Engineering 
Applied to Dentistry 
A discussion of modern ideas 
and old principles which are 
based on many years of re- 
search work, study and prac- 
tical experience. 
Presented to the Dental Profession 
by 
The International Dental Manufacturing Co. 
CHICAGO 
Copyright 1922 PROGRESS results from dissatis- 
faction with things as they are and 
the desire to make them better. 
PROGRESS demands courage and is only 
achieved through effort and sacrifice. 
PROGRESS is to do a thing first and 
better-to keep ahead of custom and 
tradition; to accept the burden of leader- 
ship and to suffer the jibes and jeers of 
the self-satisfied, who find it far easier 
to scofif and scorn than to think and do. 
John J. McGrath. Page One 
ENGINEERING APPLIED TO REMOVABLE 
DENTURES 
ARTIFICIAL Dentures are held in 
place by friction where atmos- 
pheric pressure is not the main 
sustaining force. 
This friction is increased by clasps or 
attachments. 
Clasps transfer direct friction against 
the enamel of the tooth and this is, in 
some cases, harmful. 
Attachments give a direct friction 
against some gold part only and this is 
their advantage. 
Both attachments and clasps are injur- 
ious to teeth and surrounding tissues when 
they allow leverage to be transmitted to 
the abutment, under mastication. 
Practical experience has demonstrated 
this and the following physical formulas 
will prove it. 
The powers which work against the 
abutment, attachment and the artificial 
restoration may be classified into 
1) Straight Vertical power 
2) Diagonal power 
3) Lever power 
1) Under straight vertical power we 
understand the energies which concen- 
trate in a vertical direction against the 
center axis of a tooth. 
Powers 
which 
work 
against a 
Remov- 
able 
Denture Page Two 
2) The diagonal power concentrates 
against some part on the periphery of a 
tooth and thus transfers stress sideways 
or in a diagonal direction against the 
center axis of the tooth. 
3) Lever power transmits pressure 
against a tooth and is produced by attach- 
ing dentures ridgedly to an abutment. 
In restoring lost masticatory organs 
we must base their artificial construction 
' upon the natural and resistance qualities 
of the tissues so they may not be injured 
by these devices. We must also respect 
the physical laws or laws of nature which 
guide similar constructions in engineer- 
ing. 
We know that every tooth is maintained 
in its socket and supported against the 
stress under mastication principally by 
the horizontal, oblique and apical fibers 
of the peridental membrance. 
The arrangement of these fibers is such 
that their greatest resistance is placed 
against the depression of a tooth (vertical 
power) while a lateral movement (diagon- 
all and lever powers) or tipping is more 
easily obtained. 
The thickness of the peridental mem- 
brane depends on the age of the patient, 
being much greater in young persons and 
becoming gradually less with age. 
The re- 
sistance 
force of 
Special 
T issues Page Three 
The resistance force of a tooth depends 
on the elasticity of the peridental mem- 
brane and the condition of the pulp. 
Therefore to establish some physical 
formulas which will show the leverage on 
teeth under certain conditions, the age of 
the patient and the physical condition of 
the pulp will be the guiding factors. 
Hook's law of elasticity says: "When 
a body is strained beyond a certain amount 
and then released, it fails to return com- 
pletely to its original form and volume or 
it retains a permanent set. The largest 
strain of any kind which a body may 
undergo and still completely recover from 
when released is called the limit of elas- 
ticity for that form of strain and the cor- 
responding* stress is called the limit of 
stress." 
Dr. G. V. Black demonstrated with his 
"Gnathodynamometer" the limit of elas- 
ticity of the peridental membrance. He 
showed that the average limit of elasticity 
of the peridental membrane is 171 pounds 
on the molar teeth and considerable less 
on bicuspids and incisors. 
We all know that overstress will cause 
a pathological condition and, exerted 
against a tooth it will cause either the 
death of the pulp, the absorption of the 
root or the destruction of bone cells and Page Four 
it may enforce the fracture of the enamel, 
the fracture of the tooth or of the bone. 
We must also take into consideration 
that any removable denture resting upon 
the tissues does not have its seat on a 
solid stone-like mass but upon an elastic 
gum tissue which allows an average con- 
densation of 1 mm. 
Modern Dentistry is so far advanced 
that we only extract teeth which become 
harmful to the surrounding tissue or the 
system by abscesses, phorrhea alveolaris 
or other diseases. 
These conditions may be the cause of 
constant tissue changes and the resulting 
misfit of the denture after a certain period 
of time. 
The most important physical law in 
attachment work is the law of levers. 
We know through orthodontia exper- 
ience that in young persons the tipping of 
a tooth is easily performed because the 
thickness and elasticity of the peridental 
membrane places the fulcrum near the 
apex of the root, while this or any other 
tooth movement in older persons is more 
difficult because the peridental membrane 
is thinner, less elastic and therefore the 
fulcrum lies near the gingival line. 
This may be demonstrated by driving 
a nail its length into a block of soft Page Five 
rubber and one into a block of wood and 
then applying force to the top of the nails. 
This fact forces us to establish distinct 
different lever formulas for young and 
old persons as the following diagram will 
show. 
A lever is a bar supported at a point 
called the Fulcrum F (see sketch and for- 
mulas on page 7). A force P applied 
to the bar at a certain point a will over- 
come a resistance force 0 acting at an- 
other point b. We shall suppose that P 
and 0 act at right angles to the bar and 
to the axis of rotation at the fulcrum. 
The work done by the applied force P 
is measured by the product of P and the 
distance a F through which P acts. The 
work done against the resistance is meas- 
ured by the product of the resistance 
force 0 and the distance b F through 
which it is overcome. 
This valuable information we have em- 
ployed for the construction of a general 
attachment lever formula, claiming again 
the following facts: 
a) The limit of resistance of the peri- 
dental membrane with a healthy 
pulp in the tooth is 171 pounds. 
Physical 
Laws 
to be 
observed 
Physical 
Laws 
Applied 
to the Con- 
struction 
of Re- 
movable 
Dentures Page Six 
b) The limit of resistance of the peri- 
dental membrane with a dead or re- 
moved pulp in the tooth is 80 
pounds. 
c) The force required in mastication 
is 90 pounds. 
d) As the gum tissues give under stress 
a settling of the denture will take 
place or the abutment will receive 
all the stress. 
e) The stress in mastication comes 
from a vertical and a diagonal di- 
rection. Page Seven 
STANDARD LEVER FORMULA 
P = the amount of Force (pounds) 
acting against a lever 
F = the Fulcrum 
0 = the Resistance force 
a F = the length of the P arm 
b F = the length of the 0 arm 
2 arm lever 
1 arm lever 
Applied to old persons with the Ful- 
crum near the gingival line, is a 2 arm 
lever the horizontal line representing the 
denture and the vertical line the tooth. 
Applied to young persons with the Ful- 
crum near the apex, is a one arm lever 
the horizontal line representing the den- 
ture and the vertical line the tooth. Page Eight 
The horizontal line is the length of sad- 
dle = 4 cm. 
F b length of tooth = 2 cm. 
0 = 171 pounds with live pulp 
0 = 80 pounds with dead pulp 
P = 90 pounds masticating force. 
Therefore leverage against abutment 
may be figured as follows: 
Old Persons 
Live Pulp Dead Pulp 
90 x 4 = 171 x 2 90 x 4 = 80 x 2 
360 = 342 360= 160 
Overpressure Overpressure 
= 18 pounds = 200 pounds 
Above problem proves that lever does 
not balance and that we have over- 
pressure. Page Nine 
Young Persons 
Live Pulp 
90x4 + 2=171 x2 
540 = 342 
Overpressure 
= 198 pounds 
Dead Pulp 
90x4 + 2 = 80x2 
540= 160 
Overpressure 
= 380 pounds 
Above problem proves that lever does 
not balance and that we have over- 
pressure. 
These formulas prove that in con- 
structing an attachment case we must be 
very careful not to destroy when we aim 
to rebuild, especially so since the above 
proven overpressure is figured on only 
one (vertical) power and does not include 
diagonal pressure and the constant main- 
tenance of these powers. 
Even a 5 pound force which is con- 
stantly applied against some tooth will 
produce tissue changes more or less harm- 
ful in proportion to its duration and direc- 
tion. 
With the formulas given herein the 
leverage may be figured for any fixed or 
removable bridge with one or more abut- 
ments. 
The proof 
obtained 
by physical 
formulas Page Ten 
Chapter II. 
THE BERTHOLD ATTACHMENT 
Keeping in mind the powers that work 
against the abutment and heretofore de- 
scribed as 
1) Straight Vertical Power 
2) Diagonal Power 
3) Dever Power 
and that the ideal attachment must be so 
constructed as to break or prevent the 
transmission of these powers to the abut- 
ment, The Berthold Attachment was 
devised and perfected and is now pres- 
ented to the Dental Profession. 
It will give like a hinge only in the di- 
rection of the force and act as a shock 
absorber. 
Its movability under masticating force 
eliminates all abutment strain and it acts 
as a stress breaker. 
The denture, regardless of its length, 
cannot act as a lever against the abutment 
where The Berthold Attachment is used. 
The construction of this attachment is 
based upon sound engineering principles 
and is mechanically and scientifically per- 
fect. 
It is simple for the dentist and patient 
to manipulate, therefore superior to any 
other attachment on the market. Page Eleven 
THE BERTHOLD ATTACHMENT 
IS INDICATED in Palatine and Lingual 
Bar, Buccal Restoration, Cast Clasp and 
all Removable Bridge Cases where Lever- 
age of any kind must be Eliminated. Page Twelve 
Note this typical Buccal Restoration. 
It is held firmly against the tissue when 
in normal position. Its action is down- 
ward in the direction of masticating force, 
to the amount of tissue condensation. 
The construction of The Berthold At- 
tachment prevents upward movement. No 
leverage is transmitted to the abutment. 
The denture rides like a door on a hinge. Page Thirteen 
Fig No. 1 shows the com- 
plete and assembled Berthold 
Attachment consisting of 
two parts, A and B in normal 
position. 
Fig. No. 1 
Fig. No. 2 
shows front 
and side view 
of Part A. 
This part is 
like a section 
of railroad 
track with 
friction und- 
ercuts along 
the "neck" 
Fig. No. 2 
and with a tapered top edge 
Fig. No. 3 shows Part B 
which is made of the 
highest grade clasp casting 
metal. It is a spring and 
clasps the "neck" of part A. 
Fig. No. 3 Page Fourteen 
Fig. No. 4 shows the movability 
of The Berthold Attachment down- 
ward under masticating force when 
the attachment is in normal posi- 
tion. 
Fig. No. 4 
Fig. No. 5 shows the movability 
of The Berthold Attachment down- 
ward under masticating force when 
the denture has settled below normal 
position. 
Fig. No. 5 
Fig. No. 6 shows the 
free lateral movement of 
The Berthold Attachment 
when either in normal or 
settled position. 
Fig. No. 6 Page Fifteen 
VULCANITE DENTURES 
In using The Berthold At- 
tachment with Vulcanite Den- 
tures solder a wire to spring- 
Part B, and be sure that the 
free end of this wire lies firm- 
ly against plaster model when 
the assembled attachment is 
in Normal Position. See Fig. 
No. 1 and Fig. No. 7. 
This will prevent spring, 
Part B, tipping forward when 
packing or pressing flask. 
Before waxing up case, cover crown 
and upper part of attachment with cement 
to prevent rubber adhering to crown or 
upright arms of spring, Part B, in vul- 
canizing. (See Fig. No. 8 where a thin 
sheet of pure gold is used for a similar 
purpose.) 
Fig. No. 7 
GOLD DENTURES 
When soldering spring, 
Part B, to a removable 
gold bridge cut a piece of 
36 gauge pure gold like 
pattern shown in Fig. 8 
and burnish it snugly 
against crown and the up- 
per part of the assembled 
attachment. 
Be sure that the attach- 
ment is in Normal Position 
as shown in Figs. No. 1 
and 8. 
After case is removed from model and 
ready to invest, first paint with anti flux 
the two exposed upright arms of spring, 
Part B, and then cover well with invest- 
ment. 
Fig. No. Page Sixteen 
CAST CLASPS 
To use T h e 
Berthold Attach- 
ment as a stress 
breaker or shock 
absorber in con- 
nection with cast 
clasps, solder a 
piece of 32 gauge 
clasp metal or 22k 
gold on top and 
bottom of the as- 
sembled attach- 
ment as shown in 
Fig. No. 9. Note 
must be soldered 
only to Part A. 
Then solder the 
attachment to clasp 
as shown in Fig. 
No. 10. 
When clasp is used in gold or vulvanite 
cases follow technic as described above 
under these respective headings. 
The object of the stops on top and bot- 
tom of attachment Part A is to keep the 
clasp permanently attached to denture. 
Some dentists prefer to leave off the 
above described stops on Part A of the 
Attachment for the reason that there is 
a distinct advantage in leaving the clasp 
on the tooth when the patient removes the 
denture. 
Fig. No. 10 
Fig. No. 9 Page Seventeen 
IMPORTANT POINTS TO BE OBSERVED 
All attachments are made of clasp metal 
which should not be overheated. Cherry 
red heat is the most any clasp metal will 
stand and still retain its elasticity. 
Do not solder attachment parts over 
open flame, always invest. 
The Berthold Attachment is made in 
one size, large enough for the heaviest 
cases. Where bite is close at least one- 
third of the upper ends of Parts A and B 
may be ground off without impairing the 
proper function of the attachment. 
A HOMELY COMPARISON 
But to the Point 
Sound mechanics will tell you to use a 
hinge and not nails or spikes when you 
hang a door to its frame. 
The hinge removes the leverage. 
The Berthold Attachment in dentistry 
represents the hinge. 
IN CONCLUSION 
The Berthold Attachment is the solu- 
tion of and answer to any and all trouble 
and annoyance that you may heretofore 
have experienced with removable dentures 
retained by other types of dental attach- 
ments. Page Eighteen 
Chapter III. 
VALVES IN ARTIFICIAL DENTURES 
THE Berthold Valve has been called 
the heart of an artificial denture, 
and the simile is not badly chosen; 
for this valve is a distinct and vital part 
of a modern dental plate controling and 
regulating the circulation of its life fluid 
in a manner not entirely unlike that of a 
living heart. 
It is the office of the Berthold Valve to 
direct the motion and action of the saliva, 
air and atmospheric pressure to best ad- 
vantage and without injury, so as to make 
the artificial denture an effective and 
economical appliance. 
As the valve has been designed so as 
to effect an even vacuum distribution 
under the plate, it has attained a peculiar 
significance in scientific plate construc- 
tion. 
In recognition of this fact an attempt 
has been made in this thesis to treat the 
subject with due regard to the various 
requirements of modern practice. 
The fundamental principles are fully 
explained. An endeavor has been made 
to present the subject matter in a con- 
densed form, as being best adapted to the 
requirements of practical men, and the 
author has in this respect followed the 
Intro- 
duction Page Nineteen 
suggestions of his extensive personal ex- 
perience in dental valve construction of 
various types. 
Starting with the fact that an artificial 
denture is held in place by some force and 
that the denture has been constructed for 
the purpose of doing some work, the fol- 
lowing fundamental laws of physics must 
be understood by the student who attempts 
to go into the deep study of scientific plate 
construction. 
In mechanics the term load means the 
combination of external forces acting on 
any piece of construction. 
The load on a denture would be the 
weight of the plate, friction and leverage 
while food is being masticated and the 
pressure of the tongue and muscles 
against the artificial teeth. 
The average plate weighs.. 15 dwt. 
The average force required for 
mastication is 90 lbs. 
The force the tongue may pro- 
duce is 1^ lbs. 
This shows that we must employ over 
100 pounds of retaining force or energy 
to resist this load. This we accomplish 
by using 
1) Atmospheric Pressure 
2) Adhesion 
3) Cohesion 
Physical 
Laws tha1 
Govern th 
Retention 
of 
Artificial 
Dentures Page Twenty 
In developing the idea of energy it is 
important to distinguish between an agent 
which merely transforms energy (kinetic 
energy) and an agent which actually has 
within itself the ability to do a certain 
amount of work (potential energy). 
(Adhesion, Cohesion, Atmospheric Pres- 
sure [Vacuum] represent potential ener- 
gy-) 
• The atmosphere has the potential ener- 
gy of nearly 15 pounds on a square inch 
at the 40th meridian at sea level. 
This energy acts at all times on every 
molecule or body, fluctuating only with 
the altitude where the body is placed, and 
may be turned into mechanical power 
when an airless space or vacuum is 
effected. 
Then this atmospheric column will place 
an amount of pressure against the body in 
proportion to the density and quantity of 
the air-thin space. This shows us that 
the so-called "potential energy of vacuum" 
really is the potential energy of the at- 
mosphere under certain conditions. 
We should employ this enormous at- 
mospheric energy as a balancing power 
against the dental load. 
Besides the atmospheric pressure we 
have two more forces working under an 
artificial denture: adhesion and cohesion. 
Atmos- 
pheric 
Pressure 
Adhesion 
and 
Cohesion Page Twentyone 
The forces which bind like kinds of 
molecules together are commonly called 
cohesive forces; those which bind together 
molecules of unlike kind are called adhes- 
ive forces. Thus we say that mucilage 
sticks to wood or saliva to the plate be- 
cause of ahesion; while cohesion holds to- 
gether the molecules of wood or the mole- 
cules of the saliva. 
The adhesive and cohesive power of 
the saliva indeed is so small that it only 
could be used as a balancing power against 
the weight of the plate (15 dwt.). 
Still the adhesive and cohesive energy 
of the saliva is the primary force which 
enables us to create a vacuum under a 
plate. Its molecular force is big enough 
to make an "air-tight fit" and yet small 
enough to act as a "safety device" if too 
strong a vacuum should be created under 
the plate. 
Only this molecular theory of fluids is 
responsible for the fact that there is a 
limit to the amount of vacuum you can 
create under an artificial denture, other- 
wise there would be dental plates in exist- 
ence which no one would be able to 
remove from a patient's mouth without 
fracturing his skull. Page Twentytwo 
The fluid (the saliva) which is of so 
great an importance to us, we receive from 
the salivary glands. 
It is generally understood that this term 
only includes the parotid, submaxillary 
and sublingual glands, but there are num- 
erous other small glands of similar nature 
in the palate, tongue, lips and cheeks. 
In the posterior half of the hard palate 
we find the racemouse palatine glands in- 
closed in the dense fibrous tissues which 
discharge a visible or semi-fluid secretion 
of a distinct mucus character for the pur- 
pose of doing some chemical or mechanic- 
al labor. 
We see now that when a full upper or 
partial upper denture is worn, the race- 
mouse gland will continuously discharge 
some fluid which will lodge between the 
tissues and the denture and thus will 
weaken the retaining force under the den- 
ture if this fluid is not artificially removed. 
This is one of the causes of "misfit 
plates'' which has been overlooked where 
patients have an excessive discharge of 
saliva. 
For this if for no other reason the 
Berthold Valve ("the heart of an artificial 
denture") is a vital factor in removing all 
surplus saliva from under the plate. Page Twentythree 
The cohesive power of the mucus dis- 
charged from the follicles of the palate is 
considerably stronger than that of the 
watery secretion of the 3 main types of 
salivary glands. Even chemically they 
are different, the mucus reacts acid, the 
saliva is generally neutral. 
The facility with which the saliva 
changes its shape might lead us to suspect 
that the molecules of this fluid exert al- 
most no force upon one another but a 
simple experiment will show that this is 
far from true. 
Fig. No. 1 
By means of sealing wax and string 
let a glass plate be suspended horizontal- Page Twentyfou 
ly from one arm of a balance (Fig. No. 1). 
After equilibrium is obtained let a surface 
of water or saliva be placed just beneath 
the glass plate and the beam pushed down 
until contact is made. 
It will be found necessary to add a con- 
siderable weight to the opposite beam in 
order to pull the plate away from the 
water or saliva. 
Since a leyer of water will be found to 
cling to the glass, it is evident that the 
added force applied to the beam has been 
expended in pulling water molecules away 
from water molecules, not in pulling glass 
away from water and this is the proof 
that cohesion is the third power in holding 
up plates. 
If we make a graphic representation of 
the main forces acting against an artificial 
denture, the retaining force versus the 
"chewing force" and only consider a 60 
pound pressure brought against the lin- 
gual side of the upper incisors then we 
notice the following. 
The incisal force Q (60 pounds) presses 
in a diagonal direction against point A 
(Fig. 2), trying to tip the plate, that 
means making the alveolar process under 
the upper incisors the fulcrum (F). 
The 
Creation 
of a 
Balancing 
Power Page Twentyfive 
Therefore suppose that the distance be- 
tween A-F is 1 cm. and the distance be- 
tween F-D is 5 cm. then the retaining or 
balancing force on the posterior end of the 
plate must be: 
Fig. No. 2 
60 x A-F = P x F-D 
P then is = 12 pounds 
Knowing that at least 60 pounds of 
pressure is recptired to masticate the aver- 
age food and realizing that a patient wears 
a dental plate primarily for this purpose, 
therefore we must apply all possible means 
to at least create a 12 pound retaining 
force on the posterior part of the palate. 
The same formula demonstrates the 
leverage and forces required on both oc- 
clusal sides. 
To a certain extent this leverage can 
be balanced by placing an oblong air- 
chamber along the posterior ridge of the 
plate (see Fig. 2, page 32). Page Twentysix 
By means of a valve the air from this 
chamber will be extracted and a specially 
strong retaining force under this part will 
be established. After a certain length of 
time the tissues will be drawn into this 
groove and thus postdam the plate. The 
retaining force (vacuum) will be held by 
such postdaming even during movement 
of soft palate muscles. 
In order to hold within the entire palat- 
al surface of the denture the force 
(vacuum) created through the Waive, it 
is advisable to grind a channel or shallow 
groove about 2 Millimeters wide and 1 
Millimeter deep entirely around the peri- 
phery of the denture. The tissues will be 
drawn into such channel. 
The constant advance made in Dental 
Science has changed very materially old 
methods used in constructing artificial 
dentures. Chief among these we might 
mention the present day practice of com- 
plicated impression taking, postdaming 
and contracting of mouth tissue before 
impression taking. 
The Dental Profession has created a 
public demand for perfect fitting dentures 
which must be satisfied. 
The average patient who wears a "non- 
functioning denture" is often attracted to 
Public 
Opinion Page Twentyseven 
the man who advertises his ability to make 
a plate with which the wearer may "eat 
corn off the cob, etc." 
By graphically illustrating the arrange- 
ment of the channels referred to on page 
13 and comparing them with postdaming 
we can readily see that the mechanical 
arrangement of the channel system gives 
us much better results in balancing any 
masticating force. 
In a short time the tissues will partly 
fill the channels and we will then have the 
reverse principal of postdaming. 
Witness the quantities of plates made 
by advertising dental offices (one in Chi- 
cago with a weekly average of 100 plates, 
another 60, another 150). 
Witness the enormous National sale of 
adhesive powders (Corega-Wernets Pow- 
der) used as an aid in retaining dentures. 
Does not this indicate that the majority 
of plate wearers are, after a certain length 
of time, not as well satisfied with their 
dentures as the dentist may have hoped 
or claimed? 
And it is quite natural that our present 
methods of constructing plates are far 
from being perfect when we admit our 
crude way of scraping the plaster from 
Conclusion Page Twentyeight 
the palatal side of a plate after vulvan- 
ization or using tinfoil or grinding off im- 
perfections, etc., from that part of a plate 
which is supposed to be in perfect adapta- 
tion with the tissues. 
Compare our rough work with the pre- 
cise delicate way of a fine mechanic who 
will use the most elaborate methods of 
grinding two surfaces under which he has 
to hold a vacuum force. And besides the 
initial requirement of having two perfect 
planes this same mechanic and every en- 
gineer must use a valve in order to create 
this vacuum. 
Now realizing all this it seems quite 
fitting that a Dentist should use the same 
methods and appliances that have for cen- 
turies proved absolutely successful and 
essential in other professions. Page Twentynine 
Chapter IV. 
THE BERTHOLD VALVE 
The atmosphere has a potential energy 
of approximately 15 pounds on a square 
inch (at sea level) at the 40th meridian. 
This pressure may be turned into 
mechanical power when an airless space 
is effected. 
As every denture is held in place by 
atmospheric pressure, adhesion and co- 
hesion and because atmospheric pressure 
is the greatest of these three forces, there- 
fore we should employ this enormous at- 
mospheric energy as the chief retaining 
power for artificial dentures. 
In physics we recognize the laws gov- 
erning the action of valves and their aid 
in creating and maintaining vacuum. 
Our research department has carried on 
extensive experiments for a period of over 
four years with the object in view of en- 
abling the dentist to use this natural con- 
stant force by means of a valve as an aid 
in retaining dentures. 
It is the office of The Berthold Valve 
to direct the action of the atmospheric 
pressure and saliva to the best advantage 
and without injury to the tissues. 
The object of our research work has 
been to make artificial dentures more Page Thirty 
effective and economical by keeping them 
in a proper, comfortable and useful posi- 
tion in the mouth by means of a valve. 
The patient wearing a denture equipped 
with a Berthold Valve can create at will, 
by a slight suction movement of the 
tongue a retaining force between the en- 
tire surface of the plate and the tissues 
of the mouth. 
Therefore after several years of test- 
ing and proving out in practical cases with 
perfect results and great satisfaction to 
dentist and patient, we recommend The 
Berthold Valve for retaining dentures 
firmly and comfortably in proper position. Page Thirtyone 
DESCRIPTION AND TECHNIC 
PART 
I he Berthold Valve con- 
sists of four parts as follows: 
Part A Valve Body or 
Cup. 
Part B Valve Cap and 
Stem. 
Part C Valve Packing 
to lie between 
parts A and B. 
Part D A slotted Spring 
Disk that slips 
under the end of 
the stem ("col- 
lar button" end) 
of Part B. 
The Berthold Valve is 
opened by suction but closes 
mechanically. 
We wish to acknowledge 
the great aid given to us by 
Mr. John V. Amenta in 
working out a practical and 
simple technic for applying the Valve to 
full and partial dentures. 
CROSS SECTION VIEW 
PART 
CROSS SECTION 
BERTHOLD VALVE ASSEMBLED Page Thirty two 
FIGURE NO. 1 
FIGURE NO. 2 Page Thirtythree 
RUBBER PLATES 
The following technic for inserting the 
Improved Berthold Valve into plates has 
been found to be most successful. 
(1) Outline on the impression with an 
indelible pencil height and length of 
plate (periphery outline). Fig No. 1. 
(2) Flow with a hot spatula a thin nar- 
row film of Inlay Wax all around the 
impression on the periphery outline. 
(This eliminates the inaccurate 
scraping of the model.) See heavy 
black line cn impression in Fig. No. 2. 
(3) Relieve (by scraping the impression) 
the hard area and an oblong channel 
along the posterior margin of the 
plate. With a pointed instrument 
scratch a line around the entire ridge 
terminating at the ends of the oblong 
relief as shown in Fig. No. 2. Page Thirtyfour 
FIGURE NO. 3 
FIGURE NO. 4 Page Thirtyfive 
(4) Wax the Vulcanizing Ring on the 
anterior third of the model with the 
step cavity surface of the Vulcaniz- 
ing Ring facing you. See Fig. No. 3. 
(5) Drive three pins into the model in- 
side of the Vulcanizing Ring to hold 
same firmly in position. See Fig. 
No. 4. Page Thirtysix 
FIGURE NO. 5 Page Thirtyseven 
(6) Cut off three pins flush with the 
surface of the Vulcanizing Ring and 
fill the inside of Ring with soft 
plaster. See Fig. No. 5. 
(7) Wax up, flask, pack and vulcanize 
in the usual way. Care must be 
taken not to cover Ring with tin foil 
collodiun or silex before packing. 
(8) In finishing and polishing care must 
be taken not to wear away the lingual 
surface of the Vulcanizing Ring. 
DO NOT FINISH DOWN THE 
RING. Note that the Wive must 
fit into the step cavity of the Vulcan- 
izing Ring and that the tongue sur- 
face of the Valve must be flush with 
the same surface of the Vulcanizing 
Ring. Page Thirtyeight 
FIGURE NO. 6 
FIGURE NO. 7 Page Thirtynine 
(9) After the plate has been finished 
and polished dry and clean the step 
cavity and undercut of the Vulcan- 
izing Ring and cement the Valve in- 
to the Ring with good Crown and 
Bridge Cement. The same care 
should be used in cementing the 
Wive as is taken with cementing 
Interchangeable Teeth on a bridge. 
See Figs. No. 6 and 7. 
The Berthold Wive in position must 
be flush with the bottom of relieved area 
on the palatial surface of a plate. 
After cementing the Wive into the 
Vulcanizing Ring and when the cement 
is thoroughly hardened carefully scrape 
away any surplus cement that may have 
adhered to either surface of the Wive. 
If a model, instead of an impression, is 
to be prepared, cut very thin air chamber 
metal (30 gauge) of the same outline as 
shown for relief in Fig. No. 2, otherwise 
the method is the same as when an im- 
pression is prepared. Page Forty 
GOLD PLATES 
Disassemble the Valve by removing 
circular disk spring from the bottom 
thereof and take out stem and packing 
together. 
Prepare impression or model in same 
way as heretofore described. 
Cut a round hole of exact diameter of 
Valve cup in the anterior third of plate 
and solder the Valve cup therein. 
Be sure the bottom of Valve cup is flush 
with the inside or palatal surface of the 
plate so that the Valve will not touch the 
tissue of the roof of the mouth. 
In finishing and polishing metal plates 
great care must be taken not to cut or 
finish down the valve cup body otherwise 
the Valve stem will not seat flush with 
the outside edge of the Valve cup. 
ALUMINUM PLATES 
Cut hole as described for gold plates 
but slightly larger in diameter than Valve 
cup. Cut rubber retentions in plate around 
hole and vulcanize Valve cup into position. 
Note that the outside edge of Valve cup 
has a groove into which vulcanite will set. 
OLD PLATES 
Take plaster impression using old plate 
as an impression tray the same as for a 
reline case. 
Prepare this new impression as de- 
scribed on pages 2, 4 and 6. Page Fortyone 
SEPECIAL DIRECTIONS FOR APPLYING THE 
BERTHOLD VALVE WITHOUT RE- 
VULCANIZING 
It sometimes happens that an upper 
denture, perfect as to fit and with a com- 
plete peripherial seal, will not stay up and 
for the following reason. 
When the denture is put into position 
in the mouth an air cushion instead of a 
vacuum is formed thereby dislodging the 
plate. 
For cases of this kind The Berthold 
Valve can be put into the plate in the fol- 
lowing manner without re-vulcanizing. 
Drill a whole en- 
tirely through the 
plate with a No. 7 
Round Bur and in ap- 
proximately the posi- 
tion (anterior third) as shown in cut, Fig. 
No. 8. 
With a No. 9 size 
Root Facer, (larger 
size of the two fur- 
nished by us), drill a 
step cavity in plate as 
shown in cut, Fig. No. 9. The depth of 
this first cutting should be the same as the 
thickness of the largest outside dimension 
of the valve. 
Fig. No. 8 
Fig No. 9 Page Fortytwo 
With the small size 
(No. 8) Root Facer 
next drill entirely 
through the plate and 
you will have a step 
cavity like shown in cut, Fig. No. 10 into 
which the valve will fit snugly. 
Cement the valve into the step cavity 
using a good quality of crown and bridge 
or inlay cement. See that the edge of the 
valve is flush with the lingual surface of 
the plate. 
Fig. No.