged forty to fifty years, of the blonde type, but not stout 
built, the face oval modified by the triangle form, and good 
health. The mouth has been edentulous for at least two 
years; the gums are well resorbed and oval in form; the vault 
is medium in height and oval in form. There is a moderate 
amount of submucous tissue underlying the mucous mem- 
brane; no pronounced hard or soft places, and the fluids of 
the mouth abundant but not ropy. A normal average case. 
The prognosis is favorable, provided the personal equation 
does not present unusual difficulties. 
Impressions.-For the upper impression, see Chapter II; 
classification, normal. Points to give attention: Tray with 
flanges low enough not to be displaced by any muscular 
action; palatal border wax accurately adjusted; cuspid 
eminence wax; plaster with hastener mixed thin; heel of 
tray adjusted first; lip raised while adjusting the anterior 
portion of tray; tray supported with the index finger in the 
center of the vault; lip and cheeks drawn downward marking 
the frenae, and external compression. 
For lower impression, see Chapter II; classification high 
ridge, broad. Points to give attention: Flanges; lingual 
wax roll; plaster with hastener mixed thin; the buccal tissues 
drawn from under the buccal flanges; frense marked; external 
compression, and the tray held in place by pressure of the 
thumbs in the bicuspid region. 
Casts.-The impressions are permitted to stand for a few 
minutes, then varnished with thin shellac, and when dry 
(three to five minutes) with thin sandarac. As many coats 
of sandarac should be applied as may be necessary to secure 
a glossy surface, permitting each coat to dry before applying TECHNIC FOR VULCANITE DENTURES 
249 
the next one. The cast may be made of plaster of Paris, 
Prothero's Oxychloride of Magnesium, Weinstein's Artificial 
Stone or Spence's Plaster Compound. The writer has implied 
if not expressed his appreciation of the relative merits of 
these materials. However, for emphasis he will say that pure 
plaster of Paris is far the least suited, for casts upon which to 
vulcanize, of any of the materials used. Oxychloride of Mag- 
nesium has certain properties superior to any other known 
material, but the quality of the material obtainable is too 
unreliable at the present time, and will not be reliable until 
it is properly marketed. The artificial stone is undoubtedly 
placed upon the market as a substitute for Spence Compound. 
It is very much slower setting than Spence Compound and it 
is questionable whether it has any superior qualities. The 
Spence Compound has steadily grown in favor for the past 
sixteen years and the writer is convinced that he is not justified 
in discarding it for any other known material. However, 
tomorrow he may, for his mind and practice are always open 
to conviction and acceptance of the best, which he now be- 
lieves to be Spence Plaster Compound. 
The last three named materials form very hard casts which 
are difficult to carve into form, therefore it'is desirable to have 
a technic that will produce the required form in the plastic 
state. This can best be done by wrapping or boxing the 
impression. 
Wrapping Technic.-Cut a sheet of pink paraffin wax, 
lengthwise, into thirds. Warm and wrap these strips about 
the impression so as to enclose it and produce the form de- 
sired. The joints in the wax are lapped and luted with a 
hot spatula, also the wax is securely attached to the im- 
pression by application of the hot spatula. A portion at a 
time of this wax rim is warmed and pressed closely to the 
impression so as to give the desired outline margin of the im- 
pression for the cast. This can best be done by conforming 
the wax to the impression with the thumb of one hand and 
at the same time molding the free flange of wax with the 
thumb and finger of the other hand. After which a second 
layer may be added and luted at any weak part. Fig. 129 
shows upper and lower encased impressions and Fig. 130 250 
RUBBER AND VULCANITE 
shows an encased impression filled with Spence plaster com- 
pound. Any of these materials should be well jarred into the 
Fig. 129 
impression by rapping upon a block of wood. The material 
should be jarred in until no more air bubbles can be brought 
to the surface. If the surface of the cast is not solid and free 
Fig 130 
of all air holes it is positive evidence that it was not sufficiently 
jarred in while filling. TECHNIC FOR VULCANITE DENTURES 
251 
Base-plates-Heavy tinfoil (Nos. 20 to 60) is placed upon 
the cast, over which a sheet of paraffin base-plate wax is 
adjusted (any of the resinous base-plate stock material 
may be substituted for the paraffin). Soft wax is built 
upon the base-plates to form the occlusion and contour 
models as described in Chapter IV. 
Occlusion and Contour Models.-The models formed on the 
casts are tried in the mouth, removed and added to or cut 
away as may be necessary to give the proper restoration of 
the lower third of the face at rest. The models should be 
tested with a spatula, to see that they rest with uniform pres- 
sure upon all portions of the alveolar processes. The patient 
is exercised in the forward and backward movements of the 
mandible. These movements being made at command, the 
mandible is placed in the retruded position and the occlusion 
guide lines, the high- and low-lip lines, and the median line 
recorded in the wax. The lower model is removed from the 
mouth and the bite gauges adjusted. The model is then 
replaced and the mouth closed in the protruded position, 
recording the inclination of the condyle path. The bite 
gauges are removed from the lower models and the fork of 
the face bow attached to the upper model. The face bow 
is adjusted and the relationship of the wax model to the 
condyle secured. (See Chapter IV.) 
The student could justly conclude that all of the preceding 
work is done at one appointment with the patient. However, 
it is not necessary to detain the patient after the impressions 
are secured; a second appointment may be made for the 
next step. During the absence of the patient the impressions 
are glossed, filled, and permitted to harden for an hour or 
two. The impression is then removed from the cast (see 
Chapter III), the base-plate formed, and the preliminary 
work done upon the wax model. At the second appoint- 
ment the wax models are adjusted to the mouth and the 
required data of marks and measures secured. The color 
of the teeth is selected. The detail of determining the color 
cannot be discussed; suffice to say that this phase of the 
science will be discussed in the chapters on Porcelain Teeth 
and Esthetics; also that the color for the type of the imagi- 252 
RUBBER AND VULCANITE 
nary patient must be straw yellow modified with gray, 
probably shade 39 or 41 of the S. S. W. shade bar; possibly 
as much toning with gray will be required as represented 
in shade 40 (shades 15, 16 or 20 trubyte teeth). The patient 
is again dismissed with an appointment for another sitting. 
During the absence of the patient the casts and wax models 
are mounted upon an antagonizor, the teeth selected, ground, 
and set up. At the third appointment the teeth mounted on 
wax are tried in the mouth. The details of this sitting are 
discussed in the chapter on Esthetics. At the fourth appoint- 
ment the finished dentures are placed in the mouth and 
thoroughly inspected before dismissing the patient. 
Mounting on Antagonizor.-The face bow with the wax 
models and casts are assembled and mounted on the New 
Century Antagonizor, as described in Chapter V. The face 
bow removed, the bite gauges are used to secure the inclina- 
tion of the condyle path, also described in Chapter V. . 
Grinding and Setting Up.-A section of the wax of the 
upper model, represented by the median- and high-lip lines, 
is removed with a warmed wax knife (Fig. 102). The esthetics 
involved in selecting the artificial teeth cannot now be dis- 
cussed: however, a rule may be given for determining the 
size of the teeth. Length: The length of the teeth selected 
should be sufficient to fill the space between the high-lip line 
and the occlusal plane. Width: The crest of the cuspid teeth 
beginning with its cusp should be continuous with the crest 
of the cuspid eminence developed in the contoured wax 
model (see Chapter I, also Fig. 2); therefore the combined 
width of the central, lateral, and the mesial plane of the 
cuspid is the length of the space from the median line to the 
crest of the cuspid eminence. The distal plane of the cuspid 
and the bicuspids and molars should fill the space between 
the crest of the cuspid eminence and the maxillary tuber- 
osity. This rule for length and width is only applicable to 
normal or nearly normal cases. Extreme and abnormal cases 
cannot be classified, and artificial teeth must be selected 
according to the judgment of the prosthetist. 
Grinding.-There are two stages of grinding a set of 
artificial teeth. The first stage is grinding for occlusion TECHNIC FOR VULCANITE DENTURES 
253 
at the time of setting up the teeth. The object is to gain 
as large a contact surface as may be expedient, and so to 
face the surfaces as to crush the food without dislodging 
the dentures. The second stage is at the time of final 
finishing of the dentures, and is designed to produce edges 
for catching and cutting the food; also to remove such 
points as may interfere with antagonization. The first 
stage of grinding may be done before any of the teeth are 
set up, or each tooth may be ground just before setting up. 
The first method is more expeditious for an experienced 
workman, but the second method is more comprehensible 
for the student and is the one here described. 
Fig. 131 
If the new forms of teeth of the best manufacturers are 
selected, little or no grinding of the bicuspids and molars 
will be needed. Each manufacturer has the new forms desig- 
nated by trade names implying that they are anatomical. 
Setting Up.-As the patient is in middle life, the anterior 
teeth must be ground to represent slight wear. This is done 
by slightly grinding the incisal edge of the incisors so as to 
give a moderately sharp, straight edge, removing the rounded 
edge of youth. The central incisor is set in place and secured 
with melted wax (Fig. 131). Setting up the teeth may be 
facilitated by placing a small roll of softened yellow wax 
upon the wax model into which the cervical end of the teeth 254 
RUBBER AND VULCANITE 
are pressed and thus held while the lingual portion is being 
filled with melted wax. This lingual wax may be added by 
dropping on from a pencil or stick of wax, the end of which 
is melted in the Bunsen flame, or the melted wax may be 
carried to place in a wax spoon (Fig. 102). The lateral 
incisor, with its incisal edge straightened, is 
set next to the central. The cuspid with 
its mesial incisal edge ground, thus placing 
the apex of the cusp more distally, is secured 
in place. These three teeth fill the space 
from the high-lip line to the occlusal plane, 
and from the median line to and including 
the cuspid eminence. Their labial surfaces 
describe the segment of an arc, the radius 
of which is the straight line from the mesio- 
incisal angle of the central incisor to the 
disto-incisal angle of the cuspid. The buccal surface of the 
bicuspids and molars form a straight line, but one which 
diverges from the median plane of the mouth. The bicuspids 
and molars are all ground so as to present three surfaces to its 
antagonist. This is best understood by studying Figs. 132 
Fig. 132 
Fig. 133 
and 133. The bicuspids must have the three planes upon 
both the mesial and distal occlusal surfaces, while the molars 
have but the three straight planes. The first and second 
bicuspids and first molar (see Fig. 131) are set in order 
with their buccal surface forming the straight diverging line. TECHNIC FOR VULCANITE DENTURES 
255 
If the segment of the circle described by the three anterior 
teeth is continued, it will pass through the buccal cusp of the 
first bicuspid and diagonally through the sulcus of the second 
bicuspid (Fig. 10). The second upper molar is not set until 
the lower teeth are mounted. The wax about the six mounted 
teeth (Fig. 131) is smoothed and cooled so as to securely 
hold them. 
The segment of wax between the median and high-lip 
lines upon the other side of the wax model is removed with 
a warmed wax knife. The six teeth for that side are then 
ground, set up, and waxed securely. 
The method for grinding and setting up the lower teeth 
is similar to the upper; however, there are some impor- 
tant modifications. The section of wax defined by the 
median- and low-lip line upon either side is removed and a 
small roll of wax added into which the cervical end of the 
teeth are inserted. The grinding of the lower teeth differs 
from that of the upper in this: The facet formed on the 
incisal edge of the upper looks lingually, while that formed 
upon the lower incisors looks labially. The mesial edge of 
the upper cuspid is extended, while in the lower cuspid the 
mesial edge is shortened. The mesiodistal groove formed in 
the upper bicuspids and molars is on the buccal side of the 
center of the tooth, while it is placed lingually on the lower 
(Fig. 132). 
There are two methods for setting up the lower teeth. 
One method begins by setting first the second bicuspid so 
that it shall accurately intercuspate with the upper first and 
second bicuspids. This is followed in order by the first 
bicuspid, cuspid, lateral, central, and then the first molar. 
The other method begins with the central incisor and con- 
tinues in order backward. The reason for beginning with the 
anterior is to assure the desired expression, and that the lower 
teeth shall be clear of the upper ones by nearly one-sixteenth 
of an inch. The upper anterior teeth should overlap the 
lower, but for mechanical reasons they cannot overlap one- 
third the length of the crown, as in typical natural teeth. 
The amount of the overbite will be governed by the angle 
of the condyle path, and will be adjusted at a later stage of 256 
RUBBER AND VULCANITE 
the operation. The difficulty encountered by this method is 
to get the bicuspids to interlock. This often requires that 
the anterior teeth overlap each other laterally, especially the 
cuspid overlapping the lateral. To properly overlap any of 
the anterior teeth, either lower or upper, the mesiolingual 
angle of the overlapping tooth should be ground away for 
nearly its entire length. Also to interlock the bicuspids 
it may be necessary to soften the wax about the upper 
bicuspids and molar and move them backward. However 
it may be accomplished, the bicuspids must interlock or inter- 
cuspate. These six lower teeth being secured with wax, 
Fig. 134 
the segment of wax on the other side of the median line is 
removed and the six teeth mounted on that side. Fig. 134 
shows the twelve upper and the twelve lower teeth mounted 
to a straight horizontal plane. Should any of the teeth 
be loose in their setting, they are made fast by remelting the 
wax about them with an ironing spatula (Fig. 101), and the 
wax about all of the teeth thoroughly chilled for the next 
step of setting the lower second molar. 
A portion of the hardened wax just back of the lower first 
molar is removed and a ball of softened wax set in its place. 
The occlusal surface of the second molar is ground into the TECHNIC FOR VULCANITE DENTURES 
257 
same form as that of the first molar, and set upon the softened 
ball of wax. The plane of the occlusal surface of the second 
molar should be nearly parallel with the plane of the condyle 
path, and the tooth should be so placed that the disto- 
occlusal margin of the upper first molar will glide upon the 
buccosulcus plane of the lower second molar when the teeth 
are placed in lateral occlusion. Fig. 135 shows the teeth 
in lateral occlusion and the disto-occlusal margin of the upper 
first molar in contact with the lower second molar. It is 
obvious that if all the teeth but the lower second molar 
are set in hardened wax, and it in softened wax, working 
Fig. 135 
the condyle joint forward and backward repeatedly will aid 
in properly adjusting the second molar. Correctly placing 
the three molars, the upper first and the lower first and 
second, is the key to the mechanico-anatomical antagoniza- 
tion; and the secret for success in the adjustment of these 
molars is in keeping the disto-occlusal margins of the first 
molars down. They may be depressed a trifle below the 
plane, but never elevated above the plane. Herein is the 
distinction between the mechanico-anatomical arrangement 
of artificial teeth and the variously advocated "anatomical" 
arrangement of them. By observing Figs. 1, 2, 3, and 4 it 
will be seen that the anatomical arrangement of natural 258 
RUBBER AND VULCANITE 
upper teeth is that the occlusal surfaces of all the teeth, from 
the central incisors to and including the distobuccal cusp 
of the first molars, are in a straight horizontal plane, and 
that the second and third molars are not tilted, but stepped, 
upward. So far as the author knows, no advocate of the so- 
called "anatomical articulation" has ever suggested repro- 
ducing this upward stepping of the second and third molars. 
Hence there never has been a system of anatomical arrange- 
ment for artificial teeth, for they have all been adaptations, 
and all to a greater or less extent have opposed a physical 
law. The physical law is that " force moves at right angles 
to the surface from which it emanates." Therefore it 
is evident that the system that least opposes this physical 
law is superior in at least this one respect. It is evident 
that if the molars are tilted upward at any angle (the greater 
the angle the greater the leverage), the closing movement 
of the mandible must force the upper denture forward, and 
that if it were not for the interlocking of the bicuspids the 
denture could not be retained in its place. As the first 
molars must assume the burden of crushing hard food, it 
is logical to reason that their occlusal surfaces should be 
parallel to their alveolar base of support. If the crushing 
of food were the only function of artificial dentures, then 
the second molars should be placed in the straight occlusal 
plane; however, it is important to grind the food, and to 
have the dentures so constructed that they are balanced in 
any position in which they may be occluded. To obtain this 
balanced relationship of artificial dentures it is necessary 
to have more or less of the teeth placed in harmony with 
the condyle path; but to secure the greatest effectiveness 
in crushing and grinding the food, it is necessary to have as 
few teeth out of the horizontal occlusal plane as possible, 
hence the short-balancing curve, or "compensating curve." 
This term, "short-balancing or compensating curve," is in 
contradistinction to the long "compensating curve," as first 
taught by Dr. Bonwill. 
Having developed the philosophy of this peculiar arrange- 
ment of these three molars, a return may be made to the 
technic. TECHNIC FOR VULCANITE DENTURES 
259 
In like manner the three molars are adjusted on the other 
side of the case. 
Many of the new forms of molars have long lingual cusps 
on the upper and deep sulci on the lower ones. By this 
means a nearly straight occlusal plane is secured which 
favors retention. 
Fig. 136 
Proving the Antagonization.-A critical study should now 
be made of the antagonization of the teeth as mounted. 
For this purpose the antagonizor is grasped so that the 
thumbs and fingers may manipulate the condyle paths, and 
the three movements (incisal, right and left lateral) are 
repeatedly produced. This will disclose any imperfections 
in the alignment of the teeth. Should any of the teeth 
prove to be too long and interfere in the varied movements, 
they may be intruded or ground upon the lathe. The teeth 
may be ground while mounted in wax, provided light pressure 260 
RUBBER AND VULCANITE 
is used in holding them against the stone, and the stone is 
sharp and true running. The requirements of well-antago- 
nized teeth are that there shall be sufficient points of con- 
tact in any position in which they may be closed, in ordinary 
use, to balance them, or to prevent their displacement. If 
the teeth are placed in incisal occlusion, as shown in Fig. 
136, the upper and lower incisors will be in contact, also 
the upper first molars (disto-occlusal margin) will be in 
contact with the lower second molars. It will be only 
incidental and owing to an irregularity of alignment should 
Fig. 137 
there be any points of contact between the incisors and 
molars, for the upper teeth describe a straight line and the 
lower, by inclining the second molar, describe a concave 
line; and a concave line can be in contact with a straight 
line only at its extremities. The teeth being in right lateral 
occlusion, that is, the lower carried to the right (Fig. 137). 
there will be many points of contact on the right side but 
no contact on the left side, except, because of the pivotal 
movement, the lower second molar is carried forward and 
is in contact with the disto-occhisal margin of the upper 
first molar. This gives the so-called three-point contact, as TECHNIC FOR VULCANITE DENTURES 
261 
represented by the molars upon the left and the cuspids and 
molars on the right side. The teeth being placed in the left 
lateral occlusion (Fig. 138), the same relations are established 
for that side. 
In this critical study of the antagonization of the teeth 
it should be apparent that there is a relationship between 
the lateral inclination of the bicuspids and molars and the 
angle of the condyle path. The difference in width of the 
maxilla and the mandible, in the bicuspid and molar region, 
necessitates that these teeth are more or less laterally 
Fig. 138 
inclined; and that the plane described by the lateral move- 
ment varies from straight to sharply concave, with the 
concavity upward. If the condyle path is horizontal, the 
lateral movement plane will be straight; but if the condyle 
path is nearly perpendicular, the lateral movement plane 
will be sharply concave. This is demonstrated by two blocks » 
of plaster mounted in the antagonizor, and the lateral move- 
ments made until the blocks are so ground that they will 
be uniformly in contact at every point, while in the lateral 
movement. If the teeth have not been correctly inclined 
while mounting, they may be corrected by softening the wax 262 
RUBBER AND VULCANITE 
about the cervical ends of the teeth with a hot ironing wax 
spatula and moving the cervical ends either inward or out- 
ward as required. It may be necessary to remove certain 
of the teeth and deepen the sulci and possibly shorten some 
of the cusps. When the teeth are ground and mounted 
so that they may be moved in any direction (three), and, not 
meet with interfering points, also have the largest amount of 
contact surface, the critical study and correction may be 
considered as completed. Time used in this critical work is 
well spent. 
To complete the mounting of the teeth sufficient wax is 
cut away to permit the upper second molars being set in 
occlusion with the lower second molars, which are fixed 
in position with melted wax. 
It is noticeable in some of the illustrations that there is a 
space between the lower first and second molars. The reason 
for this is that by carrying the second molar forward, surface 
contact cannot be gained, only a V-shaped space formed, 
while by carrying it backward it affords a longer gliding 
surface for the upper first molar and a larger contact sur- 
face for the upper second molar. 
OTHER METHODS FOR ANATOMICAL ANTAGONI - 
ZATION. 
What is meant by anatomical occlusion or antagoniza- 
tion? It means that the artificial teeth are mounted in a 
manner compatible with the laws of nature, but not neces- 
sarily, and rarely are they reproductions of nature, for 
nature rarely attains perfection in our conception of her 
ideals. However, nature's laws are immutable and not 
violable with impunity; therefore the prosthetist must, if 
he desires the best results, bring his artificial creation into 
compatibility with nature. 
There are three laws of nature that an artificial denture 
shall not, with impunity, violate: 
1. The law of resistance of a tissue to compression. 
2. The law of freedom of movement of a tissue. 
3. The law of direction of force. METHODS FOR ANATOMICAL ANTAGONIZATION 
263 
As an artificial denture must compress the soft tissue 
upon which it rests, it follows, as a logical sequence, that 
the larger the surface and better distributed the pressure the 
less resistance, and, consequently, nature will better toler- 
ate the artificial appliance. However, an artificial denture 
riding upon a muscle is retarding the free movement of 
that organ, and if the contracting power of the muscle is 
greater than the retaining power it must dislodge the den- 
ture; therefore there is in each individual case a circum- 
scribed surface upon which the artificial denture may rest 
securely, but beyond which it is insecure and a source of 
irritation. The base-plate outline and adaptation being 
secured, the third factor, the law regulating force, must be 
complied with. This consists of mounting the teeth in such 
a manner as best to meet opposing forces-antagonism- 
antagonization. Therefore anatomical occlusion (closed 
teeth-passive), a better term is anatomical antagonization 
(opposition-active), reduced to its low'est denomination, 
may be defined as a factor in retention of artificial teeth. 
Important as is this factor, it is only one of several factors 
equally important. It is founded upon anatomical knowl- 
edge, therefore scientific; but it is pure mechanics. This 
scientific mechanical operation is a superstructure resting 
upon a substructure (base-plate), and it is dependent upon 
the secure or insecure foundation-impression. Therefore 
a properly taken impression is the foundation, the key to 
success. The substructure (base-plate) is next in importance, 
and if made from a tested impression is quite simple; but 
as few impressions taken are tested and perfection assured, 
the base-plate constitutes a very uncertain factor as a 
support for the superstructure-anatomical occlusion. 
To more fully appreciate the relative importance of ana- 
tomical occlusion in the scheme of restoring lost dental 
organs, it is well to classify the essential factors entering 
into such restoration. 
Thus it is seen that anatomical occlusion is a control by 
the physical laws of leverage. As leverage is the most 
powerful force utilized by the prosthetist it becomes of great 
importance. Anatomical occlusion probably has had, and 264 
RUBBER AND VULCANITE 
is having, more profound study than any other phase of 
prosthetic dentistry, as evidenced by the inventive genius 
displayed since 1840, the date of the first so-called anatomical 
articulator. Nevertheless, one must not lose sight of that 
other great factor, esthetics, for a part can never equal the 
whole, and the perfect artificial denture is the thing desired. 
Classification: 
Nevertheless, one must not lose sight of that 
Anatomy 
Retention 
Esthetics 
A thorough knowledge of the various hard and soft 
tissues of the mouth-their form, action, and 
controllability. 
Impressions and casts. 
Occlusion and contour models. 
Movements of the mandible. 
Measurements 
consist of 
Factors 
Physics 
includes 
Molecular attraction. 
Atmospheric pressure. 
Leverage, i. e., anatomical occlusion. 
Color. 
Forms. 
Contours. 
What constitutes the distinction between plain occlusion 
of the teeth and the designated anatomical occlusion? 
Plain occlusion consists of arranging the teeth in the normal 
relationship of their morsal surfaces. Anatomical occlusion 
is an addition to plain occlusion, and consists of placing the 
teeth in such a position as to create the so-called "three- 
point contact." Plain occlusion is nature's perfection, and 
should always be striven for in every mounting of artificial 
teeth. The three-point contact is rarely found in natural 
dentures and is entirely unnecessary. However, three-point 
contact is essential and is perfection in antagonization of 
artificial teeth. Three-point contact is a name applied to 
the operation of arranging artificial teeth so that they 
balance in incisal and lateral occlusion as well as in normal 
(retruded) occlusion. It is the control of the laws of leverage, 
therefore essential to perfection in artificial dentures. As 
before expressed, anatomical occlusion is a factor only in 
retention of artificial dentures. Anatomical occlusion, 
viewed in the naked form, seems a very simple thing, but 
it is not; the subject has been coexistent with dentistry METHODS FOR ANATOMICAL ANTAGONIZATION 
265 
as a profession, and is still a profound subject for inves- 
tigation. It is believed that all the movements of the 
mandible are now understood, also instruments invented 
to produce them; but no one knows what the future may 
have in store for us. It is certainly true that the profession 
is being flooded with inventions designed to make perfect 
this operation. Judgment is always an essential factor even 
with the most highly developed instrument on the market. 
These questions arise in our mind: (1) Are these expensive 
and elaborate instruments necessary ? (2) Can perfect results 
be produced with them? (3) Are all the instruments called 
anatomical equally good, and, if not, which is the best? 
If an answer in a word were required to all these questions it 
would have to be, No. However, that would be a very 
unjust way of disposing of the subject, for it is probably 
true that the vast majority of the profession is not qualified 
to make use of the knowledge or the best instruments now 
obtainable. Probably the Snow, Gysi and Hall instruments 
are the most scientific and practical instruments yet placed 
upon the market. However, the Hall is of a class diametrical 
to the other two in this, the Hall is constructed upon the 
principle that the teeth and muscles direct the movements of 
the condyle, whereas the other two are constructed upon the 
principle that the condyle and muscles control the movements 
of mastication. Therefore the Snow, Gysi and Hall instru- 
ments and methods only are considered in extenso. 
Anatomy.-A thorough knowledge of the structure and 
use of the hard and soft tissues composing the masticating 
apparatus is necessary to fully comprehend anatomical 
occlusion; however, a resume only can be given here, and 
Gray's Anatomy should be consulted. Four bones enter 
into the upper jaw, the two maxillary and palatal, while 
the lower jaw has but one, the mandible. The upper jaw 
is the fixed or stationary base, while the mandible is a lever 
or swinging arm attached to the cranium by ligaments and 
muscles. The attached end of the mandible (either end) is 
called the condyle, the portion of the temporal bone into 
which it sets is called the mandibular fossa, and the anterior 
inclined curved surface of this fossa is spoken of as the 266 
RUBBER AND VULCANITE 
articular tubercle. The condyle is separated from the fossa 
by a cushion of membranes and ligamentous tissue, and the 
two (condyle and fossa) are united, in part, by a capsular 
ligament attached below the head of the condyle and at the 
periphery of the mandibular fossa. This forms a peculiar 
ball-and-socket joint. There is no fixed rotating center. In 
a simple open-and-shut movement Dr. Snow has said: "At 
first the circular surface of the condyle moves as from a pivot 
in the synovial sac, the center of the movement being at 
the center of its curved surface. When the backward swing 
of the ramus has taken up the slack in the external lateral 
ligament (sphenomandibular) the lower edge of that liga- 
ment determines the center about which further movement 
is made." The condyle instead of being spherical is an 
elongated flattened spheroid. Its long axis is approximately 
at right angles to the ramus of the mandible, but is doubly 
oblique, that is, it is slightly inward, downward, and back- 
ward with so many variations that it is difficult to recognize 
the rule. Hence the movements of mastication may be con- 
sidered as a component of the various movements of the 
mandible. To construct an instrument admitting the repro- 
duction of all the rotation points formed in the gyrations of 
the mandible Seems now to be complicated and impracticable, 
and probably entirely unnecessary. The Kerr antagonizor 
was an attempt at producing the anatomical rotation joint, 
while the Gysi Adaptable establishes an average rotation 
point variable in one direction only. 
This third movement of the mandible (lateral) was recently 
described by Mr. Norman G. Bennett, of England, and 
measured by Professor Gysi, of Switzerland. 
These three movements of the mandible-open and shut, 
forward incisal, and lateral mandibular-are the impor- 
tant factors in anatomical occlusion. The Gysi adaptable 
antagonizor, with the three measuring instruments, is a 
valuable aid in comprehending and demonstrating these 
movements and their importance. It is probably the only 
instrument upon which it is possible to approximately repro- 
duce all three of these movements of the mandible. Even 
with this instrument the teeth mounted in wax should be METHODS FOR ANATOMICAL ANTAGONIZATION 
267 
tried in the mouth for final adjustment. There is a reason 
for this: All three measurements are made by use of an 
insecure base-plate resting upon the mandible, consequently 
are not absolutely dependable. It is true that an expert, 
painstaking scientist, and operator like Professor Gysi 
will produce quite accurate results with these instruments; 
but it is hardly reasonable to expect satisfactory results 
by even the average operator, to say nothing of those inex- 
perienced in handling instruments of precision and below 
average ability. A well-developed anatomical antagonizor 
is desirable for the laboratory, but the perfection, the human 
anatomical antagonizor, is necessary for the operating-room. 
It is thought by some that the pivotal center of the open- 
and-shut movement should be reproduced in the antagonizor, 
and by other authorities that it is of no practical value 
in mounting artificial dentures. The writer is of the latter 
opinion, because this pivotal center exists only as the man- 
dible is being moved from the maxilla, and returned to 
contact, when the pivotal center is instantly transferred 
to the surface of the condyle and remains there during the 
triturating movements of mastication. The writer is 
further of the opinion that the lateral incisal movement is 
of negative importance; but that the lateral mandibular 
and the forward incisal movements are important; also 
that the essential portion of these operate from the top 
of the condyle. If this belief and reasoning are true to 
nature, then the variable lateral rotation center of the 
Gysi adaptable antagonizor is unnecessary; but the lateral 
and vertical movements of the condyle are scientific and 
necessary for the greatest accuracy; however, as these 
measurements are obtained by an insecure attachment 
to the mandible, the accuracy of the measurements are very 
questionable. In the Snow Twentieth Century Antagonizor 
the vertical movement or forward incisal only is reproduced; 
but the Snow new "Acme" has the forward incisal and lateral 
mandibular movements; as has also the Hall. However, 
these two movements, forward incisal and lateral mandibular 
are quite different in development in each of the three 
instruments, Adaptable, Acme, and Hall. 268 
RUBBER AND VULCANITE 
There is still the question of the importance of an exact 
measurement of the base line of the mandibular triangle. 
Dr. W. C. Dalbey, of Du Quoin, Illinois, in an interesting 
paper in the March, 1914, Dental Cosmos, lays much stress 
upon the importance of the length of the base line of the 
triangle. He has invented an instrument for its measure- 
ment. If the gyrations of the mandible were from a fixed 
rotating center as in a mechanical antagonizor, then un- 
doubtedly the length of the base line of the triangle would 
be an important factor; but as it is a remarkably adaptable 
joint and one of its most important movements is lateral, 
its exact measurement may be unimportant. It is important, 
however, to have all points of the occlusal plane in har- 
monious relation to the base line of the triangle. This is 
the sole function of the face bow. It must be evident to 
a reflective mind that this lateral mandibular movement 
emphasizes the three fundamental horizontal longitudinal 
planes of the bicuspids and molars as illustrated in Figs. 
132 and 133, therefore in grinding away interfering cusps 
they should be reduced in the direction to these longitudinal 
planes. However, this does not imply removing the cusps 
to a flat surface, but enough only to relieve the interference. 
Recently, while in Washington, D. C., the writer, through 
the kindness of Curator Hrdlicka, of the Smithsonian 
Institution, had the privilege of examining and measuring 
a series of mandibles of that great collection. Limited time 
only prevented a more extensive study. 
The following tabulation, while not extensive enough to 
establish the fact, is elaborate enough to be suggestive, and 
to aid in a developing conviction; that is, that the man- 
dibular equilateral triangle is the exception and not the rule: 
Totals .... 
Equilateral .... 
Isosceles 
Scalene 
Mandibular triangles. 
o 
o 
h- 00 
M Oi 00 
Mixed 
whites. 
cc 
o 
o oo to 
German 
whites. 
05 
<1 M 00 
Egyptian. 
00 
tO 
00 o H 
Eskimo. 
to 
to 
O M Ot 
Patagonian 
Indian. 
CD 
<1 to • 
Mixed 
Indian. 
Cn 
to oo: 
Mongolian. 
Cn 
i : 
Australian 
Islanders. 
292 
00 00 h- 
O *40 
woT 
0^0 
s-' 
Totals. METHODS FOR ANATOMICAL ANT AGON IZ AT ION 
269 
The average triangle of the 60 mixed whites had a base 
of 9.8 cm., and the right and left sides 10.4 cm. each.1 
The average triangle of the 30 German whites had a 
base of 9.7 cm., the right side 10.46 cm., and the left side 
10.5 cm. 
The largest side of the triangle in the 90 whites was 11.4 
cm. for both the right and left sides, of which there were 
3 of each, and 1 base reached a magnitude of 11.2 cm. 
In the mandible of the 90 whites there were 2 base lines 
longer than one lateral side and 2 base lines longer than 
either lateral side. In the remaining 202 measurements 
there were 5 instances in which the base line was longer 
than a lateral side and 6 others in which the base line was 
longer than either lateral side. 
While balance, the so-called "three-point contact" is the 
essential and fundamental factor of anatomical occlusion, 
it is dependent upon several other operative procedures. 
These associated factors can here be named only, as each 
factor is a chapter by itself. They are: impressions, casts, 
base-plates, occlusion and contour models, and measure- 
ments. Anatomical occlusion emphasizes the importance 
of each of these factors, especially the base-plate and occlu- 
sion model. A base-plate of wax is very unsatisfactory 
for this work. A well-adapted resinoid base-plate is much 
better, but perfection requires a base-plate of vulcanite or 
metal. Having suitably formed base-plates and occlusion 
models, and the measurements obtained, the casts and 
occlusion models are mounted upon the antagonizor. 
Occlusion of the Teeth.-Normal occlusion consists of 
the labial and buccal surfaces of the upper teeth slightly 
overlapping the same surfaces of the lower teeth. The 
morsal surfaces of the bicuspids and molars interlock one 
against two, except the upper third molar, and the six ante- 
rior upper teeth overlap the lower teeth (approximately) 
one-third of their length; but are not necessarily quite in 
contact with the lower ones. In normal occlusion the lower 
teeth, except the central incisors, are in advance of their 
1 10.16 cm. equal 4 inches 270 
RUBBER AND VULCANITE 
corresponding upper teeth. Plain occlusion of artificial 
teeth lays no stress upon the long axis of the teeth, but the 
long axis is the controlling factor in anatomical occlusion, 
the factor that controls the direction of force upon the arti- 
ficial dentures in the various gyrations of the mandible. 
The two physical laws of force controlling leverage in an- 
tagonization of the teeth are: (1) Force moves in a straight 
line, and at right angles to the surface of its origin, and 
(2) the combined direction of two or more forces is their 
resultant. Therefore stability of a denture requires that 
the long axis of the teeth shall be at right angles to the 
plane of the jaws upon their buccal surfaces, but an oblique 
angle upon their distal surfaces; also that the resultant 
of the incline planes of the morsal surfaces of the molars 
and bicuspids must be at right angles to the base plane, but 
oblique in the plane described by a cross-section of the 
denture. It is apparent that when an artificial denture 
has one cusp only in occlusion with the opposing dentures 
it is impossible to have the long axis of the tooth as a resultant 
of all the lines of force that may bear upon it. Hence an 
auxiliary support may be had by so mounting the teeth 
that necessarily there is a second point of contact upon the 
opposite side of the denture, and still better if there can be 
three equidistant points of contact. This s the basis of 
the so-called "three-point contact," and is exemplified in 
incisal occlusion and also in lateral mandibular occlusion. 
Arranging the Teeth.-The six upper anterior teeth are 
mounted to the Bonwill dental circle with such variations 
as may be required for esthetics. The mounting of the bi- 
cuspids and molars should be considered as mechanical 
problems, and esthetics ignored just to the extent that the 
esthetic defects are not too glaring. The upper bicuspids 
and first molars upon either side are arranged in a diverging 
straight line. Their long axes diverge slightly outward so 
as to have full-face occlusion with the lower opposing teeth 
which converge inward. This will provide for the lateral 
mandibular three-point contact, provided the occlusal sur- 
faces are properly formed and the long axes are correctly 
aligned; but it will not produce the incisal three-point METHODS FOR ANATOMICAL ANTAGONIZATION 
271 
contact, which must be secured by setting the lower second 
molar and the overlap of the central incisor in harmony 
with the inclination of the articular tubercle. It is seen 
that the normal upper incisors overlap the lower incisors 
one-third of their length; this permits the lower second 
molars, when moved forward, to occlude with the upper 
first molars provided the condyle path is horizontal. If 
the condyle path is very oblique and there is a typical one- 
third incisal overbite (as seen in natural normal occlusion) 
the lower second molar (either side) would have to be set 
at an impracticable inclination, whereas by placing the 
overbite at the minimum the inclination of the second 
molar may be reduced. 
There are two methods by which the three-point contacts 
may be produced. The one method has just been described 
and consists of placing the lower second molar in harmonious 
relation with the articular tubercle, the upper first molar 
and the central incisor. This method is necessary when 
using the older forms of artificial teeth. The second method 
consists of having molars with long lingual cusps, which 
is characteristic of the best of the newer forms of molars. 
The long lingual cusps of the upper molars, the deep sulci 
of the lower molars, and the slight or no overlap of the 
incisors compensate for the oblique condyle path and makes 
unnecessary the anterior obliquing of the long axis of the 
second molar; thereby adding to the effectiveness of the 
masticating surface of the second molars. In fact, if the 
lower second molar is placed in a very antero-oblique posi- 
tion, the stability of the dentures is enhanced by leaving off 
the upper second molar. 
Professor Gysi instructs to set the upper bicuspids and 
molars directly over the crest of the alveolar ridge, with 
the lingual cusp of the first bicuspid slightly above the 
horizontal plane of the buccal cusp; the two cusps of the 
second bicuspid are in their same horizontal plane, while 
the lingual cusps of the molars are increasingly below the 
horizontal plane of their buccal cusps. He instructs to set 
the molars so as to slightly open the bite and then force 
into occlusion by placing the teeth repeatedly in right and 272 
RUBBER AND VULCANITE 
left lateral mandibular occlusion. This is a very simple and 
most effective technic for securing the lateral mandibular 
three-point contact. This is normal occlusion, or normal 
bite. 
Cross-bites.-When there is an extensive disparity between 
the width of the upper and lower alveolar processes, better 
results may often be obtained by the cross-bite method. 
This consists of exchanging places with the molars and 
second bicuspids crisscross, that is, the upper right teeth 
exchange places with the left lower and the upper left with 
the right lower. This interchange of position necessitates 
some grinding. In time the cross-bite teeth of Professor 
Gysi's patterns will probably be upon the market. This 
cross-bite method of mounting places the buccal surface 
of the lower molars buccally to the buccal surface of the 
upper molars, thereby placing the teeth in better relation 
to the alveolar ridges and less interference with the move- 
ments of the tongue. However, in excessively resorbed 
ridges, this cross-bite is rarely required because the base 
plane is at the periphery of the base-plate rather than at 
the crest of the alveolus, and the normal bite is preferable. 
The cross-bite is especially indicated with prominent alveolar 
ridges, and contracted maxillae, usually accompanied with a 
high vault. 
Trial of the Teeth on the Human Anatomical Antagonizor.- 
If well-adapted base-plates, occlusion models, and meas- 
urements are obtained and reasonable care given to mounting 
the teeth anatomically, the wax being thoroughly chilled, 
the dentures are ready for proving in the mouth. Patients 
should be instructed that the teeth are mounted in wax 
and that they must not use force upon them • unless they 
are instructed to do so. The teeth are placed in the mouth 
in normal occlusion and studied esthetically, then they are 
placed in incisal occlusion, and, with a thin-blade spatula, 
tested to see that there is equal pressure at the three points 
of contact. They are then placed consecutively in right and 
left lateral occlusion and tested in like manner. Should 
any of the teeth prove to be too prominent the wax about 
the elongated teeth is slightly warmed, replaced in the THE NEW SCHOOL 
273 
mouth, and the teeth closed in the necessary occlusions to 
adjust them. Should any of the teeth be too short the 
wax is dried, the teeth raised and waxed, then adjusted to 
the mouth. 
The anatomically occluded teeth may now be considered 
perfect and ready for mounting on vulcanite. 
THE NEW SCHOOL. 
The preceding pages on "Other Methods for Anatomical 
Antagonization" have developed since the first edition of this 
book was written, and at the preparation of this-the fourth 
edition-the author believes he is justified in announcing 
his conviction, that is, that a new school of dental prosthetics 
is rapidly forming. However, it would be very unwise for the 
colleges, the text-books, or the profession to judge hastily 
of the merits or demerits of either school of thought and 
technic; but they should earnestly weigh the evidence and 
thus form a mature conviction. Pope's advice is certainly 
timely: 
"Be not the first by whom the new are tried 
Nor yet the last to lay the old aside." 
The progress of dental prosthetics can be divided into 
three periods: (1) Empirical; (2) Bonwill School; and (3) 
New School. 
The Empiric period was a necessary antecedent of the 
schools, and included the time up until thought upon this 
subject was crystallized into expression by Dr. W. G. A. 
Bonwill in 1864. His notable paper read before the American 
Dental Association well marks the beginning of a scientific 
school of thought and technic. All subsequent research and 
teaching have been based upon the work of Dr. Bonwill, 
hence it is only a just recognition that the followers of Dr. 
Bonwill shall be known as the Bonwill School. The Bonwill 
School was based upon five fundamental principles, namely: 
(1) mandible, a lever of the third class; (2) equilateral tri- 
angle; (3) fixed rotation centers; (4) dental circle; (5) align- 
ment of the teeth. The Bonwill School probably reached its 274 
RUBBER AND VULCANITE 
highest development under Prof. A. Gysi, of Switzerland. 
Prof. Gysi did more than perfect the Bonwill School; he 
demonstrated and established the fact that the rotation 
centers were not on the head of the condyle, but anywhere 
in a sphere one inch in diameter, located back of the base 
line and about the sagittal plane. 
About the same time Mr. Norman G. Bennett of England 
demonstrated the lateral mandibular movement from a 
vertical rotation center. 
Prof. F. W. Frahm, then of the University of Denver, but 
now of the University of Southern California, demonstrated 
that one side of the face is not an exact counterpart of the 
other; therefore, that the Bonwill triangle is rarely equilateral. 
He also demonstrated the importance of the sagittal plane. 
Dr. Rupert E. Hall, of Houston, T'exas, but now of Chicago, 
demonstrated that it was not the temporomandibular joint 
in connection with the muscles; but the teeth and muscles 
that are the dominating factors in mastication, that the joint 
functions only as a compensating or a toggle joint. He also 
conceived the self-evident fact that it is the closing movement 
of the mouth that is of importance in mastication, and that, 
not until at least two points of opposing teeth meet. Dr. 
Hall has been most practical because he has taken all of 
these fundamental principles and created a most convenient 
instrument to aid in properly constructing artificial dentures. 
That the author may not be misunderstood he quotes the 
Standard Dictionary definition of a profession: "An occu- 
pation that properly involves a liberal education or its equiva- 
lent, and mental rather than manual labor.'' He defines the 
operation of constructing artificial dentures as mental rather 
than instrumental, and would impress the fact that the knowl- 
edge of what is required is the first essential, and that an 
instrument is only a valuable aid. However, the desired 
results in denture construction may be produced upon any 
of the three modern instruments, but more simply and expe- 
ditiously upon the Hall. The author requests the reader to 
return to the first chapter of this book and study it carefully 
for therein is the justification for the new school. Following 
is Dr. Hall's description of his instrument and methods. THE NEW SCHOOL 
275 
The Hall Method of Antagonization.1-Theory.-The Hall 
theory of the mandibular movements and antagonization is 
based on an extension of Bonwill's discovery that the ground 
plan of the human masticatory apparatus is the equilateral 
triangle. 
Its development has demonstrated that the condyles are 
not the guide to the movements of mastication, but are 
merely the fulcra upon which the mandible moves; that the 
planes and the positions of the teeth are the guides of the 
mandibular movements, just as the rails guide the railway 
train. The movements of the mandible are complex, made 
up of a number of simple movements automatically operat- 
ing simultaneously in concert as guided by the teeth. Only 
movements occurring when planes of two or more teeth 
are in contact are masticatory movements and are of im- 
portance to the prosthetist. In line with this idea, and 
recognizing the coordinate relation between the movements 
of the mandible and the planes of the teeth, the Hall theory 
adapts the mandibular movements to the planes and positions 
of the teeth, and not the planes and positions of the teeth to 
the condyle paths. It is obvious, therefore, that the re- 
establishment of correct masticatory movements must be 
effected, if at all, by means of artificial dentures that restore 
the proper relations of the planes of the teeth. Practical 
tests based upon this idea prove its correctness. 
Let us first analyze these simple movements and then 
study them in combination. 
1. We have the opening and closing movement, first in 
point of order because it is this movement that occludes the 
teeth and in turn is required to unlock them before other 
movements are possible. The axis of this movement runs in a 
horizontal plane at right angles to the antero-posterior aspect 
of the movable member-the mandible-and is located in a 
vertical plane below the heads of the condyles. 
1 The following description of the Hall instrument and method has been 
furnished for this book by Dr. Rupert E. Hall, of Chicago, Ill. The author 
has been intimately acquainted with the work of Dr. Hall for more than 
five years and unhesitatingly endorses the instrument and method as in 
his opinion destined to revolutionize the mounting of artificial dentures. 
They are remarkably simple, positive, and efficient. 276 
RUBBER AND VULCANITE 
2. We have the incisive movement, a movement in com- 
bination with the opening and closing movement, second in 
point of order because incision precedes mastication. The 
location of the axis of this movement is below and parallel 
with that of the opening and closing movement. 
3. We have the mandibular lateral movement, a move- 
ment in combination with the opening and closing and incisive 
movements, third and last in point of order because its use 
is in movements of mastication which succeed those of 
incision. The axis of this movement lies in the median plane 
posterior to the condyles and in a plane oblique to the plane 
of the teeth. 
Dr. Bonwill took the mandible as the basis for measure- 
ments. While it is true that the mandible is attached to the 
cranium, of which the maxilla is an integral part, it is also 
true that in nature's processes the mandible is first developed, 
the maxilla being thrown off as a lateral from it. But in 
making calculations for artificial reproduction of the move- 
ments of the mandible, we are compelled to work from a fixed 
basis. Quite evidently the mandible, which is freely movable 
in any direction, cannot form this basis. So we take the 
maxilla as the foundation about which to make our deduc- 
tions. 
Dr. Bonwill says the measurements of the upper jaw, 
though slightly larger, must conform to those of the lower. 
Conversely, then, the measurements of the mandible must 
conform to those of the maxilla. 
The triangle of the maxilla is described by lines connecting 
the crests of the glenoid fossse of the temporal bone with each 
other and with the contact point between the upper central 
incisors. The line between the crests of the fossae is the base, 
the contact point of the incisors the vertex of the triangle. 
Theoretically, it is equilateral, with an average measurement 
of approximately four inches on each side. The triangle of 
the mandible is of the same form but slightly smaller, being 
described by lines connecting the centers of the crests of the 
condyles and the contact point of the lower central incisors. 
The altitudinal lines of both triangles are in the median 
plane or the sagittal plane of the skull. If the maxillary THE NEW SCHOOL 
277 
triangle be conceived as folded back on its base as a hinge, its 
vertex will take the position in the region of the external 
occipital protuberance. The protuberance is thus seen to be 
at the same distance approximately from the condyles as the 
contact point of the upper central incisors and to form the 
vertex of a counter triangle to the maxillary triangle which 
we may designate the occipital triangle. 
The triangle in these two positions will be in different 
planes and will form a dihedral angle corresponding approxi- 
mately to the dihedral angle between two regular triangular 
pyramids placed base to base to form a double tetrahedron. 
A straight line between the two vertices-protuberance and 
contact point-will describe the so-called occlusal plane. 
A complete geometrical demonstration would perhaps be 
too technical here, so only a brief resume is presented. 
The accompanying scheme (Fig. 139) shows the double 
regular pyramid founded on the mandibular triangle applied 
to the human skull in the development of the Bonwill idea 
to its legitimate conclusion. The maxillary triangle is super- 
imposed, showing its relations, with the mandibular. 
A B C D represents the double triangular pyramid. B 
stands for the base of the mandibular or Bonwill triangle, 
the line connecting the crests of the condyles. C is the vertex 
of the mandibular triangle, the contact point of the lower 
central incisors. A is the external occipital protuberance, 
the position assumed by the vertex when folded back on its 
base. D is a basal corner of the double pyramid. Line DB, 
is the altitude of the figure in the vertical plane and intersects 
line AC, the occlusal plane, at right angles at E. 
This demonstration points to point A-the external 
occipital protuberance-as the center of the mandibular 
lateral movement, to point E as the center of the opening 
and closing movement, to point D as the center of the incisive 
movement. 
Taking the external occipital protuberance as the center 
of the mandibular movements, we have the lateral movement 
in the arc of a circle in the horizontal plane; second, the 
deflection of this movement vertically by its guide, the cusp 
planes of the teeth, the typical guiding inclinations of which 278 
RUBBER AND VULCANITE 
are 45 degrees. The determining guiding inclination of the 
cusp, that of the upper first bicuspid, is projected line I J. 
A line projected from the occipital protuberance intersecting 
the prolongation of the line I J at right angles determines 
the axis of the resultant compound movement so produced, 
line K L. 
Fig. 139 
The center of the incisive movement, while typically, 
located at point D, automatically finds its center in the line 
E M as guided by the overbite. The length of the line E M 
may be infinite. 
The soundness of these theoretical conclusions as a basis 
for practice has been amply verified. Every practical case 
in which they are tested-without a single exception-adds 
to the cumulative affirmative evidence of their correctness. 
The Hall antagonizor affords the means for reproducing 
all these movements and their combinations, including the 
automatic shifting centers of rotation, and provides perfect THE NEW SCHOOL 
279 
antagonization and apposition of the planes of the teeth, 
giving the wearer the full advantage of the mandibular move- 
ments in the mastication of food. In centers of movements 
being adaptable, teeth of any cusp angle, any degree and 
inclination of overbite and arrangement may be mounted 
upon it with the certainty that they will work in the mouth 
precisely the same as in the articulator. 
Fig. 140 
Fig. 140 shows a diagram of the mechanical device for the 
registration and reproduction of these centers and movements. 
Fig. 141 shows a perspective view of the device. Practical 
description of the appliance is given in the Method of Use. 
Method of Use.-Base-plates and wax occlusion models are 
prepared, trimmed, contoured and adjusted to the require- 
ments of the case, but without special regard to the occlusal 
plane, as this will be established better in another way. 280 
RUBBER AND VULCANITE 
Secure the bite relation, mark the median line and the lip 
line, remove from the mouth and fuse the two waxes together 
securely with a hot spatula. Next, mark the curve of occlu- 
sion (curve of Spee), determining the position the teeth are to 
occupy. This curve normally should be equidistant between 
the upper and lower ridges; but it may vary if the absorption 
from the loss of the teeth has been unequal or if the esthetic 
Fig. 141 
requirements demand it. In all cases (the ridges permitting) 
the location of the anterior curve of occlusion will be deter- 
mined by the intersection of the lip line with the median line, 
and the curve of Spee will blend or harmonize with the an- 
terior curve. In the region of the first upper molar on either 
side indent the wax at the occlusal curve with a sharp-pointed 
instrument, and make a like indentation at the intersection 
of the median line and the lip line (Fig. 142). Next secure the THE NEW SCHOOL 
281 
base-plates to the casts and attach the bite-jig E (Fig. 141), 
adjusting the screws in the indentations previously provided 
in the wax (Fig. 143). Next adjust the bite-jig, carrying 
the casts and bite waxes in the antagonizor, and attach the 
casts to the cast plates (Fig. 144). The bite-jig establishes 
the occlusal plane and Bonwill apex. Remove the bite-jig 
and the case is properly mounted and ready to receive the 
teeth. 
Fig. 142 
The centers of movement being theoretical and automatic, 
the dimensions and characteristics of the individual Bonwill 
triangle are of no importance; therefore no attempt is made to 
ascertain and establish them in the antagonizor. Exhaustive 
tests have proved that results without accurate dimensions are 
equal to those attained with them. Consequently, the face 
bow has been eliminated from use with this appliance and all 
cases are worked upon the theoretical average four-inch tri- 
angle. Therefore the design and use of the Hall antagonizor 
simplifies to an incomparable degree the technic and work 
in denture construction. The elimination of the need for 
measurements or adjustments makes the instrument the 
most simple and easy of understanding and operation yet 
devised. 282 
RUBBER AND VULCANITE 
Setting the Teeth.-Lock screw A (Fig. 141) is locked and 
the opening and closing movement is used for the initial or 
tentative setting. The teeth are arranged to conform to the 
ridges and to the esthetic requirements. Next they are tried 
in the mouth to ascertain the correctness of the bite and the 
esthetics, after which the trial dentures are returned to the 
Fig. 143 
antagonizor to adjust the teeth in their anatomical relations. 
The wax around the teeth is warmed, lock screw A is released 
and lateral movements are made, guided by the guide pin 
B in the center guide angle C. As pressure is brought to bear 
upon the teeth, they are automatically forced (applying the 
method of Gysi) into the correct anatomical relations. Next, 
lock screw A is locked and with adjusting screw D, the lower THE NEW SCHOOL 
283 
teeth are thrown forward into the incisive relation, in which 
position they are adjusted to three-point contact or whatever 
arrangement is desired. 
Lastly, they are returned to normal occlusion for final 
adjustment, after which the case is ready for waxing and 
vulcanizing. 
Fig. 144 
No attempt is made to perfect the occlusion and antagoniza- 
tion while the teeth are in the wax, because perfection gained 
at this stage would be lost in the succeeding operations of 
flasking, packing, and vulcanizing. It is better to approxi- 
mate these relations as well as may be without grinding, and 
after vulcanization, when no slips or changes can occur, to 284 
RUBBER AND VULCANITE 
grind the teeth to occlusion and antagonization, after a 
corrected bite. This method consists in adapting a thickness 
of base-plate wax to the occlusal and incisal surfaces of the 
Fig. 145 
lower teeth, attaching it to the denture with a hot spatula, 
and inserting the dentures in the mouth and having the 
patient register the normal bite upon the wax carried by 
the lower denture (Fig. 145). Remove from the mouth and 
Fig. 146 
securely attach together in the relation established by the 
corrected bite as determined by the wax (Fig. 146). Adjust 
the bite-jig to the dentures the same as for the original bite THE NEW SCHOOL 
285 
and remount in the antagonizor (Fig. 147). Remove the 
bite-jig and wax from between the teeth and the correct 
relation of the dentures is determined and the teeth are ready 
for grinding. 
Fig. 147 
Grinding the Teeth.-First, they are ground under the lat- 
eral movement of the antagonizor to the guide pin (5) center 
in the center guide angle C. Secondly, the lower teeth are 
carried into the incisive position by means of the adjusting 
screw D and the grinding under the lateral movements con- 
tinued in this relation, bringing the lower teeth gradually 
back to normal occlusion with the adjusting screw as the 
grinding proceeds, effecting a solid cut with an unlimited 286 
RUBBER AND VULCANITE 
range that will accommodate all the milling, triturating 
mandibular movements, providing thereby accommodation 
automatically for varying rotation centers. 
Dentures mounted in the Hall antagonizor may be placed 
in the mouth with the assurance that adaptability and co- 
ordination with the tissues and the mandibular movements 
will be perfect, with no points of interference, and no need of 
further cutting or adjusting. The teeth are ground in the 
antagonizor to perfect occlusion and antagonization in every 
direction it is possible for the mandible to move. Conse- 
quently, points of interference cannot be found, as there are 
Fig. 148 
none. Other antagonizors make no provision for the milling 
movements traced by the incisor point, and provide limited 
movements only to a definite given path for either side for 
each case. It is a well-known and admitted fact that the 
movements of the mandible are not restricted to definite 
paths, but it has been considered impossible to construct 
an antagonizor capable of reproducing all of the movements 
of the mandible. And an average movement only is all that 
has been accomplished or claimed for antagonizors of the 
past. 
In the Hall antagonizor the supposed impossible has been THE NEW SCHOOL 
287 
accomplished. The mechanism is such that all of the 
mandibular movements are reproduced and under perfect 
control of the operator. Its movements are capable of com- 
bining in infinite numbers of combinations, and teeth con- 
structed in it have a like range of adaptability, insuring perfect 
coordination with the movements of the natural mandible 
when the dentures are placed in the mouth. 
Fig. 149 
Fig. 148 illustrates the correct anatomical relation of the 
teeth in lateral antagonization as interpreted and arranged 
by investigators and prosthetists at the present time. 
Fig. 149 illustrates the incorrect relation of the teeth in 
lateral antagonization, according to the same authorities. 
Dr. Hall's interpretation of these two illustrations is that 
diametrically the opposite is true, and he cites the fact that 
the relation shown in Fig. 148 provides no space for food, and 
when the antagonization is opened to receive food the balance 288 
RUBBER AND VULCANITE 
points are broken and the anatomies are nil. Therefore his 
contention is that we have had no anatomical antagonization; 
that the so-called anatomical antagonization has been in 
reality nothing but occlusion. 
Fig. 150 
With the Hall antagonizor the movements are such that 
normal overbite may be set and the teeth so arranged that 
the normal anatomical relations as shown in Fig. 149 may be 
secured as in nature (Fig. 150), and it is claimed to be the 
first antagonizor to permit of true anatomical arrangement 
of artificial teeth. 
Having discussed at considerable length "other methods for 
anatomical antagonization'' (see page 262), a return is made 
to the main subject of the chapter, vulcanite technic. FINISHING THE MODEL DENTURES 
289 
FINISHING THE MODEL DENTURES. 
The teeth being now accurately mounted and antagonized, 
care must be exercised not to disturb them in any further 
manipulation. As the outlines of the wax-model bases are 
the outlines of the finished dentures, attention should be 
given to the contour of the wax-model bases. These are 
completed by adding wax where there may be a deficiency, 
cutting away excessive wax and glossing the surface. The 
Haskell and Gritman spatulas (4 and 5 respectively of Fig. 
101) are excellent as ironing instruments, and the Nos. 1 
and 2 instruments of the Evans carvers are especially 
suitable for carving. There are two methods for glossing- 
(1) heat, and (2) a solvent. The heat may be applied to 
glossing the surface either by passing the wax-model base 
through the Bunsen flame with a moderately rapid motion, 
or the flame may be puffed upon the surface of the wax 
with a small mouth blowpipe. An expert may produce 
beautiful results with the flame, but the novice is liable 
to come to grief. The solvent method consists of wiping 
the surface over with a soft cloth (quarter of an aseptic 
napkin) moistened with a wax solvent. The most convenient 
and least objectionable solvent is chloroform. The teeth 
are cleansed of wax at the same time that the surface is 
smoothed. As the surface is covered with partially dis- 
solved wax, the case should be permitted to stand until 
the chloroform has evaporated. The evaporation may be 
hastened by using a blast of air. 
Proving in the Mouth.-The artificial dentures are now 
ready for the third appointment with the patient. There 
are two phases of constructing artificial dentures to be 
given consideration at this sitting of the patient-(1) prov- 
ing the occlusion and antagonization, and (2) developing the 
esthetics. 
Proving the occlusion and antagonization is accomplished 
by placing the well-cooled model dentures in the mouth and 
requesting the patient to close the "back teeth," but force 
should not be used upon them, as they are only in wax. If 
they close in the retruded position, as constructed upon the 290 
RUBBER AND VULCANITE 
antagonizor, the inference is that the occlusion is correct. 
However, it is well to make other tests, as there is nothing 
about prosthetic dentistry quite so uncertain as how an 
edentulous patient may close the mouth. They are more 
liable to close it in a protruded position than in the normal 
retruded one. As a further test, the head is tilted backward, 
the prosthetist parts the lips slightly, and watches the result 
while the patient performs the act of deglutition. This 
act will necessitate the mandible being in its normal retruded 
position. Should the mandible drop backward an eighth or 
a quarter of an inch, the student may feel momentarily 
disheartened, for it will be necessary to go back and do the 
work all over again, beginning with the paraffin base-plates 
and occlusion and contour models. However, the student 
will profit by such an experience and henceforth give more 
attention to his occlusion and contour models. Should the 
deglutition test prove the occlusion in retrusion to be cor- 
rect, the test for equalized pressure is applied. Before mak- 
ing this test it is better, as the wax has been absorbing 
considerable heat, to remove the model dentures from the 
mouth and again cool them. They are replaced in the 
mouth and just firmly held in retruded occlusion. An 
attempt is made to insert a thin-bladed spatula between 
the bicuspids and molars upon first one side and then the 
other. Should the pressure be even upon the two sides, 
well and good; but should there be a separation on one side, 
admitting the blade of the spatula, the blade should be 
rotated to determine the extent of the imperfection. If the 
imperfection is but slight, it may be corrected by removing 
the model dentures from the mouth, placing one in water 
to cool, drying the wax of the other (with absorbent cloth) 
about the non-contact teeth, softening the wax, extruding 
the teeth, and adding melted wax as indicated. The model 
dentures are returned to the mouth and closure made until 
equal pressure is obtained upon both sides. Should the 
separation upon one side be extreme, it is past correcting, 
and necessitates returning to the casts and beginning again. 
As the novice learns by experience, he will see that equalized 
pressure is an absolute necessity in the occlusion and contour CONVERTING MODEL BASE INTO VULCANITE 
291 
models, and this prevents the unequal pressure in the model 
dentures. 
The model dentures, meeting the tests applied for retruded 
occlusion and equalized pressure, are placed in incisal occlu- 
sion and tested with the thin spatula for equal pressure at the 
three points of contact. The dentures are then consecutively 
placed in right and left lateral occlusion and tested with the 
spatula. The dentures meeting these tests are removed 
from the mouth, laved in cold water, dried, and returned to 
the antagonizor. As slight imperfections of occlusion and 
antagonization will be unconsciously corrected in the mouth, 
and may be apparent upon the antagonizor, it will be neces- 
sary to bring the antagonizor to the proved model dentures, 
and not the dentures to the antagonizor. The antagonizor 
is conformed to the tested model dentures in this manner: 
The upper cast is removed from the antagonizor, the model 
dentures and upper cast are assembled upon the lower 
cast, and the upper bow again attached to the cast with 
plaster. However, it is not necessary to conform the antag- 
onizor to the tested model dentures unless it is desirable to 
make changes for cosmetic effects; then it is well to have a 
fixed record of the antagonization as developed in the mouth. 
It should be evident to the student that if all the procedures 
have been faultlessly performed up to the mouth test, no 
corrections will be necessary; but as there are so many 
sources for error, it is necessary for the most experienced and 
skilful prosthetist to prove the work at this stage of con- 
struction. 
The second object of the third appointment is to develop 
the Esthetics. This phase of the subject will be fully treated 
in the chapter on Esthetics. The design in this chapter is 
to treat only the art and the science of construction. 
The model dentures having been perfected are ready to 
be converted into their permanent form. This consists of 
substituting vulcanite for the wax. This conversion requires 
good workmanship and involves considerable science. 
CONVERTING THE MODEL BASE INTO VULCANITE. 292 
RUBBER AND VULCANITE 
Synopsis.-Luting the model dentures to the casts; re- 
moving from antagonizor; flasking; opening flask; removing 
wax; heating; packing; closing flask; vulcanizing; removing 
from vulcanizer and flask; finishing. 
Luting.-The model dentures are luted to the plaster casts 
by running a hot wax spatula (Fig. 101) along the peripheral 
border. It is essential to have the entire border luted so as 
to prevent the soft flasking plaster from getting between 
the model dentures and casts. 
Fig. 151 
Removing from Antagonizor.-The bows holding the casts 
are removed from the antagonizor frame. The plaster cast 
is removed from the bow by soaking in water for a minute 
or two, trimming away any luting plaster that may over- 
lap the cast, forming a notch between the cast and luting, 
inserting a plaster spatula in the notch, and tapping with a 
light hammer. 
Flasking.-The cast with its luted model denture is then 
adjusted to the vulcanite flask. The adjustment consists 
in seeing that the cast is neither too thick nor too wide for 
the flask; if such is the case, the cast must be reduced. This 
is done with a plaster knife (Fig. 67), after soaking the 
cast in water. Sufficient soft-mixed plaster is placed in the 
lower half of the flask to fill it half-full. The cast is then 
pressed into the soft plaster a sufficient depth to permit of 
the teeth being clear of the cover when the ring and cover 
are in place. Plaster is added to fill the space between the CONVERTING MODEL BASE INTO VULCANITE 
293 
edge of the base of the flask and the periphery of the model 
denture. The plaster must not be carried upon the model 
denture. When the plaster has set it is trimmed smooth 
with the plaster knife. Fig. lol shows the case properly 
inclosed in the first section of the flask. The plaster being 
set and trimmed so that no portion overlaps the rim of the 
flask, a slope extending from the model denture to the rim 
of the flask, and care exercised that no form is given to the 
plaster to act as a key and thus interlock the two sections of 
the flask, the exposed surface of plaster is varnished with 
sandarac as a separator, or, a lather of soap is sufficient. 
Flasking Upper Section.-As soon as the varnish has dried 
the surface of the porcelain teeth and wax-model base is 
wetted by holding in running water; this will favor the 
plaster flowing smoothly over the surface and filling the 
interspaces between the teeth. The model denture being 
wetted, the ring of the flask is set in place and a thick creamy 
mix of plaster of Paris is poured in to nearly half-fill it; the 
base and ring of the flask are so grasped as to hold them 
together while jarring on the bench, thus causing the plaster 
to settle into every interspace between the teeth. More 
plaster is added and settled in place by jarring. The third 
addition of plaster should fill the ring when the cover is 
placed and firmly pressed with the fingers, thus forcing out 
any excess plaster, which is wiped away. 
Opening the Flask.-The filled flask should stand until 
the plaster is hard set (thirty minutes). It is then placed in 
a three-quart stew pan and covered with cold water. The 
pan is placed upon the gas stove or large laboratory heater 
and heated until the water begins to boil, when the flask 
is removed from the water (use flask tongs, Fig. 113, or 
holder of Buffalo No. 2 press), and held in the left hand 
protected with a cloth holder. Start the separation of 
the two sections of the flask by inserting the edge of a 
plaster knife between them. As soon as the two sections 
loosen, the upper section is grasped with a cloth holder and 
carefully drawn apart, care being exercised to so manipulate 
the two sections as to release them of any slight interlocking. 
The rule for placing the knife for starting the separation is; 294 
RUBBER AND VULCANITE 
For upper cases place the knife at the heel of the flask, and 
for lower cases at the toe of the flask. This will prevent 
fracturing the overhanging anterior alveolar ridge. 
The instruction given for heating in water is subject to 
much variation. The object is to apply heat in such a way as 
to soften the wax without melting it. It is evident that some 
judgment is necessary, as there are several factors, such as 
amount of heat, water, and plaster about the wax. A little 
experience and observation will enable the prosthetist to 
closely estimate the time to open the flask. 
Another method is to have the water boiling and submerge 
the flask for one to three minutes. The time is inversely 
to the thickness of the encasing plaster about the wax, and 
the desired softness. The author has recently come to prefer 
this method. He uses one quart of boiling water, which is 
removed from the stove, into which he submerges the flask 
long enough to soften the wax sufficiently to avoid danger to 
the contents of the flask. Usually one minute is enough. 
This short time will soften the wax but slightly. Wax melted 
into the cast is detrimental to vulcanite. 
Removing Wax.-The softened wax is removed from the 
parted flask with a wax spatula so far as possible, and the 
remainder removed by a stream of boiling water. (A small 
teakettle is excellent for this purpose.) By examining the 
parted flask it will be seen that the cast is in the bottom 
section of the flask, and the teeth, with their cervical ends 
exposed, are in the upper section. If any plaster has found 
its way about the pins and cervical ends of the teeth, where 
there should be none, it should be removed with a pointed 
instrument and brush. Excess space should be cut about 
the periphery of the plaster, but without gateways. 
Heating.-The upper section of the flask is placed upon 
an 8- or 10-inch square piece of sheet iron over the gas stove, 
as shown in Fig. 152. While inspecting the upper section of 
the flask, the lower section is placed under the sheet iron, as 
seen in Fig. 152, to be dried by reflected heat. During the 
three or four minutes that the upper section is warming, the 
surface of the cast in the lower section of the flask is given 
attention. The surface of the cast should be treated so that CONVERTING MODEL BASE INTO VULCANITE 
295 
it will impart a dense and smooth surface to the vulcanite. 
There are two methods for accomplishing this-(1) painting 
the surface with a liquid finish, and (2) covering with tinfoil. 
The Silex Method.-The liquid-silex method has the 
advantage of being easily applied, and, if the surface of the 
cast is entirely free of wax or oily substances, will give good 
results. A clean ox-hair or camel-hair brush is dipped into 
the iquid silex and is then applied to the cast. It will be 
necessary to occasionally dip the brush into water, so that 
Fig. 152 
the silex may be well diluted and evenly applied. The excess 
silex should be absorbed with a cloth. Another method is 
as follows: While the thin silex is still moist upon the cast, 
dust with talcum powder, and, when dry, rub carefully with 
a soft cloth. The liquid-silex bottle should be kept well 
corked and no particles of plaster be permitted to get into 
it, as they will precipitate and spoil the silex for its intended 
use. The brush must be well washed each time it is used. 
The Tin Method.-This method is preferable because it 
gives a smoother and denser surface to the vulcanite, espe- 296 
RUBBER AND VULCANITE 
cially if any wax has been melted into the cast. A sheet of 
No. 4 tinfoil (0.0005 of an inch thick) is fitted over the cast 
with the thumb and finger. It is then removed and the 
excess tin cut away with sharp scissors, as indicated by the 
imprint of the edge of the cast upon the tin. The cast is 
now coated with sandarac varnish, and when it has dried 
to tackiness the tin is at once replaced and firmly pressed 
and gently rubbed with a wad of soft paper until there is 
perfect adaptation to the cast. The tin should be rubbed 
until it has a well-burnished surface. It is important that 
the tinned cast be coated with a lather of soap. This is accom- 
plished by wetting a soft-bristle brush and rubbing it upon 
a cake of soap and then upon the palm of the hand until a 
smooth lather is formed, which is applied to the tinned sur- 
face; or, a thin wash of Johnson's ethereal soap may be used. 
If the soap is not applied the tin and vulcanite will adhere 
very strongly, and can only be separated by dissolving the 
tin with mercury or hydrochloric acid. 
The cast, having been coated with either silex or tinfoil, 
is replaced under the sheet iron to be warmed while packing 
the rubber into the upper section of the flask. 
Packing the Rubber.-During the time the flask is being 
heated preparatory to separating, the rubber is stripped of 
its cloth covering and cut into suitable form for packing. 
For the upper case a piece of red rubber is cut of sufficient 
size to cover the central portion between the teeth; and the 
remainder of the red rubber, required for either the upper 
or lower, is cut into strips, across the sheet, about one-half 
inch wide. Sufficient pink rubber, or Walker's granular 
gum, to face the labial and buccal surfaces of the case is 
cut into the same-sized strips, also thirteen small pieces 
(triangle or square, form indifferent, size about one-fourth 
inch) are cut for packing between the teeth. For conven- 
ience of handling, the cut rubber may be placed upon a por- 
celain plate or a piece of glass. As rubber is very cohesive, 
the pieces must not touch each other while on the receptacle. 
As the flask is heated, it is unnecessary to heat the rubber; 
in fact, the cold rubber can be much more conveniently 
handled than that which is warm and adhesive. The heat CONVERTING MODEL BASE INTO VULCANITE 
297 
of the flask will sufficiently soften the rubber to cause it to 
pack easily. Care should be exercised not to overheat the 
flask. It should be about the temperature of boiling water, 
or lower. As rubber melts at 250° F., and its quality is 
impaired when melted if exposed to air, it is well to have 
a safe margin of 40° or 50°. Two instruments, one in each 
hand, will be required for packing the rubber. Any small 
and blunt instrument may be used. A small flat-blade 
burnisher held in the left hand to stay the rubber while 
packing, also useful to carry the small pieces between the 
ends of the teeth, and the Zurbrigg rubber packer (Fig. 153), 
or the No. 3 instrument of the Evans set (Fig. 100) are ad- 
mirably adapted as packing instruments. A narrow strip of 
red rubber is placed along the pins of the teeth, and as the 
rubber softens is pressed against the pins with the flat side of 
the broad end of the packer. The pins of all the teeth being 
Fig. 153 
engaged in the red rubber, one of the small pieces of pink 
rubber is engaged in each of the spaces between the ends of 
the teeth. Packing these small pieces is simple and expedi- 
tious; however, a novice is liable to waste much valuable time 
in its performance. The small pieces of rubber are carried on 
the pointed end of the No. 3 instrument to place, the edge of 
the burnisher, held in the left hand, carries it between the 
teeth, and while so held the packing instrument is used to 
turn one edge over upon the center of the space between the 
teeth and compress the rubber while withdrawing the other 
instrument. These three movements to each space should be 
sufficient. A strip of the pink rubber, sufficiently wide to 
nearly cover the buccal and labial surfaces of the denture, is 
placed with one edge overlapping the teeth for about one-half 
their thickness. The fingers are then used to compress the 
strip of rubber down upon the ends of the teeth and against 
the sides of the plaster mold. This act unites the large strip 298 
RUBBER AND VULCANITE 
and the small pieces and perfectly forms them about the 
cervical ends of the teeth. If much restoration is required 
for the gum portion, another layer of pink rubber may be 
placed upon the adjusted piece. However, the edge of this 
piece should not overlap the teeth, but extend from the teeth 
to the margin of the mold. If there is great thickness of gum 
restoration required, pink rubber should be added to nearly 
complete it. The reason for making heavy restorations with 
pink rubber in place of the stronger red rubber is: There 
is no danger of thick masses of pink rubber vulcanizing 
porous, while the same space filled with red rubber is almost 
certain to do so. If a thin gum restoration is required, one 
layer of pink is sufficient. The next step in packing the 
upper case is to place the center piece, which is done by 
adapting the piece of rubber to the plaster matrix by finger 
pressure from the center outward, permitting the edge to 
overlap the packed rubber. In the lower case one or two 
thicknesses of red rubber is placed upon the lingual surface 
of the mold. The packing of rubber is done with the fingers 
when possible, only using instruments where the fingers 
cannot effectively reach. The problem confronting the 
workman at this stage of the operation is to know when 
sufficient rubber has been placed to just fill the mold, for 
much excess rubber is liable to do harm. Various methods 
are used, as: Weighing the wax model plate and taking its 
weight plus one-fifth in rubber, the difference in specific 
gravity. Displacement method: Place the wax of the model 
plate in a suitable dish (glass tumbler) and fill it to over- 
flowing with water; the wax is removed and replaced with 
rubber. With either of these methods a little extra rubber 
should be added and good judgment used in distributing 
the rubber in packing. The preferred method is the "Trial" 
method. 
Closing the Flask.-This (trial) method consists of placing 
the rubber in the mold as has been described, until the judg- 
ment dictates there is nearly but not enough to fill the mold. 
A piece of close-woven cotton cloth, free from starch, is 
saturated with water (preferably hot) and placed over the 
packed rubber; the two sections of the flask are put together CONVERTING MODEL BASE INTO VULCANITE 
299 
and carefully closed in the flask press. The flask is then 
opened and the cloth removed, when it will be apparent 
where more rubber is required and the quantity. Should so 
large a quantity of rubber be required that it is questionable 
when a sufficiency has been added, a trial with the wet cloth 
may again be made. When the mold is found to be full, the 
flask is closed without the cloth. (The cloth stripped from 
the rubber and washed of its starch may be used, but dress 
lining cut in pieces 3 by 3| inches is better and saves valuable 
time. Should the cloth, for any reason, adhere to the rubber, 
saturate it with hot water, when they may be easily parted.) 
Attention has been called (page 224) to the danger of warping 
the denture by improper placing of the rubber and heavy 
pressure in the press. Should the rubber in the mold become 
too cold, it may be carefully warmed by reflected heat under 
the sheet iron, or the rubber-packed flask may be put in 
water and boiled before the final compression in the press; 
however, the softening that takes place in the saturated 
plaster favors warping the denture. Undoubtedly the "fit" 
of more artificial dentures is impaired by improper packing 
and closing the flask than by all other causes. The flask 
being closed is placed in a Donham clamp (Fig. 104), either 
with or without the volute spring. 
Vulcanizing.-The method and philosophy of vulcanization 
have been discussed under the physical and chemical proper- 
ties of vulcanite, in this chapter. 
Resume.-If the case has been properly flasked, packed, 
and clamped, the gas regulator should be set at 320° F., 
for approximately 80 minutes. 
Study well the philosophy of vulcanization. 
Perfected Method.-In the preceding pages stress has been 
laid upon the method usually taught by the schools and 
practiced by the profession. Now the author desires to pre- 
sent the method that he believes is scientific and produces 
the best vulcanite results. 
The model denture is constructed upon a hard plaster 
compound cast-tinned and flasked. 
For best results the flask should be kept out of water until 
after vulcanization, as water softens the plaster and favors 300 
RUBBER AND VULCANITE 
warpage of the denture. The investment plaster should set 
for one-half hour or longer. It is then placed in the Sargent 
Electric Drying Oven to warm and soften the wax, but not 
to melt it. The Electric Oven (Fig. 154) is a most valuable 
adjunct to the dental laboratory; however, it is not now in the 
dental supply house, but can be procured by them. It is a 
chemists' apparatus and is manufactured and sold by E. II. 
Sargent & Co., 155 to 165 E. Superior St., Chicago, Ill. The 
heat can be adjusted to any degree up to 00° F. If the 
temperature is set at 220° F. it will be safe for any purpose 
the prosthetist may desire a low temperature heating appli- 
Fig. 15 4 
ance. An Interval Timer, as the Victor Electric (Fig. 155) is 
also a very convenient instrument for many places in the 
laboratory. It can be set for a few seconds or any time up 
to two hours. The alarm is sufficiently long (not too long) 
and loud to be heard anywhere in a small office. It relieves 
the prosthetist of much responsibility. A little experience 
will enable any one to determine the exact time to accomplish 
a desired result. The length of time that will be required to 
soften the wax the desired amount must be learned experi- 
mentally for each office. The time required will be from five 
to twenty minutes, too long a time to watch or with which CONVERTING MODEL BASE INTO VULCANITE 
301 
to tax the memory. Should the wax be overheated it may 
be washed out with a quart or two of boiling water, in which 
Fig. 155 
Fig. 156 
a dessertspoonful of sal soda has been dissolved. The sal 
soda emulsifies the wax and better disposes of it. An excess 302 
RUBBER AND VULCANITE 
space should be cut as shown in Dr. Snow's illustration 
(Fig. 156). Notice there are no notches or vent spaces cut 
from the mold to the excess space. This method shuts in 
and retains the required rubber. The flask is then placed in 
the drying oven for ten minutes to dry and warin. The 
investment plaster should never be so hot that the fingers 
cannot be held upon it with some pressure. The case is 
packed by the separating cloth method. When the case is 
packed there should be 5 per cent, excess rubber in the flask. 
In other words, the mold should be full and the flask not 
quite closed 0.5 mm. separation. If the flask is not closed 
enough it may be placed in the flask press (Fig. 107) and 
placed in the warming oven by removing the two upper 
shelves, which are rarely needed by the dentist. Or, the flask 
may be placed in the press of the Snow Compensating Vul- 
canizer and 200 pounds spring pressure applied and placed 
in the pot, without tightening the bolts, and boiling for a few 
moments. The flask will be in the steam only. The vul- 
canizer cap can then be lifted from the pot and if the flask 
is properly closed the spring pressure is removed from the 
flask and the case or cases (one, two or three) placed in the 
vulcanizer and it properly closed for vulcanization. The 
gas regulator is set for 270° F. and the full heat applied for 
ten or fifteen minutes, depending upon whether the vulcanizer 
was hot or cold, and 500 pounds spring pressure applied. 
The blow-off may be opened and the air expelled. The 
vulcanizer is then made steam tight and held at 270° F. for 
twenty minutes. The gas regulator is then set for 280° F. 
and permitted to stand twenty minutes, when it is set for 
300° F. As the regular vulcanizer clock should have been 
set for three hours when starting the vulcanizer, the operation 
will consume one hour in raising the temperature to 300° F. 
by the thermometer and will hold that heat for two hours, 
the required time for vulcanization. The vulcanizer should 
stand until it is stone cold before it is opened; it is best to 
have at least eight hours. This permits the molecular set 
of the vulcanite and removes the greatest source of danger 
from warpage of vulcanite dentures. The prosthetist nor CONVERTING MODEL BASE INTO VULCANITE 
303 
the patient never should place a vulcanite denture in water 
hotter than the hand can be held in all the time the denture 
is in it. The danger of warpage begins at about 130° F. 
Fig. 157 
The former method detailed will give a fairly good vulcanite 
but not the best. The slow vulcanization undoubtedly gives 
the best results, but it requires special apparatus to pro- 
duce these results economically. The Snow Compensating 
Vulcanizer (Fig. 157) is the latest and especially constructed 
to meet modern requirements. This vulcanizer is modeled 304 
RUBBER AND VULCANITE 
after the Edson (which is the next to the best), it has resilient 
springs in the heads of the yoke, registered from 100 to 800 
pounds. The cap is bolted on (not screwed on) and is large 
enough for modern demands. It is well made, has the usual 
safety valve and an especially efficient blow-off. The opera- 
tion described with this vulcanizer is very simple provided 
the operator uses an Interval Timer, which takes but a 
moment and relieves the mind of responsibility and permits 
giving attention to other work. The reason that rapid vul- 
canization was advocated for the old method was that shrink- 
age of the vulcanizing rubber could be better controlled, but 
with the compensating vulcanizer an excess of rubber may 
be added at the proper time by simply adding spring pressure. 
It is a known fact that the best vulcanization is produced at 
not to exceed 320° F. actual temperature (75 pounds steam 
pressure) which is 300° F. by the thermometer set in a 
mercury bath. (The gas regulator is adjusted to read with 
the thermometer.) The thermometer reading 320° F. is 
actually 340° F. or 100 pounds steam pressure. This high 
heat damages somewhat the texture of the vulcanite. Even a 
higher heat is often inadvertently used and produces a very 
brittle vulcanite. 
Removing from the Vulcanizer.-It is always best to permit 
the vulcanizer to stand until it is cold before opening, but 
when it is necessary to expedite matters the steam may be 
blown off, the vulcanizer opened, and the flask submerged 
in a pan of cold water. This last procedure would be con- 
demned by some, but owing to the poor conducting and 
radiating property of plaster, it is doubtful if this method of 
cooling ever accounts for fractured teeth. However, the 
effect upon the vulcanite is conjectural, not having been 
determined experimentally. 
Removing from the Flask.-Under no conditions, however, 
should the flask be opened until the plaster in the center of 
the flask is cool, which will be some time after the flask 
is cold if placed in water. The flask is released of its clamp, 
held in the left hand, with the plaster knife in the right hand. 
The knife, guarded with the thumb so that only a quarter- 
or half-inch is exposed, is used as a wedge to part the sections CONVERTING MODEL BASE INTO VULCANITE 
305 
of the flask. Usually the case will remain in the ring portion 
of the flask, and is removed by cutting a groove in the encas- 
ing plaster between the denture and ring. The plaster both 
on the inside and outside of the denture is grooved and 
removed in sections, thus avoiding the danger of fracturing 
the denture. The last portions of the plaster not easily 
removed with the knife are removed by scrubbing with a 
stiff-bristle laboratory brush and water. 
Finishing.-The edges of the denture as it comes from the 
flask are rough and irregular from the extension of excess 
vulcanite. This is removed with a rather coarse file specially 
made for this work (Fig. 114). A seven- or eight-inch half- 
round file, having an oval and a flat side, a coarse and a 
fine end, is a very desirable instrument. The cutting is 
done with a push stroke. A round or rat-tail file is also 
very useful. For scraping the surfaces the No. 1 short- 
shank Kingsley scraper of the Wilson vulcanite finishers is 
used. The No. 4 instrument is useful for small places, and 
especially for removing defects on the maxillary and man- 
dibular surfaces. The chisel (No. 2 of this set) is for carving 
about the teeth, and the pick (No. 3) is for working between 
the teeth . (Fig. 115). These instruments should be kept 
very sharp by grinding and honing. The entire labial, 
buccal, and lingual surfaces of both upper and lower den- 
tures are gone over to remove excess material, give form, 
and to remove the roughness received from the plaster 
matrix. The file and scraper marks are removed with sand- 
paper. No. | for coarse paper and No. 00 for fine paper is cut 
into two and one-half inch squares, by placing the sand side 
down over a crevice and cutting with a knife. The sand- 
paper marks are removed with buffers and glossers (see pages 
242 to 244). The maxillary and mandibular surfaces require 
no finishing except to remove any excrescences formed as 
result of air-bubbles in the surface of the cast. These are 
carefully removed with the small scraper. This surface 
may be more highly glossed by using the soft-brush wheel 
and whiting. The finish grinding (see page 254) of the 
occlusal surface of the teeth is executed with small stones 
mounted on an engine mandrel and carried in the lathe chuck. 
20 306 
RUBBER AND VULCANITE 
The object sought is to deepen or reproduce the sulci and 
grooves, thus forming edges to cut the food in the process of 
mastication. The ground surfaces of the porcelain teeth 
are given their final finish with a piece of No. 00 sandpaper 
applied with the ball of the thumb. The finishing of any 
mechanical work is an important item, and in artificial 
dentures is not only indicative of superior workmanship, 
but is necessary for cleanliness and health of the tissues 
with which it will be in contact. Fig. 154 illustrates the 
completed dentures. 
Fig. 158 
Inserting the Finished Dentures.-The fourth appointment 
with the patient is a very important one. The dentures are 
inserted and the adaptation in every respect inspected. 
The dentures are wonted to their place by closing the teeth 
and swallowing; this settles and withdraws the air from 
beneath them. If the dentures are evenly seated, so that 
pressure may be made upon any part without being dis- 
turbed when opening the mouth and by the ordinary move- 
ments of the lips and tongue, and do not cause pain, and 
the occlusion and antagonization are correct, the patient 
should be instructed how to use and cleanse them. The 
patient should be instructed to keep the dentures in night 
and day, only removing for cleansing, until they have 
become masters of the artificial substitutes, after which the 
dentures may be removed at night, cleansed, and kept 
in a weak solution of boracic acid. The patient should be CONSTRUCTION OF UPPER AND LOWER DENTURE 
307 
instructed that if the dentures cause pain, they are not to 
be removed from the mouth, but that the patient is to return 
to the office for attention. 
THE CONSTRUCTION OF EITHER AN UPPER OR 
LOWER DENTURE. 
The technic involved in the construction of either an 
upper or lower denture varies from that of both upper and 
lower in a few of the processes. As the technic for con- 
structing an upper denture to natural lower teeth is the same 
as constructing a lower denture to natural upper teeth, or 
vice versa, it is necessary to describe but one, as the descrip- 
tion of either would be the same as the other except in the 
use of the terms upper and lower, which would be transposed. 
For convenience of description the imaginary patient has an 
edentulous upper jaw with a full complement of normally 
aligned lower teeth. 
The mouth is carefully examined and the conditions 
observed. A scheme is devised for taking the impression 
according to the indications, a suitable cast and the upper 
occlusion and contour model formed. The processes of con- 
struction are the same as described for the complete upper and 
lower case up to forming the occlusal surface of the wax 
model. As in the former case, the occlusal surface of the 
anterior portion of the model must mark the length of the 
upper lip when at rest and relaxed. The occlusal surface of 
the model as it extends backward must have at least three 
widely separated points of contact with the lower teeth. The 
patient is then exercised in the forward and backward or 
protrusion and retrusion movements of the mandible. The 
wax model is then removed from the mouth, cooled, and 
dried. With a roll of soft wax placed upon the occlusal 
surface of the model, it is returned to the mouth, and the 
mouth closed in the retruded position, biting the teeth 
through the soft to the hard wax. The wax model is removed 
from the mouth and a wax impression taken of the lower 
teeth. The imprint of the lower teeth in the wax model 
will not suffice for the impression. The wax impression is 308 
RUBBER AND VULCANITE 
taken by placing a roll of well-softened yellow wax in a 
warmed, suitable size, flat-floor lower tray. A good impres- 
sion should be obtained of the occlusal surfaces and at least 
one-half of the length of the teeth. The impression of the 
cervical half of the teeth is indifferent. The impression is 
filled with plaster or, better, Spence compound. When the 
plaster is hard set, the tray is removed by warming in the 
Bunsen flame and lifting it away from the wax. The wax 
will be somewhat softened in removing the tray, and may 
be further softened by passing through the flame. It is 
removed from the cast by turning the buccal and labial 
surfaces of the wax upward and inward to the lingual side, 
when it may be easily removed from the cast. The upper 
cast, wax-occlusion model, and lower cast are then assembled 
and mounted upon an occlusion frame or an antagonizor 
to be used as an occlusion frame. The student should be 
impressed with the fact that the casts so mounted are in no 
way to have their relationship changed without removing 
from the frame and remounting. It is hardly necessary to use 
a face bow in mounting a single case upon an antagonizor, 
as the occlusion is established, and, except in rare cases, it is 
not justifiable to alter these natural teeth. However, the 
face bow may be used if desired, in the same manner as for 
the full upper and lower dentures. A case so mounted 
permits of opening or closing the bite, but this will not be 
necessary if proper attention was given to forming the wax 
model. Then, again, if the case is mounted with the face 
bow, interfering cusps may be more easily detected. 
The teeth must be ground and set up so that the molars 
and bicuspids intercuspate and the six anterior teeth are 
free of contact. As it is a rare instance that a full upper 
denture will be required and the patient have a full set of 
normally aligned natural lower teeth, it becomes necessary 
to give special attention to the occlusion. The law of force 
and the law of the resultant of two or more forces must be 
taken into consideration, or the completed denture will be 
very deficient. The rule is to have the force or the resultant 
of two forces act at right angles to the normal occlusal 
plane. However, it is permissible and often desirable to PARTIAL DENTURES ON VULCANITE BASE 
309 
have the line of force, acting upon a full upper artificial 
denture, slightly distal to the perpendicular. This is accom- 
plished by having a greater stress upon the mesial than upon 
the distal facets of the upper teeth. The teeth being properly 
occluded (leaving the antagonization to be attended to at 
the time of fitting in the denture), the construction is com- 
pleted the same as in the case previously described. 
PARTIAL DENTURES ON VULCANITE BASE. 
It is a truism that the difficulties of constructing arti- 
ficial dentures are in direct ratio to the number of teeth to be 
supplied. The technic of constructing a partial vulcanite 
denture for either jaw is the simplest prosthetic procedure 
(however, the fitting in or adjusting to the mouth is more 
difficult than any other vulcanite denture); either a full 
upper or lower is more complicated, while the complete 
upper and lower present the greatest problems of prosthesis. 
A perfect plaster impression (see Chapter II) should be 
obtained to inclose a little larger surface than the base- 
plate is designed to cover. Usually an occlusion cast of the 
opposite teeth is required; however, if there are no opposing 
teeth an occlusion cast will not be necessary. In some partial 
cases the two casts will have so many points of contact that 
they may be assembled without further aids. A quash-bite 
will suffice for some cases, while for others a well-constructed 
occlusion wax model may be a necessity. The case is placed 
in an occlusion frame, a wax base-plate formed, and teeth of 
color, form, and size to correspond with the remaining teeth 
in the mouth are selected. They may be ground to favor 
adjustment, also to obtain the required occlusion. It is a 
safe rule to establish that all artificial dentures, both full 
and partials, should be adjusted to the mouth while in the 
pattern; nevertheless there is a class of partials that often 
(not always) are exceptions to the rule. The class referred 
to is where teeth and spaces alternate. Those partial cases 
that cannot profitably be tried in the mouth in the pattern 
will probably require much skill and time in adjusting the 
completed piece. The wax-model plate being contoured, the 310 
RUBBER AND VULCANITE 
cast containing it is removed from the occlusion frame. The 
rule for flasking full cases is: The separation of the two 
sections should be at the peripheral edge of the wrax-model 
plate. This rule applies to some partial cases. In these 
cases the plaster teeth should be cut down flush with the 
wax-model plate and the encasing plaster built up to the top 
of the stumps of the plaster teeth. These reinforced stumps 
must be so shaped that they will easily draw from the 
mortise they form in the upper section of the flask. There 
are many partial cases in which the porcelain and plaster 
teeth so alternate that it is better to encase the teeth in 
Fig. 159 
the first section of the flask. It is obvious that the packing 
of such a case must be from the lingual aspect. Fig. 159 
illustrates an upper model denture without labial gum 
restoration. Fig. 160 is the case in the first section of the 
flask, and illustrates the method of flasking where plaster 
and porcelain teeth alternate. 
The tinfoil used to finish the maxillary or mandibular 
surface is applied before placing the base-plate wax, because 
it will be difficult to adapt the foil in the flask. The soap 
solution is applied after the wax is removed, just prior to 
packing. Careful manipulation will be required in the PARTIAL DENTURES ON VULCANITE BASE 
311 
various procedures not to disturb the finishing tin. The 
liquid-silex method is useful in many partial cases. 
Partial cases are vulcanized the same as full ones. 
Care should especially be exercised, in removing the case 
from the flask, to have the plaster cold, and in the use of 
force. 
The finishing process consists of filing, sandpapering, 
buffing, and glossing, and are essentially the same as for 
full cases. 
Fig. 160 
Adapting the finished cases to the mouth is, as has been 
stated, a difficult and often a perplexing operation. It will 
frequently require careful study and manipulation, and often 
much trimming away of the base-plate as formed. However, 
this trimming must be judiciously performed, because as 
close an adaptation and as large a base of support as possible 
is imperative. Partial cases may require a high degree of 
mechanical ability, but complete dentures will require 
mechanical dexterity and esthetic sense. 
The retention of artificial dentures has not been mentioned 312 
RUBBER AND VULCANITE 
in discussing the technic of vulcanite construction, for the 
subject is more comprehensible when considered in the 
abstract. 
REMOVING THE TEETH FROM A VULCANITE BASE- 
PLATE. 
Sheet-iron Method.-Place the denture, teeth downward, 
upon the sheet iron over a gas stove, and when the vulcanite 
is thoroughly softened the teeth may be pushed off one at 
a time by inserting the wax spatula between the tooth and 
the vulcanite upon the lingual side. The plate is held by a 
pair of pliers and the dislodged teeth are permitted to fall 
upon wood, dr, better, upon cloth, but not upon cold iron 
or stone. Any portion of the vulcanite remaining about the 
pins should be removed. If necessary, these small portions 
of vulcanite may be softened by grasping the tooth in a 
pair of solder tweezers and holding in the Bunsen flame. 
Glycerin Method.-The denture is placed in a vessel of 
glycerin and heated to the boiling-point of the liquid, when 
the teeth can be removed as in the other method. The 
glycerin is soluble in water and easily removed. The fumes 
of the heated glycerin are more objectionable to some than 
those of the overheated rubber. 
Flame Method.-The denture is grasped with a pair of 
pliers and the outer surface of the teeth heated by passing 
repeatedly through the flame until the vulcanite is softened 
about the pins, when they are removed as before described. 
It is not advisable to remove the teeth by heat from a 
denture which is to be used again, because of the liability 
of warping the plate. In such cases the vulcanite should 
be cut from about the pins of the tooth with a burr in the 
engine, or with a chisel. 
REPAIRING VULCANITE DENTURES. 
The breaking of vulcanite dentures is usually due to over- 
vulcanizing, by which elasticity and toughness are destroyed; 
to improper arrangement of the molars, by which the strain REPAIRING VULCANITE DENTURES 
313 
of mastication is thrown on the outside instead of on top 
of the ridge; or to a warped plate. The first evidence of 
the giving way of a piece is usually a fine crack appearing 
between the two central incisors, and sometimes, in partial 
dentures, in the border surrounding a natural tooth. 
Wax Method.-A method particularly applicable to plates 
which are broken entirely in two consists in adjusting the 
two parts of the plate together, and fastening them in correct 
relation to each other temporarily by adhesive wax dropped 
on the lingual surface so that plaster can be run into the 
maxillary portion of the denture. As soon as the plaster 
hardens, the plate is removed from the cast, the line of 
division is enlarged with a file, and dovetails cut opposite 
each other with a jeweller's saw, as shown in Fig. 161. The 
dovetailed space is then filled with wax, invested in the usual 
way in a flask, packed, and vulcanized. By another method 
the edges may be adjusted as before described, and the 
piece be placed immediately in the lower half of the flask. 
After the plaster has set, the adhesive wax is to be removed 
from the lingual side of the plate and a line cut with a round 
engine burr along the full extent of the crack, or break, half- 
way through the plate and a quarter of an inch wide, with 
smooth regular edges, without dovetails. The case is then 
waxed up and the other half of the flask poured, when the 
case is packed and vulcanized. If the parts have been kept 
perfectly clean, the union will be quite strong. 
Another modification,1 which gives the best results, is 
this: After the cast is made, the portions of the plate are 
removed from the cast and with file and scraper a long bevel 
is cut, forming a thin, feathery edge along the fractured 
edge and sloping away from this for an eighth to a half- 
inch as the case will permit (Fig. 162). The pieces are then 
filed to give a slight bevel upon the maxillary surface. The 
portions of the plate which have been cut away are replaced 
with wax, and if necessary the plate may be thickened over 
the portion having the freshly cut surface. It is unnecessary 
to coat the vulcanite surface with a solution of rubber, as 
1 The method preferred by the writer. 314 
RUBBER AND VULCANITE 
the heat and pressure will make the union. Fig. 163 shows 
method of flasking. 
In this connection, attention is called to a class of repair 
Fig. 161 
Fig. 162 REPAIRING VULCANITE DENTURES 
315 
cases that perplex the novice; namely, those having an ex- 
tensive fracture upon both the lingual and buccal or labial 
surfaces. This difficulty in flasking is overcome by attaching 
one or more shafts of wax, one-fourth inch in diameter, at 
suitable locations over the fracture upon the labial or buccal 
surface. The shaft of wax must be sufficiently long to 
extend through the investing plaster. When the plaster has 
hardened, a portion of the wax shaft and the surrounding 
Fig. 163 
plaster is cut away to form a cone-shaped depression, which 
will be filled in with the plaster in the top section of the 
flask. These wax shafts will form openings through which 
the rubber can be packed, and which are to be filled with 
rubber. After vulcanization the shaft of rubber may be 
removed with a mechanical saw. 
Fusible Metal Method.-To avoid loss of strength by the 
second vulcanizing it is recommended that fusible metal, 
melting at 150° to 160° F., be used to fill the dovetailed space. 316 
RUBBER AND VULCANITE 
This can be done by pouring the melted alloy into the space 
and packing it with a hot spatula, which is readily admissible 
owing to the low fusing-point of the metal. While the 
method has the advantage of not requiring a second vul- 
canizing, the union of the metal at the point of fracture is 
not as close as when rubber is used, and it cannot be said to 
be reliable as a means of repairing broken vulcanite plates. 
A single tooth may be fastened to the vulcanite by filing 
the dovetailed space as for repairing with rubber, the fusible 
metal to be put in place with a hot spatula; or the dovetail 
can be filled with amalgam. 
Fig. 164.-Plate prepared for the addition of several teeth 
Ironing-in Method.-This method is suitable for replacing 
a tooth or two, or filling a short crack or a hole. The vul- 
canite is cut with a file to give a dovetailed form to the 
space into which a tooth is to be added; and a crack or 
hole should be prepared for the new rubber with a scraper. 
The new rubber is ironed into place by using a hot wax 
spatula and firm pressure. 
Replacing Vulcanite Method.-Much the better way is to 
fasten the parts together, run a plaster cast into the denture, 
then make a bite of plaster to serve as a guide for the replace- 
ment of the teeth, remove the latter from the broken plate, 
reset them to the cast, wax up the piece, flask, and vulcanize. 
This affords practically a new case, and the time consumed REPAIRING VULCANITE DENTURES 
317 
is not much greater than is required in repairing the old 
one. 
Additions to Old Plates.-Additions of teeth to old plates 
are accomplished after practically the same methods. Fig. 
164 shows a case where four teeth have been extracted, and 
the old plate is prepared for the addition of as many por- 
celain teeth, so that the denture could be worn until the 
resorption of the alveoli and gums would admit of the 
construction of a permanent plate. The illustration shows 
the plate bevelled off to a smooth edge, and several holes 
drilled into the filed portion. The correct occlusion of the 
new teeth is obtained by placing the plate in the mouth 
after the bleeding ceases, placing two pieces of softened wax 
along the alveolar ridge and plate, and directing the patient 
to bite into the wax, and then gently pressing the wax while 
the teeth are in contact. This gives the correct relation of 
the lower to the upper teeth, and the impression of that 
portion of the alveolar ridge to be covered by the addition 
to the plate. The preparation of the plaster cast and bite 
is done in the usual way, plain teeth being ground to the 
gums to allow for the rapid resorption which always follows 
the extraction of teeth. The waxing and flasking are done 
in the usual way. CHAPTER VII. 
PRINCIPLES OF RETENTION OF ARTIFICIAL 
DENTURES. 
The retention of artificial dentures is purely mechanical, 
and is based upon the laws of physics. Indirectly, however, 
the personal equation is an important factor, in that the 
patient may not be able to control the laws of physics. 
These vexatious cases are often spoken of as awkward or 
clumsy, but such patients will eventually succeed in over- 
coming the difficulties, provided they have sufficient perse- 
verance. 
The physical laws that play a more or less important 
role in the retention of artificial dentures are atmospheric 
pressure, adhesion by contact, leverage, tensofriction, and 
cementation. These forces are not equal in value, nor can 
any one principle be depended upon for retaining a denture. 
There will be a primary selected to bear the burden, and one 
or more secondary forces evoked or unwittingly included. 
These secondary forces may be either positive or negative. 
Thus atmospheric pressure may be selected as the primary 
retentive force, but adhesion by contact must be an asso- 
ciate retentive force, whether it be so designed or not, and 
eventually will entirely take the place of atmospheric 
pressure in any given case. The principle of leverage is 
always associated, through antagonization, with whatever 
may be the primary method selected. This force especially 
may be considered as positive when the arrangement of the 
teeth is such that it tends to force the denture more securely 
to place, and as negative when the arrangement is such that 
antagonization tends to loosen the denture. 
Atmospheric Pressure.-As is well known, atmospheric 
pressure is the weight of a column of air resting upon an 
318 ATMOSPHERIC PRESSURE 
319 
object. The weight of a column of air at the sea level is 14.7 
pounds to the square inch, and decreases in ratio to the 
height above sea level. As this pressure is equal in every 
direction upon and within the human body, it is not per- 
ceptible. Whenever a portion of this column of , air is 
removed from a circumscribed portion of the body, its 
effect is immediately felt. No substance can be placed 
between the atmosphere and the surface, or a portion of 
the surface, of the body, and remove the pressure of the 
atmosphere from the body, as the intervening substance, 
being contiguous, would be held against the surface of the 
body by the full weight of the column of air resting upon it. 
Thus we may justly conclude that an artificial denture per- 
fectly adjusted to the tissues of the mouth would be retained 
by the full weight of the column of air, or approximately 
fifteen pounds for each square inch of surface covered; also 
that a chamber cut in the maxillary surface of the plate 
would be a positive detriment, because it would be an air 
chamber equalizing the column of air upon the external 
surface of the plate to the extent of the air chamber. How- 
ever, there is a fatal obstacle to this imaginary retention of 
an artificial denture, for it is a physical impossibility to 
exclude the film of air between the soft tissues of the mouth 
and the hard base-plate except by substituting a fluid for 
the film of air. By the substitution of this fluid for the 
film of air the law of hydrostatics is introduced. The law 
of hydrostatics is, that a pressure placed upon a confined 
liquid is equal in every direction. Therefore a mechanically 
perfectly adapted artificial denture having a fluid contact 
cannot be retained by atmospheric pressure, because the 
intervening fluid equalizes, within and without, the atmos- 
pheric pressure. 
Atmospheric pressure may be utilized to retain an artificial 
denture, but through the medium only of a vacuum chamber. 
Since an absolute vacuum is an impossibility, the amount 
of retention by atmospheric pressure is contingent upon 
the area of the chamber and the vacuity obtained. To 
produce any degree of vacuity it is necessary to have the 
plate surrounding the vacuum cavity perfectly adapted to 320 
RETENTION OF ARTIFICIAL DENTURES 
the soft tissues. The extent of exhaustion of the air from 
the chamber is governed by the power of the muscles of the 
tongue and the ability of the patient to apply them. The 
exhaustion is produced by forceful swallowing. 
Retention by atmospheric pressure can only be temporary, 
and maintained only so long as there is a partial vacuum. 
The effect of the vacuum chamber upon the tissues of the 
mouth is the same as cupping in medical practice. As soon 
as the atmospheric pressure is reduced upon a circum- 
scribed portion of the body, it acts as an excitant, causing an 
increased blood-pressure in the part with a temporary 
swelling, and if continued a proliferation of tissue cells 
producing a permanent growth until the chamber is filled. 
When the chamber is filled by tissue and the fluids of the 
mouth, atmospheric pressure can no longer exist; the denture 
is then retained only by adhesion by contact. While the 
term "suction plate" is not so euphonious as "atmospheric 
pressure plate," it more nearly expresses the truth without 
attempting an explanation of how the suction is secured. 
As the amount of retention of a vacuum chamber stands 
in direct ratio to its area, so its relative permanence and 
its injurious effects stand in direct ratio to its depth. 
Emergency Vacuum Chamber.-There is a form of vacuum 
chamber that may be called the emergency vacuum. It is 
invisible and exists only during an emergency. It is best 
illustrated with a full upper denture. It is also efficient in 
favorable full lower dentures. This emergency vacuum is 
conditioned upon areal contact, peripheral adaptation and 
extension upon yieldable soft tissue. In full upper cases the 
essential extension is the entire length of the palatal border. 
This palatal border bearing upon yieldable tissue must be 
approximately one-fourth inch wide and may be much wider. 
If the labial and buccal flanges are sealed in by the lips and 
cheeks no air can be admitted at these borders, if the entire 
maxillary surface has moisture contact there is practically no 
air within and if the palatal border is well adapted to and ex- 
tends sufficiently upon yieldable tissue to form the required 
valve the conditions are perfect to produce the emergency 
vacuum. There is now no vacuum but molecular attraction; ADHESION BY CONTACT 
321 
but if force is applied in any manner, that is, downward, side- 
ways or forward the plate will be drawn away (slightly) from 
a portion of the tensest tissue enclosed thereby producing a, 
relatively speaking, perfect vacuum (14.7 pounds per square 
inch) over the entire surface from which the plate is dislodged. 
This suction will exist so long as the force is applied or until 
air can gain access to the vacuum space. 
Adhesion by Contact.-This retentive force is often confused 
with atmospheric pressure, whereas it is an entirely differ- 
ent principle. Atmospheric pressure retention is contingent 
upon a chamber which is more or less evacuated of air, while 
adhesion by contact is conditioned by uniform pressure 
and absolute contact. To comprehend this principle of 
retention, the molecular forces of attraction and repulsion 
must be appreciated. These two molecular forces, to a 
greater or less extent, exist within and between all bodies. 
In solid matter attraction predominates over repulsion, 
whereas in liquids the two forces are equal, and in gaseous 
matter repulsion predominates over attraction. Attraction 
is always stronger between like atoms than between unlike 
atoms. (This last fact is beautifully illustrated in the 
low-fusing alloys composed of tin, lead, bismuth, and cad- 
mium. These metals range in fusing-point from 442° F., 
to 617° F., yet when they are properly combined they may 
fuse at 135° F., thus demonstrating that the molecules of 
these metals create a marked repulsion for each other, and 
that it takes but a low degree of heat to render attraction and 
repulsion equal, that is, for the metals to fuse to a liquid 
state.) When like atoms are brought into atomic relation 
to each other, they are said to be held together by cohesion; 
when the interatomic space is exceeded, they can only be 
held together by adhesion, either by mass attraction or an 
intervening adhesive substance. Thus, it is apparent that 
the expression "uniform pressure" and "absolute contact" 
are misnomers, because absolute contact is an impossibility; 
but when these terms are used, they signify the closest 
mechanical contact of the mass, and do not refer to the atom 
relationships. When masses of matter are brought into 
mechanical contact and are caused to adhere by a film of 322 
RETENTION OF ARTIFICIAL DENTURES 
non-adhesive fluid, it might be thought that the adhesion is 
due to the strength of the fluid; but this is not the case 
because the thinner the film the greater the adhesion. That 
this adhesion is not due to atmospheric pressure may be 
demonstrated by suspending two masses of matter adhering 
by contact in the chamber of an air-pump and exhausting the 
air, when the adhesion will remain the same or stronger than 
under normal atmospheric conditions. Therefore, through 
an understanding of these axioms regarding attraction and 
repulsion, we can appreicate how artificial dentures are 
retained by the so-called adhesion by contact. 
Leverage.-In mechanics the lever is a rigid bar working 
upon a pivot. The pivot is called the fulcrum, and the bar is 
considered as two portions called arms, the one called the 
power arm and the other the work arm. There are three 
groups of these factors-fulcrum, power and arms-called 
classes. In the first class the fulcrum is between the power 
and the work, whereas in the second class the work is between 
the fulcrum and the power; in the third class the power 
is between the fulcrum and the work. In the retention 
of artificial dentures the lever of the first class only need be 
considered and it is of great importance. This principle, 
of physics is involved in every case of prosthetic restoration, 
either in its positive or negative sense, and too often in both. 
In complete artificial dentures the alveolar ridge constitutes 
the fulcrum, and the retention of the base-plate, by either 
atmospheric pressure or adhesion by contact, constitutes the 
power; the portion of the base-plate upon which these reten- 
tive forces exert their influence constitutes the power arm. 
The teeth form the work arm, and antagonization is the work. 
In partial artificial dentures the remaining natural teeth and 
roots may be the fulcrum or even fulcrums. 
The law governing the direction of energy should be taken 
into consideration. The law is: Energy moves in a straight 
line and at right angles to the surface from which the force 
emanates. Thus, in the line of energy there may be great 
resistance, while laterally there would be but slight resistance. 
(This is well illustrated by two moist plates of glass held 
together by adhesion by contact, which will offer much LEVERAGE 
323 
resistance to an effort to pull them directly apart, but only 
slight resistance to lateral pressure.) 
The anatomical relation of the mandible to the maxilla 
is a peculiar one, and offers many problems in physics. As 
resorption of the alveoli progresses, these adverse con- 
ditions become exaggerated. Therefore it follows that 
artificial substitutes should be inserted soon, that is, within 
a few weeks-two to six-after the rerhoval of the natural 
teeth. As the resorption of the alveolar processes progresses, 
the summit of the alveolar ridge of the upper jaw recedes 
upward and inward, whereas the summit of the alveolar 
ridge of the mandible recedes downward and outward. 
Hence, if the artificial teeth are set in the position occupied 
by the natural teeth, the problems in leverage become very 
serious. It is apparent that if the upper teeth could be 
arranged with their buccal surfaces just inside the summit 
of the alveolar ridge, it would be impossible to dislodge 
the base-plate by direct occlusion, no matter how hard or 
circumscribed the bolus of food; but it is not practical to so 
arrange the teeth; it is desirable, from a mechanical point of 
view, to approach this condition as nearly as the individual 
case will permit. If after the alveoli have thoroughly 
receded the upper artificial teeth are mounted upon the base- 
plate in their normal distance from the raphe, the work 
arm of the lever is relatively much lengthened. Therefore, 
to overcome this untoward leverage the teeth are drawn 
in toward the summit of the ridge. There is a limit to the 
inward drawing of the lingual surface of the teeth, for undue 
encroaching upon the domain of the tongue will ensue. That 
this work arm may be still further shortened, the artificial 
teeth buccolingually are made narrower than normal. As 
the shortening of a radius shortens the circumference of a 
circle, it becomes necessary to select artificial bicuspids and 
molars a little narrower mesiodistally than the natural teeth 
which they replace. This is but one of the reasons for the 
reduced size of the grinding teeth. The other reason for 
reducing the size of these teeth has to do with their power, 
and should not be discussed together with the principles 
of retention. It has already been stated that motion- 324 
RETENTION OF ARTIFICIAL DENTURES 
force-moves at right angles to the surface from which the 
motion emanates, therefore the shaping of the facets of the 
occlusal surface of the bicuspids and molars is an important 
factor in the problem of leverage. 
CONDITIONS AFFECTING RETENTION OF FULL 
ARTIFICIAL DENTURES. 
There are four factors to be considered in the retention 
of base-plates: Size, that is, the amount of surface covered; 
soft tissues; fluids of the mouth; and the shape of the 
portion covered. 
Fig. 165 
Size.-In any given case' the amount of retention by 
adhesion by contact is, like atmospheric pressure, according 
to the area of the surface (Fig. 165). Hence, other things 
being equal, the larger the denture the better the retention. 
Soft Tissue.-No one factor has so much to do with re- 
tention of artificial dentures as the soft tissues. These 
may be divided into three classes-muscles and their attach- RETENTION OF FULL ARTIFICIAL DENTURES 
325 
ments, submucous tissue, and the mucous membrane. As 
an axiom, it may be stated that a base-plate cannot rest 
upon a muscle which impinges upon or draws over the 
periphery of the plate, as the contractile power of the muscle 
is greater than the retentive force of adhesion by contact; 
but not of atmospheric pressure. The muscle attachments 
should always be observed in examining the mouth prior to 
taking the impression; then, in taking the impression, the 
muscles should be marked in the impression, so that the 
base-plate may secure a close adaptation about the muscle 
attachments, and yet not cause irritation thereby. As 
adhesion by contact is in the ratio to the surface covered, it is 
apparent that the base-plate should extend as far in every 
direction as the attachment of the muscles will permit, but 
not so far that the muscles when placed upon their greatest 
tension will impinge too heavily upon the periphery of the 
base-plate. This may give a very irregular outline, but the 
proper outlining of the periphery of the base-plate is one of 
the important operations in adapting artificial dentures. 
Beginning in the median line, the labial flange of the upper 
base-plate should be well cut away for the labial frenum, then 
gradually ascend to the cuspid eminence, where for cosmetic 
effects it must be as high as possible. After forming the out- 
line of the cuspid eminence, the border of the flange abruptly 
drops to accommodate the buccal frenum. The remainder 
of the border to the tuberosity must be kept as high as the 
attachment of the buccinator muscle will permit. In passing 
around the tuberosity, or its remains, there should be no 
sharp edge presenting, but a comparatively broad flat one, 
approximately- one-fourth inch, to rest upon the soft tissues. 
After trimming the base-plate to what seems to be the proper 
outline, it should be tested by moistening the maxillary 
surface, placing it in the mouth, and instructing the patient 
to exhaust the air from between the base-plate and the soft 
tissues, upon which it rests, by firm pressure. The patient 
should then be requested to vigorously work the muscles of 
the lip and cheeks, and see if in any way the base-plate may 
be dislodged. If so, the patient should again attach the base- 
plate, the operator grasping the lip and cheeks, one portion at 326 
RETENTION OF ARTIFICIAL DENTURES 
a time, between the thumb and finger, and firmly extend the 
tissues outward and downward to detect any excessive muscle 
bearing, which should be relieved. The base-plate (of vul- 
canite or metal) is removed from the mouth, dried, and 
modelling compound penciled on the whole length of the 
palatal border, post-dammed, and, extended backward until 
the desired retention is secured. If it is demonstrated that 
a palatal addition is required it must be incorporated in the 
finished denture, by some feasible method. 
The lower base-plate is of the horseshoe or crescent shape, 
and necessarily covers much less surface than the upper one; 
but if the impression is properly taken and the periphery 
properly adjusted for the muscle attachments, the base- 
plate can be seated, and sometimes considerable adhesion 
obtained. Some writers would lead one to believe that all 
lower artificial dentures should have a deep lingual flange, 
while other writers would have the lingual flange almost 
entirely removed. Both are partly correct, because some 
cases require the one treatment and other cases the other 
method. In those cases in which the crest of the alveolar 
process of the mandible is pronounced, and the attachment 
of the mylohyoid muscle is low upon the lingual wall, the 
lingual flange of the base-plate can and should be carried 
well down, for retention is according to the area of the 
surface, and the larger the base-plate the greater the resist- 
ance to the force of mastication; but if there is excessive 
resorption of the process, and the attachment of the mylo- 
hyoid is at or very near the crest of the slight ridge remain- 
ing, or if there is a sharp edge representing the union of the 
lingual plate of the mandible and the remains of the alveolar 
process, there should be almost no lingual flange to the 
base-plate. If in taking the impression the mylohyoid 
is compressed and depressed, the apparent space for a lin- 
gual flange will prove very delusive and troublesome: also, 
if the base-plate is carried over the sharp lingual edge often 
found upon the mandible, much irritation will be produced. 
In these cases the only means of success is to cut away 
the lingual flange, if one has been formed. In construct- 
ing the superstructure upon this properly fitted, short, lin- RETENTION OF FULL ARTIFICIAL DENTURES 
327 
gual-flanged base-plate, an extra retention flange of one- 
sixteenth to three-sixteenths of an inch in width may be 
extended horizontally into the mouth, when the glands and 
folds of mucous membranes resting upon this enlarged base- 
plate will often be of much aid in retention. The buccal 
flange should be kept as broad as the muscle attachments 
will permit. The same tests applied to the upper base-plates 
should be used with the lower. 
Submucous Tissue.-In this class is included all the soft 
tissue of whatever histological formation-except the muscle 
tissue just considered-lying beneath the mucous membrane 
upon which the base-plate rests. When a moderate amount 
of soft tissue is evenly disposed beneath the mucous mem- 
brane, the very best condition possible so far as this tissue 
is concerned is presented. In some mouths the raphe of the 
maxilla will be found overdeveloped and covered with a 
thin, tensely drawn mucous membrane, while upon either 
side there may be an area extending well toward the base of 
the alveolar process with more or less submucous tissue, and 
a portion of the alveolar ridge composed of soft, flabby tissue 
only. If an aged patient presenting such a mouth has not 
long since acquired the knack of wearing artificial dentures, 
the chances of his success are very unfavorable. The treat- 
ment for such a case would be to relieve the pressure upon 
the whole length of the raphe, let the soft tissue in the vault 
alone, and increase the pressure upon the soft portion of the 
alveolar ridge. A vacuum chamber in such a case, placed 
over a portion of the tense membrane in the highest portion 
of the vault, would be a source of irritation and use- 
less. 
Mucous Membrane.-This membrane must bear the bur- 
den of supporting all complete artificial dentures, therefore 
an appreciation of its capabilities is an important factor to 
the prosthetist. In examining the mouth prior to taking 
the impression the condition of health of this tissue over 
which the base-plate is to be placed should be noted, and 
if necessary, the required attention given. There are two 
qualities of this membrane to be considered, tone and 
tension. 328 
RETENTION OF ARTIFICIAL DENTURES 
Tone.-The mucous membrane is much influenced by the 
health of the individual, and may be finite an index of the 
condition of the general system. The patient will learn that 
when the general system is vigorous and rested, the denture 
will have its maximum retention, but when the system is 
debilitated or relaxed from temporary exhaustion-tired- 
the retention of the denture will be poor and troublesome. 
When patients complain that their dentures are not "stick- 
ing up" as well as they did, it is well to investige the tone 
of the system and explain this principle. When the mucous 
membrane loses tone for any reason, the retention of the den- 
ture will be correspondingly affected. When dissolution is 
about to take place, it may be noticed that artificial dentures 
cannot be retained at all. Because of this quality of tone 
other conditions being equal, the younger the patient the 
better the retention. Aged patients in a debilitated state of 
health and unacquainted with the use of artificial dentures 
should not be encouraged in having their mouths fitted to 
new dentures, for the tax upon their vitality may be too 
great, and hasten their death. 
Tension.-When a surface upon which a denture is to be 
worn is covered with a healthy mucous membrane, evenly 
underlaid with a medium amount of submucous tissue, and 
the tone is good, so far as the tissues are concerned, the 
very best conditions exist for retaining an artificial denture. 
When the soft tissues covering the roof of the mouth are 
thin and tense, the case is much more difficult. In the former 
case the tissues will quickly conform to the hard base-plate, 
and if there has been a reasonably skilful construction of the 
appliance, the retention will be satisfactory. In the latter 
case, with the most skilful construction, it will often require 
an hour or two before the mucous membrane conforms to the 
unyielding material of the base-plate. It is this class of cases 
that tempt the dentist to use velum vulcanite lining at the 
periphery of the base-plate, or to resort to the patent soft 
vulcanite retainers. As this condition of the mouth is the 
only logical one in which these retainers are permissible, 
little harm is done if they are never used where not indicated. 
In these cases of tense mucous tissue no sharp edges or RETENTION OF FULL ARTIFICIAL DENTURES 
329 
localized increased pressure by any means whatever can be 
tolerated. Carving of the cast is contra-indicated. 
There are rare-very rare-cases in which the mucous 
membrane is extensively underlaid with soft tissue over the 
roof of the mouth, and deeply fissured. Such cases may justly 
be classed as unfavorable for retention. The cast of such a 
case may be carved with impunity. The object sought in 
carving is to cause the periphery of the plate to imbed itself 
more firmly, or to raise a bead just inside of the periphery. 
This temporarily creates a large vacuum chamber, but as 
soon as the raised portion becomes imbedded in the soft 
tissues, adhesion by contact is secured. In some cases the 
bead acts as a barrier to the ingress of an excessive amount 
of fluid. The treatment mentioned in this paragraph is so 
rarely indicated that the writer expects never to use it again; 
but takes this means of expressing his disapproval of the 
common use made of it. 
Many cases presenting will have areas of thin, tense 
tissue, and other areas of excessively soft tissue. The treat- 
ment for this class of cases has already been stated, that is, 
relieving of the pressure upon the tense tissue in the prox- 
imity of the raphe, to the extent of its entire length. This 
can usually be accomplished by the addition of one or two 
layers of No. 60 tinfoil. The soft areas over any portion of 
the vault should not be changed, but an excessively soft 
tissue upon the alveolar ridge should have a firm peripheral 
bearing extruding beyond it. Rarely should any hard por- 
tion of the alveolar ridge be relieved, and then only when 
very circumscribed. 
Fluids of the Mouth.-The normal thin watery fluid of the 
mouth is most favorable for retention by adhesion by con- 
tact. The fluid makes the contact, but does not hold the 
base-plate so far away as to interfere with the adhesion by 
contact. When the fluids are vitiated, thick, and ropy, 
they may have sticky properties, but not enough to com- 
pensate for the interference with adhesion by contact. 
Temporarily these vitiated secretions can be removed from 
the mouth by thoroughly washing with an alkaline solution, 
then inserting the denture well moistened with cold water. 330 
RETENTION OF ARTIFICIAL DENTURES 
Shape.-The shape of the surface upon which an artificial 
denture is to rest has much to do with its retention. Side 
walls are useful to prevent lateral motion; but a flat surface 
in the vault, or floor of the mouth, is essential for the best 
retention. No matter whether the vault is high or low, or 
the alveolar process of the mandible is high or low, the reten- 
tive surface is the horizontal area covered. A high, inverted, 
V-shaped vault or prominent alveolar process of the mandible 
is especially unfavorable for suction. 
PRACTICAL APPLICATION OF THE PRINCIPLES 
OF RETENTION. 
The retention of full dentures may be said to be by four 
forces: two passive-first, base-plate outline, and second, 
resistance to force (leverage)-and two active-first, molec- 
ular (adhesion by contact), and second, atmospheric pressure. 
Base-plate Outline.-Much of the burden.of the discussion 
in Chapter I is developing the anatomy of the mouth as a 
support for and retention of artificial dentures; therefore the 
chapter may again be read with this subject, "base-plate 
outline and retention," uppermost in mind. Figs. 65 and 
66 illustrate outlines for a specific upper and lower case. 
If the impressions are properly taken the landmarks are 
defined. 
Leverage.-Figs. 166 and 167 illustrate the application 
of force through the teeth upon the base-plate. Where 
there are two facets, as in the bicuspids, the force may be 
applied from either facet, then the direction of the force will 
be at right angle to that surface; but if the force is applied 
to both surfaces, the direction of the force will be the resul- 
ant, and parallel with the long axis of the tooth or teeth. 
Each specific case should be carefully studied, and these two 
factors, outline and leverage, should be so controlled that 
they aid in retention and not in. dislodging the artificial 
dentures. These factors are classed as passive forces, because 
it is through them that active muscular force may cause 
destructive motion. Fig. 168 illustrates a practical case APPLICATION OF PRINCIPLES OF RETENTION 
331 
in which success was not attained until the tilted molar 
on each side of the mandible was cut down and crowned. 
Fig. 166 
Fig. 167 
Molecular Attraction, or Adhesion by Contact.-Adhesion by 
contact is described by the catchy phrase, " uniform pressure 
and absolute contact," while in fact, neither statement is true. 
hat is meant is, that the base-plate is so adjusted that it 
Fig. 168 
resists force applied at any point within the base plane. In 
practice this means that the heaviest bearing of the base- 332 
RETENTION OF ARTIFICIAL DENTURES 
plate is at and near the periphery. Absolute contact means 
that there are no cavities made in the surface of the denture 
as suction chambers; but it does admit of and requires relief 
of inclosed hard places. These relief spaces undoubtedly 
do cause temporary suction, but this is incidental and not 
the object. The shape of these relief spaces are usually 
different from that of vacuum chambers. They conform to 
the shape of the hard portion to be relieved, while the 
vacuum chamber is in miniature the outline of the alveolar 
process. The most commonly required relief is along the 
Fig. 169 
raphe of the maxilla (Fig. 169). This relief may be made 
by adding one or more thicknesses of number 60 S. S. W. 
tinfoil. This foil is 4| thousandths of an inch thick, hence 
the desired depth of the relief space may be obtained by 
additional layers of foil. The relief should be over the whole 
length of the hard portion, even though it extend from the 
crest of the alveolus to (and even through) the palatal border 
of the base-plate. However, the palatal border should be, 
if possible, one-fourth inch distal of the relief space. Fig. 170 
represents.three layers of relief tin. The first, the smallest APPLICATION OF PRINCIPLES OF RETENTION 
333 
one, is fastened to the plaster cast with sandarac varnish, the 
second one in size is glued over the first, and the third and 
largest is fastened in like manner. Any circumscribed hard- 
ness, as nodules, wherever located, should be relieved in the 
same manner as described for the raphe. Another method 
for relieving the hard places is by compressing the soft places. 
This should be done by the manner in which the impression 
is taken which is discussed in Chapter II. In few cases is it 
advisable to carve the impression or cast to produce this 
relief, as the amount removed cannot be correctly gauged, 
nor the original condition restored if desirable. 
Fig. 170 
Atmospheric Pressure.-Sin'ce its application to artificial 
dentures, in 1840, there has been and is much confusion of 
thought and expression over the theory and practice with 
this physical force. The student, after giving consideration 
to the truths stated in the preceding sections of this chapter, 
should have no difficulty in formulating a terse statement, for 
memory purposes, as: Molecular attraction, mass attraction, 
or adhesion by contact (used as synonymous terms) implies 
a mechamical contact; and atmospheric pressure implies a 
space with some degree of emptiness. 334 
RETENTION OF ARTIFICIAL DENTURES 
It is evident that the most advantageous position for a 
vacuum chamber is about the gravity center of the denture 
which has the least motion, and where the leverage is equal 
in every direction; provided a vacuum chamber is to be used. 
An air chamber in an artificial denture is always injurious 
to the tissues and often a positive obstruction to the best 
retention. 
Vacuum Chamber Indicated.-It may justly be said that 
a vacuum chamber is never indicated; but that its use is an 
evidence that the dentist has not confidence in his ability to 
discard it. 
If a chamber is determined upon the following instruction 
may be useful: 
Edges.-The edges of relief spaces should be almost 
imperceptible, while the edges of a vacuum space should be 
at right angle to the contact surface. The depth of the 
vacuum cavity should vary from gp- to Tg- of an inch. The 
thinner and tenser the tissue the shallower the chamber, and 
vice versa. 
Material.-Block tin or tin alloyed with lead is used to 
form the vacuum chamber. Pure lead may be used, but it 
imparts a dark discoloration to the vulcanite. The pattern 
metal found at the supply houses is tin with a small amount 
of lead. The material should be purchased in sheet form 
and cut for each case. As the metal is supplied in sheet 
form pg- of an inch thick, a small portion should be rolled 
to ^2 of an inch and the larger portion to gp of an inch in 
thickness. All fanciful forms having sharp angles (as 
heart- or shield-shape) should be avoided because they are 
an unnecessary source of irritation. 
Attaching.-There are various ways of attaching the 
chamber forms to the cast, as a thin mix of oxyphosphate of 
zinc cement (best), sandarac varnish, very small tacks, or 
a short portion of pins. Fig. 171 shows a cast with a vacuum 
chamber form attached with pins. When the cast is to be 
coated with tinfoil the varnish and foil will suffice to hold 
the chamber form. 
For Castings.-The methods described for forming relief 
spaces and vacuum chambers are suitable for all methods of APPLICATION OF PRINCIPLES OF RETENTION 
335 
base-plate formation excepting those by the casting method; 
for which, owing to the high heat required, these methods 
cannot be employed. For the casting method the relief 
spaces and vacuum chamber may be provided for by carving 
sfrom the impression, or, better, by adding to the surface of the 
cast a fine-grain investment compound. This addition is 
made by tracing, with a pointed instrument or sharp-pointed 
lead-pencil, the outline of the desired addition, thoroughly 
saturating the surface to be added to with water, and painting 
on the material as a thin mix. A mixture of two parts, by 
measure, of wash silica, one part plaster of Paris, and water 
to make a thin cream is excellent. When the added material 
is nearly hard set it is carved and burnished into form. 
Fig. 171 
Other Forms of Vacuum Chambers.-The vacuum chamber 
thus far considered and commonly used is known as the 
unilateral chamber; that is, it is one and extends equally 
on both sides of the median line. There are cases in which 
this form of chamber is not applicable, as cleft-palate, deep- 
fissured palate, an inverted V palate, also an overdeveloped 
raphe. Fig. 172 illustrates an overdeveloped raphe. In 
such cases a bilateral chamber is indicated if any is to be 
used. A bilateral chamber consists of a complete chamber 336 
RETENTION OF ARTIFICIAL DENTURES 
upon each side of the median line. Fig. 173 is an illustration 
of a case requiring such treatment. 
Fig. 172 
Fig. 173 
Soft Vulcanite.-The use of "velum rubber" (soft vul- 
canite) retainers is a questionable method. It is certainly 
unsanitary and rarely justifiable. There are two general 
plans for using velum rubber: (1) As a peripheral border APPLICATION OF PRINCIPLES OF RETENTION 
337 
of the vacuum chamber, or the outer edge of the plate. 
(2) In the form of disks, either as a large central disk or as 
small disks distributed about the surface. The rationale of 
the first method is to provide a flexible rim that may be 
readily adapted to a thin, tense, mucous membrane. In such 
cases the method has the stamp of being scientific, but it 
is unscientific and has the stamp of ignorance to use the 
method when the tissues are excessively soft and stability 
is the result desired. The second method consists of attach- 
ing soft vulcanite disks to depressions in the maxillary or 
mandibular surface of the denture (Fig. 174). The rationale 
Fig. 174 
of this method is that the thin pliable disk, by the aid of 
moisture, easily conforms to a surface covered with thin and 
tense mucous tissue; then as traction is applied to the 
denture it draws the center of the disk away from the tissue, 
thus forming a vacuum. It is obvious that such a denture 
is pendently seated, but that it will require much force to 
remove it from the mouth. The mouths where such methods 
are indicated are rare, and to insert such unsanitary appli- 
ances when other methods, properly used, would meet the 
requirements is reprehensible. As velum rubber contains 
but two-fifths as much sulphur as hard vulcanizable rubber 
it is evident that the soft vulcanite is but two-fifths " cured;" 338 
RETENTION OF ARTIFICIAL DENTURES 
therefore it is easily understood why the material is so much 
less durable, swells, changes form, acquires an offensive odor, 
and requires renewal every few months. "Velum rubber" 
should never be used in the mouth except where the con- 
ditions cannot be met by other means, and then it should be 
renewed often. 
There are conditions of the lower jaw that can be met with 
vellum rubber better than with any other material; however, 
even in these extreme cases the material should be used 
only as a last resort, and then after the patients have had 
explained to them the nature of the material and the con- 
tinued expense. 
Conditions of the mandible indicating velum rubber are 
excessive resorption with nodules and sharp ridges upon the 
surface of the bone, and soft tissues very thin and sensitive, 
especially to a sliding movement. 
The technic for constructing a hard vulcanite denture 
with a velum vulcanite lining is peculiar to the material, 
but easily comprehended. 
The Spence compound cast and wax occlusion model 
having been obtained, are mounted upon a New Century 
Antagonizor. The wax-occlusion model is now laid away for 
future use. The surface of the mandibular cast should be 
freed of all wax and the surface rubbed with talcum powder. 
A piece of thin tinfoil is smoothly and perfectly adapted 
to this powdered surface, upon which the denture is to rest, 
one thickness of pink base-plate wax, and over this a layer 
of heavy (No. 60) tinfoil are conformed. This represents 
the portion to be replaced with velum rubber, and is called 
the base-plate; upon this foundation of tin and paraffin, 
or base-plate, a small roll of soft yellow wax is placed, in 
which a soft-iron wire is imbedded for rigidity. Upon this 
roll of wax the teeth are mounted and occluded. This 
built-up trial denture is tried in the mouth and if satis- 
factory is returned to the antagonizor; the yellow-wax rim 
mounted with the teeth is thoroughly chilled and carefully 
removed from the base-plate. This teeth-mounted wax 
rim not being distorted, is flasked, packed with hard vulcan- 
izable rubber, and vulcanized. The hard vulcanite rim is APPLICATION OF PRINCIPLES OF RETENTION 
339 
thoroughly polished, except the base surface, which is 
scraped and the edges filed to a slight bevel looking outward. 
This vulcanite rim is now returned to the antagonizor, 
occluded, and waxed to the paraffin tin base-plate. The 
entire labiobuccal and lingual surfaces are nicely covered 
with heavy tinfoil, even extending upon the porcelain teeth. 
(Remember the original cast is upon the antagonizor and 
is to remain there.) The tin-covered denture is now flashed 
with French's Regular Dental Plaster so that the separation 
is exactly at the periphery of the base-plate. The flask is 
opened and the base-plate removed. The cast upon which 
the velum rubber is to be vulcanized is now in the lower 
section of the flask and was formed from the mandibular 
surface of the tinned base-plate. If the tin was carefully 
formed upon the Spence compound cast and the first half 
of the flasking carefully done the new cast will be a perfect 
reproduction of the original. This is to be covered with 
thin tinfoil and soaped. The next step is a very important 
one. The exposed surface of vulcanite must be thoroughly 
cleaned of wax and dirt; flush away the wax with hot water, 
wipe dry, and rub well with a cloth saturated with chloroform. 
This surface is then covered with a hard vulcanizable rubber 
cement (bow-spring rubber dissolved in chloroform to the 
consistency of thick cream). The cement is evenly painted 
over the surface of vulcanite, and when the chloroform has 
nearly evaporated sufficient velum rubber (preferably black) 
is packed upon it to fill the mold. Vulcanize the same as 
hard rubber. When the case is taken from the flask and the 
tinfoil removed it is finished except the peripheral edges 
of the velum rubber. These edges are trimmed away with 
sharp scissors, seared with a hot iron, and the burned soft 
vulcanite removed with chloroform. In a few moments the 
chloroform will have evaporated and the; case is finished; 
however, it is well to again gloss the hard vulcanite with a 
soft brush wheel and chalk. 
The antagonizor bows mounted with the original casts and 
wax-occlusion model are filed away for future use. 
When it becomes necessary to renew the velum rubber 
the bows mounted with the casts and occlusion model are 340 
RETENTION OF ARTIFICIAL DENTURES 
returned to the antagonizor, the velum rubber is cut away 
until a surface of hard vulcanite is obtained, a new tin 
and paraffin base-plate is formed, and the teeth upon the 
hard rim of rubber are occluded and attached to the base- 
plate. The remainder of the process is the same as con- 
structing the original velum lining. 
As all the strength of this denture is in the hard vulcanite 
it is well to use a reinforcement. This is done by inserting 
a No. 12- to 16-guage wire of clasp gold or iridioplatinum. 
This is done when packing the hard vulcanite rubber. With 
the pins of the teeth imbedded in red rubber and the pink 
rubber facing in place, the wire stiffener, previously con- 
formed, is placed at the cervix of the teeth and the packing 
completed. 
The technic for applying the tinfoil is described in 
Chapter IX. 
Fig. 175 
Fig. 176 
Speyer's Cohesion-surface Forms.-Speyer's "cohesion- 
surface forms" (cohesion improperly used) is heavy tinfoil, 
the surface of which is covered with minute papilliform 
prominences. The claim of strong adhesion due to the pecu- 
liar conformation is hardly tenable; however, they are deco- 
rative and are satisfying to the mind of some patients; 
nevertheless, the same thickness of plain tinfoil would produce 
the same physical results. Fig. 175 shows the material as it 
is procurable at the supply houses. It should be used only APPLICATION OF PRINCIPLES OF RETENTION 
341 
upon the surface requiring relief. A half-sheet properly 
shaped is usually enough for one denture. Fig. 176 is a 
section of the "cohesion-surface forms" enlarged four times 
to better show its construction. These "cohesion-surface 
forms" were used in several of the dentures illustrated in 
this book. "Contraptions" for retaining artificial den- 
tures, as sometimes seen in supply houses, are not only 
injurious to the mouth, but often a detriment to retention. 
The denture is often strongly retained in spite of the appliance. 
The student should be able, with his knowledge of anatomy 
and the laws of physics, to detect the unscientific things. 
Conclusions.-Having made a somewhat extensive study 
of the principles of retention for full dentures, and their 
practical application, it is a propos to make a critical analysis 
of the present-day technic methods. It is evident that: 
1. A centrally located vacuum chamber is very limited in 
retention power and permanence; also, it is injurious to the 
tissues. 
2. An areal contact denture, properly extended, has the 
greatest retention power, is durable and not injurious to the 
soft tissues. 
3. The principles of retention, also of cosmetics, must be 
considered in taking impressions. 
4. Modelling compound impressions are apt to and usually 
do form spaces in which there is not contact, therefore is 
deceptive and unreliable. 
5. Plaster necessarily forms a real contact, therefore is the 
reliable and positive material for impressions. 
6. There is much misunderstanding of the anatomy and 
physics involved in impression taking. 
7. The purpose of an artificial denture is for efficiency in 
mastication, and cosmetics or restoration of the features. 
Therefore, an impression method that is intent upon the one 
and ignores the other is inefficient. The modern modelling 
compound method is designed for great retention power; 
but the material is deceptive in that it produces, in ordinary 
hands, temporary atmospheric spaces. The modern plaster 
impression method is the basis for creating the greatest 
possible retention, and also for restoring the features. 342 
RETENTION OF ARTIFICIAL DENTURES 
8. The professional man should not be satisfied with suc- 
tion that is based upon empirics; but he should be intent 
upon, producing the best results. This latter category is the 
attribute of mentality, therefore professional and not em- 
pirical. 
"Muscle Trimming" and "Closed Mouth" Methods. 
-On page 125 these methods were referred to as erroneous, 
that is, based upon mistaken ideas of anatomy and physics. 
Such a statement needs substantiation; without which it is 
unjust to the authors of the methods. 
"Muscle trimming" is designed to accomplish two objects: 
(a) preventing the labial and buccal muscles dislodging the 
plate, and (5) preventing irritation of the soft tissue at the 
border of the base-plate. The former is erroneous, but the 
latter is in part true. 
In this discussion it is assumed that modern methods for 
impression taking, both plaster and modelling compound, as 
relating to retention of artificial dentures only are under 
consideration. 
The buccinator and muscles inserted into the lips are the 
ones involved. Whatever is true of the buccinator dis- 
lodging the denture is also true of the other muscles. So 
far as this study is affected the origin and insertion of the 
buccinator is at the union of the alveolar processes and the 
body of the maxilla and mandible. The buccinator is not 
a muscle of much power but sufficient for its normal function, 
that is, keeping the bolus of food between the teeth. When 
the mouth is closed it has no appreciable power unless the 
cheeks are distended with food or air. While the mouth is 
wide open the origin and insertion are far enough apart so 
that the contractile action of the muscle may exert some 
power. This force cannot dislodge the upper denture for if 
it displaces the denture any appreciable distance (even one- 
ten-thousandth part of an inch) and there is suitable adapta- 
tion and extension of the palatal border of the base-plate a 
perfect vacuum is created and atmospheric pressure (of 
approximately fourteen pounds to the square inch) is pro- 
duced upon the entire surface affected. This is true also of 
the lower denture provided the necessary conditions are APPLICATION OF PRINCIPLES OF RETENTION 
343 
present to create a vacuum. There is power enough in any 
or all of the muscles under consideration to reduce the flanges 
of the soft impression material to the extent of destroying all 
possibility of esthetic restorations. However, the "muscle 
trimming" depresses the peripheral border so much that 
there is little probability of irritation from the pressure of 
the border of the base-plate. 
The "closed mouth" method is still more destructive of 
esthetic restoration than the open mouth method, because 
the orbicularis oris including its bony attachments (the angle 
and frenal muscles) is more actively brought into action. 
The misconception of the dislodging action of the muscles 
upon the denture is just as true with this method as with the 
former. However, this method has demonstrated the action 
of the masseter upon artificial dentures. It demonstrates 
this action by its shearing effect upon the distobuccal angle 
of the upper and especially the lower modelling compound 
impression. This action of the masseter is only marked in a 
large development of. the muscle. The student may study 
the action of this muscle by placing the index finger in the 
mouth with the thumb externally grasping the muscle, 
occluding the teeth, and contracting and relaxing the muscle. 
This muscle action cannot dislodge the denture because the 
stronger the muscle acts the stronger the dentures are 
clamped in place. However, it may cause much irritation 
and necessitate the trimming of the base-plate at the location 
indicated. One should hardly need to use the closed mouth 
method for impressions, with its attendant evils, for the 
purpose of recording the action of the anterior border of the 
masseter muscle. Nevertheless the action of this muscle 
when obstructive must be accommodated. 
This condemnation of the "muscle trimming" method, 
as a rule of practise, necessitates a superior method. No 
catchy expression can be substituted for "muscle trimming" 
for establishing the peripheral border of the impression 
(and denture), for a scientific method must be based upon 
an appreciation of the anatomy and physiology (physics) 
of the parts involved. Nevertheless, the classification of 
requirements for retention, namely: (1) Areal contact, (2) 344 
RETENTION OF ARTIFICIAL DENTURES 
peripheral bearing, and (3) extension for retention, should 
be constantly in mind when determining the location of the 
peripheral border of the impression and base-plate. 
There are two extreme conditions of the alveolar process 
that must be considered in determining the periphery. The 
one is the full prominent process and the other is the exces- 
sively resorbed process. (These conditions are diagrammed 
in Fig. 16.) Necessarily all cases presenting are somewhere 
within the extremes and must be a modification of the extreme 
governing the specific case. As the one object of the impres- 
sion is construction of the denture, the peripheral border of 
the impression can best be determined by considering the 
requirements for the flanges of the denture. In the first 
extreme condition (prominent process) the flanges of the 
denture should be as thin as possible and necessarily the 
extent is only to exclude air. In this extreme condition 
the base-plane, and consequently, the peripheral bearing, is 
at the crest of the alveolar process (Fig. 16). In the other 
extreme condition (excessively resorbed process) the flanges 
are most important because they provide the peripheral 
bearing and restore the contour. Thus, it is evident there 
is value and necessity for the peripheral wax additions for 
plaster impressions as elaborated in the chapter on Impres- 
sions. In this class of cases the bearing must be as near 
the muscle attachments as possible. Also the flange may 
extend a short distance upon the muscle to act as a valve. 
Is the mental vision clear? Areal contact over the entire 
base-plane, peripheral bearing and extension for retention, 
with emphasis upon palatal extension. 
Notice. - The emphasis that has been placed upon 
extension for retention is apt to impress the novice that all 
full cases require this excessive extension; that is not true. 
The large majority of the cases presenting to the general 
practitioner are average in size, form, quantity and tone of 
soft tissues, and quantity and viscosity of the fluids of the 
mouth. Such cases are well retained with much less surface 
of the mouth covered; nevertheless, the larger the area of the 
base-plane, other factors-pro and con-being duly con- 
sidered, the greater the retention. APPLICATION OF PRINCIPLES OF RETENTION 
345 
Irritation from Extension.-Naturally a broad, flat 
surface cannot cut, that is irritate, as will a knife edge; 
therefore emphasis has been placed upon having the 
palatal extension one-fourth inch wide, and that the soft 
tissues covered with this extension must be held firmly 
against its bone support throughout its entire length. This 
compressive action should be produced by the peripheral 
wax addition to the tray. Carving of the cast, in the esti- 
mation of the writer, is the most unsatisfactory and repre- 
hensible method ever invented for creating retention in 
artificial dentures. If a scientific impression has been taken, 
the results of carving cannot be tolerated. The peripheral 
edge of the maxillary surface should be slightly rounded 
-never left angular. If irritation ensues, even after the 
most scrupulous and painstaking methods and technic, the 
student and young practitioner should not be discouraged. 
Nor should he place too much credence upon the overenthu- 
siastic statements of some modelling compound hobbyists, in 
that the peripheral border of a denture made from a well- 
taken modelling compound impression should never be 
trimmed, but that attention should be given to some fault in 
the " articulation" of the teeth. " Whoever expects a perfect 
piece to see, expects that which never was, is, nor can be." 
When the human mouth can be worked upon as positively 
as a block of wood, then dentistry will be taken from the 
category of the professions and will be only a skilful trade. 
These last remarks are designed to caution the sincere and 
troubled ones against discouragement which is often engen- 
dered by the careless and extravagant expressions of some 
members of the profession. 
Nausea.-Nausea is sometimes associated with impression 
taking and inserting of artificial dentures. Nausea is a 
result of the action of the mind, therefore its treatment is 
through the mind-suggestion. The operator should remem- 
ber that a light tickling touch of the finger, impression or 
denture upon the palate is much more suggestive than a firm 
pressure. Many dentures have been ruined by cutting off 
the palatal border. Attention should be given rather to 
creating pressure of the border and often in extending it 346 
RETENTION OF ARTIFICIAL DENTURES 
backward. Tactful handling of the patient will overcome 
the worst cases. 
Figs. 177 and 178 show two views of the peripheral border 
and palatal extension of a more than ordinarily difficult case. 
Fig. 177 
In this case it was essential that great retention and perfect 
enunciation should be obtained. The wax reenforced plaster 
impression, Spence plaster compound cast, vulcanite base- 
plate and double vulcanization were used. When the vul- 
canite base-plate was tried in the mouth it was found 
Fig. 178 
that with several repeated efforts the base-plate could be 
loosened. This fault was corrected by penciling on modelling 
compound to extend the palatal border and post-damming 
until it was impossible for the patient to loosen it by any ROOFLESS PLATES 
347 
muscle action whatever. The compound was replaced with 
vulcanite at the second vulcanization. 
Fig. 179 shows casts made by filling finished denture for 
cases that were desirous of better retention than formerly 
possessed. The line indicates the extent of the former 
denture. 
Fig. 179 
The author advises the reader to return to page 87 and 
reread the description of the technic for full upper and lower 
impressions. Begin with "Notice" and keep constantly 
in mind, while rereading the summary, areal contact, 
peripheral bearing, and extension for retention. 
ROOFLESS PLATES. 
The roofless plate may be defined as a saddle upper denture. 
Its base-plane is approximately two-thirds that of the usual 
base-plate. 
The requirements for its successful application are a 
medium to large base-plane, prominent alveolar process and 
tuberosities, favorable condition of the soft tissues and fluids 
of the mouth. 
Conditions contra-indicating a roofless denture: Small 
base-plane; alveolar process and tuberosities nearly extinct; 
soft tissues thin and tense; fluids of the mouth, ropy or defi- 
cient in quantity; and a personal equation antagonistic. 
The roofless method is desirable for those patients that are 
very much annoyed by the usual palatal extension, those 
that complain of excessive heat, loss of taste and general 
discomfort from the distal extension. It is desirable in some 348 
RETENTION OF ARTIFICIAL DENTURES 
cases of excessively hard and enlarged raphae, also excessively 
high V vault. 
Principles of Retention.-Excessive peripheral bearing except 
over the zygomatic processes, with light or no contact over the 
crest of the alveolar process. 
Material for Denture.-Vulcanite only. 
Technic.-Plaster impression using compression wax where 
bearing is desired-plaster mixed thin; make vulcanite base- 
plate. Try the base-plate in the mouth and if the adaptation 
and retention are satisfactory complete as with the usual 
base-plate. If the adaptation is satisfactory but not suffi- 
cient retention, the peripheral bearing should be increased 
with stick modelling compound, having a shallow vent at 
the maxillary zygomatic processes thus providing an escape 
for the confined air. When satisfactory retention is obtained 
proceed as usual until the flask is opened when the vulcanite 
base-plate and its modelling compound addition are removed 
with the wax and the mold packed with the desired rubbers. 
Durability of the retention of the roofless denture: Prob- 
lematical. The strong retention obtained will be for a few 
months only, but if the mental attitude is compatible the 
strong retention will last long enough for the patient to 
acquire the artificial denture habit. Do not attempt this 
method with an adverse personal equation, nor promise the 
patient impossible results. 
TENSOFRICTION. 
This term is used to cover all those methods where reten- 
tion is obtained by contact, but the surface of the contact 
is too insignificant to constitute a factor. It includes all 
forms of clasps, removable plate-bridge attachments, spiral 
springs, and spring plates. It implies that retention is 
obtained by friction through tension. The simplest form 
of tensofriction is the spring clasp, in which thenarrow 
strip of metal grips the tooth by friction through the tension 
in the metal. 
It is not relevant in this book to discuss that class of 
partial dentures known as "bridge-work;" only to say that CLASPS 
349 
there is a large class of cases where the best interests of the 
patient will be subserved with a plate denture. In all cases 
the cosmetic effects of a plate are equal and in many places 
far superior to a bridge. 
It is a good rule to consider that a natural tooth that is 
or can be made comfortable and useful to the patient is far 
more valuable than an artificial one. However, the con- 
ditions may be such that a remaining tooth or two in the 
upper maxillae may be more of a detriment to the wearer of 
an artificial denture than their loss; but it is always a subject 
for serious thought. 
In a few cases the partial denture may be retained by 
atmospheric pressure, adhesion by contact, or by the spring 
plate; but usually the best results are obtained by the use 
of clasps. 
CLASPS. 
There is an unjust prejudice in the minds of some den- 
tists against the use of clasps. This is probably due to an 
improper knowledge of their advantages and disadvantages; 
also an insufficient knowledge of the mechanical principles 
involved and their practical application. The advantages of 
the clasps may be summed up in the statement that there is 
no method by which a partial plate denture may be retained 
with so much comfort and usefulness to the patient as with 
clasps. This implies that the conditions are favorable and 
the method is properly applied. The disadvantages are that 
in some cases the method should not be used because the 
remaining teeth are not healthful nor favorably located and 
may be of improper conformation. The last condition must 
preclude clasps. The principal argument used by those who 
object to the use of clasps is that they cause disintegration 
of the teeth to which they are attached. The writer emphat- 
ically states that the cases in which this is necessarily so 
are very few indeed; but that most of these unfortunate 
occurrences are due to imperfect knowledge and manipu- 
lation of the dentist. It is awe-inspiring to see how some 
of these men who throw up their hands in holy horror at the 
idea of clasping a tooth will, in a few minutes, "disinte- 350 
RETENTION OF ARTIFICIAL DENTURES 
grate" a sound tooth to the extent of removing the whole 
crown and pulp for the purpose of attaching a bridge. 
Some argue that a tooth should never be elapsed until it has 
been crowned. Why not wait until the necessity arises, and 
then fill or crown as may be necessary? "Consistency is a 
jewel." The question should be: How can a patient derive 
the greatest amount of service from a tooth? not, How can 
the tooth be preserved the greatest length of time? A tooth 
is of value only as it is of service. 
Names.-There are various forms of clasps. A stay clasp 
is one that rests upon one side and perhaps two angles 
of a tooth, and is used as a bearing for a spring plate. A 
spring clasp is one that rests upon at least two sides and three 
angles of a tooth. Rigid clasps are clamping devices that 
telescope specially constructed artificial crowns. A ferrule 
is a continuous band about the tooth. 
Stay Clasps.-The stay clasp is represented in vulcanite 
work by the thickened edge of the spring plate. The name 
is especially applied to the short clasps used to stay metal 
plates. This means may be used to support a spring-plate 
denture carrying any or all of the six anterior teeth, provided 
the bicuspids and molars are of proper form and alignment. 
The one essential factor for retaining a denture by the 
spring-plate method is that the distance across the vault 
from the bicuspids upon one side to the bicuspids upon the 
other side of the arch shall be greater at the gum margin 
than at some other portion of the crowns of the teeth. 
When the remaining teeth have the conformation and 
alignment implied in the preceding statement, a plate of a 
"horseshoe" shape, having perfectly adapted thickened 
edges of vulcanite (Fig. 180), or metal stay clasps (Fig. 
181), may be sprung over the bulbous portion of the teeth. 
It will then rest in contact with the teeth, but without 
lateral pressure. It can only be removed by springing 
the heels of the plate inward. Should one or more of the 
retaining teeth be tilted lingually it will interfere with this 
method of retention. Perfect adaptation to the cervical 
third of the lingual surface is essential, and cannot be ob- 
tained, or at least retained, if there is an excessive inclining CLASPS 
351 
of some of the teeth. There are cases where adaptation can 
be made to the middle third without contact with the 
Fig. 180 
Fig. 181 352 
RETENTION OF ARTIFICIAL DENTURES 
cervical third. This method is especially advisable where 
the conditions are favorable and there are no spaces for 
spring clasps, or the spring clasp would be unsightly. 
Spring Clasp.-Probably the principal reason for the 
condemnation, by so many dentists, of the spring clasp is 
a lack of appreciation of the physical laws underlying their 
use and construction, and the manipulative ability to prop- 
erly adjust them even after the principles involved are 
comprehended. Doubtless there is no place in dentistry 
where there is so varied an application of the physical laws 
of leverage as in the retention of artificial dentures; both 
full and partial cases. 
Fig. 182 
The Form of Tooth for Spring Clasp.-What is commonly 
called a bell-shaped tooth is the ideal form (Fig. 182). 
The greatest diameter of such teeth is from one-half to two- 
thirds the distance from the gum line, or gingiva, where there 
is recession of gum tissue, to the occlusal surface of the 
tooth. This being true, it follows that bicuspids and some 
of the molars only are suitable for clasps; and these must 
be of more or less pronounced nervous temperament type. 
Choice of Teeth for Clasps.-Conditions permitting, the 
first choice for a tooth to clasp is the second bicuspid, the CLASPS 
353 
second choice is the first molar, and the last choice is the 
first bicuspid. Any other placing of clasps is not ideal, 
and will be resorted to only because of necessity. Clasps 
may be placed upon third molars and cuspids, or one of 
each; but they will be so placed because there is no other 
alternative. 
Fig. 183 
The Portion of the Circumference of the Tooth Clasped.- 
The spring clasp should cover two sides and three angles of 
the tooth (Fig. 183), and be placed upon the distal and 
lingual surfaces of the bicuspids and the mesial and lingual 
surfaces of the molars. By this arrangement the clasps are 
placed at or near the center of leverage and as inconspic- 
uously as possible. 
The Longitudinal Portion of Tooth Clasped.-The pressure 
must be upon the incline toward the cervix (Fig. 184, a). 
Should the excess of pressure be upon the incline toward 354 
RETENTION OF ARTIFICIAL DENTURES 
the occlusal end of the tooth, the plate will be displaced 
(Fig. 184, 6); therefore the clasp is placed over the middle 
third of the crown of the tooth. Often the tooth is not an 
ideal one, and is so formed that it becomes necessary, if a 
clasp is to be used, to carry it to, or even below, the free 
margin of the gum. These are the cases wherein there is 
danger of disintegration of the clasped tooth. Some teeth 
thus clasped, that are of a very dense nature and not prone 
to decay, may become very sensitive, which can usually 
be overcome by applying silver nitrate, 50 per cent, solution. 
Should the tooth belong to the class commonly called soft 
and chalky, and the secretion be in an abnormal condition, 
they may disintegrate very rapidly; the tooth should then 
Fig. 184 
be filled or crowned, as may be indicated. It is not often we 
have all these untoward conditions; therefore the method 
should not be condemned because of these exceptional cases. 
Where the teeth are of suitable length and form, even though 
the structure may be poor and the secretion vitiated, if 
the clasps are properly made, placed, and cleansed, there 
will be very little danger of decay. In all cases it is best 
to keep the clasps as far from the gum as the conditions will 
permit. 
Forms and Material for Clasps.-C lasps are made of either 
round, flat, or half-round clasp gold. A good formula for 
clasp gold is: Pure gold, twenty parts; pure copper, two 
parts; pure silver and platinum, of each, one part. 
Round Clasps.-The round clasp should be made of 17- to 
20-gauge clasp gold wire, and may be used either as a single CLASPS 
355 
or double strand (Fig. 185). There are several varieties of 
the round wTire clasp that are very useful and admit of a wide 
range of application. These forms are often known by the 
Fig. 185 
Fig. 186 
Fig. 187 
Fig. 188 
Fig. 189 
name of the man who introduced the special form to the 
attention of the profession. The Balkwill tee (Fig. 186, the 
Jackson-crib-a double tee-(Fig. 187) and the Roach loop 
(Fig. 188) are familiar and valuable forms. The advantage 356 
RETENTION OF ARTIFICIAL DENTURES 
claimed for the wire clasp is the slight contact with the 
tooth. 
Flat Clasp.-The flat clasp is made of 26-gauge clasp 
gold, and from to f inch in width, usually about | to 
inch (Fig. 189). The advantages of the flat clasp are: (1) 
Its thinness-when necessary to pass between the natural 
teeth, the necessary space can be secured by slight wedging; 
(2) there is no form of clasp that is so universally applicable; 
(3) it gives great stability to the denture; and (4) it is not 
liable to be broken. The disadvantage is that the broad 
surface of tooth substance covered is favorable for decay, 
and necessitates the best judgment upon the part of the 
operator in placing the clasp, also care upon the part of 
the patient to keep it clean. 
Fig. 190 
Fig. 191 
Half-round Clasps.-The half-round clasp is made of half- 
round clasp gold wire and has the disadvantages of both 
the round and flat clasps without their advantages. The 
half-round wire is valuable in forming lugs, stops and the 
stem to the tee clasp. 
Rigid Clasps.-These clasps may be made of flat clasp metal 
or 18-carat gold plate; they are usually as broad as the 
length of the crown of the tooth will permit; they are of 
sufficient length to cover at least one side and two angles 
of the tooth, and the ends are either bent L-shape to slide 
over parallel longitudinal ridges or cleats upon gold crowns 
(Fig. 190) (Bryant method), or they are provided with a PRINCIPLES INVOLVED IN RETENTION 
357 
thick end adapted to parallel longitudinal grooves in pref- 
erably porcelain crowns (Fig. 191) (Swartz method). 
Ferrules.-Ferrules are especially indicated where the 
natural teeth are remaining upon one side of the maxilla or 
mandible and absent on the other. The fer- 
rule is superior to the spring clasp for this 
class of cases because of its unyielding form 
(Fig. 192). Where conditions are favorable, 
two or possibly three may be used to advan- 
tage. Sometimes extensions may be attached 
to the buccal surface of the ferrule to act 
as stay clasps upon the proximating teeth. 
Should there not be sufficient space between 
the tooth to be ferruled and the proximating 
teeth to pass a 26-gauge plate, it will be necessary to gain 
such space by wedging with tape until such space is obtained, 
when it will be maintained by the ferrule. 
Fig. 192 
PRINCIPLES INVOLVED IN RETENTION. 
There are two propositions to be considered: first, balanc- 
ing the plate, and second, gripping the tooth or teeth. 
Fig. 193 
Balancing the Plate.-We may consider each side of a 
partial plate as a lever, the tooth clasped as the fulcrum, 
and the plate extending either way from the clasp as the 358 
RETENTION OF ARTIFICIAL DENTURES 
arms of the lever. Fig. 193 represents a partial upper of a 
horseshoe-shape carrying the six anterior teeth and the 
wings extending backward to the third molars. It is easily 
imagined what the result would be should an attempt be 
made to retain this denture by a single-strand wire clasp 
placed upon the third molars; also, should the wire clasps be 
replaced with broad, flat clasps accurately fitted to the 
surface of the teeth. With the broad clasps, the anterior 
portion of the plate would be held in place for a time at 
least, but the long leverage and the weight of the porcelain 
teeth would place such a strain upon the third molars that 
Fig. 194 
they would become very sore and loosened in their sockets. 
If these clasps are replaced with single-strand wire clasps 
upon the second bicuspids, the plate will be securely held in 
place and with the minimum strain upon the clasped teeth, 
because the clasps are at the center of leverage. This demon- 
strates why it is necessary to extend the base-plate some 
distance back of the clasped teeth. This center also explains 
why, if a clasp is placed upon a third molar upon one side, 
a clasp should be placed upon the first bicuspid, or even the 
cuspid, upon the other side of the arch. It is obvious that 
the best results are obtained when there is a tooth for clasp- 
ing upon each side of the mouth. While two teeth for PRINCIPLES INVOLVED IN RETENTION 
359 
clasping are most desirable, if the conditions for retaining 
a denture by adhesion by contact are very unfavorable, a 
single bicuspid or molar may be of much assistance (Fig. 194); 
and on the mandible even a single cuspid should be utilized. 
Gripping the Tooth.-There are many cases of failure in 
clasp dentures due to carelessness or slight accidents in 
adjusting the clasps to the teeth. The clasps should be so 
adjusted to the teeth that there will be no lateral strain. 
Theoretically, when the mouth is at rest there should be no 
strain upon the clasped teeth, because the upper plate 
(even though a narrow rim) should have sufficient adhesion 
by contact to sustain its weight, and the lower plate is held 
in place by gravitation; hence the clasps are a reserve force 
Fig. 195 
for work. Fig. 195, a, represents a broad, flat-spring clasp 
improperly adjusted. The linguocervical edge of the clasp 
rests upon the tooth, while the linguo-occlusal edge is some- 
what distant from the tooth. When the arms of the clasp 
are bent inward so as to cause the clasp to grip the tooth, 
the linguo-occlusal edge will approach the tooth, and the 
base-plate, which represents the long arm of a lever, will be 
tilted away from the vault of the mouth, as shown by the 
dotted line. If the reverse of these conditions exists (Fig. 
195, b), that is, the linguo-occlusal edge rests upon the tooth, 
and the linguocervical edge stands away from the tooth, 
then when the spring of the arms draws the clasp firmly to 
the tooth, the plate will be held securely against the vault 
of the mouth; there will be, however, a lateral strain upon 360 
RETENTION OF ARTIFICIAL DENTURES 
the tooth, tending to move the apex of the root of the tooth 
toward the vault. If either of these imperfect conditions 
is to exist, it had better be the latter, because the denture 
will be held firmly in place, and in time the tooth will be 
adjusted to the existing conditions; although sore during the 
orthodontic process. 
Adaptation of the Clasps to the Tooth.-There are two 
methods of adapting clasps: (1) The clasp is formed by 
pliers to approximately a close adaptation, so that it will be 
uniformly supported yet not so close but that the fluids of 
the mouth can pass freely between the metal and tooth. 
(2) A piece of thin pure gold or platinum (36 gauge) is 
accurately fitted to the tooth; a strip of clasp metal is then 
adjusted as closely as possible with pliers to the burnished 
metal and the two united with wax; they are then sprung 
away from the tooth, invested, and thoroughly soldered 
together. It is possible, with this perfect adaptation of the 
clasps to the tooth, the secretions being retained by capillary 
attraction, and not changed by the fluids circulating in the 
mouth, that disintegration may be invited; but with proper 
cleansing and removing the denture at night almost no ill 
effects will present. 
Forming the Clasps with Pliers.-Clasp gold is very crys- 
talline, and when it is rolled from the ingot into plate the 
crystals are elongated into fibers. The metal is easily split 
between the fibers; across the fibers there is strength, 
flexibility, and elasticity, so for this reason the fibers should 
run lengthwise of the clasp, that is, around the tooth. Before 
forming the clasp the metal should be annealed by heating 
to a cherry-red heat and permitted to cool slowly. 
PLIERS. 
Two pairs of pliers are required. One (we will call No. 1) 
with hawk-bill-shaped beaks, the under smaller than the 
over beak and oval or round in its cross-section, while the 
over beak is flat on the under surface of its cross-section 
(Fig. 196). The other pair of pliers (No. 2) is the ordinary 
clasp-forming variety, having a rounded and a concave blade PLIERS 
361 
(Fig. 197). No. 1 pliers is for general utility, and with it 
most of the shaping of the clasps is done. It gives the 
concavoconvex form to the cross-section of the clasp, and in 
Fig. 196 
Fig. 197 
Fig. 198 
Fig. 199 362 
RETENTION OF ARTIFICIAL DENTURES 
connection with the fingers give the general outline of the 
tooth. The No. 2 pliers is better adapted to bending the 
clasp to sharp angles, depressing a bulging portion or denting 
the edge of a clasp. 
Attaching the Clasp to the Plate.-In gold work the clasp 
is either soldered to the plate (Fig. 199, d), or connected 
to the plate by means of one or two standards (Fig. 198, a 
and 6). For vulcanite work a tang is soldered to the clasp 
(Figs. 185 and 189), after which the base-plate may be 
extended any distance to grip the tang. Fig. 189 shows 
union of clasp and tang. 
The attachment to the clasp should be one-eighth to three- 
sixteenths of an inch wide, and should be placed as near the 
middle of the long way of the clasp as the setting of the teeth 
will permit. By this arrangement a spring clasp will not be 
converted into an unwieldy stay clasp. Fig. 198, a, shows 
the right way to form the attachments, while Fig. 198, b, 
illustrates a wrong way. 
LOCATION OF ATTACHMENT UPON CLASP 
Fig. 200 
Flasking.-Clasp dentures may be best flasked in the wide 
rim of the Star or Wilson flask. Often a special flask, as the 
Whitney 18 A (Buffalo D.nt. Mfg. Co.), is the most efficient. LOCATION OF ATTACHMENT UPON CLASP 
363 
Fig. 200 illustrates the sections of the Whitney 18 A, and 
(Fig. 201) shows the flask in use. 
Conclusion.-Clasps properly conceived and formed are a 
blessing to both patient and prosthetist, but improperly 
used are vexatious to the dentist and a detriment to the 
victim. The retention of artificial dentures either partial or 
full is a profound subject for thought, and worthy the best 
efforts of the prosthetist. 
Fig. 201 
CEMENTATION. 
This term is used to denote that an adhesive substance, 
as cement, is used as the means of retention for crowns, 
bridges, and the so-called "alveolar dentures." Crowns and 
spanning bridges are clearly out of the scope of this book, 
while removable bridge-work is on the border line between 
bridge-work and plate-work. A spanning bridge with one 
or more saddle abutments is clearly a bridge. A saddle 
extending under the entire denture is but an extension of the 
saddle abutment, therefore there is no clear line of demar- 
cation between bridge-work and plate-work. However, a 
base-plate, of whatever material, depending upon telescoping 
crowns, bar and slot, tube and split pin, or a pin or ball 
with slit-tube attachments, are so intimately associated with 364 
RETENTION OF ARTIFICIAL DENTURES 
crown-work that they may be justly classed as removable 
bridge-work. Nevertheless the trend of the times is to a 
growing interest in partial plate dentures, and as there is not 
a very wide distinction made in practice between plate pros- 
thetics and crown prosthetics the writer is justified in men- 
tioning some of the crown and inlay attachments used as 
retainers for partial plate dentures. However, the student 
should consult his text-book on crown and bridge-work for 
instruction regarding the crowns of which the special attach- 
ments under consideration are a part, and the technic for 
their use. The writer does not wish to be understood as 
indorsing the following methods, for he does not make use of 
any of them, and believes that Hunter's expose of "Septic 
Dentistry" and the teaching of the research workers of the 
profession will eventually drive the greater part of the present 
crown and bridge methods from general practice; also that 
during the transition period to simple plate work he presumes 
that crown and inlay attachment may be quite in vogue with 
the profession. 
It does seem that the locking devices must be at their 
zenith for all three of the geometrical figures-square, triangle 
and circle-have been variously utilized. These attachments 
are all based upon the principle of the mortise and tenon, and, 
are held together by friction and by inlocking. In some of 
the devices the mortise is in the plate, and others have it in 
the anchor tooth. Some of the inventions are rigid and 
unyielding, others have a limited amount of resiliency; there- 
fore the prosthetist desiring to make use of such expediency 
may choose from an imposing collection. 
The following illustration will serve as a study of some of 
the numerous devices on the market, and methods advocated. 
When studying any device the student should give careful 
attention to its effectiveness as a retainer; strength of all the 
parts involved, for the device may cause a weakened plate or 
anchorage; effect upon the health of the anchor tooth and 
adjacent tissues; and the septic conditions involved. 
The three cardinal principles desirable in any device or 
method are simplicity, durability and cleanliness. 
Fig. 202 shows the Condit paralleling appliance, which is CEMENTATION 
365 
the prototype of all paralleling appliances. It consists of 
two bars, one of which is slotted and is attached to the other 
bar with a thumb clamping-screw. Each of these bars 
has, at one end, a right angle post which are necessarily 
parallel to each other. One of the posts is thread-cut, so as 
to be adjustable. These posts hold the split tube of the 
Condit stop-pin attachment parallel while adjusting to the 
crown supports of the removable plate-bridge. A third post 
is shown in the cut, which is a long-pointed thumb-screw to 
aid in supporting the jack while attaching the slit tubes. 
Any mechanician can construct this jack or adapt posts 
suitable for the various retaining devices. 
Fig. 202 
Fig. 203 shows the Condit stop-pin (enlarged) both united 
and separated. 
Fig. 204 shows the Morgan attachment: also a completed 
denture ready to slip into place. 
Fig. 205 shows a jack used for paralleling the Morgan 
attachments. This jack may be used for mounting any of 366 
RETENTION OF ARTIFICIAL DENTURES 
Fig. 203 
Fig. 204 
Fig. 205 CEMENTATION 
367 
Fig. 206 
Fig. 207 
Fig. 208 
Fig 209 368 
RETENTION OF ARTIFICIAL DENTURES' 
the various attachments, provided suitable clutches are 
obtained for the specific device. 
Fig. 206 shows the Gilmore clip, as used, and completed 
saddles. Saddles of this type should be joined to a similar 
one on the opposite side of the jaw, or, to an inlocking device 
at some distant point. 
Fig. 207 shows the Gilmore clip enlarged. 
Fig. 208 shows the Roach ball and slit tube. Fig. 209 
illustrates its use in connection with a contact bar. This 
attachment is probably the most resilient and has the greatest 
scope for use and for cleansing of any of the marketed devices. 
Except to condemn, the atrocities perpetrated under the 
alluring name "alveolar dentistry" are unworthy of con- 
sideration in any book. CHAPTER VIII. 
PORCELAIN TEETH 
History.-The late Professor Essig states, in the chapter on 
Porcelain in the American Text-book of Prosthetic Dentistry; 
that the history of the first use of mineral in place of animal 
substances for artificial teeth is wrapped in obscurity. One 
of the early recorded suggestions along this line is that of 
Guillemeau, in 1710, who proposed a paste compound of 
white wax, gum elemi, white mastic, coral, and pearl. Pierre 
Fauchard, in Le Chirurgien Dentiste, 1728, suggests the use 
of artificial enamel for this purpose. 
The idea of "hard mineral teeth" is to be attributed to 
M. Duchateau, an apothecary of St. Germain-en-Laye, 
near Paris. He conceived the idea, in 1774, of constructing a 
plate in porcelain, molding it after the form of his ivory one. 
M. Duchateau took as an associate a dentist of Paris by the 
name of M. Dubois de Chemant. M. de Chemant improved 
the porcelain, and in 1790 obtained a patent from Louis 
XVI for his process. Dubois Foucou, dentist to the king, 
became interested in de Chemant's work, made improvements 
in the material, and made public the first description of the 
method for making mineral teeth. In 1808 Fonzi, another 
dentist of Paris, first made separate individual teeth, and 
also baked small pieces of platinum in them to serve as a 
means of attachment to the plate. 
DeChemant moved to London in 1791 and became asso- 
ciated with Cladius Ash, and for many years experimented 
in and manufactured porcelain teeth. 
Porcelain teeth were not introduced into America until 
about 1817. The first use of them of which we have knowl- 
edge was by A. A. Plantou, a Frenchman, who began the 
practice of dentistry in Philadelphia about that time. He 
commenced the manufacture of mineral teeth about 1820 
369 370 
PORCELAIN TEETH 
Charles W. Peale, in 1822, and Samuel W. Stockton, in 
1825, were the next after Plantou to manufacture porcelain 
teeth, and they were soon followed by many others. By the 
year 1838 mineral teeth were in general use. About this 
year Dr. Elias Wildman, of Philadelphia, succeeded in 
improving the material, so that it would stand the high heat 
of soldering, and the texture and life-like appearance to such 
an extent that it has been said that it remains unexcelled 
to the present day. To him has been accredited the honor of 
placing the manufacture of porcelain teeth on a scientific 
basis. 
COMPOSITION OF PORCELAIN. 
Definition.-Porcelain is divided into three classes, as 
hard, natural soft, and artificial soft. Dental porcelain 
belongs to the subdivision hard porcelain, and may be defined 
as: A solidified suspension of one or more unfused silicious 
substances in a fused silicate. Porcelain is high or low fusing, 
dependent upon the quality and quantity of the basic ingre- 
dient. The material commonly called glass is fused silicious 
salts; therefore all porcelains may be converted into glass 
by sufficient fusing. 
Materials.-The materials entering into dental porcelain 
are feldspar, silica, kaolin or clay, alkalies, and pigments. 
The pigments used are made of titanium, cobalt, iron, tin, 
gold, and platinum. 
Feldspar.-This is generally spoken of as a double silicate 
of aluminum and potassium, and is represented by the 
formula A12O, I<20, 6SiO2. The best feldspar is found in 
the neighborhood of Wilmington, Del. It presents a distinct 
cleavage, and when broken splits into plates of more or less 
magnitude. It is of an indefinite color, between yellow and 
pink, but when fused in the furnace it becomes transparent 
and colorless, and if not exposed to a too prolonged or an 
excessively high temperature it retains its original form 
without rounding at the corners; this is one of the tests of 
good feldspar. There are several deposits of this mineral 
in eastern Pennsylvania, which, though beautiful and trans- 
parent in appearance, have been found to be entirely unfit COMPOSITION OF PORCELAIN 
371 
for dental porcelain because of their opaque-white color 
when fused in the furnace. The preparation of the spar 
consists of selecting suitable rock (some of the spar from a 
good quarry will not answer for dental porcelain), breaking 
it into fragments with a steel hammer, and grinding it into 
powder in a Wedgewood mortar. The material is sifted 
at intervals through a No. 10 bolting-cloth sieve. The grind- 
ing should not be carried too far, or its translucency may be 
greatly lessened. 
Silica (SiO2).-This material, sometimes called quartz, 
occurs in crystalline and amorphous forms; it is colorless, 
infusible at ordinary temperature, insoluble in water and 
all acids except hydrofluoric. The amorphous and gelatin- 
ous varieties are partially soluble in alkaline carbonates, 
but quite soluble in caustic alkalies. Silica combines with 
the bases to form silicates. 
The purest natural form of silica is the transparent and 
colorless variety of quartz known as rock crystal. Without 
transparency and crystalline structure, silica is met with in 
the form of chalcedony and carnelian, agate, cat's eye, onyx, 
opal, and other precious stones. Sand, of which the white 
varieties are pure silica, appears to have been formed by the 
disintegration of silicious rock. The yellow and brown dis- 
coloration is due to the presence of oxide of iron. 
Silica is used for the purpose of giving stability and firm- 
ness to porcelain, and its infusibility stiffens and keeps the 
other materials in shape so that an object made of porcelain 
may preserve its molded form while exposed to the high tem- 
perature during the process of firing. For these reasons it is 
incorporated with feldspar and clay, and is looked upon as 
the "main prop in tooth body." 
The quartz is crushed and ground in a Wedgewood mortar 
until it will pass through a No. 10 bolting-cloth sieve, when 
it is reduced, under water, to an impalpable powder. 
Kaolin.-Kaolin is the purest quality of clay freed from 
such impurities as sand and mica by careful washing. It 
is a hydrated silicate of alumina, and may be represented 
by the formula (2A12O3, 3SiO2) + H2O. It is formed by the 
long-continued action of air and water upon granite and 372 
PORCELAIN TEETH 
feldspar rock. The disintegration is probably due to both 
mechanical and chemical causes. 
Clay is infusible in an ordinary furnace when heated alone, 
but readily unites with feldspar at a high temperature. It 
is an element of strength in porcelain. 
German clay is imported from Europe and is probably the 
most infusible of the clays. 
Alkalies.-Both of the alkali metals potassium and sodium 
are used as fluxing material. Potassium is an essential 
element of porcelain. Sodium could not be substituted for 
potassium because of the green tint it imparts to the product; 
but in conjunction with potassium it is a valuable addition, 
because it increases the fusibility without increasing the 
amount of alkali. The potassium and sodium salts are all 
soluble in water. It is evident that this property in artificial 
teeth is undesirable, but concomitant with the lowering 
of the fusing-point of the porcelain. Therefore it is logical 
to conclude that the higher the fusion of the porcelain the 
less soluble, and the lower the fusion the more soluble. 
In other words, the high-fusing porcelains are practically 
insoluble, whereas the low-fusing are liable to etch and dis- 
integrate in the fluids of the mouth. Undoubtedly the 
modern makes of artificial teeth are sufficiently high fusing 
to be insoluble in the mouth; but the porcelains placed 
upon the market for the dentist's use in constructing bridges, 
crowns, and inlays, excepting the highest fusing ones, are 
dangerously near the etching point. Material has been 
placed upon the market so loaded with flux (alkali) that 
they soon prove to be unstable. In using low-fusing porce- 
lain, to be placed in the mouth, this property of solubility 
(etching) must be taken into account; as low fusion can only 
be produced by adding flux (however, excessive pulverizing 
lowers the fusing-point, also injures the texture), and the 
more flux the more soluble. 
It is interesting to study the four essential elements 
entering into porcelain-oxygen, silicon, potassium, and 
aluminum; one gas and three solids; two non-metals and 
two metals. Of the three solids, silicon melts at 1500° F., 
potassium at 144.5° F., and aluminum at 1200° F. Oxygen is THE PROCESS OF MANUFACTURE 
373 
the most abundant and silicon second most abundant ele- 
ment, while aluminum is the most abundant of all metals. 
Silicon combined with oxygen (silica) is almost infusible and 
insoluble, and there is almost no expansion or contraction 
by heat. Aluminum combined with oxygen (alumina) is 
highly refractory and non-changeable. Potassium combined 
with oxygen forms potassa; it fuses at a low temperature, 
and is very soluble in water. Silica combined with alumina 
forms kaolin (clay), is refractory, easily hydrated, and 
contracts in heating. Silica and alumina combined with 
potassa form feldspar, which material forms the largest 
portion of artificial teeth. 
Pigment.-The pigmentary substances, titanium, cobalt, 
iron, and tin, are used in the form of oxide; gold is used both 
as an oxide and in the metallic state; and platinum as a fine 
precipitate-platinum sponge. 
Titanium oxide is the only pigment used in the "body 
porcelain." It gives the creamy yellow color of the dentin. 
It is also used for the yellow color of enamel. 
Cobalt oxide produces the blue tints of enamel. 
Iron oxide is used for certain gray tints. 
Tin oxide is used only in combination with gold oxide as 
purple of Cassius to produce the pink gum color. 
Gold is used in the metallic state for reddish-brown tints 
in enamels. 
Platinum sponge produces gray tints. 
THE PROCESS OF MANUFACTURE. 
The process of manufacturing artificial teeth consists of 
(1) preparing the stock material, (2) molding, and (3) firing. 
Stock Material.-The stock material is first worked up 
into four forms, as body, frit, flux, and enamel. 
Body.-The body represents the dentin of the natural 
teeth. It is the highest fusing portion of the porcelain. It 
is composed 'of feldspar, silica, kaolin, and titanium oxide, 
with a small amount of starch to make the material plastic 
for molding. 
Each manufacturer has his secret formulae, but the fol- 374 
PORCELAIN TEETH 
lowing formula gives an idea of the proportions of the 
ingredients: Kaolin, 1 ounce; silica, 3 ounces; feldspar, 18 
ounces; titanium oxide, 65 grains; starch, 10 grains to each 
ounce. 
Frits.-The frits are the colors prepared for the enamels. 
They consist of the pigment substance mixed with feldspar 
and flux ground exceedingly fine, fused into a glass and 
reground for use. A typical formula would be: Platinum 
sponge, 1 pennyweight; feldspar, 1 ounce; flux, 20 grains. 
Flux.-Used to lower the fusing-point of enamels and 
porcelains. A good formula is: Silica, 12 ounces; glass of 
borax (sodium borate), 3 ounces; potassium carbonate, 
3 ounces. 
Enamels.-Enamels are composed of feldspar to which 
has been added a sufficient quantity of frit and flux. A 
typical formula for enamel is: Feldspar, 1 ounce; gold frit, 
6 grains; platinum frit, 4 grains; flux, 20 grains. 
Molding.-Artificial teeth are made in brass molds. As 
porcelain shrinks in firing, the desired tooth is first carved 
in plaster in enlarged form. From these enlarged forms brass 
molds are produced. Figs. 210, 211, 212, and 213 illustrate 
the molds used for two sets of fourteen upper teeth. The 
molds are made double for convenience in keying the parts 
together. 
The brass molds are oiled and the platinum pins placed 
in the little holes on the pin side of the molds. The point 
enamel is then put in the face side of the mold and arranged 
with a small spatula to the full thickness at the point and 
tapered down sparingly toward the neck. A thin coat of 
point enamel is placed on the lingual side of the front teeth 
and on the masticating surfaces of the bicuspids and molars. 
Some makers of teeth use but one enamel; instead of apply- 
ing a yellow neck enamel, they allow the body to show at 
the neck of the tooth; this is probably done to save time and 
labor, but it does not afford the best results as to translucency 
and natural appearance. 
The body is applied in small pieces slightly in excess of 
the quantity needed for each tooth. These are picked up 
with a small spatula, formed into balls, and laid on the pins THE PROCESS OF MANUFACTURE 
375 
Fig. 210 
Fig. 211 
Fig. 212 376 
PORCELAIN TEETH 
in the pin side of the mold. The two sides of the mold are 
then placed together and heavily pressed. The mold is then 
removed from the press, put in an iron clamp, and secured 
firmly together; it is then heated on a stove until the mold 
becomes hissing hot, after which it is removed and allowed 
to cool sufficiently to handle. The mold is then opened and 
the teeth dislodged and removed by striking the mold with 
a wooden mallet. If the heating has been carried to the 
proper point, the teeth will be hard enough, through the 
agency of the starch in the formula, to admit of trimming. 
This is done with fine files. 
Fig. 213 
Burning.-In manufacturing on a large scale the blocks 
are arranged in complete sets on a fire-clay slide covered 
with coarse quartz. These slides are 6| inches in width by 
9| inches long; they have raised edges to retain the quartz, 
which serves as a bed for the teeth. 
The furnaces used by the large manufacturers have a 
capacity of three or four hundred sets per day for each fur- 
nace. The furnace has a heating oven over the muffle. 
The muffle is constructed of the best fire-clay, 27 inches 
long, 8 inches wide, 5| inches high, and 1| inches thick. CLASSIFICATION OF PORCELAIN TEETH 
377 
The muffle must be thoroughly swabbed with clay, mixed 
thin with water, to fill up all cracks or defects through which 
the gases from the fuel might enter the muffle. Such acci- 
dents are of frequent occurrence in burning, and are always 
ruinous to the teeth, the gas generally imparting to them a 
ghastly blue appearance. The furnace has a flue at the top 
connected with a smokestack, and is heated with oil. 
The slide containing the teeth is placed in the heating 
oven at the top of the furnace before burning; this pre- 
liminary heating prepares them for the higher temperature 
of the muffle. The length of time required for burning the 
teeth varies with the heat of the muffle. About fifteen 
minutes is usually required. A too rapid heat tends to 
burn out or vaporize the color of the enamels. The proper 
glazing of the teeth is ascertained by placing under a gas 
jet. When the burning is satisfactorily accomplished they 
are put in the cooling muffle, protected from air drafts, and 
left undisturbed until quite cold. 
CLASSIFICATION OF PORCELAIN TEETH. 
Porcelain teeth may be divided into two general classes, 
namely, plain and gum teeth. In the former the crown of 
the tooth, and sometimes a portion of the root, is represented, 
whereas in the latter class the labial and buccal gum is 
added to the crown. The base upon which they are to be 
mounted and the means of attachment to the base further 
divides them into classes as follows: 
Vulcanite teeth (Fig. 214). 
Plate teeth (metal work) (Figs. 215, 216,217). 
Continuous gum teeth (Fig. 218). 
Plain Teeth 
Gum section teeth (for vulcanite) (Figs. 223 
to 226 inclusive). 
Single gum teeth (for metal work) (Figs. 227 
and 228). 
c t th 
U 378 
PORCELAIN TEETH 
Attaching Teeth to Base.-The means by which the por- 
celain teeth are attached to the base-plate upon which 
they are mounted is usually two platinum pins, the headed 
ends of which are imbedded in the substance of the teeth 
and firmly fixed in it when the porcelain is baked. Platinum 
and porcelain have very nearly the same coefficient of expan- 
Fig. 214 
sion, so that in a similar range of temperature they approxi- 
mately expand and contract alike, and there is small danger 
of a cracking of the tooth or a loosening of the pin. It must 
be remembered, however, that the capacity for absorbing 
heat differs greatly with the two substances, platinum having 
a much higher specific heat, which fact, coupled with its 
greater conductivity, makes it necessary that a greater 
amount of heat should be applied to the porcelain when 
teeth are subjected to high heat. The platinum does not 
fuse at the high temperature necessary to the baking of the 
Fig. 215 
Fig. 216 
body of the tooth, and its non-oxidizable surface makes it 
possible for the porcelain to adhere to it with considerable 
tenacity. One manufacturer alloys iridium in small amount 
with the platinum to give the pins greater rigidity and 
tensile strength. 
The great cost of platinum has been responsible for many CLASSIFICATION OF PORCELAIN TEETH 
379 
attempts either to substitute other and less expensive metals 
for it, or to reduce the amount of metal used for the attach- 
ment in the tooth, or to dispense with the pins altogether. 
The less expensive metal usually employed is nickel or some 
of its alloys, but as these readily oxidize during the baking, 
the intimacy of the union between pin and tooth cannot be 
so close as where platinum is used. The discoloration of 
Fig. 217 
the tooth from the dissolved oxides of the pins is frequently 
sufficient in amount to be objectionable, and the low-fusing 
body which is necessary with teeth if this sort is not so strong 
as that which may be baked on platinum pins. The attach- 
ment of pins of base metal to platinum anchorage baked in 
the tooth by soldering the pin to the anchorage is an ingenious 
method adopted by one manufacturer to reduce the amount 
Fig. 218 
of platinum (Fig. 219). The anchorage is in the form of a 
tube imbedded in the porcelain, the inner end of which is 
expanded into a flange which is for firm retention. The 
pins of alloy are made to fit the tubes and are soldered to 
them with high-grade solder, and tests seem to have 
proved that the teeth are strong enough for satisfactory 
service. 380 
PORCELAIN TEETH 
The construction of teeth whose attachment is by means 
of an undercut recess in the tooth filled with the plastic base 
upon which they are mounted is another attempt to reduce 
the cost of production by doing away with the platinum 
entirely. They are called "pinless" and "diatoric teeth." 
The mechanical difficulties in the construction of a tooth of 
this type, until recently, which shall be sufficiently strong, 
have limited their use practically to the bicuspids and 
molars, in which positions under favorable conditions they 
are eminently satisfactory. 
Fig. 219.-a, base metal pin; b, platinum anchorage; c, expanded end of 
same. 
Forms.-The forms of porcelain teeth are determined by 
three factors. The most important of these is the anatomical 
characteristics of the teeth they are to substitute. As only 
the crown is represented, the labial or buccal surfaces, the 
morsal surfaces, and such portions of the approximal surfaces 
as are presented to view, are patterned after the natural 
teeth. Teeth quite satisfactory in this respect are manu- 
factured today, although the market contains many made 
according to old designs which are poor imitations of the 
natural organs. The form of the incisors and cuspids is in 
general much better than that of the molars and bicuspids, 
the occlusal surfaces of many of which are too narrow for CLASSIFICATION OF PORCELAIN TEETH 
381 
the best masticatory results, the cusps are too poorly defined, 
and no attempt is made to have those of opposing sets fit 
together. 
The shape of the other portions of the teeth is determined 
by considerations relative to their attachment to the base 
upon which they are mounted, and by the mechanical 
requirements which the shape and relation of the jaws 
impose. Teeth for rubber and celluloid work are similar 
in design. When the latter came into use the artistic pos- 
sibilities of the new material created a demand for more 
natural forms in teeth, and so-called "celluloid" teeth were 
designed to meet it. Teeth of this form may also be used 
with a cast-metal base, but they are all designated rubber 
teeth. 
Fig. 220 
Fig. 221 
Fig. 222 
Plain rubber teeth are provided with two-headed pins to 
secure their attachment to the vulcanite. In the incisors and 
cuspids there is the so-called "pin-guard" situated between 
the pins and the morsal edge to afford a shoulder to which 
the vulcanite may be finished. The "ridge lap" (Figs. 220, 
221 and 222) is that portion of the tooth which comes into 
relation with the alveolar ridge, and may be long or short 
in accordance with the requirment of the case. The "bite," 
or "overbite," as applied to incisors and cuspids, is that 
portion of the tooth intervening between the pin guard and 
the morsal edge. The "shut of the jaws" refers to the dis- 382 
PORCELAIN TEETH 
tance between the jaws when the mandible is in the proper 
position for the occlusion of the artificial teeth. Thus, where 
the distance is marked we have a " long shut," which demands 
the use of a tooth that will fill in the space, and hence is 
known as a long-shut tooth. A long-bite tooth would fill 
in the space, but it would throw too much strain upon 
the pins to remove them so far from the point of stress. 
The bite, shut, and ridge lap, it will be seen, are all*cor- 
related. 
Countersunk pin teeth were introduced about 1885. 
Their lingual surface corresponds in shape to that of the 
natural teeth, the attachment to the molded base being 
by means of pins located in a depression in their base. Their 
close conformity in contour to the natural organs makes 
them more acceptable to the tongue than teeth backed in 
the ordinary way, and renders articulation easier and more 
distinct. 
Inasmuch as they must be mounted almost over the 
alveolar ridge, they cannot be used in cases with a short 
shut. 
For a vulcanite base the case should be flasked in the 
usual way, but in packing each countersink should be care- 
fully filled with small pieces of rubber to insure the rubber 
being thoroughly forced into the countersink and around 
the pins. 
Plain plate teeth are designed for use on a metal plate 
or in crown-and-bridge work. The incisors and cuspids, 
in either instance, are similar in form, but those for use in 
the bicuspid and molar region for crown-and-bridge work 
represent only the buccal surface of the tooth, and are some- 
times known as "veneers." 
Continuous-gum teeth are illustrated in Fig. 214. It 
will be seen that they have only one long pin, and that the 
buccal and labial portions of their roots are represented in 
porcelain. This contributes to the firmness of their attach- 
ment to the base, the porcelain body fusing upon the roots 
and uniting them to the plate. It also maintains the con- 
tours of these regions by reducing the amount of porcelain 
body to be baked, and hence the shrinkage in this locality. CLASSIFICATION OF PORCELAIN TEETH 
383 
Gum Teeth.-Gum teeth are made for metal plates and 
for the plastic bases, those for the former being at this time 
made only as single teeth (Figs. 227 and 228), while those for 
Fig. 223 
the latter are usually in sections of two or more teeth and 
designated "gum section" or "block" teeth (Figs. 223 to 
226 inclusive). The use of gum teeth is limited to those cases 
Fig. 224 
Fig. 225 
Fig. 226 
in which resorption of the alveolar process has taken place 
to such an extent as to demand considerable restoration by 
means of the denture. With the exception of that found in 
Fig. 227 
Fig. 228 
continuous-gum dentures the porcelain of gum teeth provides 
the best imitation of the natural tissues that has been 384 
PORCELAIN TEETH 
obtained, but the fixedness of the relation between the teeth 
in the section, and the difficulty of joining, particularly of 
the single gum teeth, are drawbacks which this does not 
overbalance. The artistic possibilities in arrangement which 
plain teeth offer have caused them to come into general use, 
and in most cases they are to be preferred. It must be remem- 
bered, however, that in some full dentures, and many partial 
ones, gum teeth may be used to great advantage. They are 
made in a variety of forms and offer a wide selection. 
IMPROVEMENTS IN TOOTH FORMS. 
In 1907 Dr. J. Leon Williams, of London, England, 
started a compaign in the dental journals for better tooth 
forms. The results are being seen, as some of the manufac- 
turers are placing upon the market improved forms of 
bicuspids and molars. 
Dr. Williams found it was no easy matter to induce the 
manufacturers, with their expensive equipment of molds and 
large stock of artificial teeth, to abandon their established 
methods, though unsatisfactory, and adopt a new system 
based upon an untried theory. However, being a man of a 
highly cultivated artistic personality and much deter- 
mination, he resolved that the time was ripe for the much- 
needed improvements in artificial teeth, and that it should 
be brought about. 
Since writing the text for the former edition of this book 
Dr. Williams has completely changed the scheme for his 
work. His scheme has evolved itself into a classification 
based upon his extensive anthropological studies, and is 
now in concrete form and obtainable as "Trubyte" teeth. 
Dr. Williams's studies have demonstrated that there are 
but three elemental forms of teeth, and that these forms 
are represented by the geometrical figures of the square, 
triangle, and circle. As all faces are but modifications of 
the three forms, if beauty is to exist, there must be harmony 
in the form of the face and teeth. Therefore a square type 
of face, whether long, medium, or short, must have the 
square type of tooth in its appropriately modified form; IMPROVEMENTS IN TOOTH FORMS 
385 
the pointed-triangular face must have teeth with straight 
sides and constricted necks, and the round (oval and ovoid) 
faces require teeth with their outline made up of curves. 
The scheme contemplates seven forms or modifications 
for each class, and 7 sizes of each form, or 49 models for 
each class, and 147 models for the 6 upper anterior teeth. 
It is presumable that the lower anterior teeth will not require 
so great a variety of forms of each class, but of each class 
form produced there must be a corresponding size for the 
upper. The forms of the teeth are marked in the carding 
wax with an Arabic numeral 1 to 7 inclusive, and the sizes 
by a letter. The sizes in Class I are indicated by the letters 
B to H inclusive; Class II, L to R inclusive, and Class 
III, T to Z inclusive; therefore the class to which a set of 
teeth belongs can always be told by the letter indicating 
the size. The models are charted in millimeters, giving the 
length of the central incisors and the combined width of 
the six teeth. 
The surface markings of the teeth are evidence of the 
highly artistic sense of their designer, which in combination 
with their scientific coloring and shading must produce a 
degree of perfection never before attained in prosthetics. 
The bicuspids and molars are developed upon an entirely 
different principle. While the anteriors are essentially 
esthetic the posteriors are remarkably effective in use. 
However, neither the anterior nor the posterior teeth are 
deficient in the factor in which the other dominates. 
Professor Gysi has developed the system for the bicuspids 
and molars to be used with Williams's anteriors. It con- 
sists of but one form of three lengths and three sizes, making 
but nine molds. The occlusal surfaces are so perfectly 
formed that their antagonization is perfection and rarely 
will it be necessary to use a stone upon them. These teeth 
as carded are numbered to indicate the length and the 
combined width mesiodistally in millimeters. Professor 
Gysi has also produced a block consisting of the bicuspids 
and molars. These blocks antagonize as perfectly as the 
single teeth which they duplicate. Further, they are of the 
diatoric type, and where there is sufficient room to admit 386 
PORCELAIN TEETH 
of their use they will expedite the mounting of the teeth and 
probably give additional strength. 
The system is so comprehensive that the dentist has only 
to make suitable occlusion models, take the required measure- 
ments in millimeters, select the color by number, and order 
by phone or letter. 
Dr. Frederick H. Nies presents a method for using por- 
celain crowns of the detached-pin type (as the Davis, White, 
English tube or Goslee crowns) in vulcanite work. 
The method consists of attaching crowns to a metal bar 
and posts, thereby producing the lingual bulbous portion 
of the tooth in porcelain and reducing the vulcanite base- 
plate to a minimum in bulk. Logically this method is suit- 
able only for well-resorbed and receded processes, in connec- 
tion with which the method has some valuable features, also 
presents some difficulties in antagonization and esthetics. 
The crowns may be attached to the posts with either vulcanite 
or cement; but in either case the countersink in the crowns 
should be roughened by grinding. 
Technic.-As each tooth is ground to the cast the post is 
inserted and the tooth and post waxed in place. The case 
is flasked and the wax removed. The anchor bar is now 
shaped to lie directly over the post holes, the loops in the 
posts having been gone over to see that they occupy as even 
a horizontal plane as possible. The fourteen posts are now 
strung on the bar in their places to fit the teeth to which they 
are adapted. The post holes in the crown are then partially 
filled with rubber or oxyphosphate. The posts, strung on 
the bar, are now pressed into each tooth to which they were 
adapted. The case is then packed with rubber and finished 
in the usual way. 
Another method is to nearly fill the post holes with whit- 
ing-to prevent the red rubber running in-then insert the 
pins, pack and vulcanize. When finished the teeth are easily 
removed from their sockets and the holes cleaned of whiting. 
The teeth are then recemented onto the plate. 
DETACHABLE CROWNS FOR VULCANITE WORK. DETACHABLE CROWNS FOR VULCANITE WORK 
387 
Fig. 229 
Fig. 230 
Fig. 231 388 
PORCELAIN TEETH 
Fig. 229 illustrates the posts strung on the bar. 
Fig. 230 shows the posts strung on the bar inserted in the 
teeth. 
Fig. 231 is the finished case. 
PROTESYN. 
The De Trey Brothers of Zurich, Switzerland, have in- 
vented a silicate cement gum facing for artificial dentures 
that will meet certain contingencies. It is especially indi- 
cated where considerable bulk of gum material is needed for 
lip contour, and the lip is very mobile. In such cases this 
material is second only to continuous gum dentures, which 
are often prohibitive. 
Fig. 232 
The method is simple and very pleasing effects may be 
produced with it. However, it adds nothing to the strength 
of the denture and has not the durability of pink rubber; 
therefore it should not be used indiscriminately; nevertheless 
it is a valuable addition to the dentist's armamentarium. 
Fig. 232 shows a denture properly prepared for placing the 
cement. There should be undercut space at the peripheral PROTESYN 
389 
border of the base-plate and at the cervical ends of the teeth 
for inlocking of the protesyn. The protesyn should he 
Fig. 233 
mixed on a glass slab, with an agate spatula, into a stiff 
putty-like mass. A sufficient quantity should be mixed to 
complete the operation-not two or more mixes for a denture. 
Fig. 234 
The cement is applied to the surface to be covered, with 
the spatula, and pressed firmly into place with the fingers, 390 
PORCELAIN TEETH 
which are lubricated with cocoa butter. It is then molded 
into artistic form by the aid of spatulas and brushes, as 
shown in Figs. 233 and 234. It is then heavily coated with 
the lubricant (cocoa butter) accompanying each package. 
The lubricated denture should stand twenty-four hours, 
when the butter is thoroughly washed away. Thereafter 
the denture must always be kept submerged in water when 
not in the mouth. To permit the protesyn to become dry 
injures both its color and texture. As the protesyn is very 
slow setting-twenty to twenty-five minutes-the operator 
has sufficient time to nicely adjust and manipulate the 
material. 
Protesyn is furnished in three shades: light, medium, 
and dark; and it may be removed and renewed as often as 
desired. However, its replacing should seldom be required, 
provided it is well applied and kept clean and constantly 
moist. CHAPTER IX. 
DOUBLE VULCANIZATION METHOD. 
In the preceding chapters the underlying principles, the 
nature, and the requirements for artificial dentures has 
been discussed. Chapter VI treats of the history, appli- 
ances, and primitive method of vulcanite construction, while 
this chapter presents an advanced technic of construction. 
By double vulcanization is meant that a vulcanite base- 
plate is made, and to it the superstructure is added at a 
second vulcanization. The advantages of this method over 
the single vulcanization method is that it provides a perfect 
fitting base-plate, provided the impression was a good one; 
and it very much facilitates the developing of the esthetic 
or cosmetic effects of the artificial denture. 
TECHNIC. 
The method consists of taking the impression, making the 
cast, making the base-plate, obtaining the occlusion and 
contour models, arranging the teeth, and proving the contour 
and expression; of preparing the case for flasking, packing, 
vulcanizing, and finishing. 
Impressions.-It is imperative in this as in all kinds of 
artificial dentures that a perfect plaster impression be 
obtained. The technic of this operation is described in 
Chapter II. 
Cast.-Because of the heavy pressure to which the cast 
will be subjected in molding the rubber, it should be made 
of a material that cannot be easily compressed. Spence 
plaster compound is best for this purpose (see Chapter III). 
Base-plate.-The vulcanite base-plate is constructed as 
described on page 159. The base-plate should be con- 
391 392 
DOUBLE VULCANIZATION METHOD 
structed of the purest rubber, as Dougherty's pure black 
rubber, Traun's uncolored rubber, or Ash's dark elastic 
rubber. 
Fig. 235 
Fig. 236 
Occlusion and Contour Models.-The occlusion and contour 
models are constructed as described on page 160. The 
models are mounted on the New Century Antagonizor by TECHNIC 
393 
aid of the Snow face bow (Fig. 73). Any other anatomical 
antagonizor may be substituted. 
Mounting the Teeth.-The teeth are mounted as directed 
in Chapter VI (page 253). The patient is about sixty years 
of age and of the sanguine modified by the nervous tempera- 
ment. The teeth selected for the case were S. S. W. "natu- 
ral forms," mold No. 227, Shade No. 40. It will be observed 
that the teeth are of sufficient length to nearly fill the space 
between the high- and low-lip lines, so that when the lips 
are parted to their farthest, only a slight trace of gum 
restoration will be observable-so slight, indeed, that the 
material should not be noticeable. 
The overlap may be seen in Fig. 235. The lateral incli- 
nation, compensating curve, and diverging straight line are 
shown in Fig. 236. The esthetic features may be studied 
in Figs. 235 and 236. 
Proving the Contour and Expression.-This phase of the 
subject is discussed in Chapter XVI. 
Preparation of the Case for Flasking.-Strings are used for 
outlining the festoons and periphery of the gum. The object 
of the festooning string at the cervical portion of the teeth 
is to give the proper thickness to the margin of the gum. 
The string used for this purpose is waxed dental floss, 
twisted very hard, doubled, and twisted again. In doubling, 
the loop will show the direction it should be twisted the 
second time. Wax the string well with softened wax and 
apply it by grasping the left heel of the plate between the 
fingers and thumb of the left hand, with the occlusal surface 
of the teeth upward; place one end of the string at the distal 
surface of the second molar, pressing it gently into the wax; 
outline the margin of the gum, using the wax spatula to 
carry the string well into the interproximal spaces. The 
peripheral string should be well-waxed wrapping twine, 
placed at the outer edge of the wax, and secured in place 
by melted wax made smooth with a hot spatula. Fig. 237 
illustrates the usual manner of applying the strings. The 
peripheral string should be applied at the line of separation 
of the flask, and this must be, in cases of heavy restorations, 
at the widest portion of the wax model. 394 
DOUBLE VULCANIZATION METHOD 
The next step is to cover the buccal and labial surfaces 
with a strip of No. 60 tinfoil. Instructions are necessary in 
applying the tin over the strings. The No. 3 instrument of 
the Evans set of carvers (Fig. 100) is especially adapted for 
adjusting the tinfoil. The strip of foil is placed over the 
Fig. 237 
wax and teeth and pressed as closely as possible with the 
fingers. The surplus tin is cut away with fine-pointed 
scissors. Two pairs are desirable, one straight and the 
other curved. The edge of the tin may be anywhere between 
the morsal ends and the middle of the teeth. The tin should 
be slit between each two teeth. Fig. 238 shows the tin 
trimmed and slitted. Hold the work in the left hand, seize 
Fig. 238 
the instrument by the hand grasp, rest the thumb upon the 
occlusal surface of the second molar, and burnish the tin 
closely to the tooth and against the festoon string. Continue 
this operation with all the teeth. After adjusting the tin 
about the teeth, the metal must be burnished over the TECHNIC 
395 
string to give the desired thickness of the gum and the 
contour of the festoon. This is done by holding the plate 
and burnisher in the same manner as before. The instrument 
must extend one-sixteenth of an inch beyond the string and 
at the same time must rest upon the body of the tooth while 
pressing the tin down over the festoon string. By this 
means a proper thickness and contour are given the margin 
of the gum, without forming an unnatural beaded edge. 
After all the teeth have been thus treated, the position of 
the plate should be reversed in the left hand, so that the 
thumb of the right hand may rest upon the periphery of 
the base-plate wrhile burnishing the tin from the festoons 
toward the periphery. With a pair of sharp curved scissors 
Fig. 239 
trim the tin flush with the peripheral string, but do not 
permit it to overlap the vulcanite base-plate. The case is 
now ready for tinning the lingual surface. Use No. 60 foil, 
and if the vault is a high one, slit the tin from the middle 
of one side to the center. Place the inner end of the slit 
over the middle of the vault, and one edge of the slit along 
the raphe to the palatal border; press the side of the foil 
gently against the wax and teeth; press the other half of 
the tin, in the same manner, into position, permitting the 
slit portion to overlap the first half. With sharp scissors 
trim the tin nearly down to the teeth. Remove the foil 
and place it upon a plaster or metal cast having well-defined 
rugae, and burnish the rugae into the foil. Remove the foil, 
turn it over, and fill the impressions of the rugae with wax, 396 
DOUBLE VULCANIZATION METHOD 
also smear the remainder of this surface with a thin layer of 
wax; now replace the waxed surface against the vault of the 
plate and nicely adjust with the fingers. The tin must be 
securely burnished against the teeth. The lingual contour 
of the teeth is produced by roughly carving away the excess 
of wax, with the Evans wax carvers, just before placing the 
tin. The tin is also slit between the teeth on their lingual 
aspect and nicely burnished to place (Fig. 239). 
Flasking.-A flask with a narrow rim is imperative* The 
star flask, as shown in the following illustrations, will do 
very well, but one made by the Cleveland Dental Manu- 
facturing Co., called the Wilson flask (Fig. 104), will better 
serve the purpose. This flask is designed to be used with the 
Donham clamp (Fig. 104). 
Fig. 240 
The maxillary surface of the case, having been cleaned of 
wax, is filled with Spence's compound, which forms a cast 
upon which the denture is vulcanized. This vulcanization 
cast should be not less than one-fourth of an inch thick at 
the thinnest portion of the vault, and should not overlap 
the tin facing. In one hour this cast will be sufficiently 
hard to place in the first section of the flask with regular 
dental plaster (Fig. 240). The peripheral string will be a 
great aid in outlining the denture in the flasking plaster. 
After the plaster has set, it is coated with a separating fluid, 
and then held under the faucet so as to moisten the tinfoil 
and thus facilitate the flowing of plaster into the interproxi- TECHNIC 
397 
mal spaces at the time the flasking is completed. The flask 
should stand about thirty minutes and then be placed over 
the stove in a stew-pan of cold water, to be heated up as 
before described on page 293. 
Fig. 241 
Separating the Flask.-When the heat of the water indi- 
cates the time for opening, the flask is grasped with a cloth 
holder in the left hand and separated by the point of a knife- 
blade or wax spatula inserted at the heel of the flask. The 
instrument should be guarded by the thumb and finger of 
the right hand to avoid the possibility of marring the case. 
The strings and as much of the wax as possible are removed 
with the spatula, after which the remainder is removed by 
pouring boiling water upon it; then with a cloth the tin lin- 
ing and vulcanite base-plate are wiped dry (Figs. 241 and 
242). The excess space is cut with small gate connections, 
provided the flask is to be bolted (Fig. 242), but no gate- 
ways if vulcanization is to be under spring pressure and the 
separated flask is placed over the sheet iron to warm as 
previously described (Chapter VI, Fig. 159). 398 
DOUBLE VULCANIZATION METHOD 
Fig. 242 
Fig. 243 TECHNIC 
399 
Packing.-Sufficient Gilbert Walker's granular gum or 
pink rubber is cut into strips to form a layer of one thick- 
ness over the tinned surface. First pack a narrow strip 
of red rubber about the pins (Fig. 243, c), and small square 
or triangular pieces of granular gum between the cervical 
portions of the teeth. The strips of granular gum are then 
placed over the labial and buccal surfaces of the matrix 
with the fingers and wax spatula so that no space remains 
through which the red rubber can escape. The strip of red 
rubber about the pins should be pressed down with a wax 
spatula to form a symmetrical outline. A piece forming 
a half-circle of granular gum is then placed over the anterior 
Fig. 244 
portion of the lingual surface (Fig. 243, a), and with the wax 
spatula the circular edge is joined to the red rubber about the 
pins of the teeth. A piece sufficiently large when stretched 
to half its thickness (Fig. 243, 6) is then applied over the 
remaining portion of the lingual surface, and its edges are 
united to the contiguous rubber. Red rubber may be sub- 
stituted for the pink rubber of the lingual surface and give 
additional strength to the denture. Strips of red rubber are 
then placed over the teeth to nearly, but not quite, fill the 
mold. A separating cloth of closely woven cotton, or the 
cloth removed from the rubber after the sizing has been 
washed out, is saturated with warm water and placed over 
the rubber in the mold, when the two sections of the flask 400 
DOUBLE VULCANIZATION METHOD 
are placed together. If the packing has been expeditiously 
done and the rubber is sufficiently warm, it is placed in the 
flask press and gentle pressure applied. The flowing of the 
rubber should be followed every ten seconds with a partial 
turn of the screw until the flask is closed. The flask is then 
removed from the press and separated. If there is not 
an excess of rubber, the cloth will easily separate from the 
rubber, but should there be strong adhesion, saturation of 
the cloth with water will facilitate its removal. Attention 
is again called to the danger of warping the denture while 
closing the flask. This is especially so with the double 
vulcanization method because of the small amount of rubber 
required to cover the lingual surface (see Chapter VI). 
Fig. 245 
Vulcanizing.-The case is vulcanized in the same manner 
as described in Chapter VI. 
Finishing.-After washing to remove the loose plaster, the 
tin may be easily stripped off, and the excess vulcanite filed 
from the periphery of the denture. A sharp chisel should 
be used to trim about the labial and buccal surfaces of the 
teeth, but the lingual surface should be trimmed with a 
scraper. The file marks about the periphery of the plate 
should be removed with fine sandpaper. The labial, buccal, 
and lingual surfaces are buffed with felt wheels and cones 
carrying pulverized pumice and water. The spaces between 
the teeth are best reached with a stiff-bristle brush wheel, 
using wet pumice. All the surfaces, including the maxillary, TECHNIC 
401 
are glossed by using a rapidly revolving soft-brush wheel 
and whiting wet with alcohol or water. 
Illustrations.-Fig. 244 is the completed case shown in 
occlusion. Fig. 245 presents the lingual aspect of the teeth 
and the reproduced rugae. Fig. 246 shows the maxillary and 
mandibular surfaces. 
Fig. 246 
Conclusion. -The double vulcanization method is best 
adapted to full cases, but may be used in partial cases. The 
tin-finishing method is applicable to the single vulcanization 
method as well as to the double. It is the easiest and best 
method of forming the contour of the surfaces of the denture; 
also producing a dense surface on the vulcanite. CHAPTER X. 
ALUMINUM BASE-PLATE. 
History.-Aluminum was known theoretically long before 
it was reduced to a pure metal. In the early part of the 
nineteenth century Sir Humphry Davy named the metal 
"alumium," signifying that it is the metal of alum. Other 
scientists contended that the metal should be named from 
its oxide alumina, therefore aluminium. In 1812 Davy 
compromised and called it aluminum, which name is the 
generally accepted one of today. 
Wohler was the first to reduce it to a metal in 1827. 
Deville took it from the rank of a curiosity and made it one of 
the useful metals in 1854. Deville's process of manufacture 
was known as the sodium process. August 18, 1885, E. H. 
and A. H. Cowles, of Cleveland, received a patent for an 
electrical process for making aluminum alloys. In 1886 
Charles M. Hall, of Oberlin, Ohio, applied for a patent, 
which was granted April, 1889. This process produced pure 
aluminum by electrolysis. This process is used by the Alumi- 
num Company of America, whose principal plant is located 
at Niagara Falls. In 1855 the metal was worth nearly $100 
a pound; and before the World War the purest metal on the 
market could be purchased, in quantity, at less than thirty 
cents a pound. 
Physical and Chemical Properties.-Aluminum is a silvery 
white metal. Its specific gravity is 2.56. It fuses at 657° C. 
or 1215° F. Its specific heat is high. Its lineal expansion is 
relatively high; of the common metals it is only exceeded 
by zinc and lead. As a thermal conductor it is better to 
compare it with the other metals. Ag, 100; Cu, 73.6; Au, 
53.2; Al, 31.3; Zn, 28.1; Sn, 15.2; Pb, 8.5; Pt, 8.4. Pure 
aluminum has good tensile strength; but is not very rigid, 
it will bend nearly double. It is about as hard as copper; 
402 ALUMINUM BASE-PLATE 
403 
it is just below copper in ductility, and nearly as malleable 
as gold. Aluminum powder is the ground leaf. It is electro- 
positive to all other metals used in the mouth, therefore it is 
the one that would be destroyed if a voltaic couple is formed. 
This property and its lack of rigidity unfits it for partial 
dentures. The impurities of aluminum are iron and silicon. 
The Aluminum Company of America gives the composition 
of their No. 1 grade as: Silicon, 0.30; iron, 0.15; aluminum, 
99.55 per cent. This grade is usually 99.25 to 99.40 per cent, 
pure. Their No. 2 grade contains 2 per cent, each of iron 
and silicon. The natural solvent for aluminum is hydro- 
chloric acid, the other mineral acids having little or no 
action. Sulphur at less than a red heat does not act upon 
it. Solutions of caustic alkalies, chlorin, bromin, iodin, and 
hydrofluoric acid act readily and corrode the metal. It 
withstands the action of organic secretions better than does 
silver. Therefore it is used for dental plates, for surgical 
instruments, and for articles subjected to carbolic acid or 
other organic antiseptic solutions; but antiseptic solutions 
of mineral salts should not be used upon it. It is not injured 
by the salt and vinegar used for culinary purposes. 
Aluminum Base-plate.-Aluminum is used as a base-plate 
both by the casting and swaging methods. It was first used 
for the casting method by Dr. J. B. Bean, of Baltimore. He 
cast it under pressure of a column of the metal several inches 
high. Dr. C. C. Carroll, of Ravenna, Ohio, later of Mead- 
ville, Pa., and New York City, developed a process of casting 
aluminum under air-pressure, using a rubber bulb. Dr. R. C. 
Brophy, of Chicago, invented a method and process for 
casting by jarring the molten metal into the mold. All of 
these inventors used alloys of aluminum, deeming it impos- 
sible to make dental castings of pure aluminum. Carroll's 
alloy, as given by Goddard, was Al 98 parts; Pt, Ag, and Cu 
2 parts. Richards states that Carroll's alloy consisted of 
Al, 90 to 93 parts; Ag, 5 to 9 parts; and Cu, 1 part. 
Brophy's Aerdentalloy consists of Al 90 parts, and Ag and 
Sn 10 parts. 
The writer believes that the first successful castings of 
pure aluminum for artificial dentures were made subsequent 404 
ALUMINUM BASE-PLATE 
to Dr. Taggart announcing his method of casting gold in 
January, 1907. Early in 1908 Dr. D. D. Campbell, of 
Kansas, City, Mo., presented the "cow bell" (centrifugal) 
method in the Dental Brief, and Dr. J. H. Billmeyer, of 
Norwalk, Ohio, presented his methods in the Dental Sum- 
mary and Dentist's Magazine. This method is undoubtedly 
the most successful method yet devised for casting pure 
aluminum. It uses the bucket and centrifugal force method, 
but its essential and new (to dentistry) principle is having the 
feed sprue enter at the bottom, and the vent sprues at the 
highest points of the mold. The vacuum principle is also 
used for casting pure aluminum, as exemplified in the Elgin 
Vacuum Machine. 
Technic.-The technic of making a pure aluminum casting, 
based upon the Billmeyer method, consists of a properly 
taken plaster impression, investment compound cast, wax 
model, flasking, heating, melting of metal, casting and 
finishing. 
Impression taking is described in Chapter II. 
Investment Compound Cast.-The impression is coated with 
shellac varnish and glossed with sandarac varnish. It is 
filled with any good non-shrinking investment compound. 
An excellent material consists of silica sand (white lake 
sand), wash or float silica, and plaster of Paris, equal parts 
by measure. Silica sand is the highest fusing, the least 
expanding and contracting, and the best conductor of heat 
of any material at command. It is coarse and forms centers 
toward which the shrinkage of the bond material may draw, 
thus preventing warpage and cracking of the mass of material. 
The fine silica fills the pores, and the plaster serves only as 
a bond; therefore the strength of the compound will depend 
upon the quality of the bond. As a slow-setting plaster 
is stronger than a quick-setting one, it is evident that the 
poorer grades of plaster will make the stronger investment 
compound, but slow setting, and vice versa. The ingredients 
of the compound are thoroughly mixed by passing five times 
through a sieve. 
It will require 3| or 4 parts of this compound to 1 part 
of water, by measure, to make a suitable mix for filling an TECHNIC 
405 
impression. While filling the impression the material must 
be thoroughly jarred into place, thereby producing a smooth 
surface upon the cast. 
The relief or vacuum chamber may be produced by either 
of two methods-(1) carving the impression, or (2) adding 
to the cast. If the addition method is chosen, a thin solu- 
tion of a fine-grain investment compound is painted onto 
the cast. To be assured that the added portion is thor- 
oughly attached, the cast is well saturated with water over 
the portion to which the addition is to be made. A good 
formula for a fine-grain investment compound is two or 
three parts by measure of wash silica and one part of plaster, 
thoroughly mixed by sieving. 
Wax Model Base-plate.-The object sought in forming the 
wax model for a cast aluminum base-plate is to so place the 
material that the finished product shall have at every part 
sufficient body to resist the stress to be placed upon it; to 
form square joints, thus no feathery edge of either vulcanite 
or metal; and to provide for securely attaching the teeth by 
means of vulcanite to the base-plate. 
Technic.-A sheet of pink base-plate wax is warmed and 
evenly adjusted to the cast, the excess is cut away with a 
warmed wax knife, and the edges luted to the cast. It is 
evident that the thickness of the sheet of base-plate wax 
will control the thickness of the casting, therefore a wax of 
suitable thickness to produce the desired result must be 
used. The additions to the wax base-plate are made by the 
use of rolls of pure yellow beeswax. These rolls are made by 
cutting a strip of impression wax, one-fourth of an inch wide, 
warming it in the flame, and working it with the fingers until 
it is evenly soft and in the form of a roll. It is placed upon a 
clean flat surface (top of the work-bench is excellent), and 
rolled under pressure with another flat surface (a slab of 
glass | by 3 by 6 inches is desirable). This first strip of wax 
should be reduced by rolling to | of an inch in diameter. 
The roll is warmed slightly and conformed by the fingers to 
the buccal and labial borders of the wax base-plate; the roll 
is continued to outline the lingual portion of the alveolar 
process. Necessarily judgment must be exercised in placing 406 
ALUMINUM BASE-PLATE 
the roll of wax so that its substance will give the desired 
contour to the model base-plate. The Mathews Wax Sprue 
Former is an excellent instrument for forming the addition 
wax to the base-plate (Fig. 247). This instrument has five 
Fig. 247 
nozzles for producing three sizes of round wax strips, one- 
half round and one oval shaped. A still larger round wax 
may be formed without attaching any of the nozzles. This 
large round is suitable for the peripheral wax. 
Fig. 248 
To operate the sprue former remove the screw plunger and 
fill the barrel with the desired wax. To make the strips TECHNIC 
407 
warm the barrel and nozzle in a Bunsen flame sufficient to 
make plastic the wax and screw in the plunger. Fig. 248 
shows the pink base-plate wax adjusted and the peripheral 
Fig. 249 
wax as adjusted by the fingers. The roll of wax is contoured 
and united to the base-plate by using a hot ironing spatula. 
Fig. 250 
Fig. 249 shows the wax roll so manipulated that it presents 
a square ledge against which the vulcanite attachment will 
rest in the finished denture. The next step in forming the wax 408 
ALUMINUM BASE-PLATE 
model is to make provision for securely holding the vulcanite 
attachment to the metal casting. This is best done by means 
of a row of cleats as near the edge of vulcanite and casting 
as it is possible to place them. These cleats are formed 
of wax rolled to a diameter of of an inch, or less, and 
bent into a series of loops. This looped roll is placed upon 
Fig. 251 
Fig. 252 
the model base-plate and the points of contact luted by a 
touch of a hot wax spatula. When the wax is cold the 
tops of the loops are cut away with a pair of small curved 
scissors. Fig. 250 illustrates the attached loops upon one 
side of the wax model and the cleats as formed by shearing 
upon the other side. TECHNIC 
409 
The completed wax model plate is prepared for flasking 
by attaching gate or sprue formers. These are one feed or 
pouring sprue and two vent sprues. The feed sprue former is 
a roll of yellow wax, which must not exceed of an inch in 
diameter, attached near the lowest part of the wax model, as 
it is to stand in the flask. It is obvious that the larger the 
Fig. 253 
feed sprue hole the more quickly the mold may be filled with 
the molten metal; and the smaller the sprue hole the more 
danger of an incomplete casting from the metal chilling. 
However, as the feed sprue hole connects with the bottom of 
the melting crucible, there is a limit to its size. This limit for 
safety has been found by practice to be of an inch. A 
sprue of |-inch diameter is almost certain to permit the first 410 
ALUMINUM BASE-PLATE 
molten metal to fall into and clog the lower end of the hole, 
thereby preventing the filling of the mold. The explanation 
of this fact is that the specific gravity of the metal resting 
over a |-inch diameter hole is greater than the cohesion of 
the molten metal. The vent sprue formers are 14 or 16 B. 
and S. gauge iron wire attached to the highest points of 
the wax models. Fig. 251 shows the sprues properly attached 
to the upper wax model base-plate. Fig. 252 shows the 
Billmeyer casting bucket or flask of sheet iron, with the 
handle attached. Fig. 253 is a diagram of the flask, model 
base-plate, sprue formers, and melting crucible. 
Flasking.-There are two steps to the flasking procedure- 
(1) investing the wax model base-plate, and (2) flasking the 
invested case. 
The wax model base-plate securely luted to the cast is 
covered with water while making a thin batter of investment 
compound, using the same material of which the cast was 
made. The cast and model are removed from its bath and 
excess moisture quickly absorbed with a napkin. The 
investment batter is applied to the wax model with a |-inch 
ox-hair paint brush. Fig. 254 shows the case invested. If 
the investment compound is made of slow-setting plaster, 
the invested piece should stand about ten minutes; but if 
the investment is quick setting, the second step may proceed. 
This will require a plaster bowlful of the investment com- 
pound of a little stiffer consistency than that applied with 
a brush. The material is all placed in the flask, and the 
invested case pressed well down toward the bottom of the 
flask, at the same time rapping the flask on the bench to 
assure the perfect adaptation of the second investment. 
When the investment is partially set a cavity is carved about 
the wax casting sprue former for the melting crucible. 
This is shown in Figs. 253 and 255. When the investment 
compound has thoroughly set the inside of the crucible 
mold is scraped smooth with a round-end vulcanite scraper. 
This will leave the wax sprue former just flush with the floor 
of the crucible. All particles of loose compound must be 
brushed or jarred out. The flashed case is placed in a warm 
place (not in an open flame) to dry and soften the wax; as FLASKING 
411 
soon as the wax begins to run, the vent sprue wires are 
drawn and the case inverted upon the gas stove (Fig. 256). 
Fig. 254 
Fig 255 412 
ALUMINUM BASE-PLATE 
As the wax of the model melts, it either ignites or drops 
upon the bench. There should be no smudge of burning 
wax if it is in direct contact with the flame, as the carbon, 
hydrogen, and oxygen are so proportioned in wax that it 
burns smokeless under favorable conditions. For the first 
ten to fifteen minutes the gas is turned on about one-half 
and then for the rest of the heating up it is on full. The flask 
Fig. 256 
should be heated in the inverted position for one hour or 
until there is no flame issuing from the feed sprue hole, thus 
signifying that the wax is completely burned. The flask is 
reversed, that is, the small end is down for half an hour. 
Heating for another half-hour will do no harm, but it is 
unnecessary. 
The No. 1 aluminum is purchased in bars described as MELTING THE METAL AND CASTING 
413 
small-notched bars (s. n. b.) containing about one and one- 
half pounds of metal, notched into six sections. Each section 
may be cut into three pieces of about equal size. One of these 
small pieces will suffice for any ordinary casting. The metal is 
very tough, therefore hard to cut. The author cuts it upon 
the swaging block with a cold chisel and heavy swaging 
hammer. The cutting is no light task. 
Quantity of Aluminum.-An excess of metal is necessary 
and the quantity is determined by one of two methods: (1) 
experienced guessing, and (2) weighing. The specific gravity 
of wax is 0.96, and of aluminum 2.56, therefore the aluminum 
casting will weigh 2f times as much as the wax model. The 
rule is to take twice the amount of metal as required in the 
casting. This will give a sufficient quantity for the excess 
head. 
Caution.-Aluminum is considered a connecting link be- 
tween the noble and base metals, nevertheless it is base and 
has the property of absorbing its oxides, also, markedly, the 
property of occluding gases. This latter property is evi- 
denced by the odor of garlic (carbon compound), often 
noticeable in a newly made casting, also the lack of uniform 
density shown by burnishing a buffed surface of the metal. 
This implies that aluminum that has once been melted in a 
dental laboratory should be discarded. Upon the second or 
third melting of the metal a yellowish tinge may be noticed; 
this indicates superficial oxidation. Should the color appear 
with the first melting of the metal, it would indicate that 
the metal has been overheated, and that the casting, to that 
extent, is defective. 
Melting the Metal and Casting.-Before placing the metal in 
the melting mold or crucible, the upper portion of the flask, 
including the crucible, is thoroughly heated with a large 
blue flame of the blowpipe. This precaution is to assure that 
the upper end of the casting mold is sufficiently heated, 
thus avoiding the granulated effect sometimes seen in this 
portion of the casting. The metal is placed in the melting 
mold and a yellowish-tinged flame of the blowpipe played 
upon it until it is thoroughly melted, as indicated by the 
nugget of metal settling upon the floor of the crucible, 414 
ALUMINUM BASE-PLATE 
although the upper surface is spheroidal. The metal has 
the property of holding heat, so there is no need for undue 
haste, but no time should be wasted in getting the metal 
cast. The gas is turned off the gas stove, the bail is attached 
to the bucket, and as it is lifted from the stove the chain is 
made straight. The swinging of the bucket is started with a 
steady long swing, avoiding a jerk at the start of the swing. 
The diameter of the swing is quickly reduced to the limit 
and the speed increased. The motion should be continued 
until the metal has crystallized. This will probably require 
from fifty to one hundred revolutions. 
Philosophy of the Casting Process.-By the swinging motion 
centrifugal force drives the molten metal down the feed gate 
into the mold. By the law of physics (that liquids seek their 
level) the molten metal will rise in the mold and vent holes 
until it is on a level with the head of metal, when the centrif- 
ugal force will condense the metal until the hardness of the 
crystals of metal and centrifugence are equal. This will 
probably be when the metal has cooled 50° to 100° below its 
fusing-point. It is reasonable to suppose that the metal that 
has travelled the farthest from the head of metal will be the 
first to set, therefore the vent sprues and the palatal border 
would chill, and any contraction that is taking place will be 
made good by the molten metal under pressure backing it 
up, thereby keeping the mold full and providing a perfect 
fitting base-plate. The writer, by careful visual observation, 
has not been able to detect the defects in the castings made 
by this method that have been noticed in the castings made 
by other methods. Therefore the writer confidently presents 
the foregoing method as the best yet devised for casting 
aluminum. 
Suggestion.-Sufficient free space must be provided for 
swinging the bucket, to preclude the bucket striking, and 
dumping the molten metal, thus endangering the operator 
and nearby property. Such accidents are inexcusable. It 
is well for an inexperienced person to practice with a small 
bucket filled with water and describing the same radius as 
with the casting' outfit. Confidence will soon be gained in 
the ability to start and stop the swing of the bucket. If COOLING AND REMOVING THE CASTING 
415 
a bucketful of water can be successfully handled, a crucible 
mold with nearly straight sides and only half-full of molten 
metal should be harmless. 
Fig. 257 
Fig. 258 
Cooling and Removing the Casting.-After swinging, the. 
casting bucket should be permitted to stand in a cool place 416 
ALUMINUM BASE-PLATE 
for fifteen minutes, after which the cooling may be expedited 
by submerging in cold water. A plaster spatula is passed 
between the flask and the investment, when by pressure upon 
the loose bottom of the bucket the casting and investment 
will be pushed out of the bucket. The investment is broken 
and brushed away from the casting. Figs. 257 and 258 show 
a casting as it came from the investment. The sprues are 
snipped away and the edges filed. The case is sandpapered 
and buffed with felt and pumice the same as vulcanite. 
Fig. 259 
Caution.-Cast aluminum is not elastic, therefore care 
must be exercised in manipulating light castings not to bend 
them. Probably more castings are warped by bending than 
by improper casting. Fig. 259 shows a trimmed and buffed 
aluminum base-plate. 
Use of the Aluminum Base-plate.-The base-plate of alumi- 
num is to be used the same as the vulcanite base-plate for 
obtaining the occlusion and contour wax models, mounting 
on the antagonizor, setting up the teeth, proving the antago- 
nization and contour, flasking, packing, vulcanizing, and 
finishing. 
All of these procedures as described for vulcanite work 
are sufficient for the work in hand, excepting for flasking and 
polishing. POLISHING 
417 
Flasking.-The aluminum base-plate should be so im- 
bedded in the first half of the vulcanite flask that as little 
of the metal will be exposed as possible; thus avoiding the 
scraping of vulcanite from the buffed surface. Fig. 260 
shows an upper case suitably encased in the lower section 
of the vulcanite flask. 
Fig. 260 
Polishing.-Aluminum may be scraped the same as vul- 
canite, but it may be dressed down easier with the emory 
cloth bands on the lathe arbor (Fig. 119). The lathe 
should be run at high speed, and light pressure used in holding 
the work against the abradant. Scratches are removed from 
the surface by the use of felt buffers and pumice, followed 
with a soft brush and whiting. This gives the aluminum a 
leaden polish due to fine particles of the metal and abradant 
being ground into the surface of the metal base-plate. There 
are three methods of cleansing and developing the luster of 
aluminum-(1) chemical, (2) use of special polishing prepa- 
ration, and (3) burnishing. The chemical method consists 
of treating with caustic alkali and acids alternately. This 
method is hardly suitable for the dental laboratory. How- 
ever, it gives a beautiful frosted effect, but it is doubtful if 
it is desirable. 
There are several preparations useful for the second 418 
ALUMINUM BASE-PLATE 
method. Benzin and whiting rubbed on with a buffer of 
cotton or chamois skin, or these materials used by hand. 
A paste may be made of two drams each of copper sulphate 
and potassium carbonate and one ounce of lard. To this 
paste add a dram or two of any one of several finely ground 
abradants, as chalk, rotten stone, rouge, tripoli, or buckhorn. 
Fig. 261 
Fig. 262 
The burnishing is done with an agate or bloodstone 
burnisher and a burnishing fluid composed of equal parts of 
olive oil and rum. This method is the very best for the 
maxillary and mandibular surfaces, but is open to the ob- 
jection that it shows up the unequal hardness of the dressed 
surfaces. However, it produces the hardness and best wear- Fig. 263 
Fig. 264 
Fig. 265 420 
ALUMINUM BASE-PLATE 
ing surface of any of the methods for finishing. Figs. 261, 
262 and 263 show different views of completed dentures on 
aluminum base-plates. Fig. 264 shows the lingual surface 
of a denture with the metal cast to the teeth. Figs. 265 
and 266 show the same case as the casting came from the 
flask. 
Fia. 266 
Casting to Porcelain Teeth.-The wax model must be so 
shaped that the cast metal will not overlap any edges of 
porcelain, because the contraction of the cooling metal may 
crack the porcelain teeth. The lingual surface of the denture 
must be carved to shape in the wax and smoothly finished. 
Chloroform can be used to finish the wax surface. The 
flashed case should be made very hot before pouring the 
metal; and then the case must stand until it is cold before 
removing from the investment. Platinum pin teeth should 
not be used, as the molten aluminum is a solvent for plati- 
num. The labial and buccal surfaces are finished with vul- 
canite. Casting to the teeth is of doubtful expediency. 
Fig. 267 shows the Elgin vacuum casting machine. Fig. 
268 shows the method of forming the wax model and attach- 
ing the wax sprue. The process consists of drawing the CASTING TO PORCELAIN TEETH 
421 
molten metal into the mold by exhausting the air in the 
mold, through the investment compound, with a pump. It 
is not reasonable to expect that a light and viscous sub- 
Fig. 267 
Fig. 268 422 
ALUMINUM BASE-PLATE 
stance like molten aluminum can be cast as sharply and 
densely, and with as much certainty, by negative force 
(suction) as by positive force (centrifugal). However, many 
operators are much pleased with the machine and its achieve- 
ments. 
Fig. 269 
SWAGED ALUMINUM BASE-PLATE. 
Aluminum may be swaged by either the die and counter or 
the machine method. SWAGED ALUMINUM BASE-PLATE 
423 
Die and Counter Method.-The student is referred to the 
chapter on Gold Base-plates for methods of constructing a 
die and counter; it is therefore only necessary in this chapter 
to discuss tersely the use of such a base-plate. 
Formerly the most successful base-plate of aluminum was 
made by the swaging method, but with the advent of modern 
casting methods the order has been changed, and the writer 
cannot conceive of any case in which the swaged base of 
aluminum would be preferable. However, it is well to have 
a comprehensive idea of the manner of using such a base- 
plate. 
A suitable die and counter having been formed, the die is 
oiled (sperm or lard oil) and a sheet of well-annealed No. 
18 or 20 B. & S. gauged aluminum, with its fiber at right 
angles to the raphe of the mouth, is conformed to the die 
with a horn mallet, or, better, one tipped with soft vulcanite 
(a cane or crutch tip), and then swaged in the counter-die, 
using a heavy swaging hammer. The direction of the grain 
is important, as the base-plate is easily cracked, in use, if the 
fiber is parallel with the raphe. The base-plate having been 
adjusted to the mouth, the surface is prepared to hold fast 
the vulcanite used to attach the teeth by scoring the surface 
with an engraver, or by punching loops upon the surface. 
The scoring is done either with a hand engraver or an 
automatic mallet engraver. The loops are formed with a 
punch. These three instruments are shown in order in Fig. 
269, and the work done by them is shown in Fig. 270. The 
base-plate is scrubbed with soap and water to remove oil 
and dirt, when it is ready to be used in forming the wax 
occlusion and contour models. It is flasked for vulcanizing 
the same as the cast aluminum base-plate. It is also polished 
in the same manner. 
Machine Swaging.-Various machines have been devised 
for swaging metal base-plates; they are better adapted to the 
soft metals than to hard ones. The principal argument 
for their existence is their supposed simplification of con- 
structing dies and counters; they certainly are not as effec- 
tive as the die and counter method. However, there is a use 
to which they may be put in which the die and counter can- 424 
ALUMINUM BASE-PLATE 
Fig. 270 
Fig. 271 SWAGED ALUMINUM BASE-PLATE 
425 
not readily be used; that is, in reswaging a base-plate after 
attachments have been made to it. There are various types 
of these machines; however, Fig, 271 will suffice to illustrate 
these appliances. No. 12 shot is used for the counter die, 
and a heavy swaging hammer for the power. CHAPTER XL 
GOLD BASE-PLATE. 
Material.-Pure gold is a bright, rich, yellow metal, with a 
specific gravity of 19.26, and a fusing-point of 2016° F. It 
is the most malleable and ductile of the metals, and ranks 
third as a conductor of heat and electricity. It is insoluble 
in any of the ordinary mineral acids, but soluble in the 
combination nitrohydrochloric acid. It is not oxidized by 
heat alone, therefore is a noble metal. It is nearly as soft 
as pure lead, and can be alloyed with many of the other 
metals. It is used in prosthetic dentistry principally in its 
alloyed state. The metals with which it is alloyed for use 
in plate work are silver, platinum, copper, and zinc. Silver 
has little effect upon it, except to cheapen it and modify the 
color. Platinum alone with gold has little effect upon it, 
but in combination with silver and copper it makes the gold 
very hard and elastic. Copper alone hardens gold very much 
and gives a deep red-yellow color. Zinc makes it hard and 
brittle and increases the fusibility markedly. 
There are two classes of gold used in plate-work known 
technically as plate and solder. The plate is that form of 
metal containing the properties of hardness or softness; 
rigidity, flexibility, and elasticity; high fusing or low fusing, 
according to requirements of the service to which it may be 
put. The two requirements of the other class (solder) are 
that it shall appear as near like the plate upon which it is 
to be used as possible, and melt and flow at a considerably 
lower temperature than the plate. 
The precious metals are spoken of as so many carats fine, 
or so many parts of 24 pure; thus 18-k (carat) gold plate 
means that 18 parts of the 24 parts of the alloy are pure 
426 METHODS 
427 
gold and the remaining 6 parts consists of other metals. The 
required carats of gold for base-plates are 18-k and 20-k, 
with 22-k and 24-k for special purposes. A suitable formula 
for 18-k gold plate would be pure gold, 18 parts; pure silver, 
4 parts, and pure copper, 2 parts. The 20-k and 22-k plate 
would have the indicated amount of pure gold with the 
alloying metals of equal amounts of silver and copper. The 
rigid and elastic plate known as clasp gold may be formed of 
any .of the preceding carat by substituting platinum for 
half of the named amount of silver. Solders are formed of 
the same degree of fineness as plate by substituting zinc for 
a portion or all of the silver. This was formerly true of 
solders, but today, as the result of competition in trade, the 
solders are marked "for" the indicated carat plate. It is 
knowm that the solder is two carats lower than the number 
upon the solder. 
The thickness of the gold plate should be governed by the 
method of construction, and the amount of stress to which 
it is to be subjected. For all full cases the gold should be 
26 to 28 B. & S. gauges thick. (The metal decreases in 
thickness with the increase of number.) The thinner the 
plate the more essential it is that a wire should be soldered 
on outlining the vulcanite attachment. The wire to be 
18 or 17 gauge and 20-k. A base may be swaged of 35- 
gauge pure gold (24-k) and entirely doubled with clasp or 
18-k plate of 30 to 32 guage. The solder should be that 
marked "for" the lowest carat plate used in the appliance 
being constructed. 
Methods.-Base-plates of gold are formed by both the 
swaging and casting methods. Swaged gold as a base for 
artificial dentures has been the standard from antiquity, 
and especially with the modern revival of dentistry. It is 
especially adapted to partial cases because of the ease with 
which it may be built up; its rigidity, strength, and com- 
pactness; and its purity and cleanliness. For most full cases 
it is inferior to continuous gum. The casting method for 
gold bases has but one feature in which it is superior to the 
swaged base of gold, that is, adaptation. In all other factors 
(excepting purity of material) it is inferior to the swaging 428 
GOLD BASE-PLATE 
method. It is less dense, less rigid, less elastic, more bulky 
for the required strength, and consequently more expensive 
for stock. 
TECHNIC FOR SWAGING GOLD. 
Die and Counter Method.-The processes involved in this 
method are: Taking impression, making plaster cast (or, 
better, Spence plaster compound cast), model for die, die 
and counter, and swaging; making and soldering attach- 
ments. 
Impression.-The student cannot be too strongly im- 
pressed with the fact that the first and most important 
element for success in any kind of prosthetic work is a 
suitable impression, and that the impression must be taken 
to meet the requirements of the individual case. (See 
Chapter II.) 
Cast.-The impression may be filled w'ith plaster, or, 
because of its strength and non-changing properties, Spence 
plaster compound. In filling the impression special atten- 
tion should be given to developing the truncated cone form 
as directed in the chapter on Casts. 
Model.-The model is the cast prepared for molding in the 
sand. The mold, with the exception of its face, that is, the 
surface made by the impression, must be so shaped that it 
will readily draw from the sand mold. This will require 
that the entire body of the model will slant outward to 
its base representing a truncated cone. This may be accom- 
plished by cutting away unnecessary plaster and building 
out deficiencies with wax. The thickness of the model will 
depend upon the kind of molding flask used. If it is a ring 
flask, the base of the model should be one inch thick at 
the thinnest part to afford the required strength to resist 
crushing. If the molding is to be done in a Bailey flask 
(Fig. 272) or a Lewis flask (Fig. 273), or the die is to be 
used in a swaging machine, the base of the model need be 
but a quarter- or a half-inch thick. The base of a model so 
shaped could furnish no obstacle to its withdrawal from the 
sand mold (Fig. 274). The face of the model must next be 
studied, to know that it will draw from the mold, or that its TECHNIC FOR SWAGING GOLD 
429 
conformation is such that it will not be keyed in. It is evi- 
dent that the face of the model cannot be carved to obliterate 
undercuts, but that means must be devised to reproduce 
Fig. 272 
Fig. ,273 
Fig. 274 430 
GOLD BASE-PLATE 
the undercuts in the die. This may be accomplished by one 
of three ways-(1) by tilting the flask in drawing the model; 
(2) by the use of cores; and (3) by a specially constructed 
parting flask. 
The first method answers well for a single slight undercut. 
This is illustrated in Fig. 275. The dotted lines represent 
lines of gravitation. It is apparent that if the flask is held 
at a sufficient angle the inlock is obliterated and the model 
may drop without defacing the mold. The slight under- 
cuts that may be provided for by this method are located 
at the anterior portion of the alveolar ridge or at one of the 
tuberosities. 
Fig. 275 
The second method will provide for any and alt cases that 
may present. The core is an added portion used to fill in the 
undercut and contour the model into a typical truncated 
cone. The model, having been varnished with shellac and 
sandarac (as desirable for molding), is built upon with a 
batter of investment compound (such as is used in cast 
aluminum work) to bring the model to the desired contour. 
For strength and convenience in handling, the core should 
be about one-half inch thick. It must be so trimmed that 
it will easily drop from the sand mold with the model; the 
core is to be returned to its seat in the sand mold and becomes 
a part of the mold. When the investment compound has TECHNIC FOR SWAGING GOLD 
431 
set it is parted from the model, trimmed as smooth as pos- 
sible, and then placed in a warm place to dry. It should be 
Fig. 276 
dried to such an extent that a temperature of 700° to 800° F. 
will not drive steam from it. This can be done in an hour's 
Fig. 277 
time by standing it on its edge upon a sheet-iron over the 
gas stove. The core should not be placed on its side while 432 
GOLD BASE-PLATE 
drying, as there is danger of warpage. Fig. 276 shows a core 
for the anterior undercut. Fig. 277 shows cores covering 
the entire labial and buccal surfaces of a model. The core 
may be constructed entire, and when set notched nearly 
through at the median line, and broken away from the model. 
The notch should be wide and smoothly trimmed. Fig. 278 
illustrates cores for the lingual surface of a lower model. 
Fig. 278 
Third method: Figs. 279, 280 and 281 represent Hawes' 
parting flask. This flask consists of two rings, the bottom of 
which is hinged to part at three points. 
Molding.-There are a variety of molding sands that may 
be used-the iron founder's black sand, the brass founder's 
brown sand, and marble dust. These materials require 
tempering for use. If the material is used daily it is best 
tempered with water, because of its cleanliness; but if it is 
only infrequently used, it is better to temper it with glycerin 
or sperm oil, as with these materials it remains ready for use TECHNIC FOR SWAGING GOLD 
433 
for a considerable time; however, the hot metal poured upon 
them produces a disagreeable odor. The material is mixed 
with the chosen liquid, thoroughly rubbed and sieved. 
They improve in temper by standing a few hours. If the 
molding sand is in a suitable condition it will not appear 
moist, but a handful thoroughly compressed in the hand 
will break with a clean fracture. 
Fig. 279 
Fig. 280 
Fig. 281 
Technic.-The model (with core in place if one is 
required) is rubbed with talcum powder, then placed upon 
a flat surface and encompassed w'ith the ring of the chosen 
molding flask. Molding sand is sifted into the flask until 
it is one-third full. This is firmly packed with the fingers and 
a stick (tamping stick) about the model, more sand is sifted 
in and packed firmly down upon the face of the model. Sand 
is added until the ring is filled flush. The flask is lifted from 
the bench, turned over so that the base of the model is 
upward; a thin spatula or molding trowel is passed about 
the edge of the model to relieve it of any overlapping sand. 
The flask is again turned so that the base of the model is 
downward; if there is a slight undercut upon the model not 
supplied with a core, the flask must be held at such an angle 
as will release the model without dragging the mold. The 434 
GOLD BASE-PLATE 
sand should be so firmly packed about the model that it will 
not drop of its own weight. The model is released from the 
mold by gently tapping upon the side of the flask with a 
light-weight instrument, as a wax spatula. If the mold is 
not perfectly clean and smooth at the first attempt, the 
operation must be repeated until a perfect mold is obtained. 
Caution.-If the sand is overmoist it cannot be so firmly 
packed without generating steam under the hot metal and 
thereby spoiling the casting. This may be overcome by 
packing the sand less firmly, but if the sand is not compact 
enough the weight of the metal will give a distorted and 
useless casting. Therefore the student should not yield to 
the temptation to use insufficiently packed sand. He should 
use only well-tempered and well-packed sand. 
Accessory implements that may be useful are: A 6-inch 
straight-edge to smooth the sand flush with the edge of the 
ring; a flat |-inch ox-hair paint brush, and a small-mouthed 
blowpipe. If needed, the occasion will suggest their use. 
Metal for Die.-A suitable metal for a die should possess 
hardness, toughness, sufficient fluidity to take a sharp 
imprint, and should be moderately low fusing, and non- 
shrinking. There are three types of metal used for dies, 
namely: (1) a shrinking metal (as zinc); (2) non-shrinking 
(as Haskell's Babbitt metal); and (3) low fusing (as the low- 
fusing bismuth compound). 
Zinc.-Zinc is the hardest of the metals commonly used 
for dental dies, but it shrinks the most of any of the metals. 
The advocates of this metal contend that the shrinkage 
is an advantage, that it assures a close fit. This argument is 
illogical, for if an impression has been taken to meet the 
requirements of the case all subsequent procedures should 
require exactness and not counter-balancing changes. The 
late Professor Buckingham demonstrated that in an average- 
sized zinc die the shrinkage is about of an inch across and 
of an inch in length. Such a change would be almost 
intolerable upon thin, tense tissue or properly compressed 
soft tissues. However, the metal is much used for dies. 
Babbitt Metal.-There are many alloys on the market 
known as Babbitt metal, some of which are little more than TECHNIC FOR SWAGING GOLD 
435 
lead, and all of the hardware store stock is unreliable for 
dental purposes. The alloy made after the formula of Dr. 
L. P. Haskell and carried by the dental-supply houses, meets 
the requirement. His formula consists of copper, 1 part: 
antimony, 2 parts; and tin, 8 parts (c-a-t-1-2-8). 
Care should be used not to overheat this alloy; in fact, no 
base metal or alloy should be heated much beyond its melting 
point. There are two reasons for this: (1) Oxides are formed 
and occluded, which deteriorates the metal. (2) A mixture 
of metals heated much beyond the fusing-point tends, upon 
cooling, to separate into definite compounds, mixtures, 
and pure metals, and to congeal according to the fusing 
point of each; thereby forming a very non-homogeneous 
mass. The student should be interested in the prevention 
rather than the cure for this undesirable condition, and 
exercise care in heating metals. A metal or an alloy of 
metals should be heated only to the desired fluidity, so as to 
be in the melted state as short a time as possible. As it 
requires considerable time for a mass of metal to liquefy, 
and the different portions will have absorbed different 
amounts of heat, and the liquefied metal is rapidly absorbing 
more heat, it should be apparent, when the mass is one-half 
or three-fourths melted, that it has absorbed enough heat 
for liquefaction and should be removed from the fire. The 
pot having been removed from the fire, the metal is stirred 
with a stick of wood until the last portion of metal is liquefied. 
Should the metal be too viscid, it should be returned to the 
fire and stirred for a moment, when it will be ready for 
pouring. 
Bismuth Compound.-Bismuth forms some wonderful alloys. 
They are much used in the dental laboratory. It con- 
stitutes about one-half the weight of the very low-fusing 
alloys. It and antimony are the only metals that expand 
on cooling. Hodgen states that bismuth expands of its 
volume. Combined with lead, tin, and cadmium, it forms 
alloys all of which melt below the most fusible component 
and a combination may be made to fuse as low as 140° F., 
while its most fusible component fuses at 442° F., and its 
least at 617° F. 436 
GOLD BASE-PLATE 
Thus the three principal substances for dies may be 
summed up as: Zinc, fuses at 773° F., shrinks the most of 
any metal on cooling, hardest, and brittle; Babbitt metal 
(Haskell), fuses at 500° F., non-shrinking, neither as hard 
nor brittle as zinc; bismuth alloy, melts below boiling water, 
non-shrinking, and is less hard and more brittle than zinc. 
Counter-dies.-A suitable counter-die must be prepared 
for the die. It is desirable that the counter-die shall be of a 
softer and more fusible material than the die. Softness is 
required that the compression produced in swaging shall take 
place in the counter and not in the die; fusibility, so that the 
counter may be readily formed over the die. Lead fusing 
at 617° F. is an excellent counter for zinc. Four or five parts 
of lead and one of tin fuses at about the same temperature 
as Babbitt metal (Haskell), and with care in handling forms 
a desirable counter-die. A counter-die for the bismuth 
compound alloy may be formed of the same material by 
first "smoking" the die, or coating with whiting wet with 
alcohol, and careful pouring. Modelling compound serves 
well as a counter, or the die may be driven into the end of a 
block of soft pine and it used as a counter. In the swaging 
machines various substances are used as a counter, for the 
bismuth alloy dies, as shot, cornmeal, sand, tallow, paraffin, 
or rubber. 
Pouring the Die.-A suitable mold having been obtained 
in the sand, the melted metal is poured in until the mold is 
full, when, if the Bailey or Lewis flask is being used, the top 
section is placed and the pouring continued until the desired 
thickness of die is obtained. 
The casting or die should stand until it is nearly cold 
before removing from the sand mold, as the metal while hot 
is very brittle and easily broken or defaced. 
Making the Counter-die.-The die is placed upon the 
molding block, and sand built about it so as to cover all 
but the face; that is, the fac-simile portion of the mouth. 
The sand is built out at nearly right angles to the die for two 
inches. A molding ring is placed about the imbedded die 
and pressed slightly into the sand. Sand is embanked 
about the encasing ring to the height of one-half inch. The TECHNIC FOR SWAGING GOLD 
437 
counter-die metal is placed in a clean melting ladle or pot, 
and when half-melted removed from the fire and stirred 
until in a viscous or "mush-like" state, when it is poured or 
rather dumped upon the die. There should be about twice 
the quantity of counter-die metal melted as needed, because, 
being in a semifluid state, it cannot all be poured nor placed 
as accurately as if melted into a more fluid state. However, 
the excessive quantity, viscosity, and dumping will produce 
a perfect counter-die without danger of fusing the die. If the 
counter-die metal is liquefied and poured in a small stream 
upon the die, there is much danger that a portion of the 
surface of the die will be melted and the die and counter 
spoiled; and a portion of the metal so contaminated that it 
should not be used again for either a die or a counter. There- 
fore watchfulness while melting the metal and pouring while 
the metal is in a viscoid state will save time, metal, and 
vexation. 
The die and counter-die should be cleaned of sand and ex- 
amined for and relieved of any excrescences on their swaging 
surfaces. These surfaces are oiled as a preventive against 
any of the base metal adhering to the metal being swaged. 
Swaging Gold Plate.-A suitable pattern for cutting the 
gold plate to size should be made. This pattern may be 
made of any thin pliable metal, as tinfoil or leadfoil. Tea- 
lead or tinfoil of about No. 20 serves well. The supply 
houses carry tinfoil in rolls designed for this use. A piece of 
pattern foil is placed upon the die and nicely conformed to its 
surface by pressure of the fingers and thumbs; it is removed 
and trimmed to the outline of the desired base-plate. The 
pattern base-plate is then placed upon a flat surface and 
pressed, but not rubbed, to flatness. 
Gold plate of a suitable composition, carat, and guage is 
selected for the work in hand, the pattern is placed upon it, 
and its outline traced with a sharp-pointed instrument. The 
plate is then cut to the outline of the pattern with the plate 
shears. It is expedient for the inexperienced workman to 
cut the gold | of an inch larger than the pattern as an offset 
to inaccurate manipulation. The excess gold will be trimmed 
away after swaging and saved as scrap. While it is not 438 
GOLD BASE-PLATE 
essential, it is advisable to cut the gold so that the fiber 
(crystals elongated by rolling) shall be across the denture. 
The gold, having been cut to pattern, is annealed by 
heating to a cherry-red heat and cooling in water. It is well 
to reanneal the metal two to four times during the swaging 
process. After the metal has been upon the die it should be 
wiped to remove the oil and any adhering base metal that 
may be upon its surface before heating. 
Fig. 282 
The gold is conformed to the die with a horn mallet or 
one tipped with rubber (Fig. 282). For a full upper base- 
plate the conforming is begun at the center and extended 
in concentric rings outward. Care must be exercised at all 
times not to permit the gold to "buckle," that is, fold upon 
itself. Should a fold begin to form, it must be straightened 
out with pliers, annealed, and then malleted from the inner 
end outward. The plate should be well conformed to the TECHNIC FOR SWAGING GOLD 
439 
vault before any attempt is made to carry it beyond the 
crest of the alveolar ridge. In fact, it is well to have a half- 
counter-die (one made to cover the vault portion of the 
die only) and swage the vault portion before endeavoring 
to adapt the plate to the labial and buccal surfaces. The 
swaging is done with a heavy swaging hammer. A few dead 
blows should be used. The horn mallet is used with a light 
elastic blow, thereby marring the gold the least, whereas the 
swaging hammer is used with a dead pushing blow, thereby 
conforming without a backward spring, and with less harden- 
ing of the gold. In swaging difficult cases, that is, high vaults 
and heavy undercut ridges, it is well to clamp the plate and 
half-counter to the die with a C clamp (Fig. 283) while 
carrying the labial and buccal flange to place with the horn 
mallet. (This illustration shows a full lower base-plate.) 
For this part of the conforming a horn mallet with the small 
end filed to a blunt edge is preferable. Should the die be of 
the A -shape type the conforming may be more easily done 
by slitting the labial flange in the median line nearly to the 
crest of the ridge. The edges are permitted to overlap, and 
later are soldered. The base-plate being well conformed 
with the horn mallet, it is wiped of oil and base metal. As the 
plate must be annealed before the heavy swaging, it should 
be thoroughly inspected for evidences of adhering base metal 
from the die. Should any be detected that cannot be wiped 
away, it must be " pickled." The pickling is done by boiling 
in a solution of nine parts of water and one of sulphuric acid, 
in a copper acid pan. (In forming the pickle pour the acid, 
a little at a time, into the water. An explosion is liable 
to occur if the water is poured into the acid.) The base- 
plate having been well conformed with the mallet, it is placed 
in the oiled counter-die and struck a heavy, dead blow. 
It is then removed from the counter-die and inspected. 
If a buckle is forming, it should be corrected with the pliers 
and mallet, then returned to the counter-die and struck one 
dead blow and again removed and inspected. When the 
buckling tendency ceases it is thoroughly swaged. 
It should be apparent to the student that a metal base- 
plate conformed and swaged over one die cannot accurately 440 
GOLD BASE-PLATE 
fit the mouth for the reason that the force of all the blows 
struck upon the base-plate must be received upon the high 
points (rugae and ridges) of the die; therefore the elevated 
portions of the die are compressed or "battered down." 
This condition can only be offset by annealing and swaging 
in a well-oiled second die and counter-die. 
Fig. 283 
When molding, two dies and counters should be formed, 
the better die and its counter to be reserved for the final 
swaging. If a very stiff base-plate material (as clasp metal) 
is being swaged, three or more dies and counters will be 
required. 
Swaging Full Lower Base-plates.-The gold cut to pattern 
is annealed and grooved with the plate benders (Fig. 284), 
then conformed to the oiled die, beginning upon the lingual 
side of the ridge. When the base-plate has been malleted TECHNIC FOR SWAGING GOLD 
441 
for some time it may seem quite recalcitrant, and it should 
then be cleaned, annealed, and swaged one stroke in the 
counter, which will much aid the conforming with the mallet. 
In a high-ridged case a half-counter-die, covering the lingual 
surface only, will be useful (Fig. 283). The swaging is 
accomplished in the same manner as for the upper. 
Fig. 284 
Fig. 285 
Swaging Partial Cases.-Fig. 285 shows a properly shaped 
model. The teeth stumps should be about to A of an 
inch long, just enough to give and keep a clear outline of 
the teeth, about which the base-plate is fitted by swaging, 
nipping with the plate nippers (Fig. 286), and filing with a 
rat-tail or half-round metal file (Fig. 287). 
The counter-die for partial cases should extend but little 
farther than the face of the die. Many operators imbed the 
die for both partial and full cases in the counter. This 
practice is worse than useless, because it is a trouble maker. 442 
GOLD BASE-PLATE 
In forming the counter-die, all portions of the die not desired 
to be covered with the counter are imbedded in the molding 
sand. For half-counters the sand is built flush with or 
a little higher than the crest of the alveolar ridge, when a 
small molding ring is set in place and the counter-die metal 
poured into it. 
Fig. 286 
Fig. 287 
Doublers.-A doubler is a piece of metal fitted and soldered 
to the lingual surface of the base-plate to give additional 
strength and rigidity. These are specially required for 
partial cases. The doubler is usually formed of the same 
carat and gauge gold as the base-plate, although it may be 
formed of a more rigid alloy than that of which the base-plate 
is being formed, especially if a very high carat gold is used. TECHNIC OF GOLD SOLDERING 
443 
The doubler should be placed so as to receive the greatest 
strain that is placed upon base-plate; and to interfere 
with the tongue and speech as little as possible. The doubler 
may cover but a small portion of the base-plate or it may 
cover nearly the whole surface. It should be at least enough 
smaller than the base-plate to form a ledge upon which the 
solder is placed while soldering, and thereby forming a less 
noticeable joint. 
Fig. 288 
Forming the Doubler.-A pattern is formed by pressing 
with the fingers a piece of pattern tin over the base-plate, 
and trimming to the desired form. The outline of the pattern 
is traced upon the sheet of metal to be used, then cut with 
the plate shears. The doubler is conformed by the mallet 
to the first die and swaged. It is then cleansed, annealed, 
placed upon the base-plate over the second die, and swaged. 
The edge is then filed to a bevel with the bevel on the outside 
of the doubler. This bevelling is to aid in the finishing, 
as the joint between the doubler and base-plate should be 
as nearly imperceptible as possible. The base-plate and 
doubler having been cleansed by pickling, the under surface 
of the doubler is smeared with a fine ground or liquid flux, 
clamped to the base-plate with wire clamps (Fig. 288) and 
soldered. 
TECHNIC OF GOLD SOLDERING. 
The necessary equipment for soldering gold is not large, 
but should be well chosen and their properties and use well 
understood. The necessary equipment consists of a good 444 
GOLD BASE-PLATE 
investment compound, holders or supports for the work, 
flux, and a blowpipe. 
Investment Compound.-There are a number of good invest- 
ment compounds on the market. One made after the 
formula given on page 404 will meet every requirement. 
The investment should withstand the heat to which it 
will be subjected without fusing or cracking, and it should 
conduct heat readily. Unfortunately the bond (plaster of 
Paris) that is used in the investment compounds fuses at 
a low temperature (1100° F., Price), shrinks badly, and is 
a poor conductor of heat. Therefore only enough plaster 
of Paris should be used to give binding strength. The com- 
pound should have as few basic ingredients as possible, be- 
cause it is a well-known metallurgical fact that two or more 
high-fusing basic substances may at a moderately low tem- 
perature form low-fusing compounds. Another factor to 
be taken into account in selecting an investment is that a 
material in a fine state of subdivision is more fusible than 
in a coarse. 
Holders.-Holders are of two types, as blocks composed 
of charcoal, asbestos, or magnesia; and appliances serving 
the double purpose of holder and heater. 
The charcoal block is chemically treated so that it burns 
only while in contact with a flame, therefore is safe to use 
in the laboratory. This is not true of a block of ordinary 
charcoal. The charcoal block is the best made for certain 
purposes, as it adds to the heat of the blowpipe flame and 
aids in deoxidizing metals. Its disadvantages are that it is 
black, brittle (both overcome by encasing), and is rapidly 
consumed. It is not suitable as a support for metals to be 
oxidized, nor working platinum. The asbestos blocks are 
cleanly, durable, and fire-proof, but otherwise nothing to 
commend them. The magnesia blocks are compact, cleanly 
to handle, quite durable, and so soft that some forms of work 
may be imbedded in its surface and thus be better supported. 
Figs. 289 and 290 show two combined supports and heating 
appliances. 
Flux.-Term derived from fluo, fluxus, to flow, and is 
applied in metallurgy to those substances that cleanse and aid TECHNIC OF GOLD SOLDERING 
445 
Fig. 289 
Fig. 290 446 
GOLD BASE-PLATE 
the flow of metals. In hard soldering (solder that requires 
a red or higher heat to melt) the alkali salts (preferably 
sodium borate (borax)) are used to cleanse the surface to 
be soldered by absorbing the oxides and preventing oxida- 
tion and making fluid the solder. For soft soldering (solder 
that requires less than red heat) zinc chloride and organic 
substances, as stearic acid, rosin, etc., are used. 
Blowpipe.-The blowpipe is an instrument of simple and 
complex construction, for directing, increasing the heat, and 
concentrating the flame in metallurgical work. 
The mouth blowpipe is of the simple type, and consists of 
a tapered tube either straight or bent, and is operated with 
the mouth by forming a bellows of the cheeks. This is an 
excellent instrument for light, quick service. However, it is 
questionable if it is profitable for the student to spend his 
time in mastering its technic, especially for large cases, 
when there are so many excellent mechanical devices for 
doing this work. 
The mechanical blowpipe is more or less complex. There 
are many forms of this instrument designed to develop 
certain features for its use. As these various forms are 
described in all the reference books on prosthesis, one only 
will here be shown as an illustration. 
The "Automaton" (Fig. 290) is designed to be and is to 
an extent automatic. Gas is admitted to the pipe by the 
anterior tube and air by the posterior tube. The pipe is 
equipped with a sliding arrangement of its barrel, which 
automatically regulates the quantity of gas and air, provided 
the supply of gas and air are under suitable pressure. 
The air blast is furnished either by a foot bellows, a 
compressed-air tank, or power air pump. A very ingenius 
and efficient air pump known as the "Vernon Rotary Com- 
pressor" has recently been put upon the market by the Lee 
S. Smith & Son Company. It is only 3 inches high, 1| 
inches thick, and weighs two and one-half pounds. It is 
designed to be coupled to the electric lathe or any small 
power in the office. Fig. 291 shows the complete machine 
and Fig. 292 its internal construction. TECHNIC OF GOLD SOLDERING 
447 
Use of the Blowpipe.-On page 244 the Bunsen burner is 
described as a tube with an opening near the bottom for 
the admission of air to the gas by natural draft. In the 
AIR OUTLET 
Fig. 291 
blowpipe the air is forced into the flame, which gives a 
greater range of possibilities. The object of the flame is 
Fig. 292 
to produce heat. Heat is a result of chemical action mani- 
fested in the oxidation of the carbon and hydrogen of the 
fuel. It is obvious that oxidation can be controlled, hence 448 
GOLD BASE-PLATE 
the degree of heat and its usefulness. Therefore the object 
of the blowpipe is to create, direct, and control heat. The 
blast of air increases the amount of oxygen, the rapidity 
of oxidation, and heat up to a certain point, after which 
an increasing blast cools the combining gases until the tem- 
perature is reduced below the ignition point and the flame 
is extinguished, "blown out." It is impossible for the 
operator to tell when he has reached exactly the highest 
degree of heat and the flame is beginning to cool. However, 
he knows that a yellow tinge indicates carbon imperfectly 
combined with oxygen, and that the blue color in the outer 
two-thirds of the length of the flame indicates perfect com- 
bustion and that the point of highest temperature is being 
approached or passed. (The flame is always blue at its 
base, but this is because the carbon has not yet reached the 
yellow stage.) Therefore a yellow flame indicates a com- 
paratively low degree of heat, and that as the blast is in- 
creased the temperature increases with the disappearing 
yellow color; that the succeeding blue color indicates perfect 
combustion, and that the temperature is increasing until 
the highest degree is attained, and then an increasing blast 
chills the flame until it is below the ignition point and 
extinct. 
Fig. 293 
The blowpipe flame, like the Bunsen flame, has three 
zones: the inner or gaseous zone, the middle or combustion 
zone, known as the reducing flame, and the outer mantle or 
oxidizing flame. The diagram shown in Fig. 293 illustrates 
the three zones, A, B, C. Work to be heated and soldered 
should be placed in the reducing flame at B' B', where it 
will be heated, cleansed of any oxides, and the solder nicely 
flowed; but if the work is placed at C C or advanced to C 
the work will be made dirty by oxidation and be endangered SOLDERING ATTACHMENTS TO GOLD BASE-PLATE 
449 
by burning. The soldering can be done at this portion of 
the flame only by the use of an excessive amount of flux. 
The flame is used either in the form of a brush or a needle. 
These are easily produced with a mouth blowpipe by having 
the nozzle outside of the flame for the brush form and in for 
the needle. The same results are obtained with the auto- 
maton by using a large flow of gas and light air-pressure for 
the brush and a small flow of gas and a moderately heavy 
air-pressure for the needle flame. 
SOLDERING ATTACHMENTS TO THE GOLD BASE- 
PLATE. 
There are three classes of attachments, known as strength- 
eners, finishers, and retainers. 
The strengthener may be in the form of a doubler or 
wire. The w'ire strengthener may serve as a finisher, w'hile 
the finisher is always a strengthener. 
Soldering Doublers.-The base-plate and doubler having 
been pickled and thoroughly cleaned, the doubler is smeared 
on the under surface with a fine-ground cream or paste of 
borax. (If desired the proprietary fluxes in the supply houses 
may be used. They are composed principally of borax.) 
The base-plate and doubler are firmly pressed together and 
clamped with wire clamps. (See Fig. 288. These clamps 
are formed of soft-iron wire, guage 15.) Solder, two carats 
lower than the base-plate, is cut in pieces | by | or | by | 
of an inch, fluxed, and placed upon the base-plate at the edge 
of the doubler for one-half of its circumference. The work 
is supported upon a soldering block, preferably of charcoal, 
with the solder-decked edge elevated. The yellow-tinged 
brush flame is applied to the base-plate and doubler with 
the greater heat at the farther side of the doubler from the 
solder. This will cause the solder to flow between the base- 
plate and doubler and completely fill the space between 
them. The solder flows between the two plates of metal in 
place of running away, because of three physical laws, as 
follows: (1) Solder always flows to the hottest point. (2) 
Capillary attraction. (3) Gravitation. Should every por- 450 
GOLD BASE-PLATE 
tion of the joint not be filled at the first flush, more solder 
should be added, at the deficient point, and flowed. No 
attempt should be made to remelt the first flush of solder. 
The case is pickled to remove the flux and reswaged in the 
last die and counter by two or three dead blows of the 
swaging hammer. 
Soldering Finishers.-A gold base-plate that is to have the 
teeth attached with vulcanite should have a finisher provided 
for the joining. However, the finisher is often omitted as a 
means of saving labor and expense, but always at the expense 
of strength and perfection. The finisher may be in form, 
either thin plate or wire. Upon the buccal and labial surfaces 
the thin plate finisher may be formed either by turning the 
edge or soldering on a swaged piece of plate. Finishing the 
lingual surface of the joining with thin plate can only be 
accomplished by swaging and soldering an extra piece of 
metal. A wire soldered about the periphery of the joining 
is the neatest, strongest, and best way of forming a finisher. 
Turning the Edge of Base-plate.-If a turned edge of the 
labial and buccal surfaces of the base-plate is desired, the 
impression is prepared by making the required outline of 
the edge of the base-plate and carving away, at right angle 
to the median plane of the impression, the border of the 
impression to the indicated outline. This will result in the 
forming of a ledge upon the die that will turn the edge of 
the plate at right angle. The balance of the turning is done 
with pliers. 
Swaging and Soldering the Labial and Buccal Finishers.-For 
this purpose wax occlusion and contour models are obtained, 
the case placed on the antagonizor, teeth mounted, gum 
portion restored either with porcelain sections or wax; when 
an impression is obtained of the surface for which the finisher 
is to be formed, the model, die, and counter formed, and 
the finisher swaged. The finisher will be in two sections, 
each extending from the median line. The teeth and wax 
are removed from the base-plate in a mass by warming the 
under surface of the base-plate. The finisher, boraxed, is 
clamped to the base-plate with wire clamps, solder placed 
in the crevice and drawn outward by the blowpipe flame. SOLDERING ATTACHMENTS TO GOLD BASE-PLATE 
451 
The same procedure is required for forming the lingual 
thin plate finisher. However, the work is carried on at the 
same time (not after) as the buccal and labial finisher. 
This method necessitates much labor and mechanical 
skill, and when completed is neither as strong nor cleanly 
as the wire finisher. 
Fig. 294 
Wire Finisher.-This finisher is formed by using an 18 or 
possibly a 16 B. & S. gauge, 20-k, gold wire, and forming it 
to the base-plate. The conforming is done by bending the 
annealed wire with the fingers and pliers so as to approxi- 
mate the periphery of the base-plate. Begin at either 
tuberosity and conform the wire for one inch, attach with 
wire clamps placed at both ends of the conformed portion, 
place a small portion (size of the head of pin) of boraxed 
Fig. 295 
solder at some point of contact, and melt. Continue the 
conforming and tacking an inch at a time until the wire is 
carried the entire length of the joining of the base-plate, and 
vulcanite. The base-plate is placed upon the die and the 
tacked wire closely adjusted to the base-plate for its entire 
length. This may be done with a plate burnisher (Fig. 294 
is the Prothero, and Fig. 295 is the Wilson plate burnisher), or 
a small copper riveting hammer may be used. The base- 452 
GOLD BASE-PLATE 
plate is removed from the die and inspected for base metal. 
The crevice is smeared with flux and a generous quantity of 
solder placed along the upper edge (as supported on the block) 
of the wire for its entire length; it is supported on a soldering 
block and the yellow-tinted blowpipe flame applied care- 
fully over the whole surface of the base-plate until the flux 
is dry, when the flame is placed at either tuberosity and 
concentrated at the lower edge of the wire, thereby fusing 
and drawing into place the solder, advancing piece by piece 
until all is fused. 
Fig. 296 
Fig. 297 
Fig. 298 
Retainers.-Retainers are loops soldered to the base-plate, 
about which the vulcanite is attached. It is obvious that the SOLDERING ATTACHMENTS TO GOLD BASE-PLATE 
453 
greatest efficiency of the retainers is at the periphery of the 
joining. They are formed of wire, or narrow strips of scrap 
gold plate, convoluted. The convoluted strip or wire is 
clamped to the base-plate and soldered. Figs. 296 and 297 
show a gold base-plate, with the vulcanite removed, that was 
worn for some years. Figs. 298 and 299 show a completed 
denture. 
Fig. 299 
Warping in Soldering.-The base-plate is subject to warping 
by unequal expansion of the metal while soldering. This 
can hardly be avoided. Base-plates are often unnecessarily 
warped by clamping to the soldering block with a spring 
clamp. When all metal attachments have been made to the 
base-plate it is placed upon the die and inspected; if any 
rocking or springing appears as pressure is applied on dif- 
ferent portions of the base-plate, it should be placed in a 
swaging machine, as the Parker shot swager, and reswaged. 
The base-plate is now tried in the mouth, and if satis- 
factory, wax is built upon it for the occlusion and contour 
models; when the subsequent procedures are the same as 
for a vulcanite denture. 
Soldered Gold Artificial Dentures.-Prior to the introduc- 
tion of vulcanite the teeth were soldered to the base-plate. 
This necessarily was a very unsanitary appliance. There 454 
GOLD BASE-PLATE 
is no logical or practical reason why such a denture should 
be inserted at this stage of the development of dental pros- 
thetics. However, there are a few cases in which a modified 
form of the method may be of the greatest service. Fig. 
Fig. 300 
300 shows the lingual surface of such a partial denture. The 
patient for whom this appliance was constructed had a very 
long upper lip and the lower teeth shut very close to the 
upper gum. Facings were backed with 26-gauge clasp 
gold, backings closely fitted to the base-plate, invested, and 
soldered. The labial gum restoration was made with 
vulcanite. Fig. 301 shows the labial aspect of the same 
case. 
Fig. 301 
There are some partial cases which require no gum restora- 
tion, that because of the close shut will require a metal- 
back facing soldered to the gold base-plate; or if the base- 
plate is to be vulcanite a metal tang of clasp metal is soldered SOLDERING ATTACHMENTS TO GOLD BASE-PLATE 
455 
to the backing of the facing and extended backward into the 
vulcanite base-plate. Fig. 302 shows such a facing backed 
and tanged. Bicuspids for very close shut cases may be 
provided with a porcelain-faced gold dummy (such as is used 
in bridge-work) soldered to the base-plate. For molars the 
facing may be better omitted. 
Fig. 302 
Soldering Porcelain to Metal Base-plate.-This work requires 
that a stiff rigid plate of metal be closely fitted and attached 
to the facing with solder; or the facing may be.backed with 
either 35-gauge pure gold or platinum, invested and con- 
toured with 22-k solder. The facings, however backed, are 
adjusted to the base-plate and soldered. 
Fig. 303 
Fitting the Backings.-Tinfoil patterns are made of the 
backings and traced upon the gold to be used. It is well, 
as a precaution against inaccurate workmanship, to punch 
the pinholes before cutting the backing from the stock 
piece. The English double punch (Fig. 303) may be used 
and punch both holes at the same time, or the single punch 
(Fig. 304) may be used and punch the holes separately. 456 
GOLD BASE-PLATE 
If the double punch is used the tooth to be backed will 
adjust the punch, while with the single punch the plate 
must be marked for the punch. This may be done by slightly 
smearing the metal with wax and pressing the pins of the 
tooth into it, or tinfoil punctured by the pins of the tooth 
may be laid upon the metal as a guide to punching. The 
backing is conformed to the facing as closely as possible 
by bending. The edges are filed to a bevel and burnished 
to the facing. The facing and its backing are temporarily 
held together by turning down a shaving from the side of 
the pins made by a cut with a sharp knife or chisel. 
Fig. 304 
Investing and Heating-The teeth backed and luted to 
the base-plate are removed from the plaster cast, invested 
with investment compound to a thickness of | to | inch. 
The investment is thoroughly dried, and while warm a small 
amount of flux, rubbed to a cream or mixed with vaselin 
is applied to the joints and pieces of fluxed solder placed 
upon the joint, also a small piece rested upon each pin so 
as to unite the pin and backing. The invested case is placed 
upon a combined supporter and heater (Fig. 290), and gradu- SOLDERING ATTACHMENTS TO GOLD BASE-PLATE 
457 
ally heated until it has attained a dull red heat. The por- 
celain must be heated up through the investment rather 
than through the metal backing. In other words, the por- 
celain must expand in advance of the metal pins to avoid 
cracking. The work having been heated to a dull red state 
is ready for the blowpipe. The yellow-tinted brush flame 
is played over the investment and gradually brought over 
upon the metal, and the brush flame continued until the 
solder begins to melt, when each piece of solder is touched 
consecutively with the blue needle flame and thoroughly 
flowed. Should any portion of the work require a large 
amount of solder after the first tacking, it is best done by 
feeding into the flame, held at the point to be filled with 
solder, a long strip of fluxed solder held in clamped tweezers. 
Care must be exercised not to hold the flame at one point 
long enough to melt the work. This is accomplished by 
interruping the flame contact. 
Cooling the Investment.-The fire is withdrawn and the 
case permitted to stand until cold. No precaution is re- 
quired, except to protect from drafts of air, as too rapid 
radiation of heat might craze the porcelain. The investment 
compound is a poor radiator of heat, therefore retains the 
heat and permits the metal to cool in advance of the porcelain. 
The cracking of porcelain in soldering is largely due to ex- 
panding the metal pins in advance of the porcelain in heating 
up and cooling the porcelain in advance of the pins in the cool- 
ing-off process. Hence the principal time of danger of crack- 
ing is while heating up. 
Partial Upper Dentures.-The base-plate is designed in 
outline to meet the requirements of the case. Modern 
thought requires as little of the vault to be covered with the 
base-plate as is consistent with strength and rigidity. Fig. 
305 shows a partial gold base-plate fitted about all of the 
remaining teeth. Figs. 306 and 307 show a band base-plate 
with as little surface covered as is consistent with stability. 
The band should extend across and in proximity to the high- 
est portion of the vault. Fig. 308 consists of a cast saddle 
with lugs. The clasps and swaged band are soldered to it. 
Fig. 309 shows the completed denture. 458 
GOLD BASE-PLATE 
Partial gold base-plates may be constructed by either 
the swaged or cast method. However, as has been stated, 
the quality of adaptation is the only factor of superiority 
Fig. 305 
Fig. 306 
Fig. 307 SOLDERING ATTACHMENTS TO GOLD BASE-PLATE 
459 
of the cast over the swaged base-plate; and it is questionable 
if this closeness of adaptation is desirable; if contact with a 
Fig. 308 
smooth surface is not more acceptable to the contiguous 
tissues. As contact is almost a negligible factor in the 
retention of partial base-plates, the contact over the vault 
portion of the mouth may be ignored; except that sufficient 
Fig. 309 
contact must be had to prevent the sound waves of vocali- 
zation passing between it and the roof of the mouth. 460 
GOLD BASE-PLATE 
Swaging.-The model, die and counter, swaging and 
reinforcement have been considered. Clasps as retainers, 
their form, location, and construction are discussed in 
Chapter VII, but adjusting the clasp to the base-plate will 
require attention. 
The partial base-plate with all of its attachments soldered, 
save clasps, is tried upon the die, and if found out of 
shape it is reswaged in the swager. The base-plate is then 
pickled and cleansed and adjusted to the mouth. Should 
its weight be too great for its retention by contact, the 
maxillary surface is moistened and sprinkled with powdered 
gum tragacanth and held in place for a moment until adhesion 
is established. A plaster impression is taken sufficient to 
cover the portions of the teeth to be clasped and the con- 
tiguous base-plate. Should the base-plate not leave the 
mouth with the impression, it is removed and replaced in 
the impression. Another plaster impression is taken, neces- 
sarily of the teeth to be clasped only. This impression may 
be of the teeth individually or collectively. The impression 
containing the base-plate is varnished and carefully filled 
with investment compound. The impression of the teeth 
only is varnished and filled with plaster or, preferably, Spence 
plaster compound. Some prefer filling this impression with 
bismuth alloy, but nothing is to be gained over the Spence 
compound save time, and there is danger of contaminating 
the clasp metal with the base metal of the bismuth alloy. 
The Spence compound should stand about an hour before 
taking from the impression, and then another hour or more 
to harden. The clasps are formed over the Spence com- 
pound casts, as instructed in Chapter VII, and adjusted upon 
the investment compound cast containing the base-plate. 
Contact must be had between the clasp and base-plate either 
by proximity or another piece of metal called a standard. 
Sometimes two standards are required (see Chapter VII). 
If the base-plate is securely caught in the investment com- 
pound cast and the clasps are securely held by their inherent 
elasticity, no further investment will be required; but if 
the parts to be soldered are not securely held, the cast should 
be saturated with water and invested with the spaces for CASTING METHOD 
461 
soldering as wide open as possible. The case is well dried, 
the joints supplied with flux and solder, and heated; rapidly 
if desired, as there are no porcelains to be considered. If 
the clasp and base-plate are to be connected by a standard 
the upper end should first be soldered, as otherwise the 
contraction of the solder about the lower end of the standard 
is liable to pull it away from the clasp. The soldering com- 
pleted, there being no porcelains attached, the case may 
be rapidly cooled by placing in water. The metal is then 
pickled, when it is ready for the vulcanite superstructure. 
The base-plate without porcelains may be rapidly pickled 
by heating nearly to redness and quenching in the pickle 
bath. 
CASTING METHOD. 
Pure gold is not suitable for casting for any part of denture 
construction, but must necessarily be made harder, more 
rigid, and for certain uses, as elastic as possible. The metals 
suitable for alloying the gold for casting are-silver, copper, 
platinum and palladium. Silver is used chiefly to modify 
the color; copper is used to give hardness and elasticity, it 
reduces the fusing point of the gold markedly and deepens 
the color; platinum is used to increase the hardness, elasticity 
and raise the fusing point; palladium is used to add the same 
properties as platinum and is better than a high percentage 
of platinum as it unites more uniformly with the gold and 
weight for weight raises the fusing point of the alloy more 
than platinum; however, palladium destroys the gokl color, 
reducing the mass to the color of platinum. The high fusing 
and elastic gold alloys are restricted, therefore, to bands, 
bars and clasps. 
The Ney-OrO golds made from the formulae of Mr. Louis 
J. Weinstein are undoubtedly the most uniform and scientific 
casting golds upon the market. Further than this their 
formulae are published; therefore, they are ethical and pro- 
fessional material. The dentist knows what he is using and 
can use the Ney-OrO golds intelligently, which cannot be 
said of any make of gold that does not publish its formulae. 
These golds may be melted with the gas and air blow-pipe, 462 
GOLD BASE-PLATE 
but are more suitable for the gas and oxygen or nitrous oxid 
blow-pipe. Care must be used to thoroughly melt, but not 
to overheat or burn the gold. This implies that a sufficient 
illuminating gas flame is used and not an excess of oxygen 
forced into it, but enough to accomplish the desired result. 
The Ney-OrO casting golds that will meet every require- 
ment are the following. 
"C" 
"B" 
"E" 
Per cent. 
Per cent. 
Per cent. 
Gold 
. . . 80.5 
80.0 
64.0 
Platinum 
. . . 6.5 
9.5 
11.0 
Palladium . . . . 
... 2.0 
2.5 
16.5 
Silver 
. . . . 2.0 
1.0 
1.5 
Copper 
... 9.0 
7.0 
7.0 
Total . . . . 
. 100. 
100. 
100. 
Fusing point 
. . 1800° F. 
1975° F. 
2100° F. 
Ney-OrO "C" is suitable for cast full dentures and saddles 
that are to be reinforced. It should be melted with the gas 
and air blow-pipe only. Ney-OrO "B" is designed for any 
full or partial denture requiring greater rigidity with less 
bulk than can be attained with "C." This gold can be 
properly fused with the gas and air blow-pipe provided the 
operator is expert and the mass of metal is not too great. 
Ney-OrO "E" is suitable for clasps, bars, bands and any part 
where the greatest rigidity is required. This gold may be 
melted in small quantity with the gas and air blow-pipe, but 
it can be better manipulated with the gas and oxygen or 
nitrous-oxide blow pipe, when any quantity desired can be 
properly fused. 
Investment Compounds for Gold Castings/-It is the opinion 
of the writer that the liquid graphite investment is better 
adapted to small castings as clasps and small saddles, but 
that large saddles and full dentures can be better manipu- 
lated with the silica compounds, because of their greater 
strength and porosity. However, either class of material 
may be used universally. It is the opinion of the writer that 
better results are obtained by using either one alone than by 
using both in the same flask. 
General Suggestions for Gold Castings.-There are two 
methods for making gold castings, known as the Direct and CASTING METHOD 
463 
the Indirect. The direct method consists of forming the wax 
pattern upon the cast and investing the two together; the 
indirect method consists of forming the pattern as for the 
direct method, but removing it from the original cast for 
investment and casting. The direct method necessitates that 
the cast shall be formed of the investment compound, while 
for the indirect method the cast should be formed of hard 
plaster compound. The best results seem to be obtained 
from "green" molds, that is, where the investments have 
not been permitted to dry out by long standing; therefore, 
the indirect method gives smoother and better results than 
the direct. However, if the original cast is used and it has 
become thoroughly dry then it should be thoroughly soaked 
in water before adding more investment, also before heating 
up if a flashed case has stood for a day or two. This sugges- 
tion is thoroughly empirical, for the writer is not satisfied 
with any explanation he can offer. 
If the Casting table of a pressure machine is not recessed 
a shallow recess should be cut in the investment to aid in the 
escape of gases while casting. 
Too thin casting wax should not be used, thereby avoiding 
imperfect or weak castings. Use 16 gauge (B & b) sprues and 
a sufficient number to fill every part of the mold promptly. 
Use clean metal for each melting. If the metal has been 
previously used clean it with reducing flux and acid. 
Heating the Flask.-All cases should be warmed slowly so 
that the wax model may be absorbed by the investment, if 
a small one, and partially absorbed if a large one when the 
flask can be inverted and the excess of wax permitted to run 
out of the sprue holes. The heat is gradually increased until 
the mold is thoroughly dry of wax and moisture. The mold 
is now known as a cold mold although it may be a few hun- 
dred degrees hot. The cold mold is desirable for clasps and 
very small saddles, but for large castings and where the 
molten metal must flow some distance the mold must be hot, 
red hot. The smallest-sized casting flasks may be sufficiently 
heated in a Maves' Furnace (Fig. 310) in thirty-five or forty 
minutes, but the next size flask will require fifteen to twenty 
minutes longer, while the large-sized flasks will require from 464 
GOLD BASE-PLATE 
one to two hours in the open flame. Do not attempt large 
castings in a cold mold. The Maves' Furnace is suitable 
for the "cold mold" only. 
Fig. 310 
Pressure Required for Casting.'-Very small castings will 
require 8 to 12 pounds' pressure, and medium to large cast- 
ings will require 15 to 20 pounds' pressure. 
The investment compound must not quite fill the top of 
the flask. There must be at least one-sixteenth of an inch 
of free flange to permit the flange bedding itself into the 
asbestos packing of the head of the casting machine. Suffi- 
cient force must be applied and sustained upon the closing 
lever to prevent escape of the compressed air. Necessarily 
the larger the perimeter of the flask the greater the pressure 
to make a tight joint between the flange and packing. 
Making the Wax Model for Casting Gold.-For the direct 
method of casting the investment compound cast needs no CASTING METHOD 
465 
preparation; but for the indirect method the hard plaster 
cast should be slightly lubricated with sweet or sperm oil, 
or the surface may be sprinkled with soap-stone, which should 
be well rubbed in, and the excess brushed away. The cast 
may be slightly warmed, but not above 100° F. The casting 
wax may be sufficiently warmed by holding for a moment 
between the palms of the hands and adjusted to the judi- 
ciously warmed cast. Extra heat is best applied by warming 
the thumb or hand rather than by exposing the wax to direct 
heat. For the indirect method the wax must be perfectly 
molded to the cast and luted at a few points only. Portions 
Fig. 311 
of the surface may be doubled by the same careful warming 
and conforming of the added wax. Bound wax attachments 
are more safely attached by luting with melted wax carried 
on a small spoon as the Number 1 Evans' wax carver. The 
wax sprue formers should be approximately 16 B & S gauge 
in size, the middle size round of the Mathews wax former. 
Often these feed sprues can be so attached that they will also 
form the cleats of the vulcanite attachments. Judgment 
must be used to place a stiff cient number of sprues to quickly 
and perfectly fill the mold. A clasp will require one feed 
sprue, with possibly an auxiliary, as shown in Fig. 311. Sad- 
dles will need two or more and a full denture may need 466 
GOLD BASE-PLATE 
eight or ten. These sprues must all have separate openings 
into the floor of the melting crucible. (See Fig. 312.) They 
must be so placed and sufficient metal used so that they are 
all covered with the molten metal until the mold is perfectly 
filled. Should a single one of these feed sprues be exposed to 
the compressed air the casting will be spoiled. 
Fig. 312 
Investing and Flasking.-The wax model is first invested 
and then flashed. If the direct casting method is to be used, 
the wax model is thoroughly luted to the cast, and then 
coated over with a thin mix of the investment compound, 
applied with an ox-hair brush, lapping it well upon the cast. 
As the investment begins to set it may be poured on from a 
spatula at those places needing special support, as the sprues 
and cleats. For the indirect method the wax model is luted 
only at two or three points, just enough to hold it in place, 
and then the outer surface invested the same as for the direct CASTING METHOD 
467 
method, only the investment must not lap upon the cast. 
When the investment has set sufficiently to have good rigidity 
the luting wax is freed with a sharp lance knife, when the 
partially invested wax model is carefully removed from the 
cast and the inner surface is then invested in the same 
manner as the outer surface, permitting the investment to 
well lap upon the outer investment, and then permitted to 
stand until the new investment is set enough to handle safely. 
The invested case is then flashed as shown in Pig. 312. 
Fig. 313 shows a full upper model denture formed ready for 
investing and flasking. 
Fig. 313 
The base is formed of either 28 or 30 gauge casting wax, 
palatal border is doubled, and the labial, buccal peripheral 
border and the lingual shoulder are traced with wax formed 
from the No. 1 (small) nozzle of the Mathews wax former 468 
GOLD BASE-PLATE 
(Fig. 247). The eight sprues are formed by the No. 2 nozzle 
and the auxiliary sprues of the No. 1. The eight number 2's 
are curved and drawn upward so that when the crucible mold 
is formed the entrance to each sprue hole will be downward. 
Fig. 314 
Fig. 315 
Partial Dentures.-Partial dentures are best cast in units 
and the units united by soldering. A unit is a clasp, saddle or 
a connecting bar or band. Two saddles can be joined with a 
bar by lap joints better than by butt joints. There is neces- 
sarily shrinkage in casting; however, this can be largely com- 
pensated by sectional castings, and lap joints. (See Fig. 314.) CASTING METHOD 
469 
Fig. 315 shows the five units-two clasp units-two saddle 
units and the connecting unit united with solder. 
Swaging Cast Dentures.-The casting may be swaged, often 
with advantage. The Parker Shot Swager (Fig. 271), or a 
similar swager may be used. This method is especially 
adapted to full dentures. The hard plaster compound cast 
is centered and set in the base of the swager with a fresh mix 
of plaster, or with high heat modelling compound. The 
casting is then placed upon the hard plaster cast, and covered 
with light weight rubber dam, and a sufficient quantity, to 
nearly fill the swager, of low-heat modelling compound is 
quickly adjusted, the plunger adjusted and submitted to 
heavy pressure in a screw press; or, it may be struck one dead 
blow with a heavy sledge (16 pounds). Moderately stiff 
putty may be used in place of low heat modelling compound. 
A better way than striking with the sledge is by the English 
drop swage. This is a miniature pile driver. The drop swage 
has the advantage over the sledge in that it holds the base- 
plate under pressure until the molecules of metal become set 
from the vibration produced by the swaging force. Cast 
aluminum may be swaged in the same manner. 
Amount of Gold to Use.-The same rule given for aluminum 
will serve for gold; therefore multiply the weight of wax by 
forty. How'ever, for large gold castings multiplying by thirty 
will give a sufficiency. 
The castings are finished by grinding, filing, buffing and 
burnishing. Ivory soap is a good lubricant for the burnisher 
of either steel or stone. 
Casting Methods and Machines.-There are four physical 
principles usable in dental casting methods; namely, gravi- 
tation, centrifugence, vacuum and pressure. 
The gravitation method is dependent upon a low fusing 
point and weight. It is suitable in dentistry for tin and its 
alloys only. The method is treated of in Chapter XII. 
Centrifugence is matter revolving about a rotation center, 
its power is created by the velocity and weight of matter, 
and its force is exerted toward throwing the matter off at a 
tangent from the rotation center. The principle has the 
advantage of great simplicity, as an effectual machine may 470 
GOLD BASE-PLATE 
be formed by a bucket swung at arms length; or gear wheels 
may be utilized to shorten the radius and increase the 
velocity. This principle is dangerous because of the possi- 
bility of accidentally throwing the molten metal out of the 
machine. This principle is elaborated in Chapter X; however, 
the Billmeyer method is not suitable for gold casting, because 
Fig. 316 
of the high specif c gravity and fusing point of gold, a large 
enough feed sprue cannot be used. It is necessary that a feed 
sprue shall connect with all of the high points so that the 
molten metal enters directly to every portion of the mold. 
This is illustrated in Figs. 268 and 316. THE HOLLENBACK UNIT 
471 
THE HOLLENBACK UNIT.1 
This machine is probably the best illustration of a casting 
unit, incorporating the centrifugal force and cold mold 
Fig. 317 
Fig. 318 
principles, before the profession. It is a compact, simple and 
easily operated device. The oven is designed for drying out 
1 This machine is an invention of Dr. G. M. Hollenback and manufac- 
tured by the Occidental Manufacturing Co., of Los Angeles, Calif. 472 
GOLD BASE-PLATE 
the investment for cold casting of inlays and clasps. The 
cold mold method is not suitable for castings larger than 
clasps and saddles that can be produced in the small-sized 
Fig. 319 
casting ring. The oven has a tray upon which 1 to 5 cases 
may be dried at once. The electrical units are placed upon 
each side of the tray and are regulated by a thermostat so 
that a temperature under 400° F. is constantly maintained 
Fig. 320 
for one hour and a half. In about one hour after the wax 
pattern is invested the flask is placed upon the oven tray with 
the sprue end downward. As the wax pattern melts the THE HOLLENBACK UNIT 
473 
excess water of the green investment washes out the wax, and 
does not permit of any appreciable absorption of the wrax by 
the investment compound. AV hen the investment is per- 
fectly dried the flask may be set aside and the casting made 
at any convenient time. However, the casting should be 
made before the investment absorbs moisture from the 
atmosphere. 
Fig. 321 
The casting apparatus is operated by a spring and release 
lever, therefore is uniform and reliable in action. The 
crucible is made of fire clay and is easily replaceable. It is 
impossible for any of the molten metal to enter the mold 
before the spring is released; and the molten metal can be 
suitably fluxed without danger of the flux entering the mold. 
The parts of the casting portion of the unit are so placed that 
the least possible heat is applied to the mold. The result 474 
GOLD BASE-PLATE 
is that a bright clean perfectly fitting casting is produced, 
after cleansing in hydrochloric acid. 
The large flask is for saddles and the various sections of a 
partial denture that are too large for the small flask. The 
wax pattern is carbonized and burned out and the casting 
is made in the hot flask. 
Fig. 322 
Vacuum is exhaustion of air from an enclosed space, and its 
power is the weight of the column of external air compared 
with the degree of exhaustion of the confined air. Therefore, 
the vacuum machines are a modified form of the pressure 
machines. Its advantages are that the method permits 
application of heat while the force is acting, if desired, and it 
admits observation of the disappearing metal. Its disad- BAR, LOWER DENTURES 
475 
vantages are that its power is limited (but enough for prac- 
tical use), and its force is forward, very little lateral or back- 
ward; however, this disadvantage can be practically over- 
come by manipulation. This disadvantage and the method 
of overcoming it is nicely illustrated in the instructions given 
for the Laing-Elgin method (Fig. 318). Fig. 267 is the Elgin 
Vacuum Machine, it is very efficient and extensively used. 
Pressure Principle.-This has the greatest range of applica- 
tion and power. The pressure may be created by compressed 
air or other gases, steam or explosions. The advantages of 
this principle are that the power is unlimited and may be 
continuous if desired, also it acts to force the molten metal 
in every direction, and holds it under pressure as long as 
desired. The disadvantages are that the heat must be 
removed, the compression tends to cool the metal, and the 
molten metal is out of sight. Fig. 319 shows the perfection 
with which molten metal is forced in every direction under 
direct pressure. The metal, Ney-OrO "B" was melted by a 
gas and air blow-pipe in a hot mold. It traveled downward 
over an inch and spirally upward about nine and one-half 
inches. The diameter of the casting is number 13 B & S 
gauge. It was cast with a Burns' Casting machine. Fig. 320 
shows the Burns' Casting machine fitted with a compressed 
air guage; also equipped with a tank and pump for use where 
there is not a compressed air supply. 
Fig. 321 is the Dental Mfg. Co.'s Compressed Air Casting 
Machine. It is equipped also with the tank and pump. 
Partial lower dentures may be made with a band of 
vulcanite (Fig. 334) on the lingual aspect of the remaining 
natural teeth; or with a band of reinforced gold (Fig. 322); 
or with a bar as shown in Fig. 325. The bar has the merit 
of being less cumbrous and interfering with the adjacent 
tissues the least of any method yet devised. The method 
is growing in -popularity with both patient and practitioner. 
Technic.-The saddles may be made of either swaged or 
cast gold. (There is probably no place where the cast base 
BAR, LOWER DENTURES. 476 
GOLD BASE-PLATE 
is as applicable as for these cases.) In either case the bar 
should be made of clasp gold wire soldered to the saddles; 
after which the clasps should be formed and soldered to the 
saddles. As the bar with vulcanite saddles are the most 
commonly made, its technic will be sufficient for the 
method, as the slight modification required for the metal 
saddles will suggest itself to any workman's mind. 
Fig. 323 
Material.-No. 12 B. & S. gauged clasp gold wire is the 
material used. Should it be apparent that unusual strength 
will be required, No. 11 gauge wire may be substituted, 
or two wires of No. 15 or 16 gauge, soldered one above the 
other, will serve well the purpose. An elliptical wire No. 
9 x 13, is better than either 12 or 11 round. 
Single Wire Method.-A plaster impression is taken and a 
Spence compound cast obtained. (Care should be exercised 
not to deface this cast, as it is the only one required to 
complete the denture.) Retaining clasps are fitted to the 
teeth to be clasped. A line is marked upon the lingual 
aspect of the cast to indicate the position of the lower edge 
of the bar. The bar must be kept high enough not to inter- 
fere with the frenum lingua or other soft tissues of the floor 
of the mouth. A roll of soft wax is conformed to the cast 
so that its upper surface will form a ledge parallel wTith the 
line marked for the bar. This ledge of wax is for convenience 
in shaping and supporting the bar. A bar, sufficiently long 
to extend at least j inch into each saddle, is annealed by 
heating to a dull cherry-red and quenching in water. 
This is bent with the fingers and a pair of pliers having one 
oval-faced beak. The bending is continued until the bar 
rests upon the edge of wax and is from to of an inch 
from the cast. If the wire is nearer the soft tissue than BAR, LOWER DENTURES 
477 
of an inch there is much danger that it will in time become 
a source of irritation. The bar and clasps are removed and 
the cast is painted with liquid silex above the wax ledge and 
for | inch beyond the clasped teeth. The clasps are then 
Fig. 324 
replaced with just enough tension to hold them securely, 
and the bar set in place upon the ledge of wax. The clasps 
and bar are then luted together with a batter of quick- 
setting plaster, the plaster extending from one clasped tooth 
Fig. 325 
to the other. The plaster luting should rest upon the lingual 
aspect of the intervening teeth only to give body to the lute. 
When the luting plaster has become hard and strong, it is 
removed from the cast. It will hold the bar and probably 478 
GOLD BASE-PLATE 
both clasps. However, should any one or all three of the 
pieces of metal be parted from the luting they are easily 
replaced and fastened with a little wax. Fig. 323 showrs 
the luting plaster with the clasps waxed in place. The plaster 
luting is varnished with shellac and sandarac and covered 
with investment so as thoroughly to hold and support the 
Fig. 326 
Fig. 327 
bar and clasps. Fig. 324 shows such an investment with the 
luting plaster cut away and the clasps and bar united with 
standards. Fig. 325 shows the same case removed from the 
investment and placed upon the Spence compound cast. 
The remainder of the work of construction is vulcanite work, 
and should need no further description. SOME PRACTICAL CASES 
479 
Double Wire Method.-Fig. 326 shows the two wires of 
No. 16 gauge united with wax. They are removed and 
invested as shown in Fig. 327, soldered together with 18-k 
or 20-k solder. This bar is then luted with plaster to the 
clasps and soldered as previously described. 
Fig. 328 
Too Close Fitting Bar.-Dr. S. Marshall Weaver describes 
a method for bending back the bar when unfortunately it 
presses into the soft tissues. A little wax is melted upon the 
bar opposite the impingement. The denture is then invested 
in Spence compound, heavily covering all but the portion of 
wire opposite the wax or that portion impinging upon the 
soft tissues. When the Spence compound is thoroughly 
hard the bar is bent into the space formed by the wax, with 
a punch and mallet. 
SOME PRACTICAL CASES. 
A few practical cases will offer suggestions to the student 
for improvising gold attachments for special cases. 
Fig. 328 shows a cast with clasps attached. Fig. 329 shows 
the same case waxed ready for flasking. 
Fig. 330 shows a partial upper vulcanite to supply the 
teeth distal to the cuspid on one side of the mouth, with all 
the remaining upper teeth closely articulated (knuckled). It 
was necessary to clasp the cuspid, carrying it slightly under 
the gum, as that was the only way of getting a grip on the 480 
GOLD BASE-PLATE 
tooth; besides, the natural gum was exposed when laughing, 
necessitating the clasp being accurately fitted and appearing 
as a cervical filling. The attachment for the other side of the 
mouth consisted of a crib formed by fitting a piece of clasp 
Fig. 329 
Fig. 330 SOME PRACTICAL CASES 
481 
gold plate upon both the buccal and lingual surfaces of the 
first and second molars, and these joined with a U-shaped 
staple of half-round 11-gauge clasp gold wire resting in the 
groove between the molars. 
Fig. 331 
Fig. 332 
Fig. 331 is a bar lower for the same mouth. The teeth are 
missing from the cuspid backward on the opposite side of 
the mouth from the upper shown above. This case required 
a clasp upon the cuspid. Fortunately there was a space 
between the second bicuspid and molar, so the crib was 
formed with a clasp upon both the bicuspid and the molar, 
with a lug resting upon the occlusal surface of the molar. 
Fig. 332 shows the two central incisors with two staple 
cribs. 482 
GOLD BASE-PLATE 
Fig. 333 shows crib and clasp ready for constructing a 
vulcanite denture. These cribs were necessary because 
attachment had to be made to a fixed bridge. 
Fig. 333 
Fig. 334 
Fig. 334 shows a partial lower case with gold clasps 
carrying three natural lower incisors. This method is 
possible when the teeth are recently extracted and free 
from decay. Teeth by this method are usually those lost 
by pyorrheal conditions. The natural teeth must not be 
put through the vulcanizer, as the heat and sulphur will 
completely disintegrate them. The tooth or teeth are cut SOME PRACTICAL CASES 
483 
off the desired length to fill the space and the pulp chambers 
enlarged to loosely admit a 16-gauge clasp gold wire. If 
the tooth is to be attached to a gold base-plate, the wire 
should be aligned and soldered to the base-plate and the tooth 
cemented to the pin with oxyphosphate of zinc. If the teeth, 
as in the case, are to be attached to a vulcanite base-plate, 
a small piece of gold plate is soldered upon the end of each 
of the posts. The cervical end of the teeth are wet with 
water, placed upon the posts, and imbedded and aligned in 
Fig. 335 
Fig. 336 
the softened wax. The wax is conformed and smoothed 
about the teeth, which are lifted off the posts, and the case 
completed in vulcanite. Fig. 335 shows the vulcanite base- 
plate ready for cementing the teeth. 
Fig. 336 illustrates the metal portion of a bar lower with 
a cast shoe for the left bicuspids and molars, a half-cope 
for the right second bicuspid, and spring clasps for the right 
second bicuspid, left second bicuspid, and left second molar. 
A tang is also shown for attaching the missing incisors. 484 
GOLD BASE-PLATE 
Fig. 337 
Fig. 338 
Fig. 339 PLATE DENTURES VERSUS BRIDGE-WORK 
485 
Fig. 337 is a bar lower having two incisors attached with 
vulcanite to a tang. It may be seen that the attachment 
to the right second bicuspid consists of a cope and spring 
clasp. 
Fig. 338 has a cast ferrule telescoping three crowned teeth. 
Fig. 339 illustrates the method of reinforcing the tang of 
the clasp. The tang is attached to the clasp, as shown in 
Fig. 189, and then conformed to the cast. It is removed from 
the cast, supported upon the magnesia soldering block, and 
the reinforcement of wire or a piece of scrap gold plate 
soldered on. This reinforcement is necessary to prevent the 
clasp (in time) breaking from the tang. 
Fig. 340 
If the denture to be repaired is soldered work only, it is 
repaired by investing and soldering. If it is combination 
work of gold and vulcanite and the gold is broken it will be 
necessary to remove the vulcanite, solder, and rebuild the 
vulcanite portion. If it is a clasp broken, which often 
happens, it may usually be repaired by fitting another clasp 
to the tooth, soldering a lug to it to fit into a filed groove in 
the continguous vulcanite, and attaching with vulcanite. 
REPAIRING GOLD PLATE WORK 
PARTIAL PLATE DENTURES VERSUS BRIDGE-WORK. 
Undoubtedly the trend of the times is toward the revival 
of the use of partial plate dentures, and the elimination of 
fixed bridge-work. This is logical and just in view of the 486 
GOLD BASE-PLATE 
Fig. 341 
Fig. 342 
Fig. 343 
Fig. 344 PLATE DENTURES VERSUS BRIDGE-WORK 
487 
Fig. 345 
Fig. 346 
Fig. 347 488 
GOLD BASE-PLATE 
modern status of sepsis and asepsis and accepting as a fact 
the importance of the mouth as a focus of infection. During 
the year, 1916, two notable contributions were made to dental 
literature on partial plate dentures. One by Dr. W. E. 
Cummer,1 Professor of Prosthetic Dentistry and Applied 
Physics, Royal College of Dental Surgeons, Toronto, Can., 
and the other by Dr. J. Wright Beach,2 of Buffalo, N. Y. 
Professor Cummer presents a very complete system for 
partial dentures, consisting of direct and indirect retainers for 
saddle bases. These retainers consist of clasps, lugs-both 
rest and inlocking, and bars-both connecting and extend- 
ing; also crowns, inlays and the Roach ball-and-slit tube 
attachment. 
A study of the following illustrations will explain the 
principles of use and suggest unlimited application. 
Figs. 340 and 341, bilateral restoration, show the simplest 
form of clasp for direct retainer and extension rest stud for 
indirect retainer. 
Fig. 342 shows a more complicated application utilizing 
clasps, slotted inlays for studs and extension rest studs. 
Fig. 343 illustrates the use of the Roach attachment as 
the direct retainer and a double inlocking stud as the indirect 
retainer, for a unilateral restoration. 
The Beach system is essentially a method of retaining 
saddle bases of either vulcanite or gold by bars, clasps and 
stays. The bars, clasps and stays are all made of round and 
oval wire of 11 to 20 gauge. 
A close study of Figs. 344, 345 and 346 will be self- 
explanatory to the practitioners, and will suggest a variety of 
modifications. For the helpfulness of the student it may be 
well to suggest that the festoon stays are made in units and 
the units added one at a time with solder, each clasp is also 
a unit. 
1 "Oral Health" (Toronto) March-April and June, 1916. Pacific Dental 
Gazette, July, 1916. Journal Allied Dental Societies, September, 1916. 
Bulletin California State Society, November 1816. Dental Summary, 
March, 1917. 
2 "Dental Summary" (Toledo), June, 1916. CHAPTER XII. 
TIN BASE-PLATE. 
The cheoplastic or tin method for forming base-plates was 
given to the profession about 1855 by Dr. A. A. Blandy. 
Recognizing that a casting process would provide the most 
perfect adaptation, and that pure tin was an acceptable 
metal to the tissues, the profession readily accepted the 
method. The later methods have been somewhat more 
simple than the earlier one. 
The metal consists of tin alloyed with such metals as 
bismuth, silver, gold, and possibly cadmium and antimony. 
Several of the alloys on the market were proprietary, and 
their composition not published. The formulas of the 
published ones are: 
Kingsley's alloy: Tin, 16 ounces; bismuth, 1 ounce. 
Reese's alloy: Tin, 20 parts; gold, 1 part; silver, 2 parts. 
Bean's alloy: Tin, 95 parts; silver, 5 parts. 
Watt's and Weston's alloys, proprietary preparations, are 
the principal ones on the market. These are both low fusing 
(about 400° F.) and interchangeable in manipulation. The 
method is mostly confined to lower dentures. Since the 
introduction of successful casting of pure aluminum there 
will be less occasion for its use. As the aluminum casting 
is better understood, it should entirely supersede the tin 
alloys, as it is much stronger, more cleanly and durable than 
the tin alloys. 
Technic. - The same investment compound used for 
casting aluminum serves for the tin alloys. The necessary 
implements are a Watt flask (Fig. 347) and a ladle or large 
spoon. 
The wax model is formed the same as for an aluminum 
base-plate, flasked in the first half of the flask (Fig. 348), 
489 490 
TIN BASE-PLATE 
paying no attention to the gates B and C at this time; and 
when the investment is hard, varnish and fill the second 
half, having the wax model wet and jarring the investment 
compound well into place. The flask is opened the same as 
a vulcanite flask (Chapter VI) and wax removed. The 
investment material is removed from the funnels and a small 
and large gate cut as shown at B and C respectively. The 
two sections of the flask are placed over a piece of sheet-iron 
Fig. 348 
on the gas stove and dried until no steam is given off. They 
are then bolted together, and an ingot of the tin alloy melted 
in the ladle or spoon over a Bunsen burner and poured into 
the large gate until the metal appears at the small gate. 
Should there be any bubbling the flask should be grasped 
by the handle and lightly jarred against the bench until 
the bubbling ceases. The casting should stand until it is 
cold, and then be opened. However, after the metal has 
partially cooled, it may be placed in cold water and the TECHNIC 
491 
cooling expedited. The sprues are cut from the casting 
with a mechanical saw, and the filing done with a vulcanite 
file. It is polished the same as vulcanite. 
Fig. 349 CHAPTER XIII. 
CONTINUOUS GUM DENTURES. 
By this term is meant a base-plate of platinum, the outer 
surface of which is covered with a continuous layer of 
porcelain. 
It is true, the term might equally well, or better, be applied 
to vulcanite or celluloid; but the term was applied to the 
enamelled platinum before the introduction of the other 
materials, and is universally accepted as applicable to the 
enamelled platinum only; therefore to call any other mate- 
rial by this name is a manifest deception. 
The French were the earliest experimenters in porcelain 
work for artificial dentures; but it remained for Dr. John 
Allen, of Cincinnati, and later of New York City, to perfect 
the material and method of construction. He perfected the 
process in 1846. The furnace work of the early days was 
difficult and hazardous. Within a decade of the invention 
of continuous gum work vulcanite was placed before the 
profession. Because of its inexpensiveness and ease of 
construction it nearly drove the more expensive and better 
methods from the field. However, in the last quarter of a 
century the facilities for constructing dentures of the better 
quality have been so much improved that they are gradually 
coming into their own. So much so that any student who 
is desirous of equipping himself for practice among the better 
class of patients should be thoroughly conversant with the 
construction and merits of continuous gum dentures. It is 
without doubt the most cleanly, healthful, and esthetic of 
any material or denture placed in the mouth. It is composed 
of mineral matter only and these of the greatest purity and 
compatibility to the human economy. The materials enter- 
ing into its composition are platinum, iridium, gold, and 
high-fusing porcelain. 
492 EQUIPMENT 
493 
Porcelain.-Porcelain suitable for this work is procurable 
at the supply houses. It is known as "Continuous Gum 
Body" and "Gum Enamel." The body is in boxes contain- 
ing one ounce each, and the enamel one-half ounce to the 
box. Close's product (modified Allen formulas) is the one 
Fig. 350 
most commonly used. The body fuses at 2300° F., and the 
enamel about 100° lower. They are of the same composition, 
with more flux, as porcelain teeth. 
Equipment.-For an office equipped for gold work nothing 
is required except a furnace for baking the porcelain. If 
the electric current is to be had, one of the various electric 494 
CONTINUOUS GUM DENTURES 
furnaces upon the market is to be preferred; otherwise a 
gasolene-burning furnace, of which there are several makes. 
To Dr. L. E. Custer, Dayton, Ohio, belongs the credit 
of inventing and demonstrating the first dental electric 
furnace. His first demonstration was before the Ohio State 
Dental Society in 1894. Since that date other furnaces 
possessing excellent features have been invented, but none 
have surpassed the Custer furnace in scientific construction. 
Fig. 351 
Fig. 349 shows the furnace and illustrates the method of 
wiring so as to produce an economical and evenly distributed 
heat. 
An auxiliary instrument to the furnace is the pyrometer. 
To Dr. Weston A. Price, of Cleveland, belongs the credit of 
adapting this instrument to the dental furnace. Fig. 350 
shows the Price furnace and pyrometer complete. The 
instrument is the thermopile adapted to this special use, and 
requires little experience to fuse the porcelain well; however, 
judgment must be exercised even with this perfect instru- 
ment. Without the pyrometer the operator must depend TECHNIC OF CONSTRUCTION 
495 
upon his eye to determine the heat. Either with or without 
the pyrometer the operator must have a definite method of 
manipulating the rheostat, and use judgment. The voltage 
of any current varies within certain limits, which will have 
an influence indicated by the pyrometer, and in connection 
with the rheostat can be better controlled than by the eye. 
Nevertheless, an operator of average discernment and ability 
Fig. 352 
should, with a little experience, be able to produce excellent 
results with an electric furnace, either with or without the 
pyrometer. 
Fig. 351 shows one of the gasolene furnaces. 
TECHNIC OF CONSTRUCTION. 
Plaster impression, cast, model, die, and counter-die are 
required, the same as for a full-gold denture. 
A base-plate of pure platinum 32-gauge (B. & S.) is 
formed. Care should be taken (well-oiled die and counter) 
not to contaminate the platinum with base metal. The 
base-plate swaged and trimmed is tried in the mouth and 
tested for palatal length, and freedom from impingement 
upon the muscle attachments. The peripheral border per- 496 
CONTINUOUS GUM DENTURES 
fected and the adaptation inspected, it is returned to the 
die for forming a reinforcing piece for the palatal border. 
Should the adaptation not be satisfactory, it must be cor- 
rected, at this stage of construction, even to the extent, if 
necessary, of obtaining a new impression and constructing a 
new die and counter. 
The palatal reinforcement should be | of an inch wide in 
the median line and slightly taper toward and terminate at 
the tuberosities (Figs. 353 and 355). This doubler is swaged 
of 30-gauge (B. & S.) pure platinum. After being swaged 
it is placed upon the base-plate and swaged. The anterior 
border of the doubler is turned up with pliers at an angle 
of 45 degrees so that in the finished piece the porcelain will 
be engaged under this edge of the doubler. The doubler 
will be distorted in bending the edge; this is corrected by 
wiping, pickling, annealing, and burnishing the doubler 
to the base-plate. The bending and burnishing are alter- 
nated until suitable adjustment is obtained. The base-plate 
and doubler are cleansed and clamped together with wire 
clamps; pure gold, 35-gauge, cut in small pieces, is placed 
without flux, under the turned edge and melted with the 
blowpipe so as to draw the gold as solder outward and 
perfectly attach the doubler to the base-plate. An 18- 
gauge iridioplatinum wire is soldered with 35-gauge pure 
gold to the periphery of the plate, from tuberosity to tuber- 
osity, in the same manner as wiring a gold plate. The 
charcoal soldering block should not be used, as carbon is 
detrimental to platinum. The magnesia or asbestos block 
will serve the purpose. Flux is unnecessary as a cleanser, as 
noble metals only are used; but it may serve to hold the 
solder in place. No more gold should be used in continuous 
gum dentures than is necessary to unite closely fitted 
joints. Some advocate the use of platinum solder (gold 
with 20 to 25 per cent, of platinum) and the oxyhydrogen 
blowpipe for soldering platinum for continuous gum den- 
tures. This is quite unnecessary, as the pure gold will alloy 
with the platinum base-plate while baking the porcelain; 
however, close-fitting joints are necessary, probably more 
so with pure gold used as solder than with platinum solder. TECHNIC OF CONSTRUCTION 
497 
The reinforced platinum base-plate is used in obtaining 
the wax occlusion and contour models, and mounting upon 
the antagonizor. Teeth suitable for the case (Figs. 218 
and 352) are selected and mounted in wax. The case is 
ready for trial in the mouth. It should be inspected for 
adaptation, contour, and cosmetic effects, which being 
satisfactory, the case is ready for soldering the teeth to 
the base-plate. 
Fig. 353 
Soldering the Teeth.-It is quite essential that the waxed 
trial denture should be well contoured to develop all the 
restorations required. A record is made of the thickness of 
the gum portion at the median line, at the center of each 
cuspid eminence, and of the buccal contours (if any are 
required) by measuring with calipers and making indicative 
marks on paper. The wax is cut away with a warmed wax 
knife, from the labial and buccal surfaces, leaving the wax 
on the lingual surface intact to support the teeth while 
investing (Fig. 353). 
An investment suitable for this work is composed of any 
coarse silica compound and approximately one-fifth of its 
bulk of asbestos;'either the long fiber or the short (tenax) 
fiber may be used. A soft-iron wire ring of 15 gauge is 
formed to place about the denture in its largest plane and 
be free of contact by | inch at every point. A sufficient 
quantity (half-bowlful) of investment is wet up to a soft 498 
CONTINUOUS GUM DENTURES 
putty consistency. The intaglio of the denture is filled and 
a portion quickly spread over the labial and buccal surfaces 
Fig. 354 
Fig. 355 TECHNIC OF CONSTRUCTION 
499 
of the teeth; the balance of the investment is spread on the 
flat surface, upon which plaster casts are formed; the par- 
tially invested case, with its exposed surface upward, is 
pressed into it so that the most prominent points are covered 
by at least | inch; the wire ring is placed about opposite 
the cervical portion of the teeth; and the spatula used to 
draw the spread-out investment up over the wire ring and 
the morsal ends of the teeth, so that all will be strongly 
covered. The wire serves two purposes, as a strengthener 
and as a guide to thickness. When the investment is hard 
it is set in a warm place to dry and soften the wax, which 
is picked out and the pins of the teeth bent upward. Fig. 
354 shows the invested case with the lingual surface of the 
base-plate and the teeth exposed; also some of the pins are 
seen bent upward. 
Reinforcing Wire.-A 12-gauge iridioplatinum wire is bent 
to fit closely under the pins of the teeth and with the 
ends in contact with the tuberosities. The long platinum 
pins of the teeth are bent around the reinforcement wire, 
thus holding it securely in place. The ends of a truss wire, 
of iridioplatinum 18-gauge, is placed in contact with the 
reinforcing wire in the proximity of the cuspids, and with 
its center resting upon the base-plate in the median line 
near the crest of the alveolar ridge. A small piece of pure 
gold (for solder) is placed at each point of contact of the 
wires, pins, and base-plate. The case is heated up to bright 
redness, when the gold is thoroughly fused with the needle 
flame of blowpipe. Figs. 355 and 356 show two views of 
the case, soldered and removed from the investment; thus 
giving a better idea of the palatal reinforcement, peripheral 
finishing wire, lingual reinforcement, and truss wires as 
soldered together. The case should be tried upon the die, 
and if warped it must be readjusted by pressure with the 
fingers, and by the aid of the horn mallet, copper hammer, 
and plate burnisher. However, if the case has been properly 
handled there should be no warpage. The skeleton denture 
is cleansed with a laboratory plate brush and water. It is 
placed upon the antagonizor for assurance that the teeth are 
in proper occlusion. 500 
CONTINUOUS GUM DENTURES 
It is apparent that the peculiar formation of the porcelain 
teeth, designed for continuous gum dentures, is for a purpose. 
The single long pin is to furnish a flexible attachment, and 
Fig. 356 
the root portion of the artificial tooth is to provide contact 
with the base-plate; also as an aid in contouring, and in 
controlling the shrinkage during the enamelling. When 
Fig. 357 
testing the occlusion if any of the teeth are found misplaced 
they may be brought into position by bending the platinum 
pins, although soldered to the reinforcement wire. At the TECHNIC OF CONSTRUCTION 
501 
same time the root portion of the tooth should be in contact 
with the base-plate; nevertheless, if either end of the tooth 
Fig. 358 
Fig. 359 502 
CONTINUOUS GUM DENTURES 
is to be out of the ideal position, it should not be the morsal 
end. Fig. 357 shows a case wherein the apices could not be 
in contact with the base-plate and Fig. 358 shows the 
occlusion. 
APPLYING THE PORCELAIN. 
Body.-A portion of continuous gum body (about | 
ounce) is saturated with water to the consistency of stiff 
mud, and a portion applied with a thin spatula to the base- 
plate about the apices of the teeth. The case is lightly 
held by the index finger and thumb of the left hand, and the 
body jarred and settled into place by tapping with a light 
instrument upon the periphery of the base-plate. More 
body is added and jarred until all space between the base- 
plate, reinforcement wire, and teeth is compactly filled. 
The excess moisture upon the surface, after each jarring, 
is absorbed with a napkin. The buccal, labial, and lingual 
surfaces are covered with the body; a portion at a time is 
covered with the napkin and compressed between the thumb 
and finger, the finger in apposition to the maxillary surface. 
Care should be exercised that no portion is more thickly 
covered than is desired for the completed denture, and no 
attempt should be made at contour. Any body material 
upon the base-plate or teeth when not required must be 
removed. A pointed thin-blade spatula and a small ox-hair 
brush will be useful, also an artist's medium-small pencil 
brush moistened and drawn to a point (between the lips) is 
useful in making a clean-cut gum outline. 
Controlling Shrinkage.-As porcelain shrinks about one- 
sixth of its volume in fusing, it must be controlled, or the 
teeth will be drawn out of place. It is controlled by slitting 
the body so that it will draw about fixed centers. This is 
done with a thin spatula, cutting entirely through the body 
to the base-plate, thus making each tooth a fixed center. 
Fig. 359 shows the lingual surface slit. Fig. 360 shows the 
large spaces formed on the buccal surface by the slitting, 
and shrinkage in baking. 
First Baking.-With a Custer furnace the case is placed 
in the furnace with the teeth upward. The lever of the APPLYING THE PORCELAIN 
503 
rheostat is advanced one stop and the case given ten minutes 
to dry, after which the lever is advanced two stops every five 
Fig. 360 
minutes, and upon the last stop it is left for one to ten min- 
utes, as may be necessary to produce the "biscuit" bake; 
that is, granulated with a very slight glazed appearance. 
The time will vary with the condition of the current and the 
Fig. 361 
number of times the furnace is opened for inspection. If a 
pyrometer is being used the lever must be advanced to bring 504 
CONTINUOUS GUM DENTURES 
the heat to the desired temperature in a given time, which 
should be established for each current supply and furnace. 
Every make of furnace will furnish instructions for use. The 
current is turned off and the furnace opened for a minute or 
two to stop the fusing, when it is closed until cold. The 
denture is placed upon the cast, and if warped it must be 
corrected. The anterior edge of the palatal reinforcement 
is burnished down. Checking of the body does no harm. 
Second Body.-The case, being cold, is wet and body 
applied to fill all spaces caused by shrinkage, jarred, and 
excess moisture absorbed with the napkin. Body is then 
added to form all contours. The crest of each eminence 
should be the full thickness of its corresponding caliper 
record, for the shrinkage will provide space for the glazing 
enamel. Any large restoration will require exaggerated 
body additions, as the shrinkage will be greater than the 
enamel added. 
Second Baking.-The case is placed in the furnace, dried, 
and heated up the same as the first time, but carried to a 
higher degree of fusion than the first time (probably about 
50° F. higher). The fusion is checked, and furnace closed 
until cold. 
The case is examined for shrinkage; if there are small 
shrinkage spaces only they are filled in with body and not 
baked, but if there are large crevices the case should be 
baked again at about the temperature of the first bake. 
Enamelling.-As all contours, including gum margin 
festoons, and rugae, with their corresponding depressions, 
were developed in the second coat of body, it is necessary only 
to place over the surface a smooth layer of gum enamel 
to produce the light and dark shading characteristic of 
artistically constructed continuous gum dentures. The 
entire surface of the body should be covered with the gum 
enamel wet with water and smoothed with an oval-faced 
burnisher. The gum margin must be neatly pencilled and 
all granules of the gum material removed from the teeth. 
Third Baking.-Ordinarily two bakings only will be 
required for the body and one for the enamel. The enamel 
coat should be heated up with the same care as the body APPLYING THE PORCELAIN 
505 
and fused until the surface has a "watery" appearance when 
looked at across the surface, in the hot furnace. The furnace 
is opened long enough to stop the fusion, closed, and left 
until cold. 
Fig. 362 
Polishing.-The porcelain will come from the furnace 
with a perfect polish, but the platinum may be buffed with 
Fig. 363 
the felt buffer and pumice, and glossed either with the soft 
brush wheel and whiting, or burnished. Figs. 361 and 362 
show the completed work. 506 
CONTINUOUS GUM DENTURES 
Fig. 363 shows a continuous gum section of five teeth 
attached to a vulcanite base; also the clasps. 
Fig. 364 
REPAIRING. 
Continuous gum work lends itself to the most perfect 
repair of any artificial denture. It must be first burned out, 
that is, scrubbed with soap and water, invested completely 
in the silica-asbestos compound, heated up gradually to a 
high red heat so as to remove all organic matter; when new 
material may be added and fused securely to the old. 
A broken tooth may be repaired by building up with any 
of the moderately high-fusing enamels used in inlay work, or 
by grinding out the remains of the tooth, setting in either a 
continuous gum or vulcanite tooth packed with body and 
baked; gum enamelled and baked. At all bakings the same 
attention (as described) should be given to heating and 
tempering (cooling) the porcelain. 
Cracks are repaired by placing on a cast, chipping off the 
porcelain about the crevice, then fill and bake. CHAPTER XIV. 
INTERDENTAL SPLINTS. 
An interdental splint is an appliance made of either metal 
or vulcanite and placed between the jaws to support a 
fracture of either or both the maxilla and mandible. 
Interdental splints in conjunction with submental com- 
pressors and occipitomental bandages have been used by 
surgeons in the treatment of fractured jaws since 1780. 
Drs. F. B. Gunning, of New York, and J. B. Bean, of 
Atlanta, Ga., were the first to describe methods of construct- 
ing interdental splints of vulcanite. 
When a dentist is called upon to construct an interdental 
splint it will be in consultation with a surgeon. He should, 
in justice to himself, make a critical examination of the 
case and determine if an interdental splint is indicated or 
if some other method will better serve the patient. If the 
fracture is of the maxilla only, and the teeth are nearly all 
in situ, it is quite probable that forcing the fractured portions 
into place and holding the lower teeth firmly against them 
with a cotton-padded external plaster splint and bandage is 
the preferable method of treatment. Fracture of the 
mandible may be best treated by binding the teeth of the 
mandible to those of the maxilla with bands and wires 
designed for orthodontia purposes, in conjunction with an 
external plaster compress and bandage. If the patient is 
wearing a full upper and lower artificial denture, the dentures 
may be securely united with vulcanite, the upper incisors 
removed for a feeding space, and used for the splint. How- 
ever, if an interdental splint is determined upon it should be 
constructed as recently described by Dr. George B. Snow, 
of Buffalo. 
507 508 
INTERDENTAL SPLINTS 
THE CONSTRUCTION OF INTERDENTAL SPLINTS. 
Interdental Splint.-"An interdental sp'int, when properly 
constructed, forms an efficient and satisfactory means for 
treating fracture of the mandible, and the Snow face bow 
and New Century or Gritman antagonizor are absolutely 
necessary for the attainment of the correct alignment of 
their occluding surfaces. For this reason a short description 
of the correct method for this construction is appended. 
"These instructions apply to the construction of the 
'Gunning' splint. This separates the jaws and receives 
both the upper and lower teeth. It is retained by means 
of bandages, and fixes the mandible immovably. It has a 
wide range of application, and is the most satisfactory splint 
for general use. The Snow face bow is absolutely necessary 
for its construction, as the casts must be placed in the antago- 
nizor at the same distance from its joints that the alveolar 
ridges are from the condyles, or the bite cannot be opened 
for the reception of the splint with any certainty of having 
correct occlusion when the fracture has united. The fact 
that the Snow face bow has not been used is the common 
cause of failure in interdental splints, as they have hereto- 
fore been constructed. 
" Impressions of the teeth, both upper and lower, are first 
to be secured. These are better made in plaster, rather than 
modelling compound, for the plaster is more easily managed 
and is less subject to distortion. Very shallow impression 
trays should be used, the B mouthpiece of the face bow 
answering the purpose, and only plaster enough used to 
obtain an impression of the teeth to the gum line. No 
attempt need be made to correct any deformity which may 
be present, and the operation, if properly conducted, will 
be almost painless to the patient. The impression must 
take in all the teeth present in the mouth, for if the third 
molars are not included, they will not be covered by the 
splint, and will elongate while it is in use, and so interfere 
with occlusion. Fill the palatal portion of the upper impres- 
sion with sheet wax or paper just above the gingival line 
and run a thin cast. Run a thin horseshoe cast in the lower CONSTRUCTION OF INTERDENTAL SPLINTS 
509 
impression. With a Swiss saw cut this cast at the point of 
fracture, and adjust the parts so that they make correct 
occlusion with the teeth on the upper cast. Secure the two 
casts together with a very little sticky wax. Run a little 
plaster on a piece of paper and set the lower cast into it, 
to hold its parts in their correct relation. 
"After taking the impressions, place a little soft wax in 
the B mouthpiece and use the face bow as heretofore directed. 
Place the upper cast in the antagonizor by means of the 
face bow, and it will be at the correct distance from the 
antagonizor joints, and when the lower cast is antagonized, 
their separation to accommodate the splint can be safely 
made, and normal occlusion secured when fracture has 
united. 
"Cover the teeth with No. 60 tinfoil, letting the tin 
extend beyond the teeth, buccally and lingually, and cutting 
the tin so that it can be put on without crumpling. Follow 
with one thickness of sheet wax, covering the teeth, both 
upper and lower, to the gum line. Separate the two wax 
plates (open the bite), so that a lead-pencil will pass between 
them in front. Connect them at the sides with wax, leaving 
an opening in front extending from cuspid to cuspid. 
" A No. 3 Snow flask (or a box flask) will receive both 
casts and splint. Set one cast, the splint being in place, 
the plaster covering the edge of the wax, both buccally and 
lingually. Trim and soap not only the usual parting sur- 
faces of the invested cast, but the splint and palatal surface 
of the other cast as well. Holding the loose cast upon the 
splint, run plaster into the space between the two casts, and 
build it up around the sides and rear to the edge of the wax. 
Trim to an incline to the edges of the flask all around. Soap. 
Place on ring and fill. When separating the flask have it 
warm enough to soften without melting the wax. Rap the 
edge of the flask to dislodge the centerpiece. Remove 
and save the wax, and find quantity of rubber required by 
imnlersing the wax in a glass of water. Pack and vulcanize. 
The tinfoil being left upon the casts, the impression of the 
teeth in the splint will be smooth, and also larger than the 
teeth themselves by the thickness of the foil used. This 510 
INTERDENTAL SPLINTS 
is why the use of thick foil is directed, as the additional 
space gained by it renders the splint more. easy of adjust- 
ment." 
Fig.' 365 
Fig. 364 represents both the wax model splint and the 
finished vulcanite. Fig. 365 is a diagram showing a cross- 
section of the flashed case. The flask is designated by F; the 
Fig. 366 
casts, M; the plaster encasement by P; tinfoil covering the 
teeth with extension beyond the wax splint by T; and the 
wax model of splint in the center. CONSTRUCTION OF INTERDENTAL SPLINTS 
511 
Fig. 366 illustrates a splint provided with arms of steel 
wire, I inch in diameter, arranged to come "out of the 
mouth when the splint is in position, passing back along 
the cheek on a line with the teeth." This splint was 
invented by Dr. Norman W. Kingsley, and the description 
of it is from his valuable work on Oral Deformities. The 
splint is retained in position by the submental compress 
attached to the side bars. 
Fig. 367 
"It will be seen that this splint covers the lower teeth 
only, and that its top occludes with the upper teeth to admit 
of mastication. The construction of such a splint is accom- 
plished by placing upper and lower casts in an antagonizor, 
forming the wax splint as before described, arranging the 
occlusion so that the contact of the upper teeth will be 
uniform, imbedding two stout wires with flattened ends 
in the wax, so that they will bear the strain which will be 
required of them while the splint is in position. The par- 
ticular flask best adapted for the vulcanizing of interdental 
splints is oblong in form, and is larger than ordinary vulcanite 
flasks; it is known as the box flask." CHAPTER XV. 
CLEFT-PALATE APPLIANCES. 
By cleft-palate is meant a defective condition of the roof 
of the mouth, forming an abnormal opening between the 
oral and nasal cavities. The cleft may be of the form of a 
fissure or of a rounded hole. The cleft may be either con- 
genital or acquired. The congenital cleft is due to defective 
fetal development, but not accounted for. The acquired 
cleft may be due to either accident or disease. The extent 
of the cleft may be from a slight cleft of the uvula to one 
extending through the soft and hard palates and the alveolar 
process; also may extend through the lip (hare-lip). If there 
is no hare-lip complication, the defect is noticeable only in 
speech, in which there is an unmistakable nasal intonation. 
The defect is amenable to both surgical and mechanical treat- 
ment, the latter of which only is considered in this chapter. 
Apparatus.-There are two types of apparatus for restoring 
the defects of the roof of the mouth, known as obturator and 
velum. Of these, Dr. N. W. Kingsley says: "An obturator is 
a stopper, plug, or cover, hard, non-elastic, and stationary, 
fitting to an opening with a well-defined border and shutting 
off the passage. Such instruments are applicable to perfora- 
tions of the hard or soft palate resulting from accidents or 
disease, but they are rarely applicable to a congenital fissure 
of the velum. An artificial velum is not a temporary stopper, 
but an elastic, movable valve under the control of the 
surrounding adjacent muscles, closing or opening the pas- 
sage at will, and is applicable to congenital fissures, occasion- 
ally where the soft palate has been destroyed, but never to 
perforations of either the hard or soft palate." 
Dr. Kingsley further says: "In most cases of congenital 
defects, the patient will acquire correct articulation more 
easily and more certainly with an elastic velum scientifically 
512 APPARATUS 
513 
adjusted than with any other form of appliance, because it 
more nearly resembles the action of the normal palate and 
will more readily fulfil its function. 
"That in a great majority of cases of a like defect a patient 
will never acquire distinct articulation with an obturator. 
"That where a patient afflicted with a congenital absence 
of the palate has overcome the difficulty by using an artificial 
velum until clear and distinct articulation has been acquired, 
he may change the velum for an obturator, and continue to 
articulate properly. 
Fig. 368 
"That of all obturators to supply deficiencies of the soft 
palate and induce correct articulation, the one introduced 
by Suersen contains the truest principles and is best adapted 
to the purpose." 
Fig. 3671 gives a view of a patient's mouth, showing part 
of the cleft palate and the appearance of the lip after being 
operated upon for hare-lip. 
1 Figures 357, 368, 369 and 370 are of cases of Dr. Chalmers J. Lyons, of 
the University of Michigan. 514 
CLEFT-PALATE APPLIANCES 
Fig. 368 is an illustration of a congenital cleft extending 
through the soft and hard palatesand also the alveolar process. 
Fig. 369 
Fig. 370 IMPRESSION OF THE CLEFT 
515 
Fig. 369 shows a cleft of the soft and hard palates, and 
alveolar process depressed, but not cleft. 
Fig. 370 shows a cleft of the soft palate only. 
The artificial velum should rarely extend into that por- 
tion of the cleft extending through the alveolar process, 
which may better be filled with the hard vulcanite. 
Fig. 371 
Synopsis of Technic for Constructing Velum and Supporting 
Base-plate.-Impression for velum, cast, preparation of cast 
for making model of velum, making model velum, adjusting 
model velum to mouth, flasking model velum, converting 
plaster encasement into metal encasement, vulcanizing 
velum, finishing velum, impression with the velum in situ 
for the retaining base-plate, constructing the retaining base- 
plate, and attaching the velum. 
Impression of the Cleft.-An ordinary impression tray 
will not suffice for a congenital cleft palate. A spoon with 
the convex surface of the bowl upward well serves for a tray 
to carry the plaster, or one of the two methods described 
by Dr. C. S. Case, of Chicago. He uses the index finger w'ith 
soft modelling compound wrapped about it as the foundation 
for his impression. Having obtained an imprint of the cleft 
in the compound, it is chilled and carved so that it may be 516 
CLEFT-PALATE APPLIANCES 
held in the cleft without contact with the tissues. It is then 
covered with a soft mix of impression plaster, carefully 
Fig. 372 
Fig. 373 
adjusted, and held until set; then removed by forcing it 
backward until relieved of the anterior margin of the cleft. 
Fig. 371 shows the completed impression as taken from the IMPRESSION OF THE CLEFT 
517 
mouth for a cleft of the palate only. The impression is 
varnished and filled, as shown in Fig. 372. Fig. 373 shows 
Fig. 374 
Fig. 375 
the cast after removal of the impression. Fig. 374 shows 
the cast carved for use. Fig. 375 shows the cleft filled with 518 
CLEFT-PALATE APPLIANCES 
Fig. 376 
Fig. 377 
Fig. 378 IMPRESSION OF THE CLEFT 
519 
modelling compound carved to thin edges as a model for the 
velum. Fig. 376 shows the nasal surface of the same. Fig. 
377 shows a side elevation of the model velum. Fig. 378 
Fig. 379 
Fig. 380 520 
CLEFT-PALATE APPLIANCES 
shows the finished velum in the plaster cast. Fig. 379 shows 
the skeleton base-plate upon the plaster cast. Fig. 380 shows 
Fig. 381 
Fig. 382 
F ig. 3^3 ADJUSTING MODEL VELUM TO THE MOUTH 
521 
the wax model base-plate. Fig. 381 shows a side elevation 
of the finished base-plate. Fig. 382 shows a side elevation 
of combined base-plate and velum. Fig. 383 is the lingual 
surface of the same. 
Most of the steps are comprehensible from the illustrations; 
however, there are several that are not and need elaboration. 
Fig. 384 
Velum Model.-The velum model is the first step after 
the impression that needs further consideration. Softened 
modelling compound is shaped in the carved cast by the 
thumb and finger. The anterior or body portion of the 
velum is left thick for a body, while the posterior or curtain 
portion and the flanges are made very thin with attenuated 
edges. This is accomplished, so far as possible, by molding 
the softened material with the fingers, after which it is 
further reduced with a vulcanite scraper and sandpaper. 
It is finished with a cloth wet with a solvent, as alcohol. 
Adjusting Model Velum to the Mouth.-A hole to admit a 
14-gauge wire is drilled through the body of the velum 
model from the oral to the nasal side. A wire with | inch 
of one end bent at right angle is fitted to the drill-hole in 
model; the other end of the wire is looped to form a handle. 522 
CLEFT-PALATE APPLIANCES 
This wire is used to handle the model while adjusting it to 
the cleft. The body of the model should be kept hard, but 
the curtain and flanges may be softened as required by 
dipping in warm water. It is adjusted by the patient 
swallowing, trimming away excessive material, and molding 
with the finger. Additions may be made by tracing on with 
a pencil of modelling compound. The velum must be so 
formed that in the act of swallowing it will entirely close the 
opening between the oral and nasal cavities. The desired 
form and adaptation being obtained, it is chilled and made 
smooth. It is then ready for flasking. 
Flasking the Model Velum.-A small-sized bolted vulcanite 
flask is used. The inner surface of the flask is smoothed of 
any roughness by grinding, and smeared with vaselin so 
that the encasing plaster may be easily removed. The 
model must be so encased in the flask that the sections 
of the encasement plaster may be removed, molded, and 
reproduced in metal. This will require three sections of 
the encasement plaster. Each piece of the encasement 
plaster is flasked in a suitable flask (box) with silica invest- 
ment compound and reproduced either in Babbitt or type 
metal. The operation is simple, but judgment must be 
exercised both in flasking the velum model and the sections 
of the plaster encasement. Fig. 384 shows the three sections 
of the Babbitt metal castings. Fig. 385 shows the bottom 
and middle castings assembled in one-half of the flask and 
the third section in the other half of the flask. 
The encasement in the box flask must be heated to dry 
it of all moisture so that steam will not be formed in filling 
with the molten metal. 
The surfaces of the castings, which are to give form to the 
artificial velum, must be carefully polished and burnished, 
as they should produce a finished surface upon the velum. 
A hole must be drilled in both the upper and lower sections 
of the castings to carry a wire former for the hole in the 
body of the velum to admit the coupling standard, as seen in 
Fig. 385. One end of the wire is cemented into the casting; 
the other end of the wire enters the hole in the other section 
of the casting, but is not fastened. PACKING VELUM RUBBER 
523 
The wire former should be one or two sizes smaller than 
the coupler wire. 
Fig. 385 
The surfaces of the metal mold must be soaped and dried 
each time it is to be used. This is to prevent the velum 
vulcanite adhering too closely. 
Fig. 386 
Packing Velum Rubber.-The metal mold should be as 
warm as the fingers can be held upon without discomfort. 
It is packed, without enmeshing air, with velum rubber 
(caoutchouc, 25; sulphur, 5 parts), and vulcanized, the same 524 
CLEFT-PALATE APPLIANCES 
as hard vulcanite. The packing should be carefully done, so 
as to have as little excess as possible, which will force its 
way out of the metal encasement. 
Finishing the Edges of the Velum.-This can be done only 
by trimming with sharp scissors, searing with a hot iron, 
and rubbing with chloroform. 
Impression for the Retaining Base-plate.-It is necessary 
that the artificial velum should be held accurately in place 
while taking the impression for the retaining base-plate. 
The surface covered by the impression must include the 
thick body portion of the velum, the vault portion upon 
which the supporting base-plate is to rest, and the teeth to 
which the base-plate is to be clasped. The velum is sup- 
ported by means of a 13-gauge soft-iron wire. The end 
of the wire is engaged in the coupler hole and its shaft con- 
formed to the vault and about the buccal surface of the 
teeth, and then protrude from the mouth, the external 
end being looped for a handle. The object is to so bend 
and shape the wire that it will support the artificial velum, 
and that no part of it, except the portion near the cleft, 
shall be engaged in the impression. The selected tray is 
adjusted. Should the palatal portion not extend sufficiently 
backward, it should be extended by an addition of wax or 
modelling compound. The impression is then taken in 
plaster. The impression with the artificial velum in place 
is varnished and poured with silica investment compound. 
Upon this cast the clasps are shaped and the clasp gold- 
wire skeleton is formed. The joinings of the various pieces 
of metal are covered with wax, and the rest of the wire is 
covered with investment compound, leaving the waxed 
joints wide open. The cast about the velum is cut away 
and the velum removed from the coupler wire. Investment 
is added to the exposed end of coupler wire. The case is 
heated and soldered. The skeleton frame with velum 
attached is adjusted to the mouth and impression taken for 
the vulcanite base-plate. The impression should extend at 
least f inch back of the coupler pin. The impression will 
probably be much broken in removing from the mouth. 
The impression and metal skeleton are assembled without the SUERSEN OBTURATOR 
525 
velum and the impression varnished and poured with 
plaster (Fig. 379). 
If a gold base-plate is desired, the first impression with the 
artificial velum in place is poured with plaster (in place of 
investment compound), a die and counter formed, the gold 
base-plate constructed, and the coupler pin attached with 
solder. 
Fig. 387 
Fig. 388 
Fig. 389 
Suersen Obturator.-This obturator is hard vulcanite 
hollow bulb made to fill the cleft, and upon which the 
divided palate glides while speaking and swallowing. The 
principal merit of this apparatus is that it is cleanly and 
durable. Reference has been made to Dr. Kingsley's state- 
ment as to its usefulness. Figs. 386, 387 and 388 illustrate 526 
CLEFT-PALATE APPLIANCES 
three Suersen bulbs (obturators), one of which is attached 
to a base-plate retainer. 
Velum Obturator.-A late invention for the relief of this 
distressing deformity is Dr. Case's velum obturator. This 
instrument consists of a peripheral roll and an intervening 
Fig. 390 
Fig. 391 
septum of velum vulcanite. Figs. 389 and 390 illustrate 
this apparatus. A full detailed description of the apparatus 
is to be found in Dr. Case's book. 
Case's Hard Velum Obturator.1-This is a very ingeni- 
ous and highly successful creation by Dr. C. S. Case. It is 
1 Brophy's Oral Surgery, and Dental Items of Interest, October, 1916. DENTURE OBTURATOR 
527 
adapted to those clefts extending some distance into the hard 
tissue. It is of similar form to preceding velum obturator, 
but is constructed of hard vulcanizable black rubber and 
has no attachment to the teeth. 
Fig. 392 
Fig. 393 
Denture Obturator.-Figs. 391 and 392 show two views of 
a cast aluminum denture obturator made necessary by a 528 
CLEFT-PALATE APPLIANCES 
surgical operation for the removal of a tumor of the maxil- 
lary sinus. 
Figs. 393 and 394 are two views of an obturator made 
necessary for a case in which the entire left maxillary bone, 
except the orbital plate, was removed because of a sarco- 
matous growth. When the patient was first seen the opening 
Fig. 394 
Fig. 395 
made by the operation extended from the mouth to the 
pharyngeal cavity. It was about f inch in diameter and 
circular in form. Fortunately the left palate bone and soft 
palate were intact. The cicatrix had completely everted 
the lower lid and greatly depressed the cheek. DENTURE OBTURATOR 
529 
Figs. 396 and 397 show the face with the appliance removed 
and in place. The appliance is never out of the mouth 
longer than necessary. It is difficult and painful to replace 
it when it has been out a few hours. 
There are two technic operations of interest in this 
case, taking the impression and stretching the cicatricial 
tissue. 
The hole in the roof of the mouth was filled with slightly 
warmed yellow wax. This made the margin of the cavity 
quite tense. A plaster impression was obtained, the wax 
Fig. 396 
Fig. 397 
removed from the hole and attached to the impression; 
from this a Spence plaster compound cast was obtained 
and a pure black vulcanite base-plate made. The denture 
was completed by the double vulcanization method. After 
the patient had become accustomed to the appliance and 
the mouth was free from soreness, resinous wax (sticky wax) 
was added to such portions of the obturator as necessary 
to distend and stretch the tissue in the desired direction. 
This was inserted into the mouth while the material was 
plastic, but not hot, then removed and chilled, another por- 530 
CLEFT-PALATE APPLIANCES 
tion added and chilled, until the tissues were distended as 
much as was prudent for the time. This was worn one 
night and the next day flasked in a box flask and the wax 
restoration replaced with pink rubber. This severe stretch- 
ing invariably made the mouth quite sore, but the patient 
was very persevering and would not return to the office 
until the mouth was entirely healed. The patient was 
equally persevering in keeping the apparatus clean. This 
procedure was repeated probably ten times, once after these 
pictures were taken. The dark lines show additions made. 
THE MITCHELL PALATE AND VOMER RESTORATION.1 
"The object in presenting this subject is to show by actual 
demonstration the possibilities in the improvement of voice 
and speech, in the class of oral defects, by means of an 
artificial substitute for the missing tissues, and the advan- 
tage of such a procedure over surgical operations. 
"Science has been unable as yet to solve the problem as 
to the causes. Many theories have been advanced, such 
as faulty nutrition, heredity, and maternal impressions. 
"There are two reasons for attempting to correct this 
defect, either surgically or mechanically: First, the improve- 
ment of the general health; and second, the improvement 
of the voice and speech. Nature intended that we should 
have separate channels for the air we breathe and the food 
we eat. We know that this is so because of the difference 
in the anatomical formation of these cavities. Provisions 
are made in the nasal passages for the warming, moistening, 
and filtering of the air before it passes into the lungs. The 
oral cavity does not supply these requirements. On the 
other hand, the highly sensitive mucous linings of the 
nasal passages are most unsuitable for the passage of the 
different foods. In cleft-palate cases some food necessarily 
1 The following excerpts are kindly permitted by Dr. Vethake E. Mitchell, 
of New York City, and are from a paper read before the Oral Surgery 
Section of the First District Dental Society at the Academy of Medicine, 
March 25, 1913. The paper was published in full in the Dental Digest, 
October, 1913. MITCHELL PALATE AND VOMER RESTORATION 
531 
passes through a part of the nasal passages, and by con- 
stant irritation produces a catarrhal condition of these 
tissues, and secretes a viscid mucus which contaminates 
the air breathed and the food eaten by these patients. But 
this is not all: These unfortunates are conscious that their 
defect is announced whenever they attempt to speak. This 
has a deplorable effect upon their physical and mental 
development. 
Fig. 398 
" Secondly: The palate is one of the most important organs 
of speech. Its functions are concerned in the forming of 
the tone of the voice by regulating the shape and size of the 
resonance chambers, and to close off the nasal passages in 
the emission of certain sounds. This being impossible to 
a greater or lesser extent in cleft-palate cases, speech is 
very defective and gives it that peculiar quality which all 
can recognize. 
"To understand more fully the tissues involved and their 
functions, let us refer to Figs. 398, 399 and 400. 532 
CLEFT-PALATE APPLIANCES 
"Fig. 398 shows the nasal cavities with the turbinated 
bones, superior, middle and inferior, on either side, each 
forming a resonance space, and when separated by the sep- 
tum, with the hard palate beneath, forming six distinct 
resonance spaces. 
Fig. 400 
"Fig. 399 shows these spaces better. 
"Fig. 400 shows also the large nasopharynx, another 
resonance cavity, regulated as to size and shape principally MITCHELL PALATE AND VOMER RESTORATION 
533 
by the soft palate and uvula. Here can be seen also the 
oral cavity, still another resonator, with the tongue, soft 
palate, lips, and teeth-all concerned in the production of 
voice and speech. 
"The cartilage of the septum (McClellan's Regional 
Anatomy) is a smooth, triangular plate inserted posteriorly 
into a groove in the perpendicular plate of the ethmoid 
bone: Anteriorly, where it is thicker, it is connected with 
the nasal bones and adjacent lateral cartilage, and below 
with the vomer and palatal processes of the superior maxil- 
lary bones. The septal cartilage separates the anterior 
portion of the nasal cavities. The inner wall is the smooth 
septum formed principally by the perpendicular plate of 
the ethmoid bone, the vomer bone, and the septal cartilage. 
"Appliances of many shapes and of different materials 
have been devised for the closure of the cleft, but with 
apparently little regard for the restoration of the nasal pas- 
sages, to permit normal respiration, or the restoration of the 
resonance chambers for the improvement of voice and speech. 
" In the appliance which I present to you, all these things 
have been taken into consideration, and an attempt has 
been made to restore all missing tissues and their functions. 
"The history of a case is as follows: 
"Miss K , aged thirty-one, second of four children. 
No deformity in any other member of the immediate family. 
Mother healthy, slightly tongue-tied. Father healthy. Her 
physical condition is good, but slight of build and undersized. 
DESCRIPTION OF CLEFT. 
"A division extends through the uvula, the soft and hard 
palates to the alveolar process. Width of cleft, at posterior 
border of hard palate inch. Vomer bone entirely missing. 
"At nineteen an obturator was made and considerable 
improvement in speech resulted. This was worn for seven 
years, when a second obturator was constructed on the 
same style. This was worn for almost five years. The case 
was then referred to me to see what further improvement 
could be accomplished. 534 
CLEFT-PALATE APPLIANCES 
"A plaster impression of the mouth was taken in two 
sections, first by filling the posterior nasal cavity and cleft 
with plaster, to which had been added a little asbestos 
fiber, and allowing it to harden. This was easily removed by 
slight pressure directed backward, downward, and forward. 
That portion representing the roof of the mouth was prepared 
so as not to adhere to the second part of the impression, but 
with guides, so that the two parts could easily be fitted 
together. It was then returned to its position in the mouth 
and the second part of the impression taken in plaster, as 
an impression is taken in orthodontia. After hardening, 
all parts were removed, placed together in their proper 
relation, and a model made. 
"A second impression and model are necessary for the 
swaging of the metal plate. 
" Gold was used in this case, but silver or platinum could 
be used when advisable. It could also be constructed entirely 
of hard rubber, but for strength and thinness a metal plate 
is desirable. 
"The cleft in the model is filled in, dies are made, and 
the plate swaged to cover the hard palate only. Clasps to 
go about the teeth are attached to the plate on either side, 
giving a firm attachment for the plate. To the nasal surface 
of the plate covering the cleft, four metal loops are soldered, 
for the attachment of the hard-rubber production of the 
lost bony tissue. 
"With base-plate wax an artificial vomer was formed in 
the model. Its upper margin was closely adapted to the 
remnants of the septum. Its lower margin was adapted 
to the upper or nasal surface of the metal plate. This lower 
margin was spread out and thickened to replace the lost 
tissues of the hard palate. This was tried in the mouth to 
be sure of its close adaptation to the tissues. 
"After imbedding in the wax at the posterior border that 
portion of the hinge intended for this part of the appliance, 
it was flasked and reproduced in hard rubber. 
" The next step is to close the cleft in the soft palate with 
something that will stay in position and keep the cleft closed 
during the muscular movements of the palatal tissue. A MITCHELL PALATE AND VOMER RESTORATION 
535 
piece of base-plate wax was doubled and shaped to fit the 
cleft snugly from side to side. This forms the roof of the 
mouth and the floor of the nasal passages. It widens out 
as it extends backward, forming a flange on either side. 
This flange laps over the upper edges of the palatal tissue. 
"The other part of the hinge is imbedded in the anterior 
portion of the piece which is to close the cleft in the soft 
palate. The piece for the soft palate is then attached to 
the plate by putting the pin through both parts of the hinge. 
Fig. 401.-Model of the mouth. 
The whole appliance in this stage is then placed in position 
in the mouth. By careful trimming or adding the wax of 
the soft-palate piece is given proper shape. 
"It must extend back sufficiently and be so shaped that 
when raised by the muscles in the act of swallowing, it will 
touch the posterior wall of the pharynx so as to close the 
passage into the nasal cavity. This part is then reproduced 
in hard rubber, faced with pink, to more resemble the palatal 
tissues. 
" Being solid, it has sufficient weight to keep it in position 
when the palate muscles are relaxed, and still is not too 536 
CLEFT-PALATE APPLIANCES 
heavy for them to raise when contracting. This movement 
is possible owing to the hinge joint. The whole appliance, 
Fig. 402.-Mouth showing 
cleft. 
Fig. 403.-Mouth with appliance 
in position. 
Fig. 404 
Fig. 405 
Figs. 404 and 405.-Showing two views of appliance-lingual and side, 
being constructed of metal and hard rubber, is perfectly 
hygienic and non-irritating to the tissues. MITCHELL PALATE AND VOMER RESTORATION 
537 
" While this appliance will help to restore normal function, 
education is necessary to improve speech, owing to the fact 
that the patient being unable to make sounds in the normal 
way through the lack of these parts, it has been neces- 
sary for her to bring to her aid other tissues or parts in the 
attempt to produce the various sounds. Thus habits have 
been formed which it is necessary and hard to overcome; 
but with this appliance and the cooperation and persistence 
of the patient these difficulties can be overcome. 
"Miss K 's appliance, as you see, is constructed as I 
have described (shows appliance). Without the aid of her 
appliance I shall ask her to pronounce some of the most 
difficult letters of the alphabet. 
"First, the labials-B P F V. 
"The anterior lingual palatals-C D S T. 
"The posterior lingual palatals-G K Q and X Y Z. 
"Now an awkward combination, such as "sixty-six." 
"And a still harder combination, the name of Dr. Norman 
W. Kingsley. With her appliance in the mouth she will repeat 
this combination, which I think will demonstrate to you a 
very marked change in the quality of her voice, her articu- 
lation and enunciation. {Miss K repeats the above.) 
"To show that when the palate is raised by the muscles 
the nasal passages are closed, and the breath may be forcibly 
expelled through the mouth, I shall ask Miss K to blow 
out the candle. This may seem a very simple matter, but 
I assure you that she was not able to do this before the 
introduction of this appliance, and now you see she is a 
pretty good blower! 
"Most appliances that are constructed at the present 
time are bulbous, or of the plug type, which necessarily 
interfere with the nasal resonance, the appliance more or 
less filling up these resonance cavities. To show how abso- 
lutely important it is to have the nasal passage restored 
to as nearly as possible a normal condition, I shall add 
a piece of wax to either side of the vomer bone (of the appli- 
DEMONSTRATION. 538 
CLEFT-PALATE APPLIANCES 
ance), completely closing off the nasal passages, showing 
the interference of nasal resonance. 
"To demonstrate this Miss K will say: Nae, Nah, 
Noh and Ing, N, M with and without the obstruction. 
"Now to see what is possible with the singing voice, we 
will be assisted by Miss K 's vocal teacher. 
"Through the development of her breath control, and by 
a unique card buzzing exercise used in Vocal Art Science, 
to develop certain phases of the voice, she is now able to 
blow a steady flow of breath through the lips, and she will 
open her singing demonstration by a little exercise in card 
buzzing, to show breath control. 
" Next, the scale of thirteen vowels and thirteen consonants 
will be used. These scales have been arranged so discrimi- 
nately in their sequence in "Vocal Art Science" that by their 
correct use each and every resonator from the tip of the 
nose to the epiglottis is exercised, and finally all are correlated. 
"With the use of the scale of consonants and vowels all 
muscles for articulation and enunciation, namely, the lips, 
tongue and palate, are exercised and developed, and perfect 
pronunciation is the result. 
"Miss K will demonstrate the above combination: 
first, to show her breath control and tone quality, she will 
sustain the thirteen vowels at three or four different pitches. 
"Then, to show her use of the scale of thirteen consonants 
and vowels she will sing them on chromatic scales, and 
reverse the order on descending. (Miss K- sings scales 
of thirteen vowels and consonants.) 
"To demonstrate the practical use of the mechanical 
appliance on showing the foremost and highest nasal reson- 
ance, she will sustain the combination of Ing, N, M, and will 
prolong the sound of M to show its position in the singing 
quality. (Miss K sings Ing, N, M.) 
"To demonstrate the perfect mechanical action of the 
appliance she will sing an arpeggio that moves from a lower 
to a higher pitch in the ascension. This necessitates a rise 
and fall of the normal palate and is perfectly apparent with 
the artificial palate. (Sings arpeggios.) MITCHELL PALATE AND VOMER RESTORATION 
539 
"Miss K will finish her demonstration by singing 
two ballads. This is to show the combination of articulation, 
enunciation, pronunciation, and also the legato in singing. 
The latter necessitates perfect breath resistance against 
the upper incisors, which again is made possible by the 
mechanical appliance. 
"Let me state in conclusion that Miss K , in the train- 
ing of her singing voice, and perfecting of her articulation 
and enunciation, has had only twenty lessons thus far. 
(Miss K sings two songs.) 
"Dr. E. A. Bogue said, in discussing Dr. Mitchell's paper, 
that it was well known to some of the profession that he 
came to New York originally to take charge of the practice 
of Dr. Norman W. Kingsley. This, Dr. Bogue said, had 
caused him to become acquainted with quite a number of 
gentlemen who had busied themselves in the manufacture 
of artificial vela, but that he had never seen so strikingly 
good a result." 
Reference Books.-Kingsley's Oral Deformities, Ameri- 
can System of Dentistry, American Text-book of Prosthetic 
Dentistry, and Case's Orthopedic Dentistry. CHAPTER XVI. 
ESTHETICS. 
For the purpose of establishing a clear idea of what we 
mean by "esthetics of prosthesis," we define the term 
"prosthesis" as: The science, art, and esthetics of restoring 
a lost dental organ or organs and associate parts with an 
artificial substitute. 
To understand this subject we must have well-conceived 
ideas of the three terms, science, art, and esthetics. Science 
is classified knowledge; therefore it is the involved theory. 
Art is a complex term; primarily it means doing a thing 
in a skilful manner; thus it is used to express perfection in 
any oft-repeated mechanical work, as the manual labor in 
any of the useful trades, useful arts and crafts; and to the 
working out of beautiful thoughts in concrete form, fine arts. 
As esthetics expresses the latter idea, we incorporate in our 
definition the two terms, art and esthetics. Art, to express 
the skilful doing of mechanical work, and esthetics, to express 
the harmonizing of our creation with its environment, or, 
the art of concealing art. Thus, when we mean the skilful 
construction of mechanical appliances, we shall speak of art, 
artistic, and artisan; but when we mean that which is more 
than mechanical art, the ideal, the beautiful, because har- 
monious, then we shall speak of the esthetic and esthetist 
or artist. 
Is prosthetic dentistry a trade or a profession? This 
depends entirely upon how it is practised. The science 
involved is not a factor in determining whether prosthesis 
as practised is a trade or a profession; for both the useful 
and fine arts may be highly scientific. If prosthesis is 
practised as a utilitarian art, then it is, and can only be, a 
trade; but if the utilitarian art is dominated by esthetics, 
540 ESTHETICS 
541 
then and only then can it justly be called a profession. The 
Standard Dictionary defines a profession as: " An occupation 
that properly involves a liberal education or its equivalent, 
and mental rather than manual labor." Hunter's Encyclo- 
pedic Dictionary defines a profession as: "A business which 
one professes to understand and to practise for subsistance; 
a calling, occupation, or vocation, superior to a trade or 
handicraft." Is it not conclusive that a commercial dental 
laboratory is practising "mechanical dentistry" only? In 
order to practise prosthesis (Greek, pros, to; tithemi, place, 
to place or restore) it is necessary that the patient shall be 
under the inspection and study of the prosthetist so as to 
restore the contour and harmonize the associated parts. 
If one is to practise prosthesis as a profession, he must be 
more than an artisan; he must be an artist. It is a common 
saying that art'sts are born and not made. This saying, 
like most of its kind, is only in part true. However, we can 
say there are but two sources from which artists may be 
produced, namely, made and born, cultivation and intuition. 
The idea of an artist being cultivated is in keeping with the 
Standard Dictionary definition of a profession that is: "A 
liberal education or its equivalent, and mental rather than 
manual labor." The artist must have, in addition to the 
manual dexterity of the artisan, the developed mentality 
and imagination that can create ideas and ideals, and then, 
with his artisan dexterity, he puts his ideals into concrete 
form. Thus, he makes of his useful art a fine art; and he 
becomes an esthetist, an artist, and his calling is a pro- 
fession. Therefore if one would be an esthetic prosthetist, 
he must develop himself and broaden his art. The remain- 
ing source from which artists are produced, that is, born, or, 
as we classified the idea-intuition-is an unknown quantity 
and of uncertain value. However, for a dentist to depend 
upon intuition for producing esthetic work would be like a 
preacher depending upon inspiration for his sermon; too 
often the product would only be perspiration. True it is 
that some people seem to have more natural ability than 
others; but it is more than probable that much of this 
seeming inherent or intuitive ability is the result of early 542 
ESTHETICS 
cultivation in ways that have contributed to the final 
product. 
There are two attributes of a man that are necessary for 
success in any line, namely, desire and energy. Desire and 
energy is the celestial fire which will, when sufficiently strong 
accomplish everything. Longfellow has well expressed the 
thought in this stanza: 
"All the means of action- 
The shapeless masses, the materials- 
Lie everywhere about us. What we need 
Is the celestial fire to change the flint 
Into transparent crystals, bright and clear. 
That fire is genius." 
Someone has said that "Genius is infinite capacity for 
painstaking." Thus, we must conclude that if a dentist 
does not succeed in reaching high attainments, the celestial 
fire within him is passive and not active : or, that his energies 
have not been well directed. 
Thus far we have endeavored to establish what is esthetics 
of prosthesis, and present the conclusion that it is applied, 
refined ideals of prosthesis, developed by earnest desire and 
well-directed energy. 
Dr. Charles Channing Allen has well expressed the relation 
of esthetics to dentistry in a paper read before the Kansas 
State Dental Association, May, 1908: 
"When a work is executed with the concepts of beauty, 
utility, and economy in their proper proportions, that work 
has its own individual characteristic, the evidence of design. 
This is its passport; its credential; its hall mark; its jus- 
tification. In such character it shows whether it is the 
legitimate child of orderly intelligence, or the bastard of 
bungling incompetency. If it was fathered by an under- 
standing of the requirements and a skill sufficient for their 
execution, then it must appeal to the mind as answering the 
requirements of esthetics-the beautiful. . . . Although 
in giving consideration to design over mere beauty we can- 
not accept the dictum that beauty is without definite utility. 
Beauty carries with it more of the evidence of design than 
mere utility, for the esthetic or beautiful appeals to one ESTHETICS 
543 
immediately, and does not require a systematic proof along 
the recognized lines of logic, but establishes itself in the mind 
of the beholder at once without proof. Utility alone, as 
an ultimate end, executed without embellishment, may be, 
and usually is, vague in expressing its reason for existence, 
and must be studied and its purpose analized, often labori- 
ously at tiresome length. 
"No profession has more use for the esthetic and beautiful 
than the profession of dentistry; for an esthetic restoration 
is a very important part of our obligation to our patient." 
We assume that the Creator designed that every soul 
should inhabit a perfect body. According to its type, it 
should be like the Greek creation Apollo, every line and 
every inch god-like in its perfection. Had the original 
design prevailed, there could have been no beauty associated 
with the human form, because there would have been but 
one type, and each individual would have been a duplicate 
of all others. Beauty is appreciated by contrast only. The 
Creator also gave the laws of environment. Therefore we 
have not two persons that are exact duplicates of each 
other. As the body is molded and shaped by external 
mental and physical influences through conception and 
gestation, and by both external and internal mental and 
physical influences through infancy, youth, adult, and 
senility, there can be no perfect duplicate or absolute con- 
formity to a given standard; and yet, how wonderfully alike 
are human beings. 
Ethnologists, physiognomists, and other scientists have 
divided and subdivided the human family into many classes 
for the purpose of better studying man. So far as pros- 
thetists are concerned, our studies have been confined almost 
entirely to the Caucasian race, and we consider only such 
classification as will aid us in understanding the needs of the 
profession. We first divided the race into classes-light 
(blonde) and dark (brunette)-a simple classification easily 
understood, and which call attention to certain facts. 
Another classification we may call the "dental profile" 
classification. Scientists consider this subject as a study 
of the facial angle, and make two general divisions-orthog- 544 
ESTHETICS 
nathous and prognathous. This division is of little value 
to the dentist, yet the study of the profile is perhaps the 
most important of all the classifications for the prosthetist. 
A third classification to be considered is that of the 
temperaments. 
DENTAL PROFILE. 
For convenience, we divide the dental profile into three 
classes-straight profile, convex profile, and concave profile. 
Scientists in drawing the perpendicular line of the face 
have it touch the most prominent point in the median line 
of the forehead and the most advanced portion of the 
maxillae. The dental profile line is somewhat different from 
the perpendicular facial angle line. 
The first class, or straight profile, is the Greek ideal face. 
The perpendicular line has three points of contact-the 
frontal and mental eminences, and the middle of the wing 
of the nose. The lower lip will just touch the perpendicular 
line, and the upper lip will be a little in advance of the 
line. There is no question that this is the normal profile 
of the highest ideal of beauty. 
The second class, or convex profile, has two points of con- 
tact with the perpendicular line-the frontal eminence and 
a point at the base of the nose which is the same distance 
from the middle of the back of the ear as the frontal eminence. 
In the type, this point will be the center of the wing of the 
nose. 
The ideal standard of this class has the face made up of 
rounded, graceful curves; forehead high and slightly reced- 
ing, nose of Greek or Roman type; lips full but not coarse; 
chin receding but not weak; teeth, both number and align- 
ment normal. No competent orthodontist would think of 
converting this ideal of our second class into the first or 
straight class, for he would recognize that the harmony of 
the features would be destroyed. 
The third class, or concave profile, has the frontal and 
mental eminences only in contact with the perpendicular 
line. It is not possible to conceive of this profile being a 
mark of beauty, and it is fortunate that the class is small DENTAL PROFILE 
545 
compared with the other two. It is a condition con- 
fronting the prosthetist, and he must place the features in 
as pleasing a relation to the concave line of the individual 
as possible. 
The physiognomy of man is gradually changing and 
tending toward types. The intermarriage of different 
nationalities and the modes of living, causing mental de- 
velopment and physical degeneracy, partly account for this 
condition. For the last few years orthodontists have been 
impressing upon our attention the importance of teeth in 
the physiognomy of man, and giving us a rational reason 
for many of the abnormal conditions. This same study is 
of value to the prosthetist, as it aids him to understand the 
design of nature for the individual case; also aids him in 
classification. In studying the harmonies and inharmonies 
of the face, it is important that we consider the causes as 
well as the effects. 
When the prosthetist has studied the individual case and 
classified it he is confronted with the question, What is 
one's duty, to restore the features to the natural or to the 
normal condition? It is apparent that a normal convex 
profile should not, in a portion of its outline, be converted 
into the concave type, thus forming an ogee monstrosity. 
Each individual case must be kept within its normal class, 
then it is a matter of judgment for the prosthetist and 
patient to decide to what extent the natural peculiarities shall 
be modified. 
It should be borne in mind that physiognomists make a 
distinction between anatomy and expression. Expression 
is of the soul, by and through the anatomy. Therefore 
deformities of the anatomy may belie the soul. The pros- 
thetist should study well to have the teeth of the proper 
size, color, form, arrangement, and the dentures so con- 
toured that they may harmonize with the rest of the anatomy 
of the face. The esthetics of prosthesis may be expressed 
thus: Harmonious in anatomy and pleasing in expression. 
Fig. 406 is the classic figure Apollo, and is the Greek 
type of the straight profile. For study purposes and as an 
ideal, artists have divided the face into three parts called 546 
ESTHETICS 
thirds-upper, middle, and lower (see Fig. 1). The ideal 
face has the three-thirds of equal length, but in actual life 
they rarely attain this relationship. Also the ideal head 
has the ear entirely in the middle third, and of the same 
length as the nose. 
Fig. 4071 is a fair representation of life, that is, that faces 
are not formed by rule. However, it is necessary to have a 
standard for comparison, that ideas may be conveyed from 
one to another. Therein is the only value attached to the 
Apollo in dental study. Referring to Fig. 407 it is seen that 
Fig. 406 
the tipper and middle thirds are equal in length, but that 
the lower third is very much longer. The upper two-thirds 
belong to a square type of face while the lower third belongs 
to the parallelogram (see Fig. 419). It is also seen that the 
ear does not harmonize with the middle third but does with 
the lower third of the face, therefore the face is a blend of 
two types. The square type predominates, as it is two-thirds 
square; therefore to have a perfectly harmonious face it 
1 The well-known late Dr. J. W. Greene, who probably has done more 
toward developing impression taking than any other one man. DENTAL PROFILE 
547 
would be necessary to remodel the lower third and the ear to 
conform to the upper two-thirds. It is sometimes stated in 
association discussions that the length of the nose determines 
the length of artificial teeth because the lower third when the 
mouth is closed should be of the same length as the middle 
third of the face. In this individual case if the natural teeth 
were all lost it would be impossible to construct dentures 
with a sufficiently close-shut bite to reduce the lower third 
to the dimensions necessary to make the face three-thirds 
square type. Nevertheless to restore the mouth with teeth 
Fig. 407 
of the length of tooth and bite of youth would be wrong for 
two reasons: (1) esthetics require that the teeth should be 
well aged, that is, much shortened by wear and (2) the 
natural conditions should be modified toward the normal, 
thereby producing a more harmonious relation of the three 
portions of the face. 
Figs. 408, 409 and 4101 are respectively straight, convex, 
and concave profiles. In all three of the illustrations each 
1 Figs. 408 and 409 were taken from public prints and are of persons 
notable for mentality and humanitarianism; Fig. 410 is of a drawing by 
Lavater depicting melancholia. It makes emphatic the prominence of the 
frontal and mental eminences and the depression of the maxillse. 548 
ESTHETICS 
third is in harmony with the remaining two-thirds of the 
face. A study of the profile consists of a comparison of the 
thirds of the face. Very often the lower third will not be 
in harmony with the facial type. It is in this class of cases 
that the prosthetist and orthodontist may improve upon the 
natural; that is, they may mold the lower third of the face 
Fig. 408 
Fig. 409 
Fig. 410 
toward the normal of its predominating type. The straight 
profile seems to predominate in the German, French, and 
Celtic types, while the convex profile is specially prevalent 
in the English, Scotch, and Jewish types. 
Fig. 411 is Dr. B. J. Cigrand's selection of three historical 
characters as representative of the three profiles. The lower DENTAL PROFILE 
549 
two-thirds of the face of Daniel Webster is of the straight 
profile, while the massive development of the frontal eminence 
would place the upper third with the concave class. The 
face of Cardinal Newman is equally fine, but the frontal 
and mental eminences are overdeveloped, thereby giving the 
concave profile. Henry Clay is a fine illustration of the 
convex profile. However, the lips are a trifle flat. 
Fig. 411 
Figs. 412 and 413 are taken from Angle's work on Ortho- 
dontia. This profile is also a mixed one. The upper third 
is a fine illustration of the straight profile. The middle third 
would require a careful study of the face to determine its 
classification. The cast of the upper dental arch (Fig. 412) 
shows an almost ideal alignment and complement of teeth; 
however, the apparent depression in the proximity of the 
apical ends of the teeth, also the concave form of the nose, 
would indicate an insufficient development of the upper 
portion of the maxilla. This factor would require careful 
inspection to determine whether this seeming depression 
is real or only apparent because of the greatly enlarged 
mandible. If the upper portion of the maxilla is fully 
developed, then the face belongs to the straight profile 550 
ESTHETICS 
type, complicated with a greatly malformed mandible; 
if the upper portion of the maxilla is depressed, then the 
profile is of a mixed type; the lower two-thirds, being com- 
plicated with an enlarged mandible, is of the concave type, 
and the upper of the straight type. 
Fig. 412 
Fig. 413 
Lips.-There is one other factor in the study of the profile 
that must always be given careful attention when making 
restoration with artificial dentures, and that is the lips. 
The lips may be classed as thin, medium, and thick; also 
one may be thin and the other thick. The proper contouring 
of the lips can only be done by the proper setting of the 
anterior teeth, and the contiguous gum restoration. This 
factor is not a part of anatomical occlusion, which is purely 
mechanical and scientific; but is of the esthetic and can be 
produced only by the one seeing and handling the mouth. 
Therefore a dentist who is satisfied with the mounting of 
artificial teeth by a commercial dental laboratory shows 
himself deficient in the esthetic sense, and owes it to himself 
and his patient to either develop the esthetics of prosthesis 
or eschew prosthetic dentistry. The writer trusts this 
condemnation of a very considerable portion of the dental 
profession will discourage no one, but will excite many to 
a sense of duty and an earnest effort at perfecting himself. HARMONY 
551 
The proper contouring of the lips may require that the 
anterior teeth may have end-to-end occlusion, or that there 
may be little or much protrusion of the lower anterior 
teeth; or they may require little or much retrusion. The 
setting of the six upper and lower anterior teeth with the 
amount and shaping of the contiguous gum restoration has 
more to do with the beauty of the face than the proper 
selection of teeth, because the contour of the lips is visible 
at all times, and the teeth only when speaking and laughing. 
However, perfection implies that no part is deficient, there- 
fore equal attention should be given to every factor and the 
teeth selected of suitable form, size, color, and texture, 
the teeth occluded anatomically, and the lips restored so 
that the lower third of the face may harmonize in anatomy 
and be pleasing in expression. 
HARMONY. 
The preceding chapters of this book have been devoted 
to developing the mechanical phases of prosthesis, also 
a reasonable science for the modes of procedure, and 
incidentally the cosmetics have been touched upon. How- 
ever, in teaching the science and art of prosthesis it is not 
wise to more than intimate the existence of the esthetic, 
because of the confusion and distraction of mind created. 
The prosthetist must first become an artisan, and then, 
with patient endeavor, develop the artist. The utilitarian 
art is the first consideration, and is that for which there is 
the greatest demand; but for the mechanical dentist to 
dignify his work and make himself worthy to be ranked as a 
professional man he must place the stamp of ideality upon 
the product of his hand. As there are no two individuals 
exactly alike, in fact no individual, one side of whose face is 
the counterpart of the other, it is impossible to establish 
fast rules for esthetics. It is possible, however, and is the 
province of this chapter to map out certain lines of thought, 
and some technic as a means for harmonizing the work 
of the craftsman with the environment and making pleas- 
ing the expression of the individual. To recapitulate: The 552 
ESTHETICS 
finishing touches of the artist shall conceal the work of the 
artisan. As the sculptor and painter may only express their 
thoughts in tangible substance, so it is that the dental esthet- 
ist may only express his thoughts by means of the artificial 
denture. The value, therefore, of the prosthetist's creation is 
not in the intrinsic value of the physical material entering 
into it, but in the quality and quantity of thought expressed 
in the artificial substitute. The science and art of prosthesis 
deal with the materials and manipulation of them, whereas 
esthetics has to do with contour and color regardless of the 
material used. Contour and color are concerned with the 
surface only; therefore the lingual, labial, and buccal surfaces 
are the subjects for our further consideration of artificial 
dentures. 
Lingual Surface.-The lingual surface of the maxilla is 
dome-shaped, but varies in conformation from an inverted V 
(A) to a flat surface. As the dome of the mouth is one of the 
resonant chambers, useful in articulate speech, it is evident 
that its form has much influence in sound formation. This 
does not imply that a definite shape of the vault is necessary 
to articulation, but it does imply that certain conforma- 
tions are more favorable for clear enunciation than others, 
and that clear enunciation cannot be had with every vault 
formation. Therefore the prosthetist may mar or improve 
the conditions for good enunciation. The rounded oval 
dome vault is the best devised for human speech. However, 
the genius of mankind is great, and he can overcome many 
of the impediments to sound formation. Nevertheless, when 
he has required the art of enunciation, any radical change 
in this resonant chamber will necessitate a change in the 
manner in which the tongue is conformed and placed. 
Therefore it is logical to assume that the conformation of 
the lingual surface of the artificial denture should be as near 
the size and conformation of the vault in which the subject 
has acquired good enunciation as possible; otherwise the 
individual will have to learn the art of clear speech over 
again. Chapter I, in connection with Figs. 13, 14 and 15, 
illustrate the changes that take place due to the loss of the 
teeth. Fig. 13 demonstrates that any unnecessary thickness HARMONY 
553 
of the lingual surface of the denture is an impediment to 
speech; however, as a mechanical appliance is essential to 
restore the lost tissues, good mechanics requires that the 
apparatus shall have a safe margin of resistance to the stress 
to which it may be subjected. This will require a thickness 
of material in the indirect ratio to the strength, rigidity, 
and elasticity of the material employed. Is it not evident 
that the carving of the lingual contour of the teeth, gums, 
and rugae, as seen in many of the illustrations of this book, 
are more than fanciful, that it is the acme of the practical 
in restoring enunciation? Further than this, the restoring 
of the ruga? is beneficial as an aid to the tongue in deglu- 
tition. Chapter I should be read as a further elucidation 
of this theme. The technic of restoring the lingual surface 
consists of the methods previously described and illustrated. 
The requirements of esthetics are that the original contour 
of the lingual surface of the maxilla shall be reproduced 
as nearly as possible; that excessive thickness of the linguo- 
cervical portion should be employed only when other condi- 
tions make them imperative. 
Labial Surface.-The labial surface may be defined as 
that depicted by the incisor and cuspid teeth. The contour 
of this surface of the artificial dentures is to give support 
and form to the overlying soft tissues, thus restoring the 
anatomical harmony and aiding in the expression. There 
are two portions of this surface to be considered, namely, 
the gum portion and the teeth. Chapter I describes the 
change wrought by resorption of the alveolar processes, and 
the same chapter explains the muscles and their action 
associated with this surface of an artificial denture. 
The contour of the gum portion requires that it shall not 
impinge upon the frenum labii, nor make too full the incisal 
fossae; but that it shall restore the cuspid eminences, includ- 
ing the nasobuccolabial triangles. As previously suggested, 
the contour for the individual case will be determined by the 
typal condition. The contour of the teeth will be influenced 
by the type and age of the patient. In order to understand 
the typal influences it is necessary to digress from the theme 
of study and consider abstractly the temperaments. 554 
ESTHETICS 
TEMPERAMENTS. 
Dr. Jacques defines temperament as: A state of the body 
depending upon certain combinations of the various systems 
and organs and certain functional conditions affecting 
them. 
The temperaments are physiological conditions and are 
usually considered unchangable. Dr. Jacques, than whom 
there is probably no greater authority, states, on page 110 
of his book, The Temperaments, that: 
"When once established, the temperament inclines natu- 
rally to perpetuate and increase itself, since it gives rise to 
habits that exercise the organs on which it depends. A 
change of temperament, then, implies strong counteracting 
influences brought to bear upon the constitution; and as 
such strong influences are in a majority of cases lacking, the 
inherited tendency is generally followed, and a temperament 
once established is maintained through life. This, how- 
ever, is far from being universally the case. The inherent 
predisposition is sometimes entirely overcome and the con- 
stitution radically changed." 
There are various classifications of the temperaments; but 
the one here used (because it is the one associated with the 
classification of teeth) is the one apparently adopted and 
described by Dr. Spurzheim. 
"1. The Lymphatic Temperament.-The lymphatic or 
phlegmatic temperament is indicated by pale white skin, 
fair hair, roundness of form, and repletion of the cellular 
tissue. The flesh is soft, the vital actions are languid, the 
pulse is feeble; all indicate slowness and weakness in the 
vegetative, affective, and intellectual functions. 
"2. The Sanguine Temperament.-The sanguine tempera- 
ment is proclaimed by a tolerable consistency of flesh, 
moderate plumpness of parts, light or chestnut hair, blue 
eyes, great activity of the arterial system, a strong, full 
and frequent pulse, and an animated countenance. Persons 
thus constituted are easily affected by external impressions, 
and possess greater energy than those of the former tem- 
perament. TEMPERAMENTS 
555 
"3. The Bilious Temperament.-The bilious temperament 
is characterized by black hair; a dark, yellowish, or brown 
skin; black eyes; moderately full, but firm muscles, and 
harshly expressed forms. Those endowed with this con- 
stitution have a strongly marked and decided expression 
of countenance; they manifest great general activity and 
functional energy. 
"4. The Nervous Temperment.-The external signs of the 
nervous temperament are fine, thin hair, delicate health, 
general emaciation, and smallness of the muscles, rapidity 
in the muscular actions, vivacity in the sensations. The 
nervous system of individuals so constituted preponderates 
extremely and they exhibit great nervous sensibility." 
These four divisions are spoken of as primary tempera- 
ments. It would be exceedingly difficult to find an indi- 
vidual whose organization complied with any one of these 
divisions only. Most persons show one temperament 
markedly strong, but modified with one or more of the other 
temperaments; while others possess an equal blending of two 
or more temperaments. It is this blending of the classes in 
varying degrees that causes the difference in the physiog- 
nomy of persons and peoples. However, to study the com- 
plex it is necessary to reduce it to its components; therefore 
the temperaments are first studied in the primary classifi- 
cation, as lymphatic, sanguine, bilious, and nervous; and 
then in the binary classification, as lymphatosanguine, and 
sanguolymphatic, the one being the basic and the other the 
modifying temperament. Unfortunately, writers are not 
agreed in the manner of forming the compound noun. Some 
writers first name the basic and then the modifier, as sanguo- 
nervous; others reverse the order, as nervosanguine, both 
referring to the same physiognomical condition. Because 
of this confusion of nomenclature the writer prefers using 
a phrase in place of the compound noun, as the sanguine 
modified with the nervous temperament, or the nervous 
modified by the sanguine temperament. The meaning is 
then unmistakable. 
Dr. Jacques states that it is very difficult to get portraits 
representing the lymphatic temperament, but that the 556 
ESTHETICS 
illustrations he gives show its general tendency. Figs. 414 
and 415 are reproductions of two of his examples. The one 
Fig. 414 
Fig. 415 
Fig. 416 
to the left is modified with the bilious temperament, while 
the one to the right is modified by the sanguine temperament. TEMPERAMENTS 
557 
Figs. 416, 417 and 418 are reproductions of his examples of 
the sanguine, bilious, and nervous temperaments consecu- 
tively. 
Fig. 417 
Fig. 418 558 
ESTHETICS 
Professor Prothero, of the Northwestern University 
Dental School, in his book, Prosthetic Dentistry, presents a 
condensed table of the primary temperaments and their 
appropriate teeth. The table here reproduced will aid in 
fixing in the mind the main facts pertaining to the tempera- 
ments and their application to the selection of teeth for an 
edentulous patient. 
Basal tem- 
peraments. 
Eyes. 
Hair. 
Teeth. 
Color. 
Shape. 
3 
a 
cu 
Lymphatic 
Pale blue or 
gray 
Fine and silky, 
but without 
luster 
Pallid, opaque, or 
muddy yellow 
Poorly shaped, 
broad and flat. 
1 
Sanguine 
Blue, brilliant, 
Blond-red or 
Cream-yellow, 
Well propor- 
a 
S 
and expres- 
sive 
chestnut, seldom 
dark or black 
darker at neck 
tioned, curved 
and rounded. 
ideation of 
Nervous 
Light gray or 
blue, restless, 
often morbidly 
brilliant 
Fine, light, and 
soft 
Pearl-gray, or 
blue tinge 
Long, conical, 
and rounded 
Class 
Bilious 
Black or brown, 
small and pierc- 
ing 
Coarse, dark, 
often black, 
and abundant 
Strong, bronze 
yellow 
Conical, long, 
and angular. 
There is but one object for the dentist studying the 
temperaments, and that is to aid in selecting teeth of suitable 
form and color. It is true that the classification of tempera- 
ment is not based upon scientific facts, but nevertheless 
certain facts have been grafted onto the pseudoscience, 
and if the familiar terms are used only to define certain 
combinations of form and color no harm is done. 
Madame Schimmelpennick, an English authoress, issued 
a work in 1815 on the Science of Beauty, from which Fig. 418 
is taken. This reduces the fundamental forms of faces to 
the square, triangle, and circle, with modifications. 
The form of the central incisor being obtained by the 
shape of the face was given in a paper and by demonstration 
by Dr. F. H. Berry, of Milwaukee, Wisconsin, at Buffalo, 
New York, at the annual session of the Institute of Dental 
Pedagogics, 1903. TEMPERAMENTS 
559 
Dr. J. Leon Williams uses the same geometrical figures 
to express the forms of teeth. Recently his writings have 
appeared in several publications, notably the Dental Digest 
beginning with the February 1914 number. 
Fig. 419 
The forms of teeth suitable for the patient having been 
determined, the size and color remain. The size of the 
teeth is determined by instruction given under the heading 
Grinding and Setting Up on page 252. 
Color.-There are but two primary colors that need be 
considered in the color of teeth, yellow and blue. These 
two colors are found in all teeth in varying shades. The 
brunette will have the yellow of a bronze hue, while the 
blonde will have the yellow of a creamy hue. Blue is in the 
teeth mostly as gray, and its intensity will be in the ratio 560 
ESTHETICS 
to the intensity of the color of the skin. The teeth histo- 
logically are of the dermal.tissues and derive their color from 
the circulating fluids of the body, but with this difference, 
that with advancing age the dermal tissues, with the excep- 
tion of the teeth, lose their intensity, while the teeth increase 
in intensity of color. 
Elaborate descriptions and extensive classifications of the 
temperaments may be found in both the American System of 
Dentistry and the American Text-book of Prosthetic Dentistry. 
The student is referred to these works for a further inves- 
tigation of this subject. 
APPLICATION. 
Returning to the theme, labial surface, it remains to apply 
the ideas presented under the headings Profile and Tempera- 
ments. This may best be done by use of a patient. The 
patient (Figs. 420 and 421) has been edentulous for many 
years. She is about sixty years of age, strongly sanguine, 
with a nervous temperament modification. The sanguine 
temperament is indicated by the generally rounded cast of 
features and physique of the blonde type. The nervous 
temperament is indicated by the width of the forehead and 
by the toning down of the blonde type of coloring. 
Figs. 422 and 423 present the patient wearing artificial 
dentures that do not restore the harmony of the face, there- 
fore causing her to appear more aged than she is. Notice 
the straight profile, which should be slightly convex, the 
exaggerated lines about the mouth, the compressed lips, and 
the depressed nasobuccolabial triangle. Compare this with 
Figs. 424 and 425, in which the features have been restored 
so that the lips in profile are slightly protruding, the exposed 
mucous membrane is natural and in keeping with the thick- 
ness of the lips. Observe the gradation from the thin, 
compressed, severe, and repelling expressions of the edentu- 
lous mouth, to that of the serious, but cheery and pleasing 
expression of the restoration. Surely the dentist's handi- 
work may belie the soul, or it may be in harmony with that 
of the Creator and Father Time. Fig. 420 
Fig. 421 Fig. 422 
Fig. 423 Fig. 424 
Fig. 425 564 
ESTHETICS 
Occlusion and Contour Models.-Chapter IV instructs how 
to form the occlusion models, but necessarily the contouring 
of the models could not, at that time, be discussed. Now, 
in the study of the esthetics of restoration, the required 
contours of the wax models should suggest themselves to 
the mind of the student, and he should see that a half-hour 
or even an hour spent in modelling the contour models is 
time well and profitably spent. Fig. 70 shows the wax 
Fig. 426 
models with the median portion and the incisive fossae 
depressed, and the cuspid eminence represented. The occlu- 
sal border of the upper model overlaps the lower; and the 
lower model is depressed horizontally to represent the sulcus 
mentolabialis of the external surface of the lower lip. While 
the occlusion and contour models represented in Fig. 70 
were not for this patient, their conformation is very similar to 
that which was required. However, Figs. 244, 245 and 246 APPLICATION 
565 
are of the denture in the mouth of the patient shown in Figs. 
424 and 425. 
Technic of Model Contour.-The wax models, having been 
constructed for occlusion, are placed in the mouth and, 
Fig. 427 
with the face in repose, studied for contour. The face is 
studied in profile and in full front, while the portion of the 
wax models to be added to or taken from is determined by 
gentle pressure of the fingers upon the external surface of 
the lips. While conducting this contour modelling of the 
Fig. 428 
labial surface of the wax models the prosthetist must be 
certain that the mandible is in retrusion. The anatomy of 
the parts to be considered in the model restorations are 
described in Chapter I. It is unnecessary to develop per- 566 
ESTHETICS 
fection of restoration in the wax models, for the final esthetic 
restoration is to be wrought in the model dentures; that is, 
with the porcelain teeth mounted on wax. Little attention 
need be given at this time to the linea nasolabialis, nor 
need the patient be shown the restoration; indeed, it is not 
well to call attention to this phase of the construction, 
because the work is only blocked out and a trained imagina- 
tion is required to comprehend the result, which attribute 
the average patient does not possess. 
Fig. 429 
Buccal Surface.-This surface need not be considered in 
the occlusion models from the view-point of contour, but 
it needs careful consideration at the time of proving the 
occlusion and contour of the model dentures. The patient 
shown in Figs. 424 and 425 requires no buccal restoration, 
and this is true of probably a majority of patients. EXPRESSION IN ACTION 
567 
Fig. 426 is a profile view of a patient requiring exten- 
sive restoration. Figs. 427 and 428 give two views of the 
required artificial dentures as first developed in the models 
and then reproduced in vulcanite. Figs. 429 and 430 give 
two views of the features restored. The buccal contours do 
more than reduce the excessive dimples of the cheeks; they 
modulate the linea nasolabialis, and in such a way that the 
line is flexible and graceful both in repose and action. If 
the cuspid fossae are built out in the artificial denture for 
Fig. 430 
the purpose of obliterating these lines in repose, it will 
produce an exceedingly disagreeable effect when the mouth 
is in action. 
EXPRESSION IN ACTION. 
If the face were always in repose the study of esthetics 
would be finished, but the severest test of the esthetic 
creation is when the patient is speaking and laughing; for 568 
ESTHETICS 
then the size, form, color, arrangement, and individualized 
effect of the teeth are on exhibition, and if the prosthetist 
has concealed the art, he is an esthetist, and need not be 
ashamed of his handiwork. 
TEETH. 
Size.-The size of the teeth were considered in the technic 
of construction (Chapters I and VI). 
Form and Color.-The form and color of the teeth are 
determined by the class or temperament when the patient is 
edentulous, but are selected to harmonize with the remaining 
teeth in partial cases. 
Arrangement.-The teeth are arranged as instructed in 
Chapter VI, modified slightly sc as to conform to the 
individual indications of the patient; that is, the lymphatic 
type will require the arrangement to be a trifle flatter and 
broader than described in the mechanical setting up of the 
teeth. The sanguine type will require no change in the six 
anterior teeth, but the bicuspids should be slightly more 
prominent. The bilious type will require the central incisors 
to be depressed so as to give a square effect, but no change 
distal to the cuspids. The nervous type may have the 
centrals more prominent and the cuspids slightly depressed. 
Individualization.-Here no rule can be established, for 
it is the little touches, here and there, by way of slightly 
rotating, inclining, protruding, retruding, extruding, or 
intruding one or more of the teeth; also grinding, inserting 
fillings, and staining the teeth that completes the harmony. 
This work should be done by the aid and with the approval 
of the patient, and possibly a friend. It is often wise to lead 
the patient or friend so that they will suggest the desired 
change. However, this does not imply that inartistic and 
monstrous desires of some patients are to be complied with; 
not at all, but if the patient can be led to suggest what is 
really needed, it will usually be more readily accepted. 
This will prove a good suggestion if properly used. Never- 
theless, there are many patients that have little artistic 
sense, and cannot be asked to aid in this important task. 
Unfortunately these are the persons who are later subject 
to the influence of incompetent critics. STAINING THE TEETH 
569 
Gold Fillings.-Gold fillings may at times be inserted so 
as to greatly relieve the artificial effect, especially when the 
patient has had, for years, conspicuously displayed gold 
fillings. In such cases it is well to reduce the size and number 
of the fillings and place them so as to give the appearance 
that the patient has gone to a more esthetic practitioner. 
Gold crowns for display purposes should never be tolerated 
unless the patient is markedly "loud" and nothing less will 
complete the harmony. 
Technic.-The tooth to be filled is cupped out with a 
small stone, so as to form a saucer-shaped cavity; dove- 
tailed grooves may be cut with a small knife-edged disk 
stone, and retaining pits made with a diamond drill kept 
wet with water. The tooth may be mounted with sealing 
wax on a block of wood, as a means of support while filling 
with gold. This mounting may be done before preparing 
the cavity, but preferably after the cavity is cut. 
STAINING THE TEETH. 
The manufacturers of artificial teeth are to be commended 
for the excellence of their product, but such stock cannot 
be individualized at the factory. The expert artisans in the 
factory are most competent to prepare the crude earthy 
material, grind, compress, and fuse it into blocks having the 
semblance of teeth, perfect material for the hand of the 
artist. The error has been made by the profession in that 
it demanded of the manufacturer a finished product for the 
individual case, which is an impossibility. The artist, and 
he is the dentist, must take the product of the artisan and 
individualize it. 
The manufacturer has, for convenience of marketing, 
arranged his stock of teeth in sets. These sets vary in 
number from two to twenty-eight teeth, and are of uniform 
color, that is, the color, tint and shade are the same in 
each of the teeth; while in nature the tint and shade of a set 
of teeth vary materially. 
Shade and tint are technical terms of the colorist. Shade 
implies that a small amount of black is added to deepen the 
color, while tint is produced by the addition of white. 570 
ESTHETICS 
Dr. E. A. Royce, of Chicago, has called attention to the 
fact that the upper central incisors are the foundation tint 
of the teeth in a set, while in the laterals and cuspids the 
shading is progressive and then diminishes through the first 
and second bicuspids and first molar. The lower teeth 
follow the same rule, beginning with the centrals a little 
darker than the upper centrals. 
The amount of shading in each of the classes of teeth will 
vary with the environment; that is, temperament, age, 
and the influences of waste and repair. Therefore for the 
manufacturers to attempt to supply, through the trade, 
teeth esthetically constructed for each individual case would 
result in a bewildering confusion. The artisans are doing 
well their part in supplying stock teeth, but the prosthetist 
must develop the esthetics, otherwise he is an artisan and 
not an artist. The operative dentist's claim to professional 
recognition is founded upon pathology; the prosthetist's 
professional claim is based upon esthetics; consequently he 
is, or is not, an artist. 
Materials for Staining Teeth.-The supply houses of both 
this country and Europe have placed upon the market the 
necessary equipment for staining and changing the tint and 
shade of teeth. This equipment consists of a few colors 
(either primary or mixed colors), usually a fluid as an apply- 
ing medium, a mixing spatula, brushes, and a mixing slab 
of glass or porcelain. As instructions for use accompany 
each outfit, it is unnecessary to consider the various kits. 
The colors are mineral (metallic oxides) incorporated 
with a body of the nature of glass (sometimes called porce- 
lain). They all fuse and form a glaze over the surface upon 
which they are applied. Therefore to use them to change 
the color of an artificial tooth to match the color of another 
as it comes from the factory is not their intended use. They 
are an overglaze and not an underglaze; that is, the color 
is on the surface, not under the surface. The various 
materials placed upon the market vary greatly in fusibility 
and durability. The rule is, and has been, invariably true 
in the past that the durability is in the inverse order to its 
fusibility. However, the last claimant for consideration 
(Lenox mineral stains) may be an exception to the rule. STAINING THE TEETH 
571 
It certainly is exceptional in some respects. As the fusi- 
bility of glass and porcelain products has been contingent 
upon the amount of flux (alkali), incorporated, this new 
material must be subjected to the test of time to prove 
its wearing qualities. The writer has tested the Lenox 
material with the Price pyrometer, and has found that 
it takes a very good glaze with an exposure of one minute 
at 1100° F., and that it resists the friction of the felt wheel 
and pumice stone. It is better glazed at 1400° to 1500° F. 
It is surprising that the material stands 2300° of heat almost 
as well as the White and Brewster colors, which require 
at least 2000° F. to give them a suitable glaze. The new 
product is ground exceedingly fine, and in that respect 
is a superior product. However, until it has been demon- 
strated that this new material resists perfectly the disin- 
tegrating action of the fluids of the mouth, the writer will 
place his faith in the higher-fusing materials. 
Mixing Fluid.-The fluid used has no action upon the 
paint material; it is only a means for applying and retaining 
the powdered pigment. Water, gum-arabic water, oils- 
as cloves, poppy, lavender, and turpentine-also glycerin, 
are used. Water is the most unsatisfactory fluid named. 
Of the oils, that of cloves is excellent; its unctuous nature 
is its only drawback. Glycerin has recently been recom- 
mended by Dr. Royce, and it certainly is an excellent 
medium. 
Technic.-The paint or stain is spatulated upon the 
slab with the chosen medium to the required consistency 
(thick for deep color, and thin for light tint) and applied 
to the alcohol-cleansed surface of the tooth with a soft 
pencil brush. It may be more evenly spread with a short 
stubby brush used as a stippler. Certain effects may be 
produced by a light wiping stroke of the finger. This will 
remove the color from the elevated portions and leave it in 
the depressions and grooves. Highly vitrified teeth may be 
much improved by spreading the color over the surface 
with a pencil brush and stippling with the ball of the finger. 
This produces the columnar crystalline effect of the natural 
tooth. The painted tooth is dried in a moderately warm 
place, then glazed at the required temperature. 572 
ESTHETICS 
Suggestions.-The tooth should not be handled with the 
fingers after cleansing with alcohol, but with clamping pliers 
attached to the pins. 
The tooth or teeth while in the furnace should be placed 
with the face side upward; the pins, however, should not 
come in contact with the bottom of the furnace or heating 
slab. Place a quantity of finely crushed quartz in the bottom 
of the furnace, or upon the slab, upon which the teeth may 
rest, and also as a protection for the pins from too rapid 
heating, thus avoiding danger of checking the teeth. 
To prevent blisters in the paint, heat up slowly. The slab 
or tray upon which the teeth are heated may be taken from 
the hot furnace and placed in a cooling muffle. 
Coloring.-It should be remembered that there are but two 
primary colors in the artificial teeth, yellow and blue, but 
many tones (degrees of color) of these colors. The color 
of the various teeth is produced by shading, tinting, and 
blending. Therefore in staining teeth the primary color 
must be noted and an estimate made of the amount of 
shading a darker color will produce before producing the 
characteristic color upon the surface. 
It is always easier to deepen the color of a tooth than to 
make it lighter. 
The natural teeth are constantly growing darker with age, 
just in the ratio to the change in the natural complexion of 
the patient. This is due to the fact that the teeth belong 
to the dermal tissue and both are pigmented by the cir- 
culating fluids of the body. Therefore in coloring or stain- 
ing the teeth they may be shaded a little darker than the 
natural ones and be less conspicuous. 
The natural teeth are subject to many external coloring 
influences, as smoking and chewing tobacco or other drugs, 
discolored incipient decay or white or yellow spots from 
defective calcification of the teeth. 
APPLIED ESTHETICS. 
A few practical cases will suffice to elaborate this phase 
of the subject. Fig. 431 
Fig. 432 574 
ESTHETICS 
Figs. 431 and 432 is the patient previously presented, 
laughing. Fig. 431 shows the gum of the gum-section teeth, 
although much retruded. The teeth are undersize and have 
Fig. 433 
Fig. 434 
Fig. 435 
the artificial appearance of their type. Fig. 432 shows 
another view of the contour as illustrated in Figs. 424 and 
425 properly restored, and if the teeth are of suitable form, APPLIED ESTHETICS 
575 
Fig. 436 
Fig. 437 
Fig. 438 
Fig. 439 576 
ESTHETICS 
Fig. 440 
Fig. 441 APPLIED ESTHETICS 
577 
size, color, and individualized, they appear like well-pre- 
served natural teeth. If they do not harmonize in every 
respect the artificiality of the dentures is more conspicuous 
than in the old ones. 
Fig. 442 
Figs. 433 and 434 present two views of a patient; the one 
upon the left shows the upper of a gum-section set that had 
been worn for thirty years. The gum portion shows also 
the undersized, youthful appearance of the teeth. The lower 
teeth are entirely out of sight. The mouth is much better 
restored in the view upon the right. While the dentures in 578 
ESTHETICS 
Fig. 443 
Fig. 444 
Fig. 445 APPLIED ESTHETICS 
579 
Fig. 446 
Fig. 447 
Fig. 448 580 
ESTHETICS 
Figs. 435 and 436 are not ones in the patient's mouth, 
they are almost duplicate. 
Fig. 449 
Fig. 450 
Fig. 451 APPLIED ESTHETICS 
581 
Figs. 437 to 442 show the patient and teeth constructed 
to the mouth of the Williams "Trubyte" teeth. The teeth 
were all stained except the upper second molars, which 
were left unstained to show the change produced by staining. 
The effects can be seen in the photos, but it is doubtful if 
it will be apparent in the half-tones. 
Figs. 443 to 446 show different phases of esthetic restora- 
tion in continuous gum work. This is the completed case, 
the skeleton of which is shown in Figs. 356 and 357. 
Figs. 447, 448 and 449 are views of a continuous gum 
upper and cast metal lower that have been doing service for 
some years. The dentures had been worn four years when 
the photos were taken. 
Figs 450 and 451 are two views of a case, requiring a 
unilateral restoration, for a crescent-shaped face viewed from 
the front. INDEX. 
A 
Accelerators of vulcanization, 
193 
Adhesion by contact in retention, 
321, 331 
Alabaster, 69 
Alcohol heat for vulcanite, 247 
Alkalies for dental porcelain, 372 
Alloys of gold, 426, 427 
Aluminum, 402 
base-plate, 403 
Billmeyer casting bucket for, 
404 
burnishing of, 418 
carbon compounds and, 413 
casting of, 403, 413 
Billmeyer method for, 404 
cooling of, 415 
to porcelain teeth, 420 
removal of, 415 
crucible model for, 410 
Elgin vacuum casting ma- 
chine and, 421 
flasking of, 410, 417 
impression for, 404 
inelasticity of, 416 
investment compound cast for, 
404 
metal for, 412 
melting of, 413 
occlusion of gases and, 413 
oxidation and, 413 
polishing of, 417 
preparations for, 417 
relief chamber for, 405 
sprue formers for, 409 
swaged, 422 
attachment of, to vulcanite, 
423 
use of, 416 
vacuum chamber for, 405 
Aluminum base-plate, wax model 
base-plate for, 405 
chemical properties of, 402 
history of, 402 
physical properties of, 402 
swaging of, by die and counter- 
die method, 422 
by machine methods, 423 
by Parker shot swager, 424 
Alveolar processes, 46, 57 
closure of soft tissues over, 58 
development of, 46 
examination of, 58 
influence of, on form of base- 
plate, 58 
resorption of, 46 
appearance after, 58, 59 
time of, 59 
Alveolectomy, 58 
Anatomical "articulation," Bon- 
will's, 43 
Anchorage for porcelain teeth, 378 
Annealing in swaging of gold base- 
plate, 438 
Antagonization, mechanico-ana- 
tomical, in vulcanite dentures, 
257 
of model dentures, proving of 
(Hall), 286 
in vulcanite dentures, 257 
Antagonizor, 177 
Acme, 182 
Bonwill's, 177, 178 
Christensen's, 180 
distinction of, from articulator, 
176 
Evans', 177 
Gritman's, 180 
Gysi's, 182 
mounting of casts upon, 184 
Hall's, 184 
simplex, 182 
583 584 
INDEX 
Antagonizer, Hayes', 178 
history of, 177 
mounting on, in vulcanite den- 
tures, 252 
New Century improved, 182 
Parfitt, 181 
removal of model dentures from, 
292 
simplex, 182 
Snow's, 182 
mounting of casts upon, 185 
Walker's, 179 
Arch, dental, 54 
Areal contact, 126, 343, 347 
"Articulation, anatomical," Bon- 
will's, 41 
temporomandibular, 23 
Articulator, 176. See also Antag- 
onizor. 
anatomical, 176 
definition of, 176 
distinction of, from antagonizor, 
176 
Artificial dentures, casts for, 140 
retention of, 318 
Asbestos block for soldering con- 
tinuous gum dentures, 
497 
of gold, 444 
Atmospheric pressure plate, 320 
in retention, 333 
"Automaton" blowpipe, 446 
B 
Babbitt metal, composition of, 435 
for die, 434 
Bailey flask, 428 
Baking of continuous gum den- 
tures, 502, 504 
Balancing curve, short, in vulcan- 
ite dentures, 257 
Balkwill tee clasp, 355 
Bar, lower, clasp attachment for, 
477 
cope for, 483 
correction of too close fit in, 
479 
crib attachment for, 482 
dentures, 475 
double-wire method of, 479 
materials for, 476 
Bar, lower, single-wire method of, 
476 
tang attachment for, 485 
technic of, 476 
Base-plane, 56, 65, 344 
Base-plate, 144 
cheoplastic, 489 
construction of, 154 
for double vulcanization, 391 
form of, influence of alveolar 
processes on, 57 
gold, 426 
gutta-percha, 158 
materials for, 154 
metal, 161 ' 
modelling compound, 156, 158 
for occlusion model, 154 
outline of, 156 
in retention, 330 
paraffin, 155 
plate, aluminum, 403 
platinum, for continuous gum 
denture, 495 
resinoid preparations for, 158 
retaining, for artificial velum, 524 
tin, 154, 489 
vulcanite, 159 
wax-model, for aluminum, 405 
Basle Anatomical Nomenclature, 39 
B. D. M. Co. 18A flask, 362 
Bean's alloy, 489 
Beauty, form in, 558 
Williams on, 559 
science of, 558 
Beeswax, 65 
adulteration of, 66 
composition of, 66 
manipulation of, 66 
melting-point of, 65 
solvents of, 65, 66 
white, 65 
yellow, 65 
Bennett on lateral movements of 
mandible, 266 
Bicuspids in vulcanite dentures, 
intercuspation of, 255 
Bilateral vacuum chambers, 335 
Bilious temperament, 555 
Billmeyer casting bucket for alumi- 
num base-plate, 410 
method for casting of aluminum 
base-plate, 410 
i Bismuth compound for die, 435 INDEX 
585 
Bite, 152 
dental, definition of, 152 
gauges in occlusion models, 
165 
Snow's, 165 
hunk-, 152 
mush-, 152 
quash-, 152, 153 
technic of, 152, 153 
use of, 152 
wax-, 152 
Black tray compound, 127 
Block formation, cubical, plane of 
teeth and, 20, 21 
porcelain teeth, 385 
Blow-off for vulcanizer, 226 
Blowpipe, 446 
"automaton," 446 
flame, 448 
mechanical, 446 
use of, 447 
BNA classification of teeth, 39 
Body for porcelain teeth, 373 
Bogue comment on Mitchell palate 
and vomer restoration, 539 
Bonwill's antagonizor, 177 
demonstration of parabolic curve, 
41 
school, 373 
Box vulcanite flask, 224 
Brushes, 242 
for polishing, 242 
Bryant method of rigid clasps, 
356 
Buccal restoration in artificial den- 
tures, 566 
Buckling in swaging of gold base- 
plate, 439 
Buffers, 242 
construction of, 242 
for polishing, 242 
Buffing, 243 
method of, 243 
of vulcanite, 243 
Bunsen burner, 244 
construction of, 245 
flame of, 245 
Burner, Bunsen, 244 
jeweller's triple, 245 
Burning of porcelain teeth, 376 
Burnishing of aluminum base- 
plate, 417, 418 
Byrites impression plaster, 81 
c 
Calcined plaster, 70 
Caoutchouc, 190 
chemistry of, 193 
colloid, 192 
composition of, 193, 194 
history of, 190 
impurities in, 192 
preparation of crude, 192 
properties of, physical, 191 
purification of, 192 
solvents of, 192 
Carborundum, 240 
composition of, 240 
manufacture of, 240 
for polishing, 240 
wheels, 240 
Case's method of impression for 
artificial velum, 515 
Casting for aluminum base-plate, 
403, 413 
for gold base-plate, 427, 461 
machines, Alston (D. M. Co.),475 
Burns', 475 
Elgin, 475 
Hollenback's, 471 
methods, Laing-Elgin, 475 
for tin base-plate, 489 
for vacuum chambers, 334 
Casts, 136 
for artificial dentures, 140 
velum, 517 
compounds, 138, 139, 140 
definition of, 136 
distinction of, from model, 136 
for double vulcanization, 391 
French's dental plaster for, 138 
for gold base-plate, 428 
investment compounds for, 139 
luting of model dentures to, 292 
materials for, 137 
mounting of, 184 
upon antagonizor, Gysi's, 189 
Hall, 189, 280, 281 
Snow's, 185 
upon occlusion frames, 185 
with face bow, 186 
partial, 147 
oxyphosphate of zinc cement 
for, 149 
pouring of, 147 
repair of, 149 586 
INDEX 
Casts, plaster of Paris for, 138 
removal of, from plaster impres- 
sions, 145 
Spence's plaster compound for, 
138 
uses of, 137 
for vulcanite dentures, 248 
silex method in, 295 
tin method in, 295 
wax and compounds for, 65 
removal of, in vulcanite den- 
tures, 305 
wrapping of, technic of, 249 
Celluloid models, porcelain teeth 
for, 381 
Cement plaster, 70 
Centrifugence, 469 
Chalk, prepared, for polishing, 242 
Charcoal block for soldering of 
gold, 444 
Cheoplastic base-plate, 489 
Chisels, vulcanite, 236 
Christensen's antagonizor, 180 
Clamp, C, for swaging of gold base- 
plate, 439 
Donham's spring, 220 
Clasp attachment for lower bar, 476 
gold, 427 
Clasps, 349 
adaptation of, to teeth, 360 
advantages of, 349 
attachment of, location of, 362 
to plate, 362 
balancing of plate by, 357 
Balkwill tee, 355 
disadvantages of, 349 
formation of, with pliers, 360 
Jackson crib, 355 
location of, 358 
names for, 350 
pliers for, 360 
retention by, 349, 359 
rigid, 356 
Bryant method of, 356 
Schwartz method of, 357 
Roach loop, 355 
soldering of, to partial gold base- 
plates, 462 
spring, 350, 352 
flat, 356 
forms of, 354 
half-round, 356 
materials for, 354 
Clasps spring, round, 354 
teeth for, choice of, 352 
form of, 352 
longitudinal portion of 
clasped, 353 
of circumference of 
clasped, 352 
use of, 352 
stay, use of, 350 
teeth for, gripping of, 359 
Cleft-palate, 512 
appliances for, 512 
hare-lip and, 512 
obturator for, 512, 525 
denture, 527 
Suersen, 525 
velum, 520 
velum for, 512 
Close's continuous gum material, 
493 
Cocoa butter, 390 
Cohesion surface forms, Speyer's, 
for retention, 340 
Coloring material for vulcanite, 193 
of teeth, 522 
Compensating curve, 22 
in vulcanite dentures, 258 
vulcanizer, 303 
Complete vulcanite dentures, 248 
Compressibility of plaster, 75, 79 
Concave profile, 544, 547, 549 
Condit attachment, 365 
Condyle of mandible, 24, 26 
paths, determination of, 165 
Gysi's instruments for, 170 
in occlusion models, 165 
Snow bite gauges for, 165 
Cone, truncated, view of teeth as, 
43 
Contact, three-point compensating 
curve and, 22 
Continuous gum body, 493 
dentures, 492 
asbestos soldering block for, 
496 
baking of, 502, 504 
body for, application of, 502 
second, 504 
enamelling of, 504 
equipment for, 493 
furnaces for, 493 
Custer's, 494 
gasolene, 495 INDEX 
587 
Continuous gum dentures, furnaces 
for, Price's, 494 
pyrometer for, 494 
investment for, 497 
iridoplatinum wire for, 496 
magnesia soldering block 
for, 496 
materials for, 492, 493 
platinum and, 492 
base-plate for, 495 
polishing of, 505 
porcelain for, 493 
application of, 502 
reinforcing wires for, 499 
repair of, 506 
shrinkage in, 502 
solder for, 496 
technic of, 495 
teeth for, 497 
soldering of, 497 
material, Close's, 493 
Contour models, 151. See also 
Occlusion models. 
proving of, for double vulcani- 
zation, 393 
Contraction of plaster, 75 
Convex profile, 544, 549 
Cope attachment for lower bar, 
483 
Cores for gold base-plate, 430 
Corundum, 240 
composition of, 240 
manufacture of, 240 
for polishing, 240 
Counter-die construction of, 436 
for gold base-plate, 436 
Countersunk pin for porcelain 
teeth, 382 
Crib attachment for lower bar, 
480, 482 
Cross-bar vulcanizer, Lewis, 225 
Crucible mold for aluminum base- 
plate, 410 
Cubical block formation, plane of 
teeth and, 20 
Curve, compensating, 22 
distinction of, from curve of 
Spee, 22 
three-point contact and, 22 
parabolic, 31, 41 
Bon will's demonstration of, 41 
determination of, 41 
modifications of, 41, 42 
Curve of Spee, 21 
curvature of, 22 
distinction of, from compen- 
sating curve, 22 
Custer's furnace, 494 
D 
"Dead-burned" gypsum, 71 
Deglutition test for model denture, 
290 
Dental arch, distinction of, from 
dental vault, 54 
examination of, 55 
shape of, 54 
porcelain, 370 
profile, 544 
lips in, 550 
vault, examination of, 54 
Dentistry, relation of, to esthetics, 
542 
Denture obturator, 527 
Dentures, artificial buccal restora- 
tion in, 566 
casts for, 140 
full, retention of, 324 
labial surface of, 553 
lingual surface of, 552 
retention of, 318 
soft palate and, 30 
"sticking up" of, 328 
vulcanite in, 217 
bar, lower, 475 
continuous gum, 492 
partial lower, gold base-plates 
for, 475 
upper, gold base-plates for, 457 
vulcanite, complete, 248 
Detachable crowns, Nies' method, 
386 
for vulcanite work, 386 
tray method in partial upper im- 
pressions, 115 
De Trey Brothers' protesyn, 388 
"Diatoric" porcelain teeth, 380 
Die, 434 
and counter method for gold 
base-plate, 428 
Babbit metal for, 434 
bismuth compound for, 435 
metal for, 434 
pouring of, 436 588 
INDEX 
Die, zinc for, 434 
Disks for retention, 337 
Donham clamps, 220 
Double vulcanization, 391 
Doublers, 442 
formation of, 443 
for partial gold base-plate, 442 ' 
soldering of, to gold base-plate, I 
449 
E 
Electric drying oven, 300 
lathes, 237 
Elgin vacuum casting machine, 421 
Emergency vacuum chamber, 320 
Emery, 240 
for polishing, 240 
Eminentia articularis, 23, 24 
Enamelling of continuous gum 
dentures, 504 
Enamels for porcelain teeth, 374 
Encasement, metal, for artificial 
velum, 524 
English dental tin, 126 
double punch, 455 
Enlarged raphe, impressions for, 
104 
Equalized pressure test for model 
dentures, 290 
Equilateral triangle, 268 
Eruption of teeth, 45 
Esthetics, 540 
applied, 572 
relation of, to dentistry, 542 
of occlusion models to, 564 
teeth and, 569 
Evans' antagonizor, 177 
Expansion of plaster, 73, 79 
Expression, facial, in action, 567 
muscles of, 29 
Extension for retention, 31, 126, 
326, 344, 347 
F 
Face, anatomy of, 17 
bow, mounting of casts with, 166 
occlusion models and, 166 
Snow's, 166 
interdental splints and, 498 
Face bow, technic of, 167 
use of, 167 
divisions of, 17 
ideal Greek, 18 
Facial expression in action, 567 
Feldspar, 370 
composition of, 370 
for dental porcelain, 371 
preparation of, 371 
Ferrules, 357 
for gold base-plate, 485 
indications for, 357 
Files for vulcanite, 236 
Fillers used in vulcanite, 193 
Finishers, soldering of, to gold 
base-plate, 450 
wire, soldering of, to gold base- 
plate, 451 
Finishing of artificial velum, 524 
of partial vulcanite dentures, 311 
Flame method for removal of teeth 
from vulcanite dentures, 312 
Flask, closing of, cloth for, 298 
dangers in, 298 
for double vulcanization, 396 
for gold base-plate, 428 
heating of, 294 
opening of, 293 
placing of, in vulcanizer, 304 
press, 224 
and Wilson spring, 225 
power of, 225 
removal of vulcanite denture 
from, 304 
from vulcanizer, 304 
of wax from, 294 
Snow, for interdental splints, 508 
vulcanite, 219 
box, 224 
Star, 220 
Whitney's, 220 
18A, 362 
Wilson's, 220 
Flasking of aluminum base-plate, 
410, 417 
clasp dentures, 362 
for double vulcanization, 396 
of full dentures, 292 
of model for artificial velum, 522 
of partial vulcanite dentures, 309, 
362 
Flask-tongs, 234 
I Flat spring clasps, 356 INDEX 
589 
Flooring plaster, 70 
Flux for porcelain teeth, 374 
for soldering of gold, 446 
Fossa, glenoid, 23 
Frame, occlusion, 176 
French's dental plaster for cast, 138 
Frits for porcelain teeth, 374 
Full artificial dentures, retention of, 
324 
lower gold base-plate, swaging 
of, 440 
impressions, 104 
Furnace for heating flasks, Hollen- 
back's, 471 
Mave's, 463 
Furnaces for continuous gum den- 
tures, 493 
Fusible metal method for repair of 
vulcanite dentures, 315 
G 
Gas stove heat for vulcanite, 247 
Gasolene furnace, 495 
heat for vulcanite, 247 
heater for laboratory, 247 
Gas-regulator for vulcanizer, 226, 
228 
Gilmore attachment, 367 
needles for plaster of Paris, 75 
Glandular tissues of mouth, exami- 
nation of, 60, 61 
Glenoid fossa, 23 
Glossing, 244 
method of, 244 
of vulcanite, 244 
Glycerin method for removal of 
teeth from vulcanite dentures, 
312 
Gold, alloys of, 426 
base-plate, 426, 427 
cast for, 428 
cores for, 430 
counter-die for, 436 
die for, 434 
and counter method for, 428 
edge of, turning of, 450 
ferrules of, 357 
flask for, 428 
Bailey, 428 
Hawes' parting, 432 
Lewis, 428 
Gold base-plate, full lower, swag- 
ing of, 441 
impression for, 428 
methods for, 427 
casting, 427 
swaging, 427 
model for, 427 
molding for, 428, 432 
sand for, 432 
technic of, 433 
partial, 458 
casting method for, 461 
doublers for, 442 
lower dentures, 463 
soldering of clasps to, 460 
Spence plaster compound 
for, 460 
swaging of, 441, 460 
files for, 441 
nippers for, 441 
for partial upper dentures, 457 
repair of, 485 
soldering of attachments to, 
449 
of buccal finishers to, 450 
of doublers to, 449 
of finishers to, 450 
of labial finishers to, 450 
of porcelain to, 455 
backings for, 455 
investment for, 456 
cooling of, 457 
heating of, 456 
of retainers to, 452 
of teeth in, 453 
warping in, 453 
of wire finishers to, 451 
swaging of, 427, 437 
annealing in, 428 
buccal finishers to, 450 
buckling in, 439 
C clamp for, 439 
half counter-die for, 441 
horn mallet for, 438 
labial finishers to, 450 
pattern for, 437 
"pickle" for, 439 
rubber mallet for, 438 
casting, investment compounds 
for, 462 
methods of, cold flask for cast- 
ing, 463, 471 
direct, 462 590 
INDEX 
Gold casting, method of, "green" 
mold, 463 
heat for, 461, 462 
heating flasks, 463, 471 
indirect, 463 
characteristics of, 426 
clasp, 427 
fillings, teeth and, 569 
fineness of, standard of, 426 
plate, 426 
solder, 426 
soldering of, 443 
asbestos block for, 444 
blowpipe for, 446 
charcoal block for, 444 
flux for, 445 
investment compound for, 444 
magnesia block for, 444 
technic of, 443 
swaging of, 428 
Graphite investment compound, 
462 
Greene-Supplee method, 124-127 
Greene's method for full upper im- 
pressions, 64, 122, 125 
Griffin swaged tray, 126 
Grinding of vulcanite, 236 
Gritman's antagonizor, 180 
Gum dentures, continuous, 492 
enamel, 493 
flabby, in full upper impressions, 
99 
porcelain teeth, 377, 383 
"section" porcelain teeth, 383 
Gunning interdental splints, 507 
Gutta-percha, 65, 69 
base-plate, 158 
source of, 69 
use of, 69 
Gypsum, 69 
burning, chemistry of, 70 
composition of, chemical, 69 
"dead-burned," 71 
impurities in, 69 
massive, 69 
products, grinding of, 72 
rock, 69 
Gysi on "trubyte" teeth, 385 
Gysi's antagonizor, 182 
mounting of casts upon, 189 
measuring instruments, 170 
determination of condyle 
path with, 170 
Gysi's measuring instruments for 
lateral movements of man- 
dible, 170,266 
technic for, 170-175 
H 
Half-round spring clasps, 356 
Hall method for antagonization, 
275-288 . 
for impression, 127-134 
Hands, cleansing of, for examina- 
tion of mouth, 51 
Hard casts, technic for, 249 
velum obturator, 526 
Hard-finish plaster, 70 
Hare-lip, cleft-palate and, 514 
Harmony, 514 
Hawes' parting flask, 432 
Hayes' antagonizor, 178 
Heat for vulcanite, 244 
Hevea Braziliensis, 192 
Horn mallet for swaging, 438 
Hunk-bite, 152 
Hydrogen sulphide in vulcanite, 
205, 209 
Hydrostatic law of retention, 319 
I 
Impression, 63 
for aluminum base-plate, 404 
for artificial velum, 515 
definition of, 63 
for double vulcanization, 391 
for enlarged raphe, 104 
filling of, 141 
full lower, 104 
classification of, 104 
ridge in, broad, 104, 105 
flat, 107 
high, 105 
thin, 107 
technic of, 105 
"new scheme," 64 
principles, 127 
upper, classification of, 87 
flabby gum in, 101 
flat vaults in, 99, 100 
Greene's method for, 122, 
125, 127 
high vaults in, 98 INDEX 
591 
Impression, full upper, interspersed 
hard and soft tissues in, 
101 
modelling compound for, 
120-127 
"muscle trimming" in, 122 
normal, 87 
plaster for, mixing of, 91 
position of patient in, 91 
reinforcement for, 89 
removal of, 94 
soft tissues in, 99 
technic of, 87 
tray in, adjustment of, 88 
filling of, 92 
insertion of, 92 
placing of, 92 
reinforcing of, 89 
for gold base-plate, 428 
gutta-percha for, 68 
for interdental splints, 492 
materials for, 65 
modelling compound for, 67 
partial lower, 117 
classification of, 117 
upper, 109 
alternating teeth and spaces 
in, 111 
anterior teeth in, loss of, 109 
classification of, 109 
detachable tray method in, 
115 
isolated teeth method in, 114 
posterior teeth in, loss of, 
111 
plaster of Paris for, 69 
removal of, from casts, 145 
pouring of, 141 
preparation of, 141 
for retaining base-plate for arti- 
ficial velum, 524 
scheme for, 63 
separating fluids for, 141 
separation of, from casts, 145 
trays, 81 
body of, 82 
definition of, 81 
distinction of, from cups, 81 
flanges of, 82 
floor of, 82 
forms of, 82 
handle of, 82 
materials for, 82 
Impression trays, nomenclature of, 
82 
removal of, in vulcanite den- 
tures, 308 
surfaces of, 82 
for upper vulcanite dentures, 308 
use of, 141 
varnishes for, 141, 142 
for vulcanite dentures, 248 
wax for, 63, 64 
Incisor path, registration of, 170 
India-rubber, 190. See Caout- 
chouc. 
Inferior maxilla, 25. See Man- 
dible. 
Interdental splints, 507 
cast for, 508 
construction of, 508 
Gunning, 508 
impressions for, 508 
Snow face bow and, 509 
flask for, 509 
Interval timer, 300 
Iridoplatinum wire for continuous 
gum dentures, 496 
Ironing-in method for repair of 
vulcanite dentures, 316 
Isolated teeth method in partial 
upper impressions, 114 
Isosceles triangle, 268 
J 
Jackson crib clasp, 355 
Jaw, development of, eruption of 
teeth and, 45 
lower, 25. See Mandible. 
Jeweller's triple burner, 245 
K 
Kaolin, 371 
composition of, 371 
for dental porcelain, 371 
use of, 372 
Kingsley's alloy, 489 
Knives, plaster, 150 
L 
Labial surfaces of artificial den- 
tures, 553 592 
INDEX 
Lateral movements of mandible, 
266 
Bennett on, 266 
Gysi on, 266 
Latex, 191 
Lathes, 237 
care of, 240 
electric, 240 
polishing, 240 
power for, 240 
Le Chatelier's theory of setting of 
plaster, 72 
Lenox mineral for staining of teeth, 
570 
Leverage in retention, 322, 330 
Lewis cross-bar vulcanizer, 225 
flask, 428 
Ligaments, 26 
function of, 26, 27 
Line, naso-auditory-meatus, 18 
Lines in occlusion models, marking 
of, 163 
Lingual surfaces of artificial den- 
tures, 552 
Lips in dental profile, 550 
Lower impressions, full, 104 
partial, 117 
jaw, 25. See Mandible. 
Luting of model dentures to casts, 
. 291 
Lymphatic temperament, 554 
M 
Magnesia block for soldering 
continuous gum dentures, 
596 
of gold, 444 
Magnesium oxychloride, 140, 249 
Mallet, horn, for swaging, 438 
rubber, for swaging, 438 
Mandible, 25 
body of, 25 
condyle of, 23, 24 
relation of, to glenoid fossa, 24 
importance of, 25 
mastication and, 26 
movements of, 25 
lateral, 266 
Bennett on, 24, 266 
measurement of, 266 
Gysi on, 266 
Mandible, muscles of, 27 
not a lever, 34-36 
rami of, 25 
Mandibular surfaces, size of, sig- 
nificance of, 56 
Manifolder for vulcanizer, 228 
Massive gypsum, 68 
Mastication, 48 
loss of teeth and, 40 
mandible in, 25 
muscles of, 27 
purpose of, 48 
Mathew's wax sprue former, 406, 
467 
Maxilla, inferior, 25. See Mandible. 
Maxillary raphe, examination of,55 
surfaces, size of, significance of, 
56 
suture, examination of, 56 
Measuring instruments, Gysi's, 170 
for occlusion models, 170 
Mechanico-anatomical antagoniza- 
tion in vulcanite dentures, 257 
Metal base-plate, 161 
Mineral wax, 66 
Mitchell on palate and vomer res- 
toration, 530 
Model, antagonization of, proving 
of, 289 
for artificial velum, 521 
contour, 151. See also Occlu- 
sion models. 
technic of, 565 
conversion of, into vulcanite, 291 
deglutition test for, 290 
distinction of, from cast, 136 
equalized pressure test for, 290 
finishing of, 288 
flasking of, 292 
for gold base-plate, 428 
luting of, to casts, 291 
occlusion, 151 
proving of, 289 
opening of flask in, 293 
proving of, 289 
removal of, from antagonizor, 
292 
for vulcanite dentures, 288 
Modelling compound, 67 
base-plate, 156, 158 
composition of, 67 
formula for, Williams', 68 
for full upper impressions, 120 INDEX 
593 
Modelling compound, manipula- 
tion of, 68 
Schoenbeck on, 67 
Molars in vulcanite dentures, posi- 
tion of, 257 
Molding for gold base-plate, 428, 
432 
of porcelain teeth, 374 
sand for gold base-plate, 432 
Molecular attraction in retention, 
331 
Morgan attachment, 365 
Mounting of casts, 184-189 
Mouth, 17 
examination of, 52 
fluids of, 60 
hands in, cleansing of, 51 
method of, 52 
mouth mirror in, 52 
muscular attachments of, 60 
protection of patient during, 51 
seating of patient during, 51 
tissues of, glandular, 60 
mucous, 60 
submucous, 60 
use of, 48 
Mucous membrane in retention of 
full artificial dentures, 327 
tissues of mouth, examination of, 
60 
Muscle trimming in full impres- 
sions, 124-127, 342 
Muscles of expression, 29 
of mastication, 27 
of maxillae, 30 
Mush-bite, 152 
N 
Naso-auditory-meatus line, 18 
occlusion models and, 161 
Nausea, 345 
treatment of, 345 
Nervous temperament, 555 
New impression plaster, 81 
scheme, 60 
school of dental prosthetics, 373 
Ney-OrO golds, 461, 462 
Nielsin impression plaster, 81 
Nitrohydrochloric acid, vulcanite 
and, 218 
Nomenclature, Basle Anatomical, 
39 
O 
Obturator for cleft palate, 512, 
526 
denture, 527 
Suersen, 525 
velum, 527 
Occlusion frame, 176 
mounting of casts upon, 184 
use of, 184 
models, 151 
base-plate for, 154 
bite gauges in, 165 
condyle path in, 165 
construction of, 161 
definition of, 151 
for double vulcanization, 392 
face bow and, 166 
lines in, marking of, 164 
materials for, 152 
measuring instruments for, 170 
naso-auditory-meatus line and, 
162 
plane of teeth in, 162 
protrusion of chin in, 163 
relation of, to esthetics, 564 
retrusion of chin in, 163 
testing of, 163 
use of, 152 
for vulcanite dentures, 251,300 
of teeth, 41 
Oxyphosphate of zinc cement for 
repair of casts, 150 
vacuum chambers and, 334 
P 
Packing for double vulcanization, 
399 
of rubber for vulcanite dentures, 
296 
Palate, cleft, 512 
soft, 30 
artificial dentures and, 512 
and vomer restoration, Mit- 
chell on, 530 
Parabolic curve, 41 
Paraffin base-plate, 155 
Parallelogram of forces, 33 594 
INDEX 
Paris, plaster of, 69 
Parker shot swager, 425 
Partial casts, 147 
gold base-plate, 457 
impressions, lower, 117 
upper, 109 
plates, Beach method, 488 
Cummer method, 488 
vs. bridge dentures, 485 
vulcanite dentures, 309 
Perfected method of vulcanization, 
299-305 
Peripheral bearing, 127, 344, 347 
Petroleum heat for vulcanite, 247 
Philosophy of casting of Aluminum 
(Billmeyer), 414 
Physics of mastication, 32 
Physiognomy, relation of, to teeth, 
545 
"Pickle" for swaging of gold base- 
plate, 439 
Pigments for dental porcelain, 373 
Pink rubber for double vulcaniza- 
tion, 399 
"Pinless" porcelain teeth, 380 
Pins, countersunk, for porcelain 
teeth, 362 
platinum, for porcelain teeth, 380 
Plain porcelain teeth, 377, 381 
Plane of teeth, 18 
cubical block formation and,20 
in occlusion models, 162 
Plaster, calcined, 69, 70 
casts, shape for, 144 
cement, 70 
classification of, 69 
compound, Spence's, 138 
manipulation of, 139 
Portland cement in, 138 
compressibility of, 75, 79 
contraction of, 75 
expansion of, 75 
flooring, 70 
hard finish, 70 
knives, 150 
Wilson's, 150 
of Paris, 69 
for casts, 138 
formula of, 69 
Gilmore needles for, 75 
physical properties of, tables 
for, 74, 76 
pulverization of, 74 
Plaster, setting of, Le Chatelier's 
theory of, 72 
stucco, 70 
wall, 70 
Plate attachments, Condit, 365 
Gilmore, 368 
Morgan, 365 
Roach, 368 
gold, 426 
porcelain teeth, 382 
Platinum base-plate for continuous 
gum dentures, 495 
continuous gum dentures and, 
492 
pins for porcelain teeth, 378 
Pliers for clasps, 360 
Polishing of aluminum base-plate, 
417 
brushes for, 242 
buffers for, 242 
carborundum for, 240 
of continuous gum dentures, 
505 
corundum for, 240 
emery for, 240 
lathes, 237 
powders for, 242 
prepared chalk for, 242 
pumice stone for, 242 
stones for, 240 
of vulcanite, 236 
Polyprene in vulcanite, 205, 207 
Porcelain for continuous gum 
dentures, 493, 502 
dental, 370 
alkalies for, 372 
composition of, 370 
definition of, 370 
feldspar for, 370 
kaolin for, 371 
materials for, 370 
pigments for, 373 
potassium for, 372 
silica for, 371 
sodium for, 372 
soldering of, to gold base-plate, 
455 
teeth, 369 
anchorage for, 380 
attachment of, to base, 378 
"block," 384 
body for, 373 
burning of, 376 INDEX 
595 
Porcelain teeth, casting of, to alu- 
minum base-plate, 420 
for celluloid models, 387 
classification of, 377 
countersunk pin for, 382 
"diatoric," 380 
enamels for, 374 
flux for, 374 
forms of, 381 
improvements in, 384 
Williams', 384 
frits for, 374 
gum, 374, 384 
"gum section," 384 
history of, 369 
manufacture of, 373 
molding of, 374 
"pinless," 380 
plain, 377, 380 
plate, 382 
platinum pins for, 378 
stock material for, 373 
Porritt on rubber and vulcanite, 
191, 192, 193 
Portland cement in Spence's plaster 
compound, 138 
Potassium for dental porcelain, 372 
Powders for polishing, 242 
Prepared chalk for polishing, 242 
Pressure, atmospheric, in reten- 
tion, 318 
equalized, test for model den- 
tures, 290 
Price's furnace, 494 
Profile, concave, 544 
convex, 544 
dental, 544 
lips in, 550 
straight, 544 
Prosthesis, definition of, 540 
Protesyn, 388 
Prothero's cast compound, 140, 249 
Pumice stone for polishing, 242 
Punch, English "double," 455 
single, 455 
Pyrometer, 494 
Q 
Quality of Aluminum for a cast- 
ing, 413 
Quartz, 371. See Silica. 
Quash-bite, 152, 153 
R 
Raphe, enlarged, impressions for, 
104 
maxillary, examination of, 55 
Reese's alloy, 489 
Relief chamber for aluminum base- 
plate, 405 
Repair of vulcanite dentures, 312 
Replacement method for repair of 
vulcanite dentures, 316 
Resinoid preparations for base- 
plate, 158 
Restoration, unilateral, 581 
Retainers, soldering of, to gold 
base-plate, 452 
Retention, adhesion by contact in, 
321, 325, 331 
of artificial dentures, 318 
atmospheric pressure in, 318, 333 
balancing of plate in, 354 
base-plate outline in, 330 
by cementation, 363 
by clasps, 349 
disks for, 337 
by ferrules, 357 
of full artificial dentures, 324 
conditions affecting, 324 
fluids in, 329 
mucous membrane in, 327 
shape in, 330 
size in, 324 
soft tissues in, 324 
submucous tissue in, 327 
tension in, 328 
tone in, 328 
hydrostatic law of, 319 
leverage in, 322, 330 
of lower base-plate, 326 
molecular attraction in, 331 
of partial vulcanite dentures, 349 
physical laws of, 318 
principles of, 318, 330 
application of, 330 
soft vulcanite in, 336 
Speyer's cohesion surface forms 
for, 340 
by tensofriction, 348 
vacuum chambers and, 334 
velum rubber in, 336 
Rigid clasps, 350 -356 
Roach attachment, 368 
loop clasp, 355 596 
INDEX 
Rock gypsum* 69 
Roots, examination of, 53 
Round spring clasps, 354 
Rubber, 190. See Caoutchouc. 
for artificial velum, 524 
mallet for swaging, 438 
packer, Zurbrigg's, 297 
packing of, for vulcanite den- 
tures, 190 
pink, for double vulcanization, 
399 
velum, 336 
S 
Safety-valve for vulcanizer, 226 
Sand, molding, for gold base-plate, 
432 
Sanguine temperament, 587 
Scalene triangle, 268 
Schoenbeck on modelling com- 
pound, 67 
Schwartz method of rigid clasps, 
356 
Scrapers, vulcanite, 236 
Selenite, 69 
Separating fluids for impressions, 
142 
Setting of plaster, Le Chatelier's 
theory of, 72 
Sheet-iron method for removal of 
teeth from vulcanite dentures, 
312 
Shrinkage in continuous gum den- 
tures, 502 
Silex method in cast for vulcanite 
dentures, 295 
Silica, 371 
composition of, 371 
for dental porcelain, 371 
preparation of, 371 
use of, 371 
Single punch, 455 
Snow's antagonizor, 181 
mounting of casts upon, 185 
bite-gauges, 165 
compensating vulcanizer, 303 
face bow, 166 
interdental splints and, 507 
flask for interdental splints, 509 
research on vulcanite, 214-216 
Sodium for dental porcelain, 372 
Soft palate, 31 
tissues in retention of full arti- 
ficial dentures, 324 
vulcanite, 320 
Solder for continuous gum den- 
tures, 496 
gold, 426 
Soldering of gold, 443 
Spatulas for wax, 218 
Spee, curve of, 21 
Speech, teeth and, 49 
artificial, 49 , 
loss of, 50 
Spence's plaster compound for 
casts, 138 
for double vulcanization, 
396 
for partial gold base-plates, 
460 
in vulcanite dentures, 249, 
308 
Speyer's cohesion surface forms for 
retention, 34 
Splints, interdental, 507 
Spring clasps, 350, 352 
Sprue formers for aluminum base- 
plate, 406 
Staining of teeth, 569 
Star vulcanite flask, 220 
Stay clasps, 350 
Steam gauge for vulcanizer, 226 
pressure in vulcanizer, 231 
"Sticking up " of artificial dentures, 
328 
Stones for polishing, 250 
use of, 252 
Straight profile, 544 
Stucco plaster, 70 
Submucous tissues of mouth, exam- 
ination of, 50 
in retention of full artificial 
dentures, 327 
"Suction" plate, 320 
Suersen obturator, 525 
Sulphur in vulcanite, 205' 
Supplee credit, 64 
hot-water heater, 127 
Surfaces, mandibular, size of, sig- 
nificance of, 56 
maxillary, size of, significance of, 
56 
Surgical treatment of alveolus, 
58 
velum, 336 INDEX 
597 
Suture, maxillary, examination of, 
55 
Swaged aluminum base-plate, 422 
tray, 127 
Swaging of aluminum by die and 
counter-die method, 422 
of full lower gold base-plate, 440 
of gold, 428 
base-plate, 428, 437 
method for partial gold base- 
plates, 460 
T 
Tang attachment for bar, lower, 
483 
Teeth, 38 
and spaces, alternating, in par- 
tial upper impressions, 111 
anterior, loss of, in partial upper 
impressions, 109 
arrangement of, 568 
artificial, speech and, 49 
classification of, 38-41 
color of, 568 
coloring of, 572 
eruption of, 41 
development of jaws and, 41 
order of, 45 
esthetics and, 567 
examination of, 53 
form of, 568 
function of, 38 
gold filling and, 569 
grinding of, in vulcanite den- 
tures, 252, 308 
individualization of, 508 
loss of, importance of, 50 
mastication and, 50 
results of, 50 
speech and, 49 
occlusion of, 41 
parabolic rows of, 38 
plane of, 19 
in occlusion models, 162 
porcelain, 369 
posterior, loss of, in partial upper 
impressions, 111 
1 relation of, to physiognomy, 545 
removal of, from vulcanite den- 
tures, 312 
setting up of, in vulcanite den- 
tures, 252, 253 
size of, 568 
Teeth, speech and, 49 
for spring clasps, form of, 352 
staining of, 569 
by Lenox mineral, 570 
materials for, 570 
metallic oxides for, 570 
technic of, 571 
"trubyte," Gysi on, 385 
Williams on, 384 
view of, as truncated cone, 43 
Temperaments, 554 
bilious, 555 
classification of, 554, 558 
definition of, 554 
lymphatic, 554 
nervous, 555 
sanguine, 554 
Temporomandibular articulation, 
23 
Tensofriction, 347 
retention by, 347 
Thermometer for vulcanizer, 226, 
233 
Time-regulator for vulcanizer, 228 
Tin base-plate, 154, 489 
alloys for, Bean's, 489 
Kingsley's, 489 
Reese's, 489 
Watt's, 489 
Weston's, 489 
casting of, 489 
metal for, 489 
technic of, 489 
Watt's flask for, 489 
method in cast for vulcanite 
dentures, 295 
Tinfoil for double vulcanization, 
394, 395 
Tongue, 28 
function of, 28 
Trays, impression, 81 
Triangle, equilateral, 268 
isosceles, 268 
scalene, 268 
Trimmers, vulcanite, 236 
"Trubyte" teeth, Gysi on, 385 
Williams on, 384, 581 
Truman on porosity of vulcanite, 
213 
U 
Unilateral restoration, 581 
vacuum chambers, 335 598 
INDEX 
Upper impressions, full, technic of, 
87 
partial, 109 
V 
Vacuum chambers, 334 
for aluminum base-plate, 405 
attachment of, 334 
bilateral, 335 
for castings, 334 
construction of, 334 
edges of, 334 
forms of, 335 
indications for, 334 
materials for, 334 
oxyphosphate of zinc cement 
and, 334 
retention and, 334 
soft vulcanite for, 336 
unilateral, 335 
velum rubber for, 336 
Varnishes for impressions, 142 
Vault, dental, distinction of, from 
dental arch, 54 
examination of, 54 
value of, 55 
flat, difficult, in full upper im- 
pressions, 100 
in full upper impressions, 99 
high, in full upper impressions, 
98, 99 
maldevelopment of, 55 
Vegetable wax, 66 
Velum, artificial, 512 
cast for, 517 
for cleft palate, 512 
construction of, 575 
finishing of, 524 
impression for, 515 
Case's method of, 515 
for retaining base-plate for, 
524 
model for, 519, 521 
adjustment of, to mouth, 521 
flasking of, 522 
metal encasement for, 522 
retaining base-plate for, 524 
rubber for, 524 
obturator, 527 
palati, 31 
rubber in retention, 336 
Velum, rubber, for vacuum cham- 
bers, 336 
Volute spring, 221, 225 
Vulcanite, 190, 194 
advantages of, 218 
in artificial dentures, 218 
attachment of swaged aluminum 
base-plate to, 423 
base-plate, 159 
advantages of, 159 
disadvantages of, 159 
technic of, 159 
buffing of, 242 
chemistry of, 202 
chisels, 236 
coefficient of expansion of, 201 
coloring of, 193 
composition of, 196 
dentures, antagonization in, 257 
proving in, 259 
base-plates for, 251 
bicuspids in, intercuspation of. 
256 
casts for, 248 
silex method in, 295 
tin method in, 295 
compensating curve in, 258 
complete, 248 
contour model for, 307 
conversion into, of model den- 
tures, 291 
diagnosis for, 248 
examination of mouth for, 307 
finishing of, 305 
flask in, closing of, 298 
ope'ning of, 293 
impression for, 248 
flask in, removal of, 304 
insertion of, 306 
lower, construction of, 307 
mechanico-anatomical antag- 
onization in, 257 
molars in, position of, 257 
mounting on, antagonizor in, 
252 
occlusion and contour models 
for, 251 
partial, 309 
flasking of, 309 
finishing of, 311 
retention of, 311 
prognosis for, 248 
removal of, from flask, 304 INDEX 
599 
Vulcanite dentures, removal of 
teeth from 312 
flame method for, 312 
glycerin method for, 312 
sheet-iron method for, 312 
repair of, 312 
additions to old plates for, 
317 
fusible metal method for,315 
ironing-in method for, 316 
replacement method for, 316 
wax method for, 313 
rubber for, packing of, 296 
short balancing curve in, 258 
specific gravity of, 200 
table for, 201 
Spence plaster compound in, 
249 
teeth in, grinding of, 252 
setting up of, 252, 253 
upper, construction of, 307 
impressions for, 307 
wax casts in, removal of, 307 
disadvantages of, 218 
double vulcanization of, 391. See 
Vulcanization, double. 
files for, 236 
fillers, 193 
flasks, 219 
formula for, chemical, 203 
formulas for, 197, 198 
glossing of, 244 
grinding of, 236 
heat for, 244 
alcohol, 247 
Bunsen burner, 244 
gas stove, 247 
gasolene, 247 
jeweller's triple burner, 245 
petroleum, 247 
history of, 194 
hydrogen sulphide in, 206 
nitrohydrochloric acid and, 218 
polishing of, 236 
polyprene in, 205 
porosity of, 199, 208, 209, 217 
Truman on, 217 
properties of, physical, 199 
repair of, 200, 312 
research, Snow on, 214-216 
scrapers, 236 
soft, for vacuum chambers, 336 
in retention, 337 
Vulcanite, solvents of, 199 
sulphur in, 200 
trimmers, 236 
Weber's experiments with, 193, 
203 
Vulcanization, 208, 211 
chemistry of, 203, 207 
double, 391 
base-plate for, 391 
cast for, 391 
finishing of, 400 
flask for, 396 
separation of, 397 
Wilson's, 396 
flasking for, 396 
preparation of case for, 
393 
impressions for, 391 
mounting of teeth for, 393 
occlusion and contour models 
for, 392 
packing for, 399 
peripheral strings in, 393 
pink rubber for, 399 
proving of contour of, 393 
separating cloth for, 399 
Spence's plaster compound for, 
396 
technic of, 391 
temperature for, 212-215 
tinfoil for, 394 
Walker's granular gum for, 
399 
temperature for, 212 
Vulcanizers, 225 
blow-off for, 226 
gas-regulator for, 226, 228 
leakage in, 234 
Lewis' cross-bar, 225 
manifolder for, 226 
operation of, 228 
placing of flask in, 212 
removal of flask from, 304 
safety-valve for, 226 
steam gauge for, 226 
pressure in, 231 
elastic force of, 232 
thermometer for, 226, 232 
time-regulator for, 229 
operation of, 231 
setting of, 229 
use of, 228 
Vulcanizing, technic of, 234 600 
INDEX 
W 
Walker's antagonizor, 178 
granular gum for double vulcan- 
ization, 399 
Wall plaster, 70 
Warping in soldering of gold base- 
plates, 453 
Watt's alloy, 489 
flask, 489 
Wax, 65 
characteristics of, 65 
and compounds for casts, 139 
instruments for, 218 
method for repair of vulcanite 
dentures, 313 
mineral, 66 
composition of, 66 
model base-plate for aluminum 
base-plate, 405 
removal of, from flasks, 294 
spatulas for, 218 
vegetable, 66 
Wax-bite, 152 
Weinstein's cast compound, 132 
gold formulas, 461, 462 
Weston's alloy, 489 
Wheels, carborundum, 240 
White wax, 65 
Whitney's vulcanite flask, 221 
Williams' forms of porcelain teeth, 
384 
on form, 559 
formula for modelling compound, 
68 
on "trubyte" teeth, 384, 581 
Wilson's flask for double vulcani- 
zation, 396 
plaster knife, 150 
vulcanite flask, 221 
Wire method, double, for bar, 
lower, 479 
single, for bar, lower, 476 
reinforcing, for continuous gum 
dentures, 499 
Y 
Yellow wax, 55 
Z 
Zinc for die, 434 
oxyphosphate of, cement, for 
repair of casts, 149 
Zurbrigg's rubber packer, 297