HflUDBOOK 
FOR THf 
Dental Assistant 
ROD 
(Dectianic H fl n D B 0 0 ti 
for the 
Dental Assistant 
and 
mechanic fORtUIORD 
Many complex problems confront the Dental 
Corps at the present time in the development of 
its various activities in the expansion program. 
One of the principal problems concerns the de- 
velopment of our laboratory service and the train- 
ing of our dental technicians and enlisted per- 
sonnel who are trained as dental assistants. The 
entire training program depends very largely 
upon a standardization of our dental service. This 
even involves all the activities of our enlisted 
personnel. 
The chapters in this Manual cover the essential 
phases and all activities of our dental technicians 
and chair assistants. The lectures were prepared 
as a part of the activities of the Army Dental 
School, Colonel Lowell B. Wright, Director, with 
the collaboration of officers of his staff. 
The collaboration of both the Army Dental 
School and the American Dental Trade Associa- 
tion in the publication of these lectures is grate- 
fully acknowledged. 
For The Surgeon General: 
Leigh C. Fairbank, 
Brigadier General, 
Medical Department (D. C.) Copyright 1941 
Major General James C. Magee 
The Surgeon General 
United States Army TflBLt Of conitflis 
DENTAL PROSTHESIS 
CHAPTER I 
Paragraph Page 
SECTION I. General 
Scope 1 1 
SECTION II. Impression Materials 
Description and Limitations 2 1 
SECTION III. Plaster Impressions 
General 1 3 2 
Assembling of Parts 4 3 
Boxing 5 4 
Pouring of Cast 6 5 
Separation of Cast 7 6 
SECTION IV. Modeling Compound Impressions 
General 8 6 
Boxing 9 7 
Separation of Cast 10 8 
SECTION V. Hydro-colloid Impressions 
General 11 8 
SECTION VI. Construction of Full and Partial 
Vulcanite Dentures 
Relief Areas 12 9 
Trial Denture Base 13 10 
Bite Plates 14 12 
Mounting Casts on Articulator _ 15 14 
Selecting Artificial Teeth 16 15 
Requirements of Tooth Forms _ 17 16 
Arranging the Upper Anteriors_ 18 16 
Arranging the Upper Posteriors 19 19 
Arranging the Lower First Molar 20 22 VI 
Paragraph Page 
Arranging the Lower Second 
Bicuspid - 21 25 
Arranging the Lower Anteriors 22 26 
Arranging the Cuspids 23 27 
Arranging the Lower First 
Bicuspid _ 24 28 
The Incising Bite 25 29 
The Balancing Bite 26 30 
C. D. L. Assortment of Teeth 27 30 
Denture Waxing 28 33 
Denture Flashing (Full) 29 34 
Denture Flashing (Partial) 30 35 
Paching the Case 31 37 
Vulcanization 32 40 
Cleansing and Polishing of 
Dentures 33 41 
SECTION VII. Acrylic Resin Dentures 
General 34 42 
Procedure 35 43 
SECTION VIII. Denture Repair 
Simple Repair 36 46 
Loose or Brohen Teeth 37 47 
Teeth Added 38 48 
Loose Clasp 39 48 
Refacing 40 49 
Rebasing 41 49 
Duplicating a Denture 42 50 
Repairing Acrylic Resin 
Dentures 43 50 
SECTION IX. Clasps and Bars for Partial Den- 
tures 
General 44 51 
Wrought Clasps 45 53 
Occlusal Rests 46 54 
Heat Treatment of Gold 47 55 
Crib Clasps 48 55 
Cast Clasps 49 56 
Indirect Retainers 50 57 
Lingual and Palatal Bars 51 58 
Duplicating a Master Model 52 58 Paragraph Page 
SECTION X. Fixed Bridge 
General 53 59 
Anterior Bridge 54 60 
SECTION XI. Waxing and Casting of Three- 
Quarter Crowns 
General 55 61 
Procedure 56 62 
SECTION XII. The Gold Crown 
General 57 65 
Procedure 58 66 
SECTION XIII. Splints 
General 59 68 
Vulcanite Splints 60 69 
Acrylic Resin Splints 61 71 
Cast Silver Splints 62 72 
THE DENTAL HYGIENIST 
CHAPTER II 
SECTION I. General 
Purpose and Scope 63 75 
SECTION II. Saliva and Calculus 
Composition and Function of 
Saliva 64 75 
Formation of Calculus 65 76 
SECTION III. Instruments 
Instruments Commonly Used 66 76 
SECTION IV. Technique of Dental Prophylaxis 
Instrumentation 67 77 
Polishing of Teeth 68 79 
Use of Dental Floss 69 80 
Disclosing Solution 70 80 viii 
Paragraph Page 
SECTION V. Instructions to the Patient 
Method of Toothbrushing 71 81 
Massage 72 81 
THE CHAIR ASSISTANT 
CHAPTER III 
SECTION I. Duties of a Chair Assistant 
General 73 83 
SECTION II. Cleaning of Dental Clinic 
General 74 83 
SECTION III. Care of Equipment and Materials 
Medicaments 75 84 
Hand Instruments 76 84 
Sharpening of Instruments 77 85 
Dental Burs 78 85 
Sterilization of Dental Instru- 
ments 79 86 
Sterilization of Handpieces 80 86 
Care of the Sterilizer 81 86 
SECTION IV. Duties at the Chair 
General 82 87 
Anesthetic Solution 83 87 
Impression Materials 84 88 
Filling Materials 85 89 
Silver Amalgam 86 89 
Copper Amalgam 87 90 
Oxyphosphate of Zinc Cement 88 90 
Silicate 89 90 
Zinc Oxide 90 92 
SECTION V. Clerical Duties 
General 91 92 DENTAL PROSTHESIS 
CHAPTER I 
Section I 
General 
1. Scope 
The term prosthetic dentistry or prosthodontia may be defined 
as that branch of dentistry which has to do with the replacement 
of any lost or missing parts of the dental apparatus by suitable 
artificial substitutes. Dental laboratory mechanics is that part of 
the science or art of prosthodontia which has to do with the con- 
struction of these appliances. The instructions contained in this 
section of the manual include the laboratory procedures for the 
construction of full dentures, partial dentures, crowns, bridges, 
and splints. A full denture may be defined as a structure re- 
placing the full number of teeth in either jaw. A partial denture 
is a structure replacing the missing natural teeth in either jaw 
and is retained by mechanical means against the remaining nat- 
ural teeth. A crown is an artificial restoration of the crown of 
a natural tooth. A bridge is a fixed appliance which replaces lost 
teeth, retained by attachments other than clasps to abutments 
supported by the roots or crowns of adjoining teeth. A splint is 
any apparatus, appliance, or device employed to prevent motion 
or displacement of fractured or movable parts. 
Section II 
Impression Materials 
2. Description and Limitations 
An impression is an exact negative reproduction of a patient’s 
oral arch and teeth. A positive form or cast is obtained from the 
impression that is identical to the mouth. The first contact that 
the dental technician has with the work which he has to per- form is when he receives the completed impression from the 
dental officer. As a great deal of painstaking care is needed to 
secure an accurate impression, the importance of skillful han- 
dling of the impression by the technician cannot be stressed too 
much. Any deviation from this, will result in the completed 
denture being unsatisfactory. In an edentulous or toothless 
mouth there are usually no undercuts present, or at least very 
few. Therefore, no great problem is presented in getting the 
impression from the mouth. For this reason a material such as 
modeling compound can be used. This material becomes plastic 
upon the addition of heat, and returns to its hard state when 
allowed to cool in the mouth. However, a dental arch contain- 
ing some natural teeth presents quite a different problem; that 
is, one concerning the selection of a suitable impression material. 
As can be seen by looking in any mouth, there are always under- 
cuts when natural teeth are present. If an impression of this 
type was taken in modeling compound, it would be very difficult 
to remove and when once removed, it would be distorted to such 
an extent as to render it useless. Therefore, another type of 
impression material must be used. There are two materials 
commonly used for this type of case, each having entirely dif- 
ferent characteristics, but both giving equally good results. The 
first is plaster of paris, which is placed in the mouth while in its 
plastic stage and allowed to set. It is then broken into several 
fragments, which permits its removal from the mouth, and, at 
the same time, preserves the details of all the undercuts. These 
fragments are later reassembled in their proper relationship, 
which gives an accurate reproduction of the dental arch. The 
other type of impression material is the hydro-colloid. This ma- 
terial can be softened by moist heat, placed in the mouth, and 
allowed to cool. Due to its great elasticity, it can be removed 
over the undercuts without any distortion of the impression. 
Various combinations of materials may also be used, and these 
will be discussed later. 
Section III 
Plaster Impressions 
3. General 
Plaster impressions for partial dentures consist of several pieces 
that must be reassembled in the tray in their proper position and 
relationship. Great care must be taken in the handling of these broken fragments, as any further breakage or rubbing of the 
edges will seriously interfere with the accuracy of the impres- 
sion. The steps taken in the assembling of the plaster impres- 
sion are as follows: 
4. Assembling oj Parts 
(1) Allow the fragments to dry before beginning to assemble 
the impression. 
(2) Remove all crumbs of plaster from the tray. 
(3) Gently remove all adhering particles of plaster from the 
fractured edges of the impression with a camel-hair brush. 
(4) Assemble the parts in the tray consecutively so as to avoid 
undercuts. Never force any fragment in position, as this 
will mar the edges. If the pieces are assembled in the 
proper order, they will easily slip into their correct places. 
(5) After the parts are assembled in the tray, apply a slight 
amount of finger pressure on the various pieces of plaster 
so that the lines of fracture are barely noticeable. Be sure 
that the entire impression fits snugly in the tray. 
(6) Maintain this pressure, and, with a warm spatula, care- 
fully apply sticky wax to join the edges of the impression 
to the tray. Never allow the wax to touch the tissue sur- 
faces of the impression. 
(7) With a camel-hair brush, apply an alcoholic solution of 
orange shellac to the impression. It must be thin enough 
to penetrate the plaster to a slight degree without obliter- 
ating any of the fine details. This is used as a staining 
medium. Allow to dry. 
(8) With a camel-hair brush, apply a coat of sandarac varnish 
over the shellacked surface of the impression and allow 
to dry. It should be thin enough so as not to obliterate 
the fine details. The varnish may be made thinner with a 
little alcohol, if necessary. This is used as a separating 
medium and the impression should now have a glossy, 
smooth finish. A solution of soap in water may be used in 
place of sandarac varnish as a separating medium. 5. Boxing 
The impression is now ready to be “boxed” preparatory to the 
pouring of the model. By this step the impression is reenforced 
by a retaining wall which confines the stone to the impression 
and simplifies the trimming of the cast after it is poured. 
(1) With a sharp knife, cut a strip about three-sixteenths of 
an inch in width along the entire length of the strip of 
boxing wax. 
Fig. 1 
Boxing of upper impression by a method not re- 
quiring heat: (A) Board. (B) The impression. (C) 
The moldine or clay support which attaches the im- 
pression to the board. (D) The sheet-lead or tin 
box. 
(2) Seal this strip around the outer edges of the impression 
about one-eighth of an inch away from the crest of the 
impression’s rim, and across the posterior border. Care 
should be exercised to prevent the wax from covering any 
portion of the impression. 
Fig. 2 
Boxing of a lower impression: (A) Board. (B) Im- 
pression. (C) Clay, moldine or plaster support. (D) 
Sheet-lead or tin box. 
(3) Mold the balance of the boxing wax to the outer border 
of the impression. With a warm spatula, seal the wax to 
the impression and along the edges of the boxing wax it- 
self. Before sealing it is necessary to make certain that 
the top of the wax is not too high from the top of the 
impression, as this will create needless bulk in the cast; 
1/3 inch is sufficient. See Fig. 1. (4) The technique for lower impressions is exactly the same, 
with the exception of one step. In the lower it is neces- 
sary to apply a small piece of moldine or wax in the space 
that is occupied by the tongue. After this has been done, 
the case is boxed, as described above. See Fig. 2. 
6. Pouring of Casts 
This consists of transforming a negative impression of the den- 
tal arch into a positive reproduction of the same arch. 
(1) After the plaster impression has been shellacked, varnished, 
and boxed; it should be immersed in water for ten minutes 
prior to pouring the cast. This is to allow the plaster to 
absorb a certain amount of water which will make the 
later separation much easier, and also will prevent a chalky 
cast. 
(2) Remove impression from water and dry off all excess mois- 
ture. 
(3) The casts must be made of a material of sufficient strength 
to withstand usage during the construction of the denture. 
It must withstand the pressure and temperature changes 
during vulcanization. It must not set too quickly as suffi- 
cient time is needed for manipulation, and, when setting, 
it should not expand or contract. Such a material is quick 
setting stone. As stone requires less water for mixing 
than does ordinary plaster, the correct proportion is ap- 
proximately one part of water to three parts of stone by 
weight. This varies slightly according to the manufac- 
turer, and his directions should be followed. 
(4) Place the correct proportions of stone and water in a clean 
plaster bowl. Tap the bowl gently against the bench so 
that all air bubbles will be expelled. Leave sufficient time 
for the stone to absorb the water, as this will aid in the 
spatulation. 
(5) Hold the bowl in one hand, and, with a plaster spatula, 
mix the stone with a cutting motion until it assumes a 
putty-like consistency. Never whip the stone as this will 
incorporate air into the mix. Excessive spatulation after 
a putty-like consistency has been secured will reduce 
working time, which condition must be guarded against. (6) Never add water to a mix after spatulation in order to 
make it thinner. If such is done, crystallization which 
already has begun will be broken up resulting in a weak 
cast. Place a small portion of this stone in the rear of the 
impression, which is held in the hand. Gently jar it against 
the bench until the mix covers the tissue surface of the 
impression with a thin layer of stone. 
(7) Continue adding the stone and allow each addition to settle 
in the impression before the next is deposited. Continue 
adding the stone until the impression is completely filled. 
Wait until the mix sets before proceeding. 
(8) Remove boxing wax and score the top of the cast with a 
sharp knife to facilitate attachment to plaster when mount- 
ing on the articulator. 
7. Separation of Casts 
(1) With a sharp knife, very carefully scrape off the impres- 
sion plaster until the brown color of the staining material 
becomes visible. This will weaken the impression so that 
it will be easy to remove without injuring the cast. 
(2) Insert the sharp point of a knife in the line of fracture and 
apply slight pressure away from the teeth and thin parts 
of the cast. It is best to remove the plaster from around 
the teeth and undercuts before removing that from around 
the tissue surfaces. Great care must be taken in this step 
to prevent the breaking of teeth on the model. 
(3) Remove any adhering separating media from the casts with 
cotton and alcohol. 
(4) All rough edges and overhanging margins are removed 
with knife, file, or sandpaper and the casts trimmed and 
shaped as desired. 
Section IV 
Modeling Compound Impressions 
8. General 
A large percentage of the impressions that a dental technician 
must work with, is taken in impression compound. It may be 
white, black, red, or brown in color. The boxing of the com- pound impression will require more care than those made from 
plaster. Whereas plaster that has hardened or set is unaffected 
by the application of hot wax in the boxing process, the com- 
pound will absorb some of the latent heat from the wax and 
soften sufficiently to distort it under hand manipulation, thus 
ruining the impression. Therefore, it must be boxed by a method 
that does not require heat. A simple technique is as follows: 
9. Boxing 
(1) Place the impression on some moldine or art clay which 
is molded to give evenly distributed support to the im- 
pression. This material is carried around the labial and 
buccal flanges of the impression to within one-eighth of 
an inch from the crest of the impression and its posterior 
border. The sides should be perpendicular. A piece of tin 
or lead sheet is conformed to the periphery of the impres- 
sion and held secure by elastic bands. The casts may then 
be poured without danger of distortion. See Fig. 1. 
(2) The method of handling the mandibular or lower impres- 
sion is similar but the tongue area space of the lower re- 
quires a different treatment. The impression is seated on 
some moldine or art clay which is carried around the out- 
side flanges as in the maxillary impression. Then the clay 
or moldine is carried into the tongue area space, filling it 
up to within one-eighth of an inch from the crest of the 
lingual flanges. A strip of tin or lead sheet is then carried 
around the circumference of the impression, as before, and 
held with elastic bands. The cast is then poured. If it is 
impossible to obtain the moldine used in this technique, 
ordinary plaster may be used in its place. It is a little 
harder to manipulate but will serve the same purpose. See 
Fig. 2. 
(3) The modeling compound impressions do not need a stain- 
ing and separating media unless a plaster wash has been 
used. This consists of a compound impression with a very 
thin layer of plaster over the entire tissue surface. In an 
impression of this type it is necessary to apply a light coat 
of sandarac varnish to the surface of the plaster so that 
7 the casts may be more readily separated from the impres- 
sion. A staining coat of shellac is unnecessary. 
10. Separation of Cast 
(1) In the removal of the compound impression from the cast, 
it is necessary to apply sufficient heat to return the com- 
pound to a soft or plastic state. This is accomplished by 
immersing the impression in warm water for a sufficient 
length of time to allow the entire thickness of the com- 
pound to become soft. If the water is too hot, the com- 
pound will become sticky and will adhere to the cast. 
(2) Insert a knife blade under the edge of the impression and 
gently tease the compound away from the model. If it is 
sufficiently plastic, it should come away very easily. If it 
is too hard, there is danger of breaking the model. Take 
a small section at a time and then return the impression to 
the warm water for additional heating. In this way grad- 
ually remove the entire impression from the cast. 
(3) The cast is then trimmed and shaped as usual. 
Section V 
Hydro-colloid Impressions 
11. General 
The third type of impression material that is commonly used 
is the hydro-colloid. It possesses unusual plasticity, some elas- 
ticity, and slight compressibility. The impression can be removed 
from undercuts without distortion and gives the finest detail. 
Casts are obtained without the use of separating media and with- 
out the danger of injury or breakage incident to the removal of 
the impression compound. Duplicate casts may be obtained by 
the careful removal of the model from the impression and re- 
pouring the impression or by making a second impression of the 
cast. This material is generally used in the making of impres- 
sions for partial dentures, although it may be used in conjunction 
with modeling compound for full denture cases. In either case, 
it is treated the same by the dental technician. The cast must 
be poured immediately after the impression is taken, otherwise 
the material will dry out and distort the impression. If this is 
impossible, it may be kept in cold water for a short time and 
then poured. Section VI 
Construction of Full and Partial Vulcanite Dentures 
12. Relief Areas 
The mucous membrane covering the bony tissues of the mouth 
is not of uniform thickness over the entire surface. There are 
areas where the membrane is very thin and the bone is quite 
prominent. This is especially true along the median raphe of 
the palate and the crest of the ridge. There are other areas of 
the mouth that have an abundance of connective tissue over- 
lying the bone, examples of which are the tissue bearing areas 
of the palate and the slopes of the ridge. In constructing a 
denture it is necessary to relieve these hard areas so that the 
soft tissues overlying them will not be compressed when the 
denture is worn, and, at the same time, allow the tissue bearing 
areas to be evenly compressed. In addition to these bony areas, 
it is sometimes necessary to relieve pressure on nerves and blood 
vessels, especially where they come through the bony openings. 
Relief areas may be prepared in two ways; 
(1) The dental officer may prepare the areas to be relieved in 
the impression before the cast is made, or 
Fig. 3 
Showing area to be relieved on upper model. 
(2) The dental technician may prepare the areas indicated by 
the dental officer to be relieved, by burnishing on the cast, 
one or more layers of #40, #50 or #60 tinfoil, which has been cut to fit the area for that particular case. As there 
can be no standard size and shape, the tinfoil must be cut 
for each case. The hardest areas are covered most thickly, 
but the thickness of the relief area should never be carried 
to the extent of creating a suction chamber, as in time this 
space would fill with hypertrophied tissue, thus defeating 
the purpose for which it was made. If tinfoil is unavail- 
able, two or three layers of lead foil from x-ray films may 
be used in the same manner. See Fig. 3. 
13. Trial Denture Base 
Since a denture must fit the mouth accurately, it is first made 
on a trial base, such as wax, or other material which can be easily 
molded. This material should be of sufficient strength to hold 
its shape while the denture is tried in the mouth. Baseplate is 
preferable to wax as a trial denture base, however, because it 
holds its shape better and is not easily distorted by the tempera- 
ture of the mouth. 
Procedure of adapting baseplate to cast 
(1) Pass the baseplate through the flame several times until 
it shows signs of wilting. Do not heat it too much as this 
will melt or burn the material. Fig. 4. 
Fig. 4 
Fig. 5 
(2) Place the softened baseplate over the upper cast and adapt 
the palatal portion closely to the cast by pressing lightly 
with the fingers. Reheat the baseplate when necessary 
and continue adapting it over the alveolar border and over 
the buccal and labial surfaces. Fig. 5. (3) Avoid buckling or creasing of the baseplate. 
(4) Heat the partially adapted baseplate; and, using plate 
shears, trim away the surplus extending beyond the outer 
edges of the extension on the cast made by the carding 
wax rim in the boxing process. This is illustrated by c-c-c 
in Fig. 6. 
Fig. 6 
Fig. 7 
(5) Heat the baseplate which rests on the extension of the 
cast material by passing it once through the flame and 
folding the heated portion upon the buccal and labial sur- 
faces by pressure, as shown in Fig. 8, and continue to the 
finished form, shown on the right side in Fig. 9. The folded 
portion is not heated enough to fuse with the baseplate 
against which it is folded. Fold the extension across the 
Fig. 8 
Fig. 9 
heel in the same manner. The margins thus shaped must 
conform to the muscle trim margins of the impression and 
constitute a valuable reenforcement of the baseplate. 
(6) Chill the baseplate with cold water and then carefully re 
move from the cast. (7) In lower casts adapt the trial baseplate material over the 
highest part of the alveolar ridge in the anterior region of 
the cast and work backwards towards the heels. Treat the 
lingual, buccal, and labial margins of the lower baseplate 
the same as the upper. 
(8) If the trial baseplate should be broken, it may be repaired 
by placing the broken pieces on the cast with the edges 
together and fusing with a hot wax spatula. Melt some of 
the baseplate material in a flame and drop it over the 
break. Smooth the surface. 
(9) In partial cases, after adapting the baseplate to the palate 
and alveolar ridges, heat the material in the region of the 
plaster teeth and remove with a hot spatula or shears. 
This material should be removed to within one thirty- 
second of an inch from the gum margins of the plaster 
teeth, and the edges of the baseplate smoothed with a file. 
(10) In partial lowers, it is necessary to reenforce the baseplate 
extending about the teeth by imbedding a hot wire or 
paper clip in the baseplate and smoothing the surface with 
a hot spatula. 
14. Biteplates 
The mandible or lower jaw, is movable, and is attached to the 
skull by two movable joints, giving it a hinge-like motion. How- 
ever, this is not a fixed motion as the jaw may also be moved in 
other directions within limits. In a mouth with natural teeth in 
place, the occlusal surfaces of these teeth act as guides which 
permit the jaws to come together in a rest or centric position. 
When the teeth are gone this relationship is missing. Therefore 
it is necessary to construct biteplates which will help the dental 
officer in reestablishing this relationship. Since the dental tech- 
nician does not see the patient, he can only approximate the re- 
quired size and shape of the bite plates. 
(1) Mark on the cast, in a place where it can be seen, with the 
trial denture base in place, a line designating the crest of 
the alveolar ridge. This is for future reference in setting 
up the artificial teeth. 
(2) Soften a sheet of basewax, by passing it over a flame sev- 
eral times, and fold it along its lesser length into a tight 
roll. (3) Bend the wax roll to the approximate shape of the alveolar 
ridge of the cast. 
(4) Replace the trial baseplate on the cast and attach the roll 
of wax, sealing it with a hot spatula. 
(5) Using a template, or any flat surface, press the wax to the 
desired height. This is usually about 10 to 13 millimeters 
in height from the anterior portion of the alveolar ridge, 
and less in the molar region. 
Fig. 10 
(6) With a knife and a hot spatula, trim the sides of the base- 
plate to a width of not more than 8 millimeters. 
(7) Add melted wax where necessary to fill in spaces between 
the wax roll and the baseplate on the buccal, labial and 
lingual surfaces. 
(8) In partial cases be sure that the biteplate does not inter- 
fere with the teeth on the cast and cut the wax roll to fit 
the alveolar ridge where the teeth are missing, extending 
the wax about one-sixteenth of an inch above the teeth 
of the cast but not covering the teeth. 
(9) Square up the sides and angles of the biteplate, making 
certain that it conforms to the cast and that it is directly 
over the crest of the alveolar ridge, 
(10) Polish the biteplate with wet cotton. See Fig. 10. 15. Mounting Casts on Articulator 
The cast or casts, with the biteplates constructed, are returned 
to the dental officer, who records the relationship of the patient’s 
lower jaw to the upper jaw. This is known as “taking the bite” 
This established, the casts and biteplates come back to the dental 
technician ready to be placed on the articulator. The articulator 
used in the Army dental service is known as the Gysi Simplex 
Articulator, which simulates the movements of the jaw and has 
the plane of the condyle paths set at 30 degrees. 
Procedure in Mounting Casts 
(1) Attach the biteplates to the casts with wax at several 
points. 
(2) Place the casts in water until all bubbling has ceased. 
(3) Place the incisor guide pin in the sleeve of the upper ex- 
tension arm, keeping the top of the pin level with the top 
of the sleeve. 
Fig. 11 
(4) Place the incisal guide on the pin, with the set-screw in 
the depression of the pin and the point directed backward 
to the median line. 
(5) Extend the median line mark on the front of the upper 
cast or bite rim, vertically upward to the top of the cast. 
Make a similar vertical mark on the rear of the cast, start- 
ing from the median line of the palate. Draw a straight 
line across the cast connecting these two lines. (6) Place an elastic band about the set-screw on the incisor 
guide point and in the notches on the outer sides of the 
vertical part of the frame. This line, as given by the 
elastic band, will establish the approximate occlusal plane. 
(7) Place three small pieces of wax or moldine in a tripod 
arrangement on the lower extension arm, and force the 
lower cast down over these pieces until the occlusal plane 
of the biteplate is level with the elastic band, and the 
median line of the biteplate touches the tip of the incisor 
guide. Adjust the casts so that the median line of the 
upper cast is directly below the median line of the upper 
extension arm. 
(8) Attach the upper cast to the upper extension arm with 
plaster and allow to set, then invert the articulator and 
attach the lower cast to the lower extension arm in the 
same manner. 
(9) Allow plaster to set and trim off all excess plaster. See 
Fig. 11. 
(10) Carefully separate the biteplates and remove the biteplates 
from the casts. 
16. Selecting Artificial Teeth 
Before taking up the technique of setting the teeth, to which 
stage the case has been brought, we will consider the question 
of selection of artificial teeth, of vital importance to both the 
efficiency and appearance of artificial dentures. In selecting 
artificial teeth, the two principal requirements to be considered 
are appearance, which includes form, proportion and shade, and 
mechanics, such as the length of bite and ridgelap necessary to 
the proper adaptation of the teeth to the ridges. These two fac- 
tors are so often dependent upon each other that any apparent 
antagonism between them calls for judgment in making the nec- 
essary compromise. It may be stated, as a safe rule to follow, 
that whenever the mechanical requirements interfere with thp 
final appearance, the mechanics should be sacrificed as much as 
possible. While this may be questioned by some authorities, 
experience proves that appearance is the most important factor 
with the patient and many dentures which are mechanically 
perfect are unsatisfactory because they do not “look right.” 17. Requirements of Tooth Forms 
Briefly, all teeth must correspond or harmonize in form and 
contour with the form and contour of the face which “frames” 
them in order to blend into the individuality of the person wear- 
ing them and insure the most pleasing effect. There are three 
typal forms of faces—Square, Tapering and Ovoid. These forms 
are further modified by an admixture of the elements of two or 
more of these typal forms. There are, likewise, the same typal 
forms of teeth. Whenever the face forms and tooth forms corre- 
spond and harmonize, the effect is fine. To the extent that the 
teeth differ in form with faces, there is a disharmony which is 
displeasing in degree. For instance; when square teeth are 
framed in an ovoid face, the effect is unpleasant and the teeth 
are conspicuous, whereas when ovoid teeth are framed with an 
ovoid face the effect is pleasing in that the teeth do not seem 
to obtrude—they “belong” with the face. Tooth shade, form, and 
approximate size are always selected by the dental officer to 
conform with the requirement of the individual case, and such 
instructions should be followed as closely as mechanically pos- 
sible. In the selection of teeth for partial cases the teeth should 
be of such size, that after they have been contoured to the 
adjoining clasps or teeth they will completely fill the edentulous 
area. 
18. Arranging the Upper Anteriors 
Procedure. 
Remove the upper bow from the articulator. Procure an oc- 
clusal plane or a flat piece of wood or aluminum 21/z inches square, 
and use it as shown in the illustrations to take the place of the 
occlusal surface of the lower bite rim. See Fig. 12. 
Before waxing the upper central in place, try for mechanical 
suitability. If necessary carve away the baseplate under the 
tooth or grind the ridgelap, or do both, so that the tooth will not 
rest directly against the cast. The long axis of the upper central 
should be vertical when seen from the front and inclined down- 
ward and forward when seen from the side, as in “B” and “C”, 
Fig. 12. The incisal edge is in contact with the occlusal plane. 
The upper centrals are not set at right angles to the median line, 
but the distal angles are inclined slightly backward and begin the 
curvature of the tooth row to follow the contour of the bite rim. Cut a space through the upper bite rim for the upper lateral 
and try it in place as the central was tried. Set it so that the in- 
cisal edge is about % of a millimeter above the level of the oc- 
Fig. 12 
clusal plane and so that the long axis is inclined as in “B” and “C”, 
Fig. 13. This downward and forward inclination of the vertical 
axis of the upper laterals results in making the neck of this tooth 
less prominent than that of the upper central. This depression 
will be found very valuable when giving expression to the teeth. 
Fig. 13 The incisal edges of the laterals are set to maintain the curvature 
established by the incisal edge of the upper bite rim, as shown 
at “D” 
Cut a space clear through the upper bit rim to receive the upper 
cuspid. Try the tooth for length as the central and lateral were 
tried. Set the tooth so that its tip just touches the occlusal plane 
Fig. 14 
and its long axis is inclined as shown in “B” and “C” and at the 
edge of the tooth continue the curve of the bite rim as shown at 
“D,” Fig. 14. The labial ridge of the cuspid is properly the divid- 
Fig. 15 ing line between the labial and buccal sections of the ridge. The 
labial surface mesial to the ridge faces the lip and maintains 
the general curvature established by the central and lateral. The 
surface distal to this ridge faces the cheek and begins the curva- 
ture characteristic of the bicuspids and molars. The effect of 
setting the cuspids in this position is to carry the distal angles far- 
ther inward toward the median line. When the cuspids are set in 
this way, only the mesial aspect can be seen from the front. This 
permits the use of teeth large enough for the mouth, without 
their appearing too large. The esthetic effect of this arrange- 
ment is greatly enhanced by the natural shading of the teeth in 
the set and gives prominence to the neck or cervical third of both 
cuspids. 
When the central, lateral and cuspid of one side have been set, 
set the central, lateral and cuspid on the other side in the same 
manner, Fig. 15. 
19. Arranging the Upper Posteriors 
Having determined the type of arch, the upper bicuspids and 
molars are set with their vertical axes in the lines shown in 
Fig. 16. 
RELATION OF CUSPS TO OCCLUSAL PLANE — BUCCAL ELEVATION 
RELATION Of CUSPS TO OCCLUSAL PLANE — CROSS SECTION 
Fig. 16 
The buccal cusp of the upper first bicuspid touches the occlusal 
surface of the lower trial plate, but the lingual cusp does not 
quite touch. Both cusps of the upper second bicuspids touch the 
wax. See Fig. 17. The buccal cusps of the upper first molar are 
elevated about a millimeter above the wax to begin the compen- 
sating curve formed by the buccal cusp of both upper molars. The lingual cusps of the second molars are in contact with the 
opposing trial plate, but the buccal cusps are elevated about 2 
millimeters above the wax. They continue the compensating 
curve which the buccal cusps of the first molars began. 
It is necessary, while establishing these relations, to secure such 
positions of the teeth over the ridge as to give the dentures maxi- 
Fig. 17 
mum stability and efficiency. Fit each posterior tooth to its posi- 
tion before waxing it in place, as the anteriors were fitted. Make 
sure that each tooth is short enough so that there is a free space 
of at least a millimeter between it and the baseplate. Cut a strip 
one-half inch wide along the side of a sheet of baseplate wax and 
soften one end of it in the flame. Detach a small portion and form 
it into a cone. Soften the end of the cone in the flame and force 
it about the pins or into the recess in the diatoric tooth. Using 
the tooth as a handle, soften the other end of the cone and press 
it upon the ridge with the tooth in approximately the correct 
position. Close the articulator so that the incisor guide pin comes 
into contact with the incisor guide incline. Adjust the teeth so 
that the center of the longitudinal groove is over the front-to-back 
line on the occlusal surface of the lower bite rim. The buccal 
cusp of the upper first bicuspid should touch the occlusal surface of the lower bite; the lingual cusp should be raised about one-half 
millimeter above that rim. When the tooth is first placed, the 
long axis of the tooth, as seen from the buccal, should be vertical, 
as shown at “A” in Fig. 17. This may be slightly modified in es- 
tablishing articulation. The second bicuspid should be set like 
the first except that both cusps touch the opposing bite rim, as 
shown at “B” in Fig. 17. Rotate both bicuspids upon their long 
Fig. 18 
axis so that the occlusal surfaces are inclined as shown by the 
lines in “C”, Fig. 17. With the straightedge of the occlusal plane, 
test the position of the buccal surface of the bicuspid in relation 
to the cuspids. When these teeth are in proper relation for the 
average case, the straightedge should touch the buccal surfaces 
of all three teeth. 
Attach the upper first molar to the ridge as the bicuspids were 
attached. The long axis of this tooth, when seen from the buccal, 
is inclined downward and backward as shown at “A”, Fig. 18. 
Only the mesio-lingual cusp of this tooth should touch the occlusal 
surface of the opposing bite, the disto-lingual cusp being slightly 
raised and the buccal cusp being raised about three-quarters of a 
millimeter out of contact, as shown in “A”, Fig. 18. This arrange- 
ment produces the average compensating curve. When a greater 
curvature is required, the distal cusps should be elevated more. The tooth should be rotated upon its long axis as shown at “C” 
in Fig. 18. 
The upper second molar is now placed in position, with its 
lingual cusps lightly touching the occlusal plane and the buccal 
cusp raised about one and one-half millimeters out of contact as 
shown in “B” Fig. 18. If a greater curvature is desired, the 
lingual cusp should be elevated out of contact and the buccal 
Fig. 19 
Fig. 20 
cusp elevated in a corresponding degree. The long axis, seen 
from the buccal, is inclined downward and backward more than 
was the first molar. 
20. Arranging the Lower First Molar 
Apply a cone of wax to a lower first molar. Open the artic- 
ulator and attach the molar to the ridge in approximately the cor- 
Fig. 21 
Fig. 22 
rect position, but too high. Close the articulator, forcing the 
molar toward the ridge. Guide it to correct occlusal relations with the uppers as in Fig. 19. Wax the molar firmly in position. 
Move the articu1ator so as to throw this molar into working bite 
with the uppers, as in Fig. 20. A black line has been drawn along 
the buccal ridge of the middle cusp of the lower molar. It should 
be continuous with the black line in the buccal groove of the 
upper molar. The break in the line in Fig. 21 shows that the 
lower molar is too far forward for articulation. Figs. 19 and 21 
Fig. 24 
show that teeth may be in good position for occlusion without 
being in position to articulate. In Fig. 20 the lower molar has 
been moved backward so that the black line is continuous with 
the line on the upper, in working bite, but the buccal cusps do 
not interdigitate with the upper cusps. Errors of this kind can 
usually be corrected by depressing the buccal cusps of the upper 
molar, but in this case the steep descending inclination of the 
condyle path, with the slight lateral inclination, necessitated 
grinding the teeth to a deeper bite. With a fine-grit, inverted 
cone stone the mesial marginal ridge of the upper molar and the 
distal marginal ridge of the lower molar were ground until they 
could be properly interdigitated. In Fig. 22 the molars are shown 
in working bite after deepening the sulci by grinding has been 
completed and the lower molar reset to proper contact with the 
upper. The space between the upper second bicuspid and the 
lower molar in Fig. 20 has been decreased by deepening the bite 
of the molars and raising the lower molar. The lower first molar 
in Fig. 23 is in the same position on the ridge that it occupied in 
Fig. 22, but the articulator has been moved so as to throw this 
side into balancing relation. The triangular ridge of the mesio- 
lingual cusp of the upper molar should slide in the disto-buccal 
groove of the lower molar, but cusp and groove are separated 
Fig. 23 by a slight space. A defect of this kind can usually be corrected 
by depressing the lingual cusp of the upper molar until contact is 
established and waxing the upper firmly in that position. It may 
be necessary to rotate either the upper or the lower on its vertical 
axis until the cusp works smoothly in the groove. Examine the 
working bite articulation from the lingual, as shown in Fig. 25. 
Fig. 25 
Fig. 26 
The slight prominence of the mesio-lingual cusp of the lower 
molar, indicated by the arrow, prevents correct relations in the 
working bite. Grind this away with the inverted cone stone, 
being careful to maintain the original inclination of the cusp 
planes. Do not grind a flat surface on the tip of the cusp. The 
upper and lower molars, in occlusion, should mesh as in Fig. 24. 
Fig. 27 
Fig. 28 
The buccal cusp of the lower should fill the V-shaped longitudinal 
groove between the lingual and buccal cusps of the upper. The 
lingually inclined plane of the lower buccal cusp should be in 
contact with the buccally inclined plane of the lingual cusp. Fig. 26 shows the relation of the upper and lower molars in working 
bite. 
21. Arranging the Lower Second Bicuspid 
After completing the articulation of the upper and lower molars 
for the case here illustrated, the distal marginal ridge of the upper 
Fig. 29 
Fig. 30 
second bicuspid was ground in the manner described for the 
first molars until the buccal cusp of the bicuspid could be brought 
down in contact with the buccal cusp of the lower molar when 
in working-bite relation. The tooth was then examined from the 
Fig. 31 
lingual and adjusted to mesh properly with the lower molar in 
working bite. Attach a cone of wax to the neck of the lower 
second bicuspid and place it on the ridge in the manner described 
for the molar and with a spatula press it into approximate oc- 
clusion with the upper second bicuspid. Move the articulator so 
as to test the articulation in working bite, which is shown in 
Fig. 28. The space between the lower second bicuspid and the molar in 
Fig. 28 will exist whenever the conditions of the case necessitate 
a compensating curve of more than average steepness. The exist- 
ence of such spaces compensates, in part, for the shrinkage of 
rubber in vulcanizing and reduces the liability of error from 
the teeth being forced into improper contact through that shrink- 
Fig. 32 
Mesial facet of upper cuspids (A) before grinding 
to correct relation in working bite, (B) after grinn- 
ing, (C) relation of center of stone to the long axis 
of cuspid for grinding bucco-lingual pitch on the 
facet. Solid circle, center 1, shows correct posi- 
tion; dotted circles, centers 2 and 3, show incorrect 
positions. 
age. Occlude and articulate the lower second molar as shown 
in Fig. 29. Set the lower second bicuspid for occlusion and then 
for articulation by the methods described. Arrange the lower 
molars and the second bicuspid of the opposite side, using the 
same technique. Set the lower anteriors to approximate posi- 
tions to determine whether they meet the requirements of the 
case as to width and length. If insufficient space exists between 
the lower bicuspid to permit setting the lower anteriors because 
of irregularities in the alignment of the upper anteriors, additional 
space may be made by grinding the distal side of the lower cus- 
pids or the mesial side of the lower first molar. 
If sufficient space cannot be provided by such grinding, select 
lower anteriors of the next smaller size in the same form. 
22. Arranging the Lower Anteriors 
The roots of the lower centrals and laterals are parallel, but 
those of the lower cuspids diverge strongly as will be pointed out 
later when the lower cuspid is articulated. The lower centrals 
slope strongly outward from the neck to the incisal edge. This prevents the overfullness of the gums so common to lower den- 
tures. The lower laterals slope outward very much less than do 
the centrals. This is shown in Fig. 34. 
23. Arranging the Cuspids 
The upper lateral adjoining the cuspid should be removed from 
its place without heating the wax, so that it can be easily re- 
placed. This will facilitate articulating the lower cuspid. 
PLANE OF 
OCCLUSION 
Fig. 33 
Cuspids in rest and beginning of working 
bite relation, showing dotted line indicating 
proper bucco-lingual inclination for these 
cusp facets. 
Set the lower cuspid in position and grind the mesio-distal in- 
clination of the distal half of the cutting edge to be parallel to the 
inclination of the cutting edge of the mesial half of the upper cus- 
pid as in Fig. 31. The facet on the mesial slope on the upper 
cuspid is to be ground to the lingual inclination shown by the 
outline in Fig. 32, so that a straightedge placed in contact with 
the facet will touch the wax at the mesio-lingual cusp of the 
first molar. Grind the facet on the distal slope of the cutting edge 
of the lower cuspid to a labial inclination which is the comple- 
ment of the lingual slope of the upper cuspid with which it oc- 
cludes as shown in Fig. 33. The inclination of the long axis of 
the lower cuspid is also shown in Fig. 33. In the left part of Fig. 
33 the complementary inclination of the facets on the cutting 
edges of the cuspids is shown with the cuspids in occlusion. In 
the right part of the figure, the cuspids are shown in articulation 
with the lower about to begin the return from an extreme lateral 
excursion. The complementary inclinations of the facets make it 
possible for the cuspids to remain in contact throughout these movements. This form of articulation by the cuspids is very im- 
portant in maintaining the stability of the dentures and in pro- 
tecting the upper laterals from breakage. If the lower cuspids 
are set to too deep an under bite, the dentures are almost sure to 
be tipped out of position by improper cuspid contacts; the force 
of the closure will be brought upon the thin-edged laterals which 
Fig. 34 
Relation of lower cuspids and incisors 
to ridge, and average inclination for 
long axes. 
are not fitted to stand it, and they will be broken from the plate. 
This form of improper contact is very apt to occur in finished den- 
tures unless guarded against and is disastrous. 
Replace the upper lateral but do not attach it. Move the artic- 
ulator to produce the working and balancing relations and grind 
the mesial edge of the lower cuspid so that it clears the slope on 
the distal angle of the upper lateral. The upper laterals and the 
lower cuspids should not come into contact in any movement of 
the jaw. The facet on the cutting edge of the upper lateral should 
incline upward and backward more than that on the edge of the 
cuspid. When this facet has been ground, articulate the lower 
lateral with it. Do not grind facets on the cutting edges of the 
lower incisors. Grind facets on the edges of the upper centrals 
and articulate the lower centrals with them. The lower incisors 
should be set with the necks directly over the ridge and the long 
axis of the teeth should be inclined as is shown in Fig. 34. 
24. Arranging the Lower First Bicuspid 
The lower first bicuspid is the last tooth to be placed. It is 
articulated in the same manner as the second bicuspid. If the 
indicated space is not adequate to accommodate the lower first 
bicuspid, the mediodistal width of the tooth is reduced by grind- ing. Never crowd the lower anterior teeth out of position and 
off the ridge in order to place this tooth. Fig. 35 shows the tooth 
in position. 
25. The Incising Bite 
Before the teeth are tried in the mouth, hold the articulator in 
the incising position and slightly alter the arrangement of the in- 
cisors and cuspids if necessary so that they will come into proper 
contact. The upper centrals should touch the lower centrals. The 
upper laterals may, in certain arrangements, touch the lower 
laterals, but they should not touch the lower cuspids. Most in- 
stances of broken laterals, not due to careless handling, have 
been found to be due to a cuspid striking the lateral in the incis- 
ing or the working bite. The lower cuspids should touch the up- 
Fig. 35 
Fig. 36 
per cuspids but not the upper laterals in masticating movements. 
Fig. 36 shows the average over-jet of the upper anteriors over 
the lower teeth. 
When the lower is in central occlusion the lower incisors and 
possibly the lower cuspids should not be in contact. The lower 
incisors should not be allowed to support the dentures in lateral 
protrusive movements but should share this strain with the bicus- 
pids and the cuspids. The pressure on the cuspids should be 
heavier than on the upper laterals or the lower incisors. The 
danger of breaking the incisors during mastication will be elim- 
inated if the foregoing instructions are observed and the errors 
seen in the finished denture are corrected by grinding with a 
stone while the dentures are examined for these contacts in the 
mouth. The lower first bicuspid should be in contact with the upper cuspid which acts as a protector for the upper lateral and 
prevents the incisors from receiving any excessive strain. The 
tip of the cusp of the lower second bicuspid may touch the tip 
of the upper first bicuspid cusp but this is not essential. The tip 
of the upper second bicuspid should come into contact with the 
mesio-buccal cusp of the lower first molar. The lingual cusps of 
the bicuspids and molars also come into contact in the incising- 
bite relation. Occasionally the lingual cusps will touch so heavily 
that the buccal cusps cannot come into contact. If any cusp rides 
so heavily on an opposing cusp as to prevent the teeth from com- 
ing into the proper relation with their antagonists, a little careful 
grinding will correct the trouble. 
26. The Balancing Bite 
The depth of this bite is the distance the lower teeth on the 
balancing side move vertically to maintain balancing relations be- 
tween the dentures during articulation. It is much greater than 
the depth of the working bite, because the steep lingual inclines 
of the lower buccal cusps articulate with the steep inclines of the 
lingual cusps of the upper teeth, and because the lower cusps 
often travel directly across the steepest parts of the upper cusps 
instead of following the sulci. 
27, Central Dental Laboratory Assortment of New Trubyte Teeth 
The following charts give the assortment of teeth chosen for 
the Central Dental Laboratories for shades and moulds. The data 
given in the last four columns assist in choosing teeth and match- 
ing the lower anteriors and posteriors with the upper anteriors. 
The shades of the New Hue and the New Trubyte Teeth, as 
selected for Army use, are given below, with the corresponding 
shades for the Old Trubyte Teeth. 
New Hue 
New Trubyte 
Old Trubyte 
63 
40 
5 
66 
41 
6 
67 
43 
7 
77 
46 
9 
81 
49 
14 
69 
52 
15 
79 
55 
16 
83 
57 
20 UPPER ANTERIORS 1 x 6 SQUARE TYPE 
Mould No. 
Width of 
Central mm. 
Posteriors 
Required 
Lower Anteriors 
Required 
115 
8.5 
34M—31L 
25 
117 
9.5 
34L —35L 
27 
123 
7.5 
SOL —29L 
33 
124 
8. 
32L —31L 
34 
126 
9. 
34L —33L 
36 
133s 
7.5 
SOM—29M 
43s 
134 
8. 
32M—31M 
44 
135s 
8.5 
32L —31M 
45s 
136s 
9. 
34M—33M 
46s 
155 
8.5 
32M—31M 
34 
UPPER ANTERIORS 1 x 6 TAPERING TYPE 
Mould No. 
Width of 
Central mm. 
Posteriors 
Required 
Lower Anteriors 
Required 
214 
8. 
32L —31L 
34 
217 
9.5 
34L —35L 
27 
222 
7. 
28S —29S 
31 
224 
8. 
SOL —31M 
33 
225s 
8.5 
32L —31L 
45s 
225 
8.5 
32L —31L 
34 
226s 
9. 
34M—33 L 
46s 
233 
7.5 
SOM—29L 
32 
234 
8. 
32L —31L 
34 
235 
8.5 
34M—31L 
35 
244 
8. 
32L —31M 
34 
262 
7. 
28L —29L 
22 
263 
7.5 
SOL —29L 
23 
264 
8. 
32L —31L 
24 
265 
8.5 
34L —31L 
25 
266 
9. 
34L —33L 
26 
267 
9.5 
34L —35L 
27 
275 
8.5 
32L —31M 
45 UPPER ANTERIORS 1 x 6 OVOID TYPE 
Mould No. 
Width of 
Central mm. 
Posteriors 
Required 
Lower Anteriors 
Required 
314 
8. 
32L —31L 
24 
315 
8.5 
32L —31L 
25 
317 
9.5 
34L —35L 
27 
324 
8. 
32L —31L 
24 
333 
7.5 
SOL —29M 
23 
334 
8. 
32L —31M 
24 
335 
8.5 
34M—31L 
25 
346 
9. 
34L —33M 
46 
LOWER ANTERIORS 1 x 6 
Moulds available: 
22-23-24-25-26-27-31-32-33-34-35-36 
43-43s-44-45-45s-46-46s. 
UPPER POSTERIORS, REGULAR 1 x 8 
LOWER POSTERIORS, REGULAR 1 x 8 
Moulds available: 
28S-28M-28L-30S-30M-30L-32S-32M-32L-34S-34M-34L-32X. 
UPPER POSTERIORS, 20 DEGREE 1 x 8 
LOWER POSTERIORS, 20 DEGREE 1 x 8 
Moulds available: 
29S-29M-29L-31S-31M-31L-33S-33M-33L-35L. 28. Denture Waxing 
After the teeth are arranged, the technician proceeds with the 
carving of the wax so that he has an exact duplicate of the 
finished denture. By this method the wax denture may be placed 
in the mouth and checked for appearance and mechanical effi- 
ciency by the dental officer, and, if any changes are necessary, 
they can be made at this time. 
Procedure 
(1) Add melted wax to the case in deficient areas, especially 
along the buccal and labial surfaces of the denture. This 
Fig. 37 
will later be carved so as to simulate the irregularities of 
the gum caused by the roots of the natural teeth. 
(2) With a knife, or wax spatula, festoon all teeth at right 
angles to the long axis of the teeth. This should be carried 
to the necks of the teeth on the buccal, labial, and lingual 
surfaces. Do not festoon too deeply in the interproximal 
spaces between the teeth. 
(3) Smooth the entire surface of the wax by passing a flame 
quickly over the area. It may be further polished by rub- 
bing with a piece of cotton while holding it under running 
cold water. 
(4) The waxed denture is now ready for try-in. See Fig. 37. 
33 29. Denture Flashing (Full) 
This is the process by which the wax or trial denture is started 
on a new series of procedures, from which will emerge the fin- 
ished denture. The denture base, after having been checked in 
the patient’s mouth by the dental officer, is sealed to the cast and 
invested in a flask so as to retain the exact relationship of the 
teeth and preserve the space from which the wax will be elim- 
inated so that it may be filled with dental rubber or some other 
material. The flashing process will maintain this space and rela- 
tionship while the denture is being vulcanized or cured. 
Procedure. 
(1) Seal the waxed denture to the cast along its entire peri- 
phery and make sure that all the teeth are securely waxed 
in place. 
(2) Remove the models from the articulator. 
(3) Cut out the palate of the trial denture base and adapt one 
and one-half thicknesses of baseplate wax to the palate of 
the case. 
(4) Place the cast in the lower part of the flask. Then place 
the upper or counterpart of the flask in position, making 
sure that there is sufficient room in the flask for the case. 
Place the cover on the flask, making certain that the teeth 
do not touch the top of the flask. At least one quarter 
inch of space should be maintained. 
Showing undercut (A) 
when cast is flashed level. 
Fig. 38 
Showing elimination of 
undercut (B) when cast is 
flashed at an angle. 
Fig. 39 
(5) Remove the cast from the flask and immerse in cold water 
for a few minutes until all bubbling ceases. 
(6) Make a plaster of paris mix, of a heavy creamy consist- 
ency, and fill the lower portion of the flask to about two- 
thirds of its capacity. If the plaster is too thin, it is difficult 
to control, and will extend upon the waxed surfaces. (7) If no undercuts are present on the cast, settle it in the 
plaster mix so that the occlusal plane of the teeth will be 
parallel with the bottom of the flask. If undercuts are pres- 
ent, as they sometimes are around the anterior region or 
the heels, it is necessary to place the cast in the plaster at 
such an angle so as to compensate for the undercut. For 
instance, if the anterior ridge is undercut, it is necessary to 
raise the anterior portion of the cast above the level of the 
heels. See Figs. 38 and 39. 
(8) Remove all excess plaster between the peripheral rim of the 
denture and the rim of the lower portion of the flask, 
smoothing the surface of the plaster. 
(9) Allow plaster to set until hard and then apply a little petro- 
latum or green soap to the surface of the plaster to act as a 
separating medium. 
(10) Set the upper portion of the flask in position. 
(11) Make a plaster mix and fill the upper portion of the flask, 
pouring the plaster carefully, and gently jarring the case 
so as to prevent inclusion of air bubbles. 
(12) Place the top of the flask in position and wipe off all excess 
plaster. 
30. Denture Flashing (Partial) 
(1) Holding of clasps and framework to models upon separa- 
tion. 
The first method to be described consists of flashing the denture 
similarly to that just described, but in addition, cutting of the re- 
maining teeth from the cast to within one-sixteenth of an inch 
from the wax. This exposes all the clasps. When removing the 
plaster tooth from within a clasp, extreme caution should be 
exercised. It is often advisable to remove such teeth with a bur. 
After removal of the plaster tooth from the clasped area, any 
adjacent voids in the wax should be filled with wax. These 
clasps as well as any other metal parts such as lingual bars, etc, 
are then covered with plaster mix in the lower portion of the 
flask, leaving just the wax surfaces and artificial teeth exposed. 
From this point the flashing is carried out as given above. See 
Fig. 40. (2) Removal of clasp and framework from the model upon 
separation. 
Another method of flashing partial dentures is frequently used, 
especially in the acrylic resin cases that require tin foiling. It 
consists of cutting off all the teeth from the model to within one- 
sixteenth of an inch from the wax. The exposed clasps, bars, etc 
Fig. 40 
are then incorporated into the upper portion of the flask instead 
of the lower. It is often advisable in the case of palatal and 
lingual bars to remove a portion of the cast from about the bar 
to insure their retention and more stable relationship when using 
Fig. 41 this method. When the plaster in the upper half has set, the wax 
eliminated and the flask opened as described in the next step; the 
clasps, etc., will be pulled away from the model, but still will 
maintain their correct relationship. See Fig. 41. 
Either method of flashing may be used, depending upon the 
individual case under construction. In either method, prior to 
the pouring of the upper half of the flask, make doubly sure that 
all undercuts are eliminated in order to prevent fracture or ir- 
reparable damage to the models upon separation of the flask. 
31. Packing the Case 
The case is now ready to be packed with any material that has 
been selected. Dental rubber or vulcanite, and acrylic resin are 
the most satisfactory and the most commonly used. Therefore, 
we will deal only with these materials. All cases should be care- 
fully packed with the right quantity of material. There is no 
reason for overpacking and thus inviting danger of breakage of 
the cast and the destruction of the occlusion of the teeth. The 
“dry” method of packing vulcanite cases is the most desirable. 
(1) The pink gum rubber is cut into strips which are wide 
enough to cover the ridge lap of the teeth and extend to the 
border of the matrix. A narrow strip is then cut into small, 
triangular pieces which will fill the spaces between the 
teeth. The base rubber is cut into the desired-sized pieces 
for the lingual and hidden parts of the case. Pink rubber 
is used on the labial and buccal surfaces of the denture be- 
cause it has a much more natural appearance. Base rubber 
is used on the palatal and hidden surfaces of the denture 
because it is much stronger and durable than the pink 
rubber. 
(2) The lower part of the flask is placed in a heated oven, and 
warmed throughout, to a temperature of about 212 degrees. 
It is then removed from the oven and placed on a towel 
which will serve as a heat retainer during the packing 
process. 
(3) Using suitable packing tools, carefully place the triangular 
pieces of rubber between the interproximal spaces of the 
teeth. 
(4) Fold a strip of dark rubber about one-quarter inch wide 
along its greater length, and cut a piece long enough to fit from the first-bicuspid region of one side to the first-bicus- 
pid region of the other. Insert this piece of rubber under 
the pins of the anterior teeth. 
(5) Pack the small square pieces of the dark rubber into each 
one of the diatoric openings of the posterior teeth. See 
Fig. 42. 
Fig. 42 
(6) Place two strips of the pink rubber, about one-half inch in 
width, one over the other, and lay them over the triangular 
pieces and the edge of the teeth, along the buccal and labial 
surfaces, from the median line to the region of the second 
molar. Place two more strips of the pink rubber in ident- 
ical positions on the other side. These pink strips should 
extend from about 1 mm. above the pins and diatoric open- 
ings to about 1 mm. above the rim of the denture. 
(7) Place small strips of the dark rubber close against the pink 
rubber in the region of the buccal surface of the second 
molars. 
(8) Place additional strips of dark rubber against the bicus- 
pids and molars on the palate. 
(9) Cover the remaining portion of the palate with the dark 
rubber, and add sufficient rubber over the entire surface to 
completely fill the space formerly occupied by the wax. It 
should be filled so that a little excess may be squeezed out around the edge of the denture when the flask is closed. 
See Fig. 43. 
(10) The lower denture is packed in a similar manner as the 
upper with the exception of having a tongue space instead 
of the palate. The lingual flanges of the lower denture are 
packed with the dark rubber, and are carried just 1 mm. 
beyond the periphery of the denture. The tongue space of 
course is left free from rubber. 
Fig. 43 
(11) If much time has been consumed in packing the case, and 
it has become cold before the packing operation is com- 
pleted; it may be returned to the oven and reheated. 
(12) When the packing of the case has been completed, a piece 
of wet cellophane is laid over the entire lower half of the 
flask, and the two parts of the flask are then brought to- 
gether. 
(13) Place the flask in a flask press and immerse both in a pan 
of boiling water for about 15 minutes. Remove from water 
and cautiously apply pressure with the screw. Too much 
pressure must not be applied in closing the flask. 
(14) The flask is removed from the press and opened. If too 
much rubber has been expressed, the excess is removed 
and the operation repeated. 
(15) If rubber is insufficient, add more and repeat the process. 
See Fig. 44. (16) Adapt a piece of wet cellophane to the cast before the final 
closing of the case. As the tissue surface of the completed 
denture is never polished, this step is necessary to insure 
a dense, smooth surface. Tin-foil may be adapted to the 
case in place of the cellophane, if desired. 
Fig. 44 
32. Vulcanization 
(1) Fill the vulcanizer pot with warm water to a depth of one 
inch. 
(2) Place the flask clamp containing the flask in the vulcanizer 
and adjust the vulcanizer cover. 
(3) Open the blow-off valve. 
(4) Light the burner under the pot and adjust it until the blue 
flame just covers the bottom of the vulcanizer. Never 
allow it to reach up the sides. 
(5) Set the gas regulator to 320 degrees, or, according to vul- 
canizing directions. 
(6) Allow all air to escape and when steam begins to be ex- 
pelled, close the blow-off valve, using a wrench. 
(7) Set the time clock to shut off the gas at the required inter- 
val. 
(8) Vulcanize for one and one-half hours from the time the 
blow-off valve is closed. Allow 35 minutes to reach 320 
degrees. Maintain this temperature for 55 minutes. (9) The time regulator will shut off the supply of gas as reg- 
ulated. 
(10) Allow vulcanizer to cool for 15 minutes, then open blow-off 
valve, until steam begins to escape. 
(11) After all steam has escaped, remove the vulcanizer cover. 
(12) Remove flask from vulcanizer and allow to cool for 15 
minutes. Then place it in cold water until thoroughly 
chilled. 
33. Cleansing and Polishing of Dentures 
(1) Remove the flask cover. 
(2) Using a plaster knife, remove the plaster from around the 
edges of the upper part of the flask until the teeth are ex- 
posed, as well as the bucal and labial surfaces of the den- 
ture. 
(3) With a knife inserted between the upper and lower por- 
tions of the flask, carefully open it without applying too 
much pressure. 
(4) Carefully remove the denture from all surrounding plaster. 
(5) Wash all excess plaster from the denture with a stiff bristle 
brush, while holding it under cold water. 
(6) With a sharp pointed knife, peel away all the tin-foil or 
cellophane from the tissue surface of the denture. 
(7) Cut away all excess vulcanite from the rim of the denture, 
being careful not to mar the peripheral border. 
(8) Partial dentures are removed in the same manner, only 
more care must be taken in their removal as they are 
easier to distort or fracture. 
(9) Using either a half-round vulcanite file or an abrasive 
wheel mounted on the lathe, remove all excess vulcanite 
from around the edge of the denture. 
(10) In partial dentures, use a rat-tail vulcanite file around the 
cervical edges to bring it to the proper limits. 
(11) Remove all roughness from labial, buccal, palatal, and 
lingual surfaces of dentures by using a vulcanite scraper. 
(12) Carefully smooth the denture with sandpaper. In using 
sandpaper it is easy to take away too much vulcanite, thus exposing some dark rubber on the labial surface or making 
the denture too thin. It is also possible to permanently 
harm the denture by generating too much heat in this 
polishing process. 
(13) Carefully trim the vulcanite about the necks of the teeth on 
the buccal, labial, and lingual surfaces with sharp vulcanite 
trimmers. A sharp trimmer must always be used in this 
procedure to avoid undue pressure and to give a polished 
finish to the vulcanite. 
(14) All the steps previously described are preliminary to put- 
ting the final polish on the denture. It is necessary to ob- 
tain this high polish for the health and comfort of the 
patient. Vulcanite dentures are more or less porous and 
have a tendency to absorb saliva and accumulate food par- 
ticles. High polish will reduce this porosity. Make a 
putty-like mix of fine pumice and water and, with a brush 
wheel rotating toward the operator, proceed to polish the 
denture. It should be held firmly in the hands, rocking it 
in a semi-circular motion so that grooves will not be cut 
into the vulcanite. Always keep the surface of the denture 
wet with pumice and use gentle pressure. Too much pres- 
sure will warp and burn the denture. 
(15) Repeat this process using a linen rag wheel with pumice in 
place of the brush wheel. 
(16) Mount large or small felt cones to the chuck of the lathe and 
polish all areas inaccessible with the rag wheel. 
(17) Make a mixture of chalk and water and with a soft flannel 
wheel continue to polish all surfaces of the denture. 
(18) Wash with water and check to make sure that all scratches 
have been removed. Then with a soft flannel wheel apply 
powdered oxide of tin for the final polish. 
Section VII 
Acrylic Resin Dentures 
34. General 
The acrylic resins are used by the dental profession, in order 
to have a denture material with better esthetic qualities than vul- 
canite and, at the same time, without sacrificing strength and 
durability. A great many synthetic materials have been de- veloped and marketed from time to time, but the acrylic resins 
seem to be the best so far developed. There are various acrylic 
resins on the market and the procedure may vary slightly accord- 
ing to the material, but the basic technique is very much the 
same. 
35. Procedure. 
(1) Wax up as if the denture were to be made of vulcanite, ex- 
cept that the wax should be a little fuller in the inter- 
proximal spaces to allow for tin-foiling. 
(2) Invest the case in the lower portion of the flask as for a 
vulcanite denture. 
(3) The cast is now ready for tin-foiling. This is a most im- 
portant procedure in the construction of acrylic resin den- 
tures as any error in this step will result in the final den- 
ture being weakened and spotted. It is necessary to have 
all surfaces covered completely with tin-foil. For the upper 
cast cut four pieces of tin-foil. One piece to fit the palate, 
two to fit the buccal surfaces, and one to fit the labial sur- 
face of the denture. Additional tin-foil is then cut to cover 
the plaster in the flask. The tin-foil for the lower case is 
the same with the exception of the part that will cover the 
lingual surfaces and the tongue spaces. This should be cut 
square and then rounded in front. 
(4) Cut the palatal piece of tin-foil into two triangular pieces. 
With a small piece of cotton, burnish the tin-foil on the 
wax of the palatal surface of the upper denture and over- 
lap these two pieces in the center of the palate about one- 
fourth of an inch. Extend the tin-foil to about one-eighth 
of an inch below the incisal and occlusal surfaces of the 
teeth. 
(5) Cut little V-shaped grooves in the tin-foil, covering the 
teeth on the labial, lingual, and buccal surfaces so it may be 
adapted into the interproximal spaces between the teeth. 
(6) Remove one side of the palatal tin-foil and apply glue to the 
overlapping margin and replace on the waxed case. 
(7) Adapt the labial and buccal pieces of tin-foil to the waxed 
surfaces from about one-eighth inch below the incisal and 
occlusal surfaces of the teeth. Use the separate pieces of tin-foil to cover the plaster surface. Seal the overlapping 
margins with glue. See Fig. 45. 
(8) In lower cases adapt a piece of tin-foil to cover the tongue 
space. 
(9) The remainder of the flashing procedure is identical to that 
used in vulcanite. 
(10) Boil out the wax in the same manner as previously de- 
scribed, washing the cast with chloroform followed by ace- 
tone. Make sure all acetone has evaporated before proceed- 
ing to pack the case. 
Fig. 45 
(11) In acrylic resin dentures it is necessary to tin-foil the cast. 
This is done after the case has been flashed and separated. 
(12) Acrylic resins usually come in two types. One type is the 
cake, and the other is the powder and liquid. The last men- 
tioned is preferable and will be the one described. Have a 
clean sheet of paper about eight inches square on the bench. 
Place the powder cup, in which the material comes, in the 
center of the sheet of paper and pour the powder into the 
cup until it overflows. Scrape off all excess powder with 
a straight edge until the powder is level with the rim of the 
cup. Do not pack the material, or jar it into the cup. Pour 
the powder so measured into any porcelain vessel, such as a 
coffee cup. Measure out about 8 cc. of the liquid and add to the powder in the cup. Immediately begin mixing 
vigorously with a clean, stiff, stainless-steel spatula. Con- 
tinue this mixing until the material begins to be homogen- 
eous and loses most of its stickiness. This should take 
about one minute. Then roll the mixed material between 
the palms of the hands for five to ten seconds. The hands, 
of course, should be clean and dry. For repairs, or if it is 
desired to make smaller or larger mixes than by the mea- 
suring cup, different quantities in correct proportions 
should be used. 
(13) The case is then ready to be packed. This should be done 
as quickly as possible after mixing. When first mixed, the 
material is very soft and easy to pack, but upon standing, 
it becomes stiffer and requires more pressure to close the 
flask. The flashing should be done soon after boiling out 
so that the flask will be warm but not hot. A good tem- 
perature is 100 to 125 degrees F. Roll, between the hands, a 
piece of the material about the size of a lead pencil and suf- 
ficiently long to cover the teeth. Pack this well down 
against the teeth, making sure that no air is inclosed. Next 
roll up another piece about the thickness of the little finger 
and long enough to go around the arch. Immediately press 
this to place with the fingers. In upper cases it is neces- 
sary to put a sheet of the material over the palate. 
(14) The flask may be trial separated by placing a strip of moist 
cellophane over the material in the flask before closiflg; 
Close as quickly as possible in any convenient press. Do 
not apply any extra heat to the flask to facilitate closing as 
this will only hasten the setting of the material. The flask 
is then reopened and material either added or cut away as 
necessary. It is now ready for curing. 
(15) The case may be cured in a vulcanizer or in boiling water. 
Either way gives good results. In the vulcanizer, any 
curing temperature from 212 to 320 degrees F. and a mini- 
mum time of one hour may be used. Cooling, after curing, 
is done in the same manner as for vulcanite. 
(16) The simplest manner in which to cure the denture is to 
place the case and the flask in a pan of cold water. This 
water is then brought to a boil and allowed to boil for 
about 40 minutes. The case is then allowed to cool very gradually (preferably overnight) before opening. The 
case is opened, the denture removed and polished in the 
same manner as previously described. 
Section VIII 
Denture Repair 
36. Simple Repair 
(1) Bring the fractured edges of the denture into apposition 
and seal them together with a little sticky wax. Pieces of 
stiff wire are laid over the fractured denture at right angles 
to the line of fracture and waxed in place. This gives the 
denture additional support. 
(2) Lubricate the tissue surface of the denture with petrolatum, 
(3) Place boxing wax around that part of the periphery of the 
denture that makes contact with the natural teeth. 
(4) Make a plaster mix and pour a matrix or cast of the den- 
ture as described in pouring impressions. 
(5) When the plaster has set, remove the denture parts and 
with abrasive chucks and vulcanite burs, grind away a 
large portion of the palate on each side of the fracture. 
Also remove about two mm. of vulcanite from the peri- 
phery of the denture over those areas containing artificial 
teeth. The margins of the palatal area are then dovetailed 
as shown in the illustration. 
Fig. 46 (6) Replace the fractured parts on the cast, fill in the missing 
parts of the vulcanite with wax, making this wax a little 
thicker than the original vulcanite. This will allow for the 
finishing and polishing of the denture. See Fig. 46. 
(7) Pour the lower and upper portions of the flask as done in a 
new case. 
(8) After the plaster has set, the wax is eliminated and the flask 
carefully opened. The denture will be contained in the 
upper half of the flask. 
(9) With a vulcanite bur, remove about one-half mm. of vul- 
canite from the entire tissue surface of the denture. The 
surface is roughened. See Fig. 47. 
Fig. 47 
(10) Proceed to pack the case as usual and then place a piece 
of wet cellophane over the case before the final closing. 
(11) The case is then vulcanized and finished as previously de- 
scribed. 
37. Loose or Broken Teeth 
(1) When the original tooth has become loosened and can be 
replaced, it is only necessary to make certain it fits in its 
exact position as marked on the vulcanite. Then cut a 
dovetail in the lingual or palatal surface of the vulcanite 
adjacent to the tooth, replace the tooth in its original posi- tion and secure it by wax. The case is then carried for- 
ward as in the simple repair. 
(2) When the tooth has been broken or lost and a new tooth 
is necessary, but the denture base at the site of the tooth 
is intact, it is necessary for the dental officer to supply the 
technician with a wax bite indicating the relationship of 
the teeth of the opposing jaws. Proceed as in simple re- 
pair until matrix is poured. Fit the teeth of the denture 
into the depressions on the bite, and seal it to the denture. 
Fill the depressions left in the bite by the teeth of the 
opposing jaw, with plaster. The matrix of the denture 
and the poured bite are then mounted on an articulator, 
after which the bite is removed. Place the new tooth in 
the correct position, as governed by the adjacent and op- 
posing teeth. Do not grind away any of the vulcanite 
from around the neck of the tooth, but do all necessary 
grinding on the tooth itself. Wax into position and pro- 
ceed as in simple repair. 
38. Teeth Added 
Often a tooth is extracted requiring the addition of an artificial 
tooth to a partial denture. The technician receives the impres- 
sion of the mouth that has been taken with the denture in place. 
If the impression has been taken in plaster, it must be painted 
with a separating media. A wax rim is placed around the periph- 
ery of the denture and the cast is poured. The bite is placed in 
its correct position on the denture and waxed in place and poured. 
The denture, cast, and bite are then mounted on an articulator. 
The bite is removed and the additional teeth are added to the 
denture, as described above, and the process followed as in a 
simple repair. 
39. Loose Clasp 
The dental officer has taken an impression of the clasped tooth 
with the clasp and denture in position. The impression is poured 
as directed for adding teeth to a partial denture. The vulcanite 
is cut out from around the tail piece of the clasp, and this area 
filled with wax. The case is then carried to completion as pre- 
viously described. 40. Refacing 
Lubricate the inner surface of the denture and fill with plaster, 
forming a matrix. Allow to set. Cut away the labial and buccal 
vulcanite to about one half of its original thickness, making cer- 
tain the rubber is removed from around the necks of the teeth. 
Honeycomb the remaining gum rubber to roughen it. Wax the 
labial and buccal surfaces of the denture. Flask the case by 
Fig. 48 
filling the lower part of the flask with fairly stiff plaster and 
setting the denture into this plaster with the teeth down. Make 
sure that the teeth are at least inch from the bottom of the 
flask, and that all the waxed parts are exposed. Smooth the 
plaster around the teeth and over the rear of the denture. The 
upper part of the flask is poured after lubricating and the case 
is continued as in simple repairs. See Fig. 48. 
41. Rehasing 
Often the gums will shrink or pull away from the denture after 
it has been worn for some time. This causes the denture to 
become loose and irritating to the patient. If the denture is in 
good condition otherwise, it may be repaired by adding a new 
base or foundation of vulcanite. The technician receives the 
denture, to the base of which has been added a sufficient amount 
of material to correct the deficiency in the mouth of the patient. 
This material is usually modeling compound, but it may be 
plaster, or, both. A strip of boxing wax is placed around the periphery of the denture and the cast is poured as described. 
The case is then flashed the same as if it were a new denture. 
After the two parts of the flask have been separated, the impres- 
sion material is removed. The tissue surface of the denture is 
roughened by vulcanite burs and stones to facilitate the addition 
of the new vulcanite. Sufficient vulcanite should be removed to 
allow for about 1 mm. of new rubber. The case is packed with 
strips of base rubber, the flask is closed and the case carried to 
completion as previously described. 
42. Duplicating a Denture 
Frequently it is necessary to replace the entire denture base 
with new material. The technique as given here does not re- 
quire the case to be mounted on an articulator. Proceed as in 
any simple repair until the matrix is poured. Make several deep 
grooves on the buccal and labial surfaces of the old denture. 
Lubricate the teeth and the buccal and labial surfaces of the 
denture and matrix. Build a plaster index around the entire 
outer surfaces of the denture and matrix, extending the plaster 
to about one-fourth inch from the incisal and occlusal surfaces 
of the teeth. Before the plaster sets too hard, make a cut oppo- 
site each cuspid tooth. This weakens the plaster index which 
is carefully removed as soon as it is sufficiently hard. Lift the 
denture from the matrix and remove all the teeth from the 
denture by covering them with a layer of melted basewax and 
then passing the denture several times through a flame to soften 
the vulcanite. The teeth are arranged in their proper position 
as indicated on the plaster index, and are secured with sticky 
wax. A baseplate is constructed over the matrix and the plaster 
index containing the teeth is arranged around the matrix with 
the baseplate. Melted basewax is flowed into the spaces between 
the teeth and the baseplate. The sticky wax holding the teeth 
is removed as well as the index. The waxing is finished where 
necessary without disturbing the position of the teeth. Proceed 
with the flashing as described. It is sometimes necessary to use 
basewax instead of the baseplate to avoid displacing the teeth 
in the index. 
43. Repairing Acrylic Resin Dentures 
Bring the broken parts of the denture into apposition and wax 
them securely together. A cast is then poured, as in the vulcanite case. The model is then removed and tin-foiled. Replace the 
denture on the model and rewax if necessary. Tin-foil the com- 
plete denture, holding it in place with a little thin glue. Do not 
tin-foil the wax portions. Flask as for a vulcanite repair. Boil 
out the wax, but do not use chloroform or acetone to clean the 
cast. Tin-foil the plaster in the upper half of the flask that will 
come in contact with the denture or the repair portions. A small 
mix of the powder and liquid is made, as previously described, 
and this material is packed in the repair portion and the flask 
closed. The denture is cured as for a full denture. If the case 
has undercuts so that the denture can not be removed from 
the cast, it is necessary to tin-foil the denture before pouring 
the model. 
Section IX 
Clasps and Bars for Partial Dentures 
44. General 
Clasps are simple, direct retainers applied to two or more op- 
posite, sloping or convex surfaces of remaining natural teeth, 
which are chosen for that purpose during the designing of the 
denture. For convenience clasps may be divided into three 
classes; namely, one arm, two arm, and three arm clasps, ac- 
cording to the number of arms which are applied to the surfaces 
of the tooth. These may be either wrought or cast clasps. The 
former are constructed by bending a piece of gold clasp wire to 
conform to the tooth, and the latter are constructed by casting 
the clasps using a special gold alloy. Both types have a definite 
place in dentistry and although there are many variations of 
both, this manual will deal only with those types that are com- 
monly used. In order to understand the construction of a clasp 
—no matter what type it may be—it is necessary to study the 
shape and contour of the crowns of the teeth so that these sur- 
faces may be used to the best advantage. The fundamental rea- 
son behind all clasps is to obtain the maximum amount of reten- 
tion for the denture, and still allow it to be easily inserted and 
removed from the mouth. It must be understood that it is 
impractical to clasp some teeth, due to their anatomical charac- 
teristics or position, therefore, it is essential that the dental officer 
take great care in the designing of the case. The three simple 
diagrams in Fig. 49 will clarify the fundamental mechanical theory which must be understood in order to construct efficient 
clasps. 
Diagram A shows that each tooth is divided into two separate 
parts by its line of greatest circumference. Nothing above this 
line can be used for retention. Therefore the parts of the clasp 
from which no retention is obtained are placed on this half of 
the tooth. This includes the body or rigid portion and the occlusal 
Fig. 49, Diagram A 
Diagrammatic sketch il- 
lustrating line of greatest 
circumference of tooth. 
Fig. 49, Diagram B 
(A) Body of Clasp. (B) 
Shoulder of clasp. (C) 
Arm of clasp. (D) Line 
of greatest circumference 
on tooth. 
Fig. 49, Diagram C 
Sketch of clasp illustrat- 
ing various parts. (A) 
Body of clasp showing oc- 
clusal rest. (B) Shoul- 
ders of clasp. (C) Arms 
of clasp. 
rest. The parts of the clasp that extend out from the body for 
a short distance are known as the shoulders. As we rely on the 
shoulders for rigidity and not for retention, they should be placed 
either on the line of greatest circumference or just crossing it. 
Extending from these shoulders are the thin flexible arms from 
which the retention is derived. These arms must always be 
below the guide line and in the undercut of the tooth. Therefore, 
they are placed below the line of greatest circumference, as 
shown in diagram B. The body and occlusal rest of the clasp are above the line, the shoulders on or crossing the line, and the 
arms below the line. If this rule is followed, the clasp will give 
maximum efficiency. It is the duty of the dental officer to sur- 
vey each case before giving it to the dental technician, marking 
on the cast the teeth to be clasped, the outline of the clasp and 
rest areas, and the outline of the entire denture. In a partial 
denture with two or more clasps, it is necessary to take into 
consideration the fact that while one clasp may be easily re- 
moved from the tooth, another clasp when attached to the den- 
ture may be in such a position as to make its removal impossible. 
Therefore, a mean vertical plane must be determined when the 
case is surveyed, which will coincide with the path along which 
the clasps will tend to seat themselves, when attached to the 
denture. This is known as the path of insertion. 
45. Wrought Clasps 
Wrought clasps, as stated above, are constructed by bending 
a piece of either round or half-round gold clasp wire of the de- 
sired gauge to conform to the tooth to be clasped. One of the 
most commonly used methods is to clasp a tooth adjoining a 
space caused by the extraction of one or more teeth. This allows 
sufficient room for the body of the clasp. However, it is fre- 
quently necessary to clasp a tooth which is in contact with the 
teeth on each side of it. As there is no room between the teeth 
to accommodate the body of the clasp, a different design must 
be used. However, the actual bending of the wire is done the 
same in each case. In the simple three arm clasp, using a tooth 
adjoining a space, the following technique is followed: 
(1) Anneal the wire before any bending is attempted. This is 
done by holding it in an open flame until it assumes a 
cherry red color. It is then plunged in cold water, which 
removes the stiffness from the wire and makes it much 
easier to bend into shape. This annealing process should 
be repeated after each bending during the construction of 
the clasp. 
(2) Place one end of the wire on the lingual surface of the 
tooth, where the outline of the clasp terminates, and note 
the point where the wire leaves the surface of the tooth. 
Grasp the wire with suitable wire bending pliers and bend 
it slightly so that a greater length of the wire comes in contact with the tooth when tried on the model. It is then 
annealed and the point where it again leaves the tooth is 
noted and bent as before. This procedure is carried out 
until the clasp is conformed to the entire outline of the 
clasp on the model. As the buccal end of the clasp is 
approached, the length of wire to be used is judged and 
the remainder cut off with a pair of cutting pliers. The 
ends of the clasp are rounded with stones and burlew discs. 
46. Occlusal Rests 
In practically every partial denture case it is necessary to con- 
struct a third arm or occlusal rest as part of the clasp. This part 
will extend from the body of the clasp, over the marginal ridge 
of the tooth and rest on a small section of the occlusal surface. 
Fig. 50 
Diagram of the con- 
struction of an oc- 
clusal rest. 
In this way the tooth can actually be made to bear most of the 
stresses of mastication instead of the tissue surfaces, and prevent 
the denture from settling down and forcing the clasp onto the 
gingival tissue around the neck of the tooth. Since the occlusal 
rest must bear quite a load it must be of sufficient strength to 
prevent breakage. A small piece of 36 gauge pure gold plate is 
Fig. 51 
Fig. 52 
placed against the model at a point corresponding to the body 
of the clasp. This is shown in Fig. 50. 
The clasp is placed over the tooth and the end of the gold plate 
below the clasp is bent up and around the wire clasp, and se- cured with sticky wax. The lug and the clasp are removed from 
the model and soldered together with a very small piece of solder, 
making certain that the relationship is not destroyed. The clasp 
with the lug is then replaced on the model and the pure gold is 
burnished over the small part of the occlusal surface, as outlined 
on the model. The gold is trimmed to conform with the outline, 
leaving a small excess around the margins. See Fig. 51. 
A short piece of half round wire is bent to the shape of an L 
and laid over the rest as shown in Fig. 52. When soldered, this 
wire will reenforce the occlusal rest. 
The clasp, lug, and wire are removed from the model and care- 
fully invested in a small amount of investment material. The 
investment is allowed to come just to the margins of the lug. 
The investment is allowed to set and then gradually heated over 
an open flame until quite hot. Using a blow torch, small pieces 
of either 18 or 20 carat gold solder are fused over this lug, fur- 
ther attaching it to the clasp and at the same time adding thick- 
ness to the lug so that it will have sufficient strength to with- 
stand the stresses of mastication. The clasp with the occlusal 
rest is removed from the investment and polished. It is returned 
to the model and checked for accuracy. This procedure is re- 
peated for all clasps requiring occlusal rests. 
47. Heat Treatment of Gold 
As the repeated annealing of the gold clasp wire causes it to 
become soft and pliable, it is necessary to restore its hardness 
and elasticity by retempering after the work has been finished. 
To do this, the clasp is placed in an oven and heated to a tem- 
perature of 840 degrees F., and held at that temperature for 10 
minutes. It is then allowed to cool to 480 degrees F., over a 
period of 30 minutes. If an oven is not available, heat in an open 
flame to a cherry red and allow to cool in air. 
48. Crib Clasps 
As stated previously, the design of the clasps may be altered 
to suit the case. Frequently, it is necessary to construct a clasp 
for a tooth which is in contact with the adjoining teeth. An 
example of his type of clasp is shown in Fig. 53. 
In this type of attachment the body of the clasp is placed in 
the embrasure between the teeth instead of beside the distal or 
mesial surfaces. Preparation for this should be made in the mouth before the impression is taken, and the technique of bend- 
ing the clasp is exactly as described previously. This may be 
either a single clasp or a double clasp, as shown in Fig. 53. In 
the double crib clasp a slight modification is used. Instead of 
bending the gold clasp wire around one tooth, it is bent in the 
shape of an S, starting at the lingual surface of one of the teeth 
to be clasped, continuing to the proximal surface of the tooth, 
Fig. 53 
and crossing the embrasure between the teeth, as described. But, 
instead of continuing around the buccal of the same tooth, it is 
bent so as to form the buccal arm of the clasp for the other tooth 
to be clasped. When this S-shaped wire is formed, two other 
pieces of wire are bent to complete the unfinished arms of the 
clasp. These pieces are soldered to the S-shaped wire in their 
correct positions, thus completing the double crib clasp. Always 
construct an occlusal rest for all crib clasps in order to prevent 
the wire from separating the teeth, thus endangering their con- 
tinued usefulness. 
49. Cast Clasps 
The designs, as already given for wrought clasps, will also ap- 
ply to cast clasps. Frequently, in the designing of partial den- 
tures this is the type indicated. The impression of the teeth to 
be clasped is usually taken in plaster or hydro-colloid impression 
material. The impression is boxed in either moldine, if a metal 
model is to be made, or wax, if the model is to be poured with 
investment plaster. The fit of the clasp is usually more accurate when cast directly on the investment plaster model. Therefore, 
this will be the technique described in the manual. The outline 
of the clasp is traced on the model by the dental officer. A piece 
of 30 gauge base wax is wrapped around the tooth and sealed 
with a warm spatula so that it will not move from position. The 
outline of the clasp which shows through the wax is then covered 
with a thin layer of either green or blue casting wax. After 
Fig. 54 
applying the wax, it is carved and smoothed to the shape of the 
clasp, which should also include the tail portion or that part 
that is to be used for anchorage. It is much easier to cast the 
tail piece as part of the clasp, than to make it of wire and then 
solder the two parts together. This anchorage should be of suffi- 
cient length to allow maximum retention in the denture material 
and should be made in the form of a loop to facilitate this re- 
tention. The outline of this loop should be marked on the model 
at the same time that the clasp is outlined and the waxing done 
as the clasp is waxed. When the wax clasp and tail piece are 
carved and smoothed, the case is sprued by attaching a tapered 
wire, such as a phonograph needle to the wax clasp, and holding 
it in place until it has cooled sufficiently to secure it. The clasp 
can then be invested and cast the same as any gold inlay or 
three-quarter crown. (See crown casting.) 
50. Indirect Retainers 
In addition to the direct retainers or clasps, it is sometimes 
necessary to incorporate in the design of a partial denture, an additional form of retention. This is known as an indirect re- 
tainer. It may be defined as the utilization of a force, remote 
from that part of the denture to be retained, between which an- 
other of the direct forms of retainers is interposed; the resultant 
force tending to seat the denture more firmly in position. In Fig. 
54 it can be seen that the extension arm or bar, touching the 
lingual surfaces of the lower incisor teeth, checks the denture 
and prevents its distal portion rising under stresses of mastica- 
tion. The work (retaining the denture), coming from the power 
(the contact of the indirect retainer upon the teeth), through the 
fulcrum (the direct retainers on the clasped teeth). There are 
many modifications of this design, both for upper and lower den- 
tures, that will depend upon the individual case. 
51. Lingual and Palatal Bars 
A lingual bar consists of a connecting piece of material run- 
ning adjacent to the soft tissue on the lingual side of the lower 
front teeth, beneath the tip of the tongue, joining the two sides 
of a lower partial denture and making it one unit. Palatal bars 
may be defined as metal bars constructed to fit the surface of the 
vault of the palate and connecting the two lateral sections of an 
upper partial denture. Lingual bars may be obtained in a ready- 
made form and all that is required is to adapt it to the individual 
model. However, in a few cases this is not entirely satisfactory, 
and it is better to cast the lingual bar as well as the palatal bar 
for these cases. The design of the bar is drawn on the model 
with an indelible pencil by the dental officer. It is frequently 
necessary to place a strip of adhesive tape on the model to pro- 
vide relief before adapting the wax. The outline of the bar on 
the model is oiled, and over this outline is adapted a piece of 
30 gauge baseplate wax. Blue inlay wax is melted and placed 
over this outline, which shows through the first layer of base 
wax. It is then trimmed and carved to the exact shape of the 
completed lingual bar. See Fig. 55. 
After smoothing the wax it is sprued, removed from the cast, 
washed with green soap and water, invested, and cast in saddle 
and bar gold. 
52. Duplicating a Master Model 
It is frequently necessary to make a duplicate model or an 
exact reproduction of a master model. An example of this is 
58 the construction of any cast appliance. Lubricate the master 
stone model and place in the duplicating flask with the teeth up. 
If no duplicating flask is available, a tin can may be used that 
has had the ends removed. Pour the hydro-colloid duplicating 
material around the sides of the model and then all over it, com- 
pletely filling the flask. The hydro-colloid material is boiled in 
any pan or coffee pot and then cooled to a temperature of be- 
Fig. 55 
tween 140 degrees and 160 degrees F. Immediately put on the 
top of the flask, tighten and set screw, and immerse in a pan of 
cold water. When the hydro-colloid material has completely set 
(15 to 30 minutes) the bottom of the flask is removed, and the 
master model carefully removed. Dry off any excess water from 
the surface of the impression and immediately pour with invest- 
ment plaster. As soon as the investment is poured, dust some 
dry investment powder on the back of the model to absorb the 
excess water. Allow the investment to set forty-five minutes. 
The hydro-colloid is then broken away from the model. 
Section X 
Fixed Bridge 
53. General 
The dental technician need not concern himself about the de- 
tails involved in the preparation and construction of the crowns 
or inlays used to attach the bridge to the abutment teeth of the patient. The dental officer performs all of this preliminary work 
and the case usually comes to the technician with the attach- 
ments made and in place on a model. This manual will deal 
with the construction of the bridge from this point. A fixed 
bridge is a replacement for missing natural teeth, either in the 
front or back of the mouth, with the abutment teeth to which 
the bridge is attached bearing the entire stress of mastication. 
This is differentiated from a partial denture where the attached 
teeth bear only part of the load. A fixed bridge is, as the name 
implies, fixed in the mouth and may not be removed by the 
patient. 
54. Anterior Bridge 
(1) Assuming that the bridge to be constructed is an upper- 
anterior, six-tooth bridge supplying the upper centrals and 
laterals with attachments on the cuspid teeth, and the 
models have been mounted on an articulator, select four 
facings of the correct shade and mould that will snugly fit 
into the space. This may be done by placing a little soft 
wax in the space, and trying-in various sizes and moulds 
of teeth until the proper effect is obtained. 
(2) Grind these facings to fit the model. All of the grinding 
is done on the gingival end of the facing and never on the 
incisal end. Therefore, it is necessary to select facings that 
fit the case as nearly as possible to minimize this grinding. 
(3) Select a backing for each one of the facings, being certain 
that the backing is just a little longer towards the incisal 
than the facing. This is very important, as a short back- 
ing will not protect the porcelain facing during the stresses 
of mastication, thus causing it to break. 
(4) Trim the backing mesially, distally, and on the gingival 
end to fit the facing that has been previously ground to fit 
the model. Leave the incisal end of the backing longer 
than the facing. Have the facing in place on the backing 
and file obliquely across the incisal edge from gold to 
porcelain with the point of the file pointing gingivally; 
finish the metal down to almost a continuous line with the 
porcelain. Leave just enough backing so that the metal 
will take most of the biting stress instead of the porcelain, and still not show more than a hair line of gold at the 
incisal edge. This procedure is followed on all the teeth. 
(5) Assemble the facings and backings on the model in the 
exact position that they will be in when the bridge is com- 
pleted. Make certain that there is just a hair line of space 
between each one of the backings to allow for expansion 
of the metal during soldering. Wax them into position by 
flowing a little sticky wax between the junctions of the 
backings. Remove the porcelain facings, leaving the back- 
ings in the correct position. Paint the post sides of the 
backings with a little antiflux. 
(6) Invest the model with the backings in place in a suitable 
soldering investing material. The investment should cover 
everything but the posterior surfaces of the backings and 
the abutting surfaces of one backing to the other. 
(7) In a case requiring three or four facings, further reenforce- 
ment than just the solder is indicated. A piece of 16 gauge 
clasp metal gold wire is bent so that it rests against each 
backing between the contact point and the angle and 
reaches from abutment to abutment. 
(8) Carefully flow 18 carat gold solder over the entire exposed 
surfaces of the backings until sufficient thickness is ob- 
tained for strength. Make certain that the solder has 
united the backings to the abutment crowns and that the 
reenforcing wire is completely covered by solder. 
(9) Allow the case to cool slowly and then remove it from the 
investment. Cleanse the gold by washing with water and 
then boiling in sulphuric acid. 
(10) Put on the facings and return to the dental officer for try- 
in and finishing. 
Section XI 
Waxing and Casting of Three-Quarter Crowns 
55. General 
Three-quarter crowns are generally used as attachments for 
fixed bridges. They have the advantage over the full gold crown 
of not showing as much gold but still having sufficient retention to hold a bridge in place. This retention is brought about by 
two parallel grooves made in the tooth preparation, one on the 
mesial and one on the distal. 
56. Procedure 
(1) The dental officer will prepare the tooth and take an im- 
pression. This impression is generally taken by fitting a 
copper band around the tooth so that it fits snugly at the 
gingival margin. This band is filled with soft impression 
compound, pushed over the tooth, and held in place until 
it hardens. It is then removed. 
(2) An amalgam model is then made from this impression, by 
mixing in a mortar and pestle seven parts of amalgam alloy 
and five parts of mercury, by weight, and triturating for 
three minutes. This amalgam is worked in the palm of 
the hand for two or three minutes, until it has thoroughly 
mixed. Then, using a small amalgam plugger, it is packed 
into the impression of the tooth, a little bit at a time. 
When the impression is filled, an additional piece is added 
so that a root-like extension is formed, thus giving the 
technician a handle with which to hold the model. It is 
allowed to set until the amalgam becomes hard. The im- 
pression material can be removed by putting it in a little 
warm water, thus softening the compound. Then gently 
pull it off the model. The model is then examined for 
defects. It should be a perfect reproduction of the pre- 
pared tooth. 
(3) With a warm spatula carefully apply melted blue inlay 
wax over the oiled model. This should be of sufficient 
thickness to allow the carving of the wax to simulate the 
anatomy of the tooth in the finished crown. 
(4) The wax is then carved with all the anatomical character- 
istics of the tooth. Make certain that the wax is the cor- 
rect thickness. If it is too thin, the amalgam model will 
show through the wax. It is polished with a small piece 
of cotton and cold water. 
(5) Attach the sprue to the wax model, preferably to either 
the mesio-incisal angle or the disto-incisal angle, and gently 
remove the wax from the model. The oil will act as a separating medium and allow the wax to be easily re- 
moved. 
(6) Wash the wax preparation with green soap and room-tem- 
perature water until all the oil has been removed. 
(7) The technique of investing the casting will be taken up 
now and as it is practically the same for all gold castings, 
it will apply to all the other casting procedures mentioned 
in this manual. The purpose of investing an impression 
for a gold casting is fundamentally the same as investing 
a case for a denture. That is, to replace the space occu- 
pied by wax with another material. In this case it is gold 
instead of vulcanite or acrylic resin. Gold may be either 
cast or swaged, but the most efficient type of crown is the 
cast crown; so that is the method described. The appa- 
ratus used in casting dental gold consists of a sprue former 
or base in which the sprue sets, a casting ring which fits 
down over the sprue former, a casting machine or bucket 
to force the molten gold into the ring by centrifugal force, 
and a blow torch which heats the gold to its molten state. 
The sprue with the wax pattern attached is placed in the 
sprue former so that the top of the pattern will be at least 
one-half inch below the upper rim of the ring. The cast- 
ing ring is then lined with a strip of wet asbestos and 
placed over the sprue former. A mix is made from any 
inlay investing material, according to the directions of 
that particular manufacturer. With a fine camel-hair 
brush, the wax pattern is carefully painted with this in- 
vestment after removing the ring temporarily for this step. 
Make certain that no air bubbles are in the investing ma- 
terial. After the wax pattern is completely covered, the 
ring is placed back on the sprue former and the remainder 
of the investment material is then slowly poured into the 
ring until it reaches the top rim. A file may be rasped 
over the top of the ring during this pouring so that any 
air bubbles present will be brought to the top. Do not 
jar the case as this might knock the pattern from the 
sprue. Allow the investment to set for at least an hour, 
or until it is hard and the heat caused by the setting of 
the material has been dissipated. The importance of fol- 
lowing the manufacturers’ directions in the mixing of the investment material cannot be over-emphasized. Gold is 
said to shrink 1.25 percent before the casting is made. If 
the investment material did not compensate for this, it 
would be impossible to cast a gold crown or inlay that 
would fit the tooth. Although the investment materials 
will cancel the gold shrinkage, it must not be forgotten 
that unless some form of control is exercised, the results 
may be over-expansion as well as under-expansion. This 
is due to the various sizes of the inlays or crowns to be 
cast. The investment technique has been standardized as 
much as possible by using a super-expanding investment, 
such as Cristobalite with the control affected through the 
medium of a control powder. Depending upon the size 
of a wax pattern, a certain amount of this control powder 
is substituted for a certain amount of Cristobalite, as given 
in the directions covering the use of these materials. Due 
to the fact that this balance is obtained before the mix is 
spatulated, it is possible to burn out all the cases to the 
same degree of mould temperature and still have the cor- 
rect amount of expansion. Weigh out room-temperature 
water, Cristobalite, and control powder on the automatic 
scale. Spatulate, and invest the pattern in an asbestos- 
lined ring, using a single mix. Let the investment set at 
lease 30 minutes. Place in a cold oven and burn out grad- 
ually. Cast when a temperature of 1300 degrees F. is 
reached. Whether the casting is done in a casting machine 
or a hand bucket, the end-result is the same. In preparing 
the gold for casting it should be melted in the reducing 
flame of the blow torch. This is the area just ahead of 
the inner cone and the area that keeps the metal bright. 
This is done to prevent oxidation of the gold, and the ad- 
dition of a little reducing flux to the melted gold at this 
time will further prevent oxidation. The melting should 
be done rapidly. When the gold takes on somewhat the 
appearance of mercury, the casting is made. Allow to cool 
slowly and then remove the casting from the ring. It is 
washed and pickled in fifty percent sulphuric acid. All 
castings are made according to the procedure just given 
whether they are crowns, inlays, or parts of a bridge. The 
only variation is in the investment material. The direc- tions for the particular type of the casting that is to be 
made, must be followed in the investing of the pattern. 
Section XII 
The Gold Crown 
57. General 
One of the most important means of restoring a tooth deeply 
involved by caries, or providing a means of support for a bridge 
or partial denture, is the cast gold crown. Due to the require- 
Fig. 56 
ments of esthetics, it is employed for restoring posterior teeth 
only. The primary requirement in the construction of the cast 
gold crown is an accurate fit at the gingival line. One of the 
most serious faults of the full gold crown is the frequent occur- 
rence of caries under the band. This can nearly always be traced 
to the failure in securing close adaptation of the band to the 
tooth at the margin. In order to obtain this adaptation the dental 
officer will take two measurements with a dentimeter of the 
prepared tooth stump. The first is taken around the neck of the tooth at the gum line and the second measurement is taken 
in a similar manner at a point about one-third the length of the 
stump from the occlusal surface. These measurements are taken 
by looping a piece of wire around the tooth at each one of the 
points mentioned above, and tighten the wire by twisting the 
ends. The two loops thus formed are removed from the tooth 
and cut. When they are straightened out they will give the exact 
circumference of the crown of the tooth at each one of these 
points. See Fig. 56. 
58. Procedure 
(1) The measurement wires are cut and straightened out. 
(2) A piece of 22 carat, 30 gauge, gold plate is cut slightly wider 
than the length of the tooth stump. It is cut to a length 
that is one-half millimeter longer than that of the longer 
measurement wire to allow for beveling. The shorter wire 
is placed along the lower edge of the gold plate, equidis- 
tant from the ends and its length marked on the gold with 
a pointed instrument. This measurement is also increased 
one-half millimeter to allow for beveling. It is seen that 
since one of the measurement wires is shorter than the 
other, the gold plate will not be cut as a rectangle, but the 
ends will converge slightly toward the shorter wire. Cut 
the band along these guide lines, as illustrated in Fig. 56. 
(3) Bevel the gold band at each end at an angle of forty-five 
degrees using a flat file. The file is passed over the band 
in only one direction. The bevel is placed on the opposite 
side at the other end of the band so that the two beveled 
surfaces will overlap when the band is curved. 
(4) The best method of uniting the ends of the band is auto- 
genous soldering or sweating. This can only be done when 
pieces of gold of the same carat are to be united. By this 
means, the parts are melted or welded together without 
using solder. When this method is used there is no danger 
of the joint becoming disunited in subsequent solderings. 
The beveled ends of the band are bent around and under 
each other until the ends overlap. These ends are then 
pulled back and allowed to spring together upon each other, 
thus pressing together by the elasticity of the metal. This 
exact contact of the ends is necessary in autogenous solder- ing. The joint is fluxed with a saturated solution of borax, 
and the band is placed on a piece of charcoal with the 
lapped edges up. Using a blow pipe, start with a small 
brush flame, continue to apply heat until the band is 
brought to a cherry red. When the gold begins to glisten 
the surfaces are nearly ready to fuse. Remove the flame 
immediately after the parts are united. The band is re- 
turned to the dental officer, who trims and fits it to the 
gum line of the tooth. 
(5) The united band is then placed upon a flat surface and 
the occlusal edge is filed until it is in flat contact with the 
file. When the band is in place on the tooth stump, the 
occlusal edge should be the exact height of the occlusal 
surface of the preparation. 
(6) In constructing a gold crown for a pulpless tooth, a piece 
of 22 carat, 30 gauge gold plate of a size large enough to 
cover the occlusal end of the band is selected. One side 
is coated with a solution of borax. The gold band is then 
placed on the gold plate and they are held in a bunsen 
burner, with a pair of tweezers, until the band is sweated 
to the gold plate. The excess gold of the plate is cut away 
so that the margins are smooth and the crown box-like. 
This step is only used for pulpless teeth. The technique 
for vital teeth will be taken up a little later. 
(7) A wax bite and a plaster impression are now taken by the 
dental officer. 
(8) Select a porcelain tooth having a well developed occlusal 
anatomy and of a width which will fill the space for- 
merly occupied by the natural tooth. The occlusal sur- 
face of this tooth is covered with a coating of oil and 
then forced into a small block of modeling compound, the 
surface of which has been sofetened. The compound is 
chilled and the porcelain tooth removed, leaving an impres- 
sion of its occlusal surface in the compound. The surface 
of the impression is covered with a thin coat of oil and 
softened inlay wax is forced into the impression. The wax 
is chilled and trimmed flat and level with the block of 
modeling compound. It is then removed from the block. 
The gold coping is placed on the cast and the wax occlusal 
form is placed in position on the coping. The wax is then carved and adjusted where necessary to conform to the 
occlusion of the opposing teeth. Inlay wax is added to the 
approximal, lingual, and buccal surfaces of the gold coping 
and carved until the proper contour of the tooth is obtained. 
About one millimeter of gold band is left exposed at the 
gum margin. 
(9) Attach the sprue at one corner of the crown, invest, and 
cast as described under the three-quarter crown. 
(10) Twenty-two carat gold solder is fused over the exposed 
band with the blowpipe, to perfect the contour around the 
gingival margin of the crown. The crown is cleaned in 
acid and polished. 
(11) When the cast gold crown is used on a vital tooth, no at- 
tempt is made to place a gold floor on the band, due to the 
irregular border at the occlusal surface, which is usually 
unavoidable in vital teeth. After the gold band has been 
accurately fitted at the gingival margin, the occlusal surface 
of the band is reduced with stones to the same heighth as 
the tooth stump. An impression and bite is then taken 
with the modeling compound, and the gold band is placed 
in the modeling compound impression. From this bite- 
impression articulated stone casts are prepared. Wax cusps 
are added and carved to occlusal adaptation and the crown 
is then cast and finished, as described. 
Section XIII 
Splints 
59. General 
Splints are becoming more and more important in the Army 
Dental Service. In warfare, injuries to the face and jaws are 
very common, and are becoming increasingly so. The most prac- 
tical method of controlling fractures of the jaw is by splinting. 
It must be understood that no two cases will be the same or will 
use exactly the same design of splint. But they are all suf- 
ficiently similar to follow the same general basic principles of de- 
sign and construction. The following designs can be used for 
either maxillary or mandibular splints and can be constructed of 
vulcanite, acrylic resin, or cast silver. The variations in material 
and design will be taken up in detail. 60. Vulcanite Splints 
(1) The prepared model will come to the dental technician for 
the construction of the splint. 
(2) The designing of the case will be done by the dental officer 
and will be outlined on the model. It is important that the 
dental technician know the following principles in the de- 
signing of all splints so that the maximum efficiency and 
serviceability will be obtained. 
a. The splint should cover all free gingival margins on the 
lingual, buccal, and labial surfaces at least two or three 
millimeters from the necks of the teeth. 
b. The splint must cover the cervical two-thirds of the teeth 
and must include as much of the occlusal third as pos- 
sible without interfering with the masticatory processes. 
(3) Adapt a piece of 28 gauge casting wax to the model to 
cover the design of the splint. Make certain the wax is in 
all the interproximal spaces. 
(4) Soften a piece of baseplate wax and fold it over on its self, 
making a double thickness. Adapt this wax over the wax 
already in place, on both the lingual and buccal surfaces of 
the cast. Trim wax to conform with design of splint, as 
outlined on the cast. 
(5) Make a small button of the labial surface of the wax pat- 
tern in the median line. This wax button may be stamped 
out of a piece of wax, using a lead pencil from which the 
rubber has been removed. This small disc is attached to 
the wax pattern, forming the small button which will be 
used to secure the finished splint in place in the mouth. 
(6) The edges of the wax must be sealed to the model. 
(7) Chill the wax in cold water and polish with cotton. 
(8) Flame the wax and repolish, which will give a very smooth 
finish to the splint and will minimize the amount of polish- 
ing to be done later. 
(9) A piece of 14 gauge half-round wire is bent to conform to 
the distal surface of the last molar tooth. It extends for- 
ward on both the lingual and buccal surfaces of the tooth only touching the tooth, however, on the distal surface. 
The ends should come forward to almost the mesial of the 
tooth and then bend out at right angles, extending beyond 
the surface of the wax pattern. These two projections of 
the wire, along with that portion around the distal of the 
tooth, will be imbedded in plaster during the flashing proc- 
ess, thus holding the wire in its correct position. 
(10) In some fractures, it is necessary to design the case so 
that a loose or broken fragment of bone in an area which 
is edentulous, may be held in place. This is accomplished 
by constructing projections of wire which will extend out 
from the splint and hold these fragments in place. A piece 
of nickel tubing 10 x 14 gauge is incorporated into the 
splint by soldering it to the buccal surface of the half-round 
wire, so that it will be parallel to the buccal surface of the 
teeth. A piece of 14 gauge square wire is inserted into the 
tubing and the other end is bent so that it will rest on the 
buccal tissue over the fragment requiring stabilization. 
(11) Wax is melted around the nickel tubing so that it is flush 
with the surface of the wax pattern. 
(12) The case is now ready for flashing. Trim off all occlusal 
surfaces of the teeth flush with the wax pattern. Soak the 
model in cold water until all bubbling has ceased. Flask 
the case in the lower part of the flask, as described in 
“Flashing of Denture”, making certain that the plaster 
comes up to the lower border of the wax splint. The tubing 
and wires are left exposed. Use any type of separating 
medium on the plaster surface and then pour the upper 
half of the flask, as previously described. 
(13) The wax is eliminated, the case is packed with rubber, vul- 
canized and polished, as previously described. 
(14) In every space where there is a tooth missing the buccal 
and lingual parts of the splint are separated by sawing. 
The button in the median line is also sawed vertically in 
half. Thus, the splint is in two parts connected by wire, 
which can be placed in the mouth, brought into position 
and the two halves of the button wired together. 
Vulcanite Splint illustrated in Fig. 57. 61. Acrylic Resin Splints 
The construction of a splint, using the acrylic resin material in 
place of the vulcanite, is exactly the same as previously described 
with the exception of tin-foiling the wax pattern and the model. 
Fig. 57 
This tin-foiling procedure is carried out the same as already de- 
scribed under acrylic resin dentures. The acrylic resin used in 
the construction of the splints is colorless, which has the ad- 
Fig. 58 
vantage of being transparent, allowing the dental officer to ob- 
serve the condition of the teeth and gums underlying the splint 
at all times. Frequently a fracture case will have one or two missing anterior teeth. It is a simple procedure to add the neces- 
sary artificial teeth to the splint, which will replace the missing 
teeth until the splint can be removed. When teeth are added, it is 
necessary to tin-foil over the labial surfaces of the artificial teeth 
before the case is waxed. This will prevent the material from ad- 
hering to the labial surfaces of the teeth. Acrylic resin splint 
showing teeth added is illustrated in Fig. 58. 
62. Cast Silver Splints 
The third type of splint that is commonly used is the cast silver 
splint. 
(1) Prepare a duplicate model of investment plaster. 
(2) Adapt one thickness of 28 gauge wax to the investment 
plaster model as outlined by the dental officer. 
Fig. 59 
(3) Soften a piece of baseplate wax and adapt one thickness 
of it over the wax already in place. 
(4) Add sufficient wax so that the surface of the wax pattern is 
smooth and even. 
(5) 14 gauge wire is used, as previously described. 
(6) The button in the median line is constructed as usual and 
smaller buttons are placed in the cuspid and first molar 
region of both sides. (7) Seal the edges of the wax to the model. 
(8) Smooth and polish the pattern as this will save needless 
work in the final polishing. 
Fig. 60 
(9) There are various ways of sprueing the case preparatory to 
investing and casting, but the method described in this 
manual will be found very satisfactory. Drill a hole 
Fig. 61 
through the center of the model about the size of a dime. 
On the inner lingual surface of the pattern are attached six 
small 14 gauge sprues. On the outer surface leading from the main sprue, are attached four 14 gauge sprues attached 
to the buccal surface of the wax pattern. From the cuspid 
and molar regions of the buccal surface of the pattern, are 
attached 14 gauge sprues for air vents. These air vents 
stop at the edge of the model. Grooves should be cut in 
the model, both lingual and buccal, to accommodate these 
sprues. See Figs. 59 and 60. 
Soak model until bubbling ceases. Using a camel-hair brush, 
paint wax pattern with casting investment, making certain that 
all air bubbles are eliminated. Select casting ring to fit the case 
and fill with remaining investment. Place the model in the in- 
vestment with the teeth down and the main sprue which comes 
through the hole in the center of the model sticking out of the in- 
vestment material. Let set for at least one hour. Place casting 
ring in cold oven and heat for two hours at 1200 degrees F. Add 
not more than 10 percent copper to the amount of silver. Melt 
silver and copper in crucible. Place ring in casting machine. Add 
borax or any reducing flux to molten metal and cast. Remove 
from investment and polish. Make cuts the same as previously 
described. A finished splint is shown in Fig. 61. THE DENTAL HYGIENIST 
CHAPTER II 
Section I 
General 
63. Purpose and Scope 
The duties of the enlisted dental hygienist are; the administer- 
ing of prophylactic treatment or the removing of the calcareous 
deposits from the exposed surfaces of the teeth and roots, their 
polishing, and instructing the patient as to the proper method of 
brushing the teeth. Oral hygiene simply means sound teeth and 
healthy gums in a clean mouth. Hygiene teaches how to culti- 
vate health and avoid disease, and the same thing may be said 
for oral hygiene. The purpose of hygiene is to establish a proper 
attitude toward disease and to maintain the best possible health 
under any given condition. The two main premises upon which 
the teaching and practice of oral hygiene are based are: (1) A 
clean tooth resists decay better than an unclean one. (2) Healthy 
gingiva or gum tissue resists infection better than inflamed tissue. 
It is the duty of the dental hygienist to teach the patient how to 
care for his mouth, and to practice certain measures at the chair 
that will assist him. This section of the manual will describe in 
detail the instructions to be given and the measures taken. 
Section II 
Saliva and Calculus 
64. Composition and Function oj Saliva 
Gingivitis or inflammation of the gums, caused by dental cal- 
culus or tartar, is no different from gingivitis caused by other me- 
chanical irritants. It is very common in neglected mouths, and is 
of a progressive nature due to the gradual accumulation of the 
calculus. In order to understand the formation and deposition of calculus, it is necessary to know something about the saliva, as 
this is the medium from which it is deposited upon the teeth. The 
saliva is manufactured by three pairs of glands situated in the 
region of the mouth. They are the parotid, submaxillary, and sub- 
lingual glands, and they pour their secretions into the mouth. 
Saliva itself is colorless and watery, but secretions from mucous 
glands imbedded throughout the lining of the mouth, give it a 
ropy or slimy quality. The salivary portion has the function of 
starting certain digestive processes, while the mucous serves to 
lubricate the bolus of food in order to facilitate swallowing. 
65. Formation of Calculus 
The saliva contains certain organic and inorganic substances 
which are deposited on the teeth or any other hard structure in 
the mouth. This deposit, called dental calculus, may be defined 
as a soft amorphous or crystalline substance which is formed on 
the teeth in concentric layers. It is a mixture of colloids, crystal- 
loids, food debris, and bacteria, and is clear or yellow in color 
upon the exposed surfaces of the teeth, but may be green or black 
in the gingival crevices. The deposit is soft at first, but soon the 
protein substances decompose and wash away, while the crystal- 
line calcium salts are freed and left as a hardening mass which 
cannot be removed with a brush after a few hours. For dental 
calculus to form it is necessary for three predisposing factors to 
be present: (1) The presence of some hard object in the mouth 
such as natural or artificial teeth. Calculus never forms on soft 
tissue. (2) There must be a starting point for the formation. This 
is usually a roughened surface which has not been sufficiently 
cleansed by the friction of the food and the washing of the saliva. 
(3) There must be a film of organic matter spread over the tooth 
or hard structure. 
Section III 
Instruments 
66. Instruments Commonly Used 
The technique of instrumentation, as described in this manual, 
will confine itself to those instruments available in the Army 
dental clinics and to the minimum number with which it is pos- 
sible to perform a thorough prophylaxis. It will sometimes be 
necessary to substitute certain other similar instruments for those described. Scalers number 3 and 6 are sickle shaped instruments 
and are used chiefly to remove gross deposits from the teeth. 
Scaler number 15 has a smaller blade and is used to remove small 
deposits of calculus from more inaccessible places, such as be- 
tween the teeth. Scalers number 33 and 34 are used for the re- 
moval of extremely heavy deposits especially from the lingual 
surfaces of the lower anterior teeth and the buccal surfaces of the 
upper molar teeth. See Fig. 62. 
Fig. 62 
In addition to these instruments, it is necessary to have rubber 
polishing cups, brush wheels, dental engine and handpiece, pu- 
mice, chalk, mouth miror, dental floss, disclosing solution, and a 
spray atomizer with a pleasant tasting mouth wash. 
Section IV 
Technique of Dental Prophylaxis 
67. Instrumentation 
(1) The patient should be instructed to present himself for 
treatment with his mouth in as clean a condition as pos- 
sible. (2) The teeth are thoroughly sprayed on all their surfaces with 
a compressed air atomizer containing any pleasant tasting 
mouth wash. The air pressure should be about 25 pounds 
so that it will have enough force to blow the spray between 
the teeth and aid in their mechanical cleansing. 
(3) In using instruments in the mouth it must be remembered 
that each and every motion of the hand and fingers should 
always be under the control of the operator as a slip might 
cause a great deal of damage to the mouth tissues or the 
teeth. An instrument must never be used unless the hand 
holding it is properly steadied against some adjoining part 
of the mouth. The proper way to hold an instrument is to 
grasp it very much the same as a pencil, that is between the 
thumb and index finger. The blade of the instrument is 
placed against the surface of the tooth to be scaled and the 
hand steadied by resting the tip of the middle finger against 
the biting surface of one of the adjoining teeth. The blade 
is carefully carried under the shoulder of the calculus de- 
posit; and, with a slight pulling motion of the hand and 
fingers, the mass is removed. This same motion is repeated 
a sufficient number of times to thoroughly clean the surface 
of the tooth. 
(4) Starting with the disto-lingual surface of the lower right 
last molar and using either a number 3 or 6 scaler, the 
lingual surface of the tooth is cleaned as described. This is 
continued until the lingual surfaces of all the lower teeth 
are cleaned. Frequently it is necessary to use scalers num- 
ber 33 and 34 for the lingual surfaces of the lower anterior 
teeth. 
(5) Then starting on the disto buccal surface of the lower left 
last molar and using scalers number 3 and 6, the calculus is 
removed from the buccal surfaces of all the lower teeth. 
(6) With the number 15 scaler, carefully remove all deposits 
of calculus from between the lower teeth in the interproxi- 
mal spaces. Special care must frequently be taken in clean- 
ing the lower anterior teeth, as they may be rather irreg- 
ular, creating areas that are difficult to reach. 
(7) Repeat the same routine and instrumentation for the upper 
teeth. 68. Polishing of Teeth 
(1) After the calcareous deposits have been removed there still 
remain some stains, plaques, film and soft accretions on the 
exposed surfaces of the teeth. The purpose of polishing the 
teeth after instrumentation is to remove this debris and, at 
the same time, to slightly stimulate the margins of the 
gums. 
(2) Using the same system as described for instrumentation, 
that is starting at the disto-lingual surface of the lower 
right last molar, the lingual surface of the tooth is polished 
by passing a rotating rubber cup, charged with pumice and 
glycerine across the surface of the tooth until all stains have 
been removed. Care must be taken so that no great amount 
of heat is generated by having the cup revolve too fast, 
or by applying too much pressure. Just a few revolutions 
will usually suffice to remove all the stains and too much 
polishing will wear away the surface of the tooth. The 
rubber cup should be carried just to the margin of the gum, 
care being taken not to injure it in any way. 
(3) The buccal surfaces of all the lower teeth are polished in 
the manner described, as well as the lingual and buccal sur- 
faces of the upper teeth. 
(4) The main benefit, derived from the polishing of the teeth, is 
the prevention of initial decay. All efforts at thoroughness 
especially on the masticating surfaces of the teeth where a 
great majority of cavities occur, will do much in reducing 
or preventing caries. The masticating surfaces of the bi- 
cuspids and molars are so uneven that it is impossible to 
polish them with the rubber cup. Therefore, it is necessary 
to use a brush wheel to reach into the grooves of the teeth. 
After dipping in water to moisten the bristles, touch the 
brush to some pumice. Run the engine at moderate speed 
and polish the fissures and grooves of the teeth with the re- 
volving brush wheel. 
(5) The entire polishing procedure may then be repeated if 
necessary, this time using powdered chalk in place of the 
pumice. This gives a high polish to the teeth and aids the 
patient in keeping them clean. 69. Use oj Dental Floss 
After the teeth have been polished with cup and brush wheel, 
there still remain the contact points and areas on the approximal 
surfaces that have not been reached. These areas are best 
cleaned with dental floss. A piece of floss about 10 inches long is 
used for this purpose, and is wrapped around the index finger of 
one hand and held tightly by the thumb of the other hand. The 
finger and thumb should not be more than an inch apart as this 
will prevent the floss from snapping against, and injuring the gum 
tissue between the teeth. The dental floss is carefully worked be- 
tween the teeth and through the contact points until the approxi- 
mal surfaces of the teeth are reached. It is then drawn over these 
surfaces several times until all food debris has been loosened and 
removed. It is then pulled straight out from between the teeth 
and not past the contact point again. This is repeated between 
all the teeth, and to facilitate the polishing, the floss may be damp- 
ened and dipped in pumice before using. 
70. Disclosing Solution 
The teeth are then checked for cleanliness by painting a dis- 
closing solution on the dried surfaces. This will make visible all 
stains and mucinous plaques that have not been removed. A very 
effective iodine disclosing solution consists of the following: 
Iodine crystals 3.3 gm. 
Potassium iodide 1.0 gm. 
Zinc iodide 1.0 gm. 
Glycerine 16.0 cc. 
Distilled water 16.0 cc. 
A substitute solution of tincture of iodine and glycerine, equal 
parts, may be used if desired. The patient is allowed to rinse his 
mouth at frequent intervals during the entire prophylatic treat- 
ment. When all the teeth have been thoroughly cleaned and 
polished, the mouth is sprayed with any pleasant tasting mouth 
wash. Section V 
Instructions to the Patient 
71. Method of Toothhrushing 
Prevention in dentistry is one of the most important factors to 
be considered. It is much better to prevent the occurrence of a 
dental disease than to treat it after it has obtained a start. Prob- 
ably the most common of all dental conditions is caries or de- 
cayed teeth. For a tooth to decay, the process must have a 
starting point. This is usually brought about by the retention 
of food debris against the tooth surfaces, which when not re- 
moved, will be incorporated into the tartar deposits and, if al- 
lowed to remain for several hours, cannot be removed with a 
brush. Therefore one of the most important duties of the dental 
hygienist is to understand a good practical method of tooth brush- 
ing, and to be able to instruct the patient in this methpd. The in- 
struction will consist of the following: Advise the patient to 
buy two hard bristle brushes, preferably with different colored 
handles. One brush to be used in the morning and the other 
brush at night. The different colored handles will enable him to 
know exactly which brush to use. The brushes should be rather 
small, preferably with two rows of bristles. Place some tooth- 
paste on the dry brush and, using a slight wrist motion, start with 
the bristles against the gums and sweep them down, over the sur- 
faces of the teeth, toward the biting edges. The motion should 
always be from gum to biting surface, and never crosswise. The 
posterior or back teeth should be brushed first. Then proceed 
forward until all the teeth are brushed, both inside and out. In 
this manner, the upper and lower teeth are brushed for three 
minutes by the clock, twice daily. Patients with badly neglected 
mouths should be told that this manner of brushing might cause 
their gum tissues to be slightly sore for a day of two, but shortly 
their mouths will be improved by the massage action of the brush. 
After the teeth have been thoroughly brushed, there still remain 
certain areas that are impossible to reach with the brush and must 
be cleaned with dental floss. Instruct the patient in the use of 
dental floss as previously given in this chapter. 
72. Massage 
Frequently the gums of a neglected mouth will be inflamed and 
swollen. This condition, known as gingivitis, can generally be cured or remedied by prophylaxis and massage. Instruct the 
patient to massage his gums at least twice a day by squeezing or 
milking the inflamed or soft gums between the ball of the thumb 
and index finger, downward for the upper arch, and upward for 
the lower arch. In other words the motion, as in brushing, should 
always be toward the biting surfaces of the teeth. THE CHAIR ASSISTANT 
CHAPTER III 
Section I 
Duties of a Chair Assistant 
73. General 
The duties of an enlisted chair assistant are so many and varied 
that it is absolutely essential to establish a definite daily routine 
if they are to be performed in a proper manner. He must closely 
observe the dental officer at work and be able to anticipate his 
wants as to instruments and materials. He must be personally 
clean and neat in appearance and his contact with the patients 
must always be courteous and respectful. He must have a 
thorough knowledge of the name and location of each instrument 
in the office and must make certain that they are always kept in 
their correct place. He must see that all the instruments are 
sterilized before returning them to the cabinet. These are just 
a few of the chair assistants many duties which are described in 
this manual in detail. 
Section II 
Cleaning of Dental Clinic 
74. General 
One of the duties that the chair assistant will be required to 
learn will be the proper cleaning and care of the dental clinic. 
This includes the reception room for patients, hallways, operat- 
ing rooms, and the equipment in the rooms, laboratory and 
private offices. A certain time should be set aside each day for 
this policing so that it will not interfere with the daily work in 
the clinic. This time will be determined by the dental surgeon, 
but it is usually done at the close of the days work, rather than 
leave the clinic in disarray until the following morning. The 
floors should be dusted, or waxed and polished when necessary, 
the chairs arranged in order, reading matter neatly placed, re- 
83 moving such as will not be needed again. The accumulated trash 
should be emptied, the dirty laundry disposed of and replaced by 
clean. The entire clinic should be dusted and the equipment in 
the operating room, such as the dental unit and chair, should be 
wiped down daily. The unit is equipped with a cuspidor contain- 
ing a straining screen. This screen will become filled with par- 
ticles of filling material etc. necessitating a daily cleaning. The 
bowl of the cuspidor must be washed with soap and water to re- 
move all traces of saliva, blood, etc. This is done after each 
patient if necessary. The headrest of the chair is usually covered 
with either a linen or paper towl. This should be changed after 
each patient. 
Section III 
Care of Equipment and Materials 
75. Medicaments 
The dental cabinet should contain only those instruments and 
medicaments that are frequently used. It should never be used 
as a storage space for surplus supplies as this will only complicate 
the care of the cabinet. Medicaments are best kept in small, 
square, ground-glass-stopper bottles, well labeled, with the stock 
bottle left in the storage room. As the materials are used, they 
should be replaced from the bulk of the supply. Each bottle 
should have a certain place in the cabinet and should be kept 
there when not in use. Number and label the bottles so that the 
numbers one and two will contain the medicaments most fre- 
quently used. They must be spaced on the cabinet shelf so that 
selected bottles may be removed without tipping one of the others 
over. In arranging them, it is best not to have medicaments of 
the same color next to each other. For example eugenol should 
not be next to phenol. The alcohol bottle may be placed between 
them. The danger of taking the wrong bottle is greatly reduced 
and the speed in selecting is materially increased. Iodine should 
never be kept in the cabinet as it will tend to rust the instruments. 
76. Hand Instruments 
Hand instruments should be arranged in the cabinet drawers 
to suit the dental officer. They should never be mixed indis- 
criminately, but should have a definite order. The scalers should be placed together, preferably pairing the rights and lefts. The 
same is done with the cutting instruments such as chisels, 
hatchets, excavators, etc. 
77. Sharpening of Instruments 
The assistant will keep all the cutting instruments sharp by 
frequent use of the Arkansas stone. The dental officer will in- 
struct the assistant in the proper method of sharpening. 
78. Dental Burs 
The assistant should avoid having a large number of each type 
and size of burs out in use at one time. With many of the burs 
partly worn, it is difficult for the operator to find a sharp one. 
Consequently, he gets a new one from stock. This is used once 
and then is placed with the remainder of the old burs and prob- 
ably never used again. This goes on indefinitely, and conse- 
quently many burs that are still serviceable are needlessly thrown 
away. A very satisfactory method of handling the burs is by 
the use of any type of bur block that may be available whether 
it be round or square. The block will contain many holes in 
which the burs may be placed in regular order. They should be 
placed so that all types and sizes are readily available but having 
no more than two or three burs of each kind in the bur block. 
There are two lengths of burs; those for the straight handpiece 
and those for the contra-angle handpiece. The burs should be 
placed so that those for the two handpieces are in the same sec- 
tion of the block for convenience sake. The cross cut fissure burs 
should be placed in one group with the large size burs to the left 
and graduating down to the small sizes. The tapered fissure, 
round, inverted cone, wheel, and cutting burrs, etc. are placed 
similarly. If after using, the bur is still serviceable, it may be 
cleaned with a wire brush and sterilized and then replaced in the 
block. If the bur is not serviceable it is thrown away and a new 
bur replaces it in the bur block. In this manner all the types and 
sizes of burs are always available, there is no waste by discard- 
ing serviceable burs, and it is a simple matter to immediately re- 
place all discarded burs. It is not the purpose of this manual to 
set down specific instructions as to where each and every bur 
must be placed, but only to suggest a method that is simple to 
use, and to impress upon the chair assistant the fact that a definite system must be followed, no matter what it may be. This not 
only applies to this one particular duty, but to all duties that 
must be performed. All the other dental materials are handled 
in a similar manner, whether they be sandpaper discs, mandrels, 
matrix bands, etc. 
79. Sterilization of Dental Instruments 
A thorough knowledge of the methods of sterilization, their 
correct uses, and their limitations is absolutely necessary for the 
dental assistant. Practically all the dental instruments with the 
exception of those that are classified as cutting instrument can be 
sterilized in boiling water. It is first necessary to render them 
mechanically clean by scrubbing with soap and water. They are 
then placed in the sterilizer and boiled for a minimum of twenty 
minutes. They are then removed from the water and dried with 
a clean sterile towel and placed in the cabinet. A small amount 
of some alkaline substance such as sodium carbonate one-half per- 
cent should be placed in the sterilizer to prevent rusting of the in- 
struments. Cutting instruments such as knives, chisels etc., 
should be sterilized by some other method than by boiling, in 
order to preserve their cutting edges. One of the most efficacious 
methods is by keeping them in a lysol solution. Lysol is a liquid 
containing about 50 percent cresol in a netural potassium soap 
and is three times as germicidal as phenol. Lysol acts well in the 
presence of organic matter and destroys spores. For the steriliza- 
tion of instruments, it is used in the dilution of 1 to 3 percent. 
80. Sterilization of Handpieces 
The dental officer will instruct the assistant in the sterilization 
and oiling of the dental engine handpieces. 
81. Care of the Sterilizer 
At the end of each day, the sterilizer must be drained and dried 
with a towel. If this is not done the instruments will be coated 
with rust when they are removed from the sterilizer. Under no 
circumstances will instruments be left in the sterilizer overnight. Section IV 
Duties at the Chair 
82. General 
During the time that the dental officer is working on the 
patient, the chair assistant should stand by, ready to render any 
assistance that may be necessary. If there are other duties to be 
performed in the operating room, he may do them but always 
within sight of the operator. The best procedure to follow is to 
stand on the opposite side of the chair from which the operator 
is working and observe the progress of the work. With a little 
experience the assistant will be able to anticipate most of the 
dental officer’s wishes and have the necessary instruments ready 
before they are called for. He should note on the appointment 
sheet the type of work that is to be done for the patient so that 
he can have the necessary instruments and materials ready. If it 
is a prophylaxis, a mouth mirror, scalers, fine pumice, rubber 
cups and brush wheels for the handpiece should be placed on the 
operating tray. If a carious tooth is to be prepared, a mouth 
mirror, exploring points, handpiece, burs, alcohol, phenol, silver 
nitrate etc. should be placed on the tray. This routine is carried 
out for every patient. 
83. Anesthetic Solution 
Ringer’s solution may be made up in 100 cc. lots as often as 
necessary. Equipment necessary for making the anesthetic solu- 
tion is; dissolving cup with holder, procain tablets, sterile gauze, 
alcohol or gas flame, and a 10 cc. graduate with straight sides. As 
this solution is to be injected into the patient, it is absolutely 
necessary for it to be sterile. Any carelessness on the part of the 
assistant might endanger the life of the patient. The dental officer 
will state how many cc’s of anesthetic solution he wants. If three 
cc’s are desired, three tablets of procaine hydrochloride are 
emptied from the little vial upon the sterile gauze. They should 
not be touched by the hands at any time. The use of cotton pliers 
is indicated in the handling of the tablets. 
Measure three cc’s of Ringers solution in the graduate and pour 
into a clean dissolving dish. Heat the solution over the flame 
until it reaches the boiling point. Drop into the solution the 
three tablets of procaine and heat a little more until they are 
completely dissolved. The solution is now ready to be placed in the syringe. Since it is convenient not to remove the needles 
from the syringe once they are placed on, two syringes should be 
available. One having the one and five-eighths inch needle, and 
the other syringe equipped with the one inch needle. Take 
whichever syringe is indicated from the cabinet, and remove the 
little piece of wire that is placed through the needle. This is 
carefully laid to one side where it can be found again after the 
syringe has been used. Place the needle in the solution and draw 
up until the syringe is filled with the anesthetic solution. Place 
the barrel of the syringe against the inside of wrist to test for 
temperature. The ideal temperature for the solution is about 
body temperature. If the barrel feels too warm, place the syringe 
under a stream of cold water making certain that the water only 
touches the glass barrel. Place against the wrist and again test 
for temperature. The needle is then passed several times 
through the flame until it becomes slightly red in color. 
This can only be done with iridio-platinum needles, however, and 
if steel needles are used they should not be flamed. Hold the 
syringe so that the needle is pointing upward and slowly push the 
plunger until all the air has been expelled from the syringe. It 
is then handed to the dental officer or placed on the operating 
tray, taking precautions so that the needle does not touch any- 
thing. If this happens it is necessary to reflame the needle before 
using. After the syringe has been used, the plunger is removed 
from the barrel, the wire is placed in the needle and the entire 
syringe is placed in the sterilizer and boiled for a minimum of 
twenty minutes. After sterilizing, the syringe is assembled and 
placed back in the cabinet where it is ready to be used again. 
84. Impression Materials 
If an impression is to be taken, the necessary impression ma- 
terials will be made available depending upon the type of impres- 
sion. If modeling compound is used, the assistant should place a 
pan of water over the fire and heat it until the water is just a little 
too warm to allow the hand to be kept in the water. Several 
cakes of modeling compound are laid on a clean towel beside the 
hot water. The tray that has been selected by the dental officer is 
oiled slightly over its inner surface. If a hydro-colloid material is 
used, it is necessary to heat the pan of water to the boiling point. 
After the tray has been selected and attached to the water con- nections of the unit by rubber tubing, the stick of hydro-colloid 
material is placed in the boiling water. The manufacturers’ di- 
rections are followed as to the length of time that it is to be 
heated, but it is usually about 8 minutes. The tube containing 
the softened material is removed from the hot water and placed 
in water that is luke warm. The tube is kneaded between the 
fingers for a minute and then placed against the wrist to test the 
temperature. When it is warm but not uncomfortable it is ready 
to be taken into the operating room for use by the dental officer. 
There are numerous other duties that are too many to mention, 
but all will be mastered by the assistant if he is observing, and 
willing to learn. 
85. Filling Materials 
The mixing of the various dental filling materials is one of the 
most important duties of the chair assistant. The durability and 
appearance of the filling will depend upon its proper manipula- 
tion during this stage. There are several types of materials that 
are used, namely; gold, silver amalgam, oxyphosphate, copper 
amalgam, zinc oxide, silicate, gutta percha, etc. The filling ma- 
terials that the chair assistant must prepare are known as plastics. 
In other words they are prepared and inserted while in a plastic 
stage and become hard after being placed in the tooth. This in- 
cludes the amalgams and silicates which are known as perman- 
ent filling materials; and also oxy phosphate, zinc oxide, and gutta 
percha which are known as the temporary filling materials. 
86. Silver Amalgam 
The most common type of material that is used is the silver 
amalgam. It consists of the powdered metal portion containing 
silver, tin, and copper. This is mixed with mercury in the pro- 
portion of seven parts of alloy to five parts of mercury by weight 
or according to the manufacturers’ directions. The mixture is 
placed in a glass mortar and triturated for three minutes or until 
the particles of metal have been thoroughly incorporated into the 
mercury. The mix is then placed in the palm of one hand and 
using the thumb of the other hand, it is thoroughly mixed until 
the material gives a slight metallic sound. Excess mercury 
should be expressed from the amalgam by the operator. 87. Copper Amalgam 
Copper amalgam comes in small pellets with the mercury al- 
ready included in the material. The pellet is placed in a spoon 
and heated slightly over a flame until the amalgam becomes soft. 
It is then placed in a mortar and triturated as was the silver amal- 
gam. The excess amalgam that is left over after the filling is 
inserted may be saved and used again. 
88. Oxyphosphate of Zinc Cement 
Oxyphosphate of zinc cement can be used as a temporary fill- 
ing material, or as a cement for gold crowns and inlays. The 
consistency of the mix should vary slightly according to the use 
to which it is put. If it is to be used for cementing crowns and 
inlays, the cement should be of a rather thin consistency so that 
it will occupy a minimum of space under the filling. If it is to 
be used as a filling material it should be mixed a little heavier 
in order to obtain a greater degree of strength for the filling. 
The more powder that is used in the mix, the stronger the 
cement will be. The powder comes in various shades ranging 
from dark yellow to snow white. When the shade of the powder 
is determined by the dental officer three small portions of the 
powder are placed on a clean glass slab. Three or more drops 
of the phosphoric acid liquid are placed on the slab about an 
inch away from the powder. Using a small metal spatula, the 
powder is gradually incorporated into the liquid, adding small 
portions of powder at a time and spatulating thoroughly. If the 
powder is added too fast, the mix will become hard and un- 
manageable as the setting time will be decreased. Continue 
adding small portions of powder and spatulating with a rotary 
motion until the cement has a tendency to string out from the 
spatula when it is raised, and then falling back forming a little 
mound which retains its shape. A great deal of practice will be 
required before the proper mixture can always be obtained. The 
chair assistant should always mix the cement under the super- 
vision of the dental officer until he has attained this proficiency. 
89. Silicate 
The silicates or synthetic porcelain filling materials require 
the greatest care in mixing. There are so many variable factors 
that influence the silicates that the most rigid routine must be followed. The silicate powders come in numerous shades, each 
one having a number. The desired shade is determined by the 
dental officer from the silicate shade guide. The shade decided 
upon, the next step is to make certain that all the equipment that 
is necessary for the filling is ready. None of the materials such 
as glass slabs, spatulas, etc., should be used for any other pur- 
pose than for silicate fillings. The metal spatula for mixing and 
the plastic instruments used in inserting the filling in the tooth, 
are made from a special metal alloy, either stainless steel or 
stellite. As the various powders may be mixed to give the exact 
shade desired, a special silicate shade guide is used on which 
are given the correct proportions of each powder to obtain this 
shade. Some of the shades will require an even mix of two 
powders and other shades will require one portion of one powder 
to two portions of another shade. Each silicate set contains a 
metal scoop used to determine the correct amount of the powder. 
This scoop has small spoon-like ends, one end smaller than the 
other. The small end is used to measure the powder when a 
mix calls for one portion of one powder to two portions of an- 
other powder. The larger end is used to measure the powder 
when the mix calls for equal portions of two powders. Depend- 
ing upon the shade selected, the powder is measured as directed, 
and placed upon a clean, dry glass slab. A word of warning 
about the slab; in hot weather the slab should first be cooled 
with cold water and dried before attempting to mix the silicate. 
The ideal temperature is between 65° and 75° F. Moisture of 
any sort will affect the strength of the final filling. The silicate 
set contains a box of celluloid strips. One or two of these strips 
are placed upon the operating tray. They will be used by the 
dental officer as a matrix in the insertion of the filling. Three 
full drops of the liquid are always used when the powder is 
measured out as directed. These three drops are placed on the 
glass slab about an inch away from the powder. Add about one 
third of the powder to the liquid and spatulate for not more than 
20 seconds. Add another third of the powder and spatulate for 
the same time. The final third of the powder is then added and 
the spatulation is completed when the mixture has the consis- 
tency of soft putty. The entire mix should never be spatulated 
for more than one minute, and the spatulation should be done 
lightly, using a patting motion instead of the rotary motion used 
in mixing cements. 90. Zinc Oxide 
Zinc oxide and eugenol are used extensively as a temporary 
filling material because of their sedative action. Three or more 
drops of eugenol are placed on a glass slab. Enough zinc oxide 
powder is placed on the slab for that particular filling. The 
powder is incorporated into the eugenol with a metal spatula 
until it is thoroughly mixed. The resultant mixture is rolled 
into a small ball and squeezed between two pieces of gauze, thus 
expressing some of the oil. When the mixture is of the proper 
consistency for insertion in the cavity, it is placed on the oper- 
ating tray. 
Section V 
Clerical Duties 
91. General 
At a large number of military posts it is the duty of the chair 
assistant to obtain from the patient the necessary information 
for the dental forms, to make appointments and to do some cler- 
ical work. All dental work should be done by appointment un- 
less it is of an emergency nature. That is the purpose of the 
daily sick call. Each station has a time set aside every day to 
perform the emergency work. These patients are always given 
priority over the routine appointments. As is often the case, the 
chair assistant is required to perform some of the clerical duties; 
the following procedure may be used as a guide. 
When a patient reports for dental treatment, he is asked if he 
has had any dental treatment at the present station during the 
calendar year. If he has had treatment, his previous register 
card is taken from the files. If he has had no treatment during 
the current year, the clerk should ascertain if the patient was a 
member of the command at the time the annual survey was made 
and to which organization he belonged at the time. If surveyed, 
the clerk will find the name on the survey record. He then fills 
in the heading of Form 79 with the proper data, making certain 
that all the information is complete. If the patient is serving 
with an organization of which he is not a member, his proper 
organization should be given in the allotted space and his pres- 
ent temporary assignment noted at the top of the form merely 
for locating the patient. If the individual has been surveyed, 
his classification will be noted in space 2 of the register card. 
If the patient has not been surveyed during the current year, only the heading is made out by the clerk. The assistant then 
ushers the patient into the office and seats him in the chair. His 
record card is brought in for the information of the dental officer. 
A clean towel is placed around the patient’s neck and the assis- 
tant stays in the same room, so that he may assist the dental 
officer whenever needed. After the dental work has been com- 
pleted on the patient for the day, the patient is dismissed and if 
necessary another appointment is given him at this time. The 
operation performed is then noted by the dental officer on the 
card with the change of classification, if any. While the oper- 
ator is making these notations, the assistant prepares the room 
for the next patient. The operating tray is cleared of all instru- 
ments and a clean piece of paper is placed on the tray. All the 
used instruments are scrubbed and placed in the sterilizer. The 
handpiece is carefully sterilized and clean exploring points and 
mouth mirrors are placed on the tray. In general this is the 
procedure to be followed for each patient during the day’s work 
and although the duties of the assistant will vary depending upon 
the type of work being done for the patient, these fundamental 
duties will always be performed. 
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