NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

311.05-11-3110561 May 27, 1971 10 421

Progress Report

on RESEARCH TECHNICS USED IN EVALUATING DENTAL MATERIALS

G. C. Paffenbarger*, DDS and N. W. Rupp**, DDS

* Senior Research Associate Emeritus, American Dental

Association Research Unit, National Bureau of Standards,

Washington, D. C. 20234.

** Research Associate for the American Dental Association

Research Unit, National Bureau of Standards, Washington,

D. C. 20234.

This investigation was supported in part by the National

Institute of Dental Research and is part of the dental research

program conducted by the National Bureau of Standards, in cooperation with the American Dental Association; the United

States Army Medical Research and Development Command; the

Dental Sciences Division of the School of Aerospace Medicine,

USAF; the National Institute of Dental Research; and the

Veterans Administration.

NATIONAL BUREAU OF S

for use within the Government

and review. For this reason, t whole or in part, is not auth Bureau of Standards, Washing

the Report has been specirical 1

IMPORTANT NOTICE

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015.

ress accounting documents intended

is subjected to additional evaluation

re listing of this Report, either in

the Office of the Director, National

, by the Government agency for which

copies for its own use.

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Introduction

There is nothing that will take the vagueness out of

one's thoughts as much as reduction of them to writing.

This does not mean that all the haze is gone--it just

infers that the fogginess is somewhat dispersed, as will

become evident when one takes the written version of one'

s

thoughts and attempts to carry them out in the laboratory.

Here the refinement is only partial and almost always requires further improvement. Such improvement comes when

others read the revised version of the procedure and

attempt to follow the written instructions. Precise

description of test methods is a difficult task which requires meticulous care.

All of the foregoing factors apply to any research

procedures used in evaluating materials of any type. However, today your speaker is just hitting a few highlights

in describing some research technics used in evaluating

dental materials.

Specifications

A specification for a material should characterize it

by physical, chemical and biological tests with minimum

and maximum value limits for the pertinent properties. Thus,

it should be possible to so design the specification that

inferior or unsatisfactory materials would be rejected and

that only suitable materials would comply with the requirement of the specifications.

The design of suitable specification tests that are

both reliable and valid is no mean research task. By

reliable it is meant that the tests can be repeated by
- 2 -

different laboratories with satisfactory agreement in

results. By valid it is meant that the laboratory testing

will predict the behavior of the materials in service.

So in order to obtain a high degree of validity it is necessary to design the laboratory test to simulate the conditions

of use as closely as possible and at the same tine have a very brief test. In other words, the laboratory test should

predict in one hour or one day or in one week what the

clinical behavior will be after several years. It is usually

necessary to characterize materials, especially new materials,

first in the laboratory and then clinically. If there is a high degree of correlation between the laboratory and the

clinical test results, then the laboratory test does indeed

have a high degree of validity.

Since the laboratory test must be brief it is often

necessary to use abusive testing—made abusive by exaggerating

the severity of normal deteriorating influences of use or by

increasing the frequency of them or both.

Service Tests

If you wish to know how a material will behave in

service, the most direct answer can be obtained by using

it in service and in observing its behavior. This is not

an easy task as good clinical testing requires a proper

and definitive characterization of the material being

tested. This is lacking in so many clinical tests. Even

if one did have the personnel, the facilities and the

finances it is ridiculous to test only by clinical trial

because progress is slow, costly and often indecisive.

Whenever a practitioner is using a material he is

usually giving it a service test consciously or unconsciously.

However, it should be iterated over and over again that since
-3-

much clinical service testing is not controlled and has

little or no discipline in it it has little value. Usually

the trial use of a material is conducted by a large group of

practitioners with little or no centralized control so that

the securing of reliable service statistics is difficult,

if not impossible.

Therefore, prior testing in the laboratory is absolutely

imperative in modern technology as the gap between the raw

materials becomes greater and greater. Hence, the laboratory

testing of materials is becoming more and more important.

Other Tests

In addition to actual testing of the material in a laboratory one can assemble the material into a structure

or appliance and test it. There are many examples where

such tests are imperative because assembling the material

into a structure will require fabrication procedures that

may vastly change the properties. Some examples are stress

concentration, surface treatment and thermal history.

If the structure or appliance is large it is often

desirable to prepare a smaller model and test it but this

is not really encountered in biomaterials. In fact, in

dental materials it is often necessary to make comparatively

miniature physical test specimens as conventional sizes alter

values for significant properties.

Some rules for the formulation of specifications

( 2 ) Charpy, the old master, gave in 1907 some excellent

advice that is as good today as the day he gave it decades

ago:
-4 -

(a) Avoid composition requirements and define

the material by performance tests

.

(b) Give a meticulously precise description

for all tests.

(c) Avoid all vagueness that permits or necessitates

any arbitrary decisions on the part of the

personnel during the testing.

(d) Specify the relationship between the precision

of the testing machines and the precision required in the results of the tests.

(e) State how the data are to be derived and recorded.

It is difficult to go in the wrong direction if one

adheres to these.

Biological Testing

Most of the discussion on physical testing applies

equally well to biological testing. To recapituiate--reduce

the test method to writing, conduct the necessary laboratory

tests, design the tests to simulate actual conditions of use,

develop laboratory screening tests prior to biological testing in order to establish their degree of reliability and

validity

.

One has to use certain axioms in the design of laboratory

screening tests prior to tests employing animals or humans.

One axiom is that the mouth presents a rigorous environment.

This is why dental restorative materials are confined to

porcelain, precious metal alloys, chromium-based alloys,

polymers or composites. The material has to be relatively

inert, that is, it should have a high degree of passivity.
-5-

If it does not it will not stand up when embedded in teeth.

Even more rigorous passivity is required if the material is

embedded in bone or soft tissue. Materials almost invariably

fail as a restorative material if they will not withstand a watery environment, mild alkalis and organic acids in foods

or resulting from degradation of foods. Hence seme of the

ceramic materials that are being developed should be given

some standard laboratory tests prior to animal experimentation.

Perhaps the test for the chemical resistance of containers--

glass as given in the U. S. Pharmacopoeia or a slight modification of it would be considered as an initial screening test.

Also consideration should be given to the ASTM Designation

C225-59T Tentative Methods of Test for Resistance of Glass

Containers to Chemical Attack.

There is too much uncontrolled and undisciplined

biological testing of biomaterials as so often the material

that is being tested is not characterized even in the most

elemental way.

Examples of Research on Test Methods

Silicate cement. Solubility is the chief defect of

silicate cement, a life-like restorative material for the

front teeth. Thus, the average life of a silicate cement

restoration is roughly 4/2 years. Therefore, solubility

is one of the pertinent properties and requires research to

design a laboratory test that will evaluate in a short time

the long term behavior of a silicate cement restoration in

the mouth

.

First one must set up a standard test consistency based

upon the powder/liquid ratios in common usage. Of course all

such tests have to use amounts of cement comparable to that
which the dentist uses. Hence the test specimens are small

compared to customary test specimens.

The consistency was determined on a parallel plate

(4) viscometer (Fig. 1) using the diameter of the slumped

mass as the numerical designation of the consistency. Of

course, no such apparatus was available —one had to be

designed. The diameter of the disk varied according to the

powder/liquid ratio used under standard experimental conditions

which closely followed clinical practice. Curves showing the

relationship between the powder/liquid ratio and the diameter

of the disk, the measure of the consistency, are presented in

(4) Figure 2 for many cements. The consistency selected as

the standard was, as before stated, the average used by

practicing dentists.

After the standard consistency test was designed a test

for solubility naturally followed. What should be the

corroding liquid —water, artificial saliva, natural saliva,

an aqueous solution of one of several organic acids, or of

alkalis? All are present in the mouth. The first chosen

liquid in which silicate specimens were immersed was distilled

water and a test for weight loss was invented using disks

(5) suspended in tared weighing bottles as shown in Figure 3.

Here, in Figure 3 are two tared weighing bottles each containing two specimen disks in 50 ml of distilled water. After

storing the disks for one hour at a relative humidity of

100 percent at 37 °C they are placed in the empty tared weighing bottle and weighed and then submerged in the water.

After storage for one week (now for 24 hours) the specimens

were removed, the weighing bottles dried at 149 °C to constant

weight and reweighed. The difference between the final and

initial weight of the bottles was the amount of material lost
-7-

from the cement. Values for six cements were determined

for one week, then the same specimens were transferred to

another tared weighing bottle and immersed in 50 ml of

distilled water for one week and the weight loss was determined again. This was repeated for 5 weeks and the totals

computed as shown in Table 1. These are selected data from

reference (4)

.

Obviously the cements had a variety of

solubilities but there were no clinical tests made to determine if these differences would be reflected in the mouth.

Instead, it was reasoned that cements with low water

solubility would be superior. Later, as it will be shown

in the report, clinical tests confirmed this assumption.

Additional long time tests, up to 14 months, on compressive strength were carried out after submerging the

specimens in distilled water, natural saliva and oil

(Table 2) . These data, too, are from reference (4)

.

Generally an increase in strength proceeds from water to

saliva to oil (immersed specimens) . The solutions were

changed each week. From these data it can be concluded that

distilled water is a good immersion liquid because it is

easily standardized and is more corrosive than natural saliva.

This is needed in an accelerated test. Also data to compare

long time with relatively short time test values, as provided

in Table 2, are needed to fix maximum solubility values in a specification

.

( 6 ) Several years later some clinical testing was done,

an example of which is shown in Figure 4. These two restorations were of the same silicate cement, were in the same

environment and were placed by the same operator but were

placed with two different procedures. The two procedures
- 8 -

were devised at the desk and were based on purely laboratory

findings. There is a great difference in the appearance of

these two restorations which were apparent soon after the

restorations were placed. Restoration A was made from a mix

of cement spatulated for 30 seconds on a cool glass slab.

Immediately after hardening the restoration was coated with

petrolatum and was not dressed down flush with the enamel

until five days later. Restoration B was made from a mix

spatulated for 1 /2 minutes on a warm slab and was finished

immediately after hardening.

The laboratory tests on which the handling procedures

were based showed that a cement mixed on a cool slab had a

higher powder/liquid ratio at a fixed consistency than a mix made on a warm slab. Thus, the mix made on the coolest

slab had less solubility, was stronger, and shrank less

than the mix made on the warm slab. Also mixing for a long

time adversely affects the solubility and strength according

to laboratory tests. The strength of cement increases

rapidly with time especially in a few days. Hence the finishing should be delayed until the strength is sufficient to

resist the disruption of the hard particles of unused powder

imbedded in the comparatively soft matrix and to prevent the

breakage of the margins during finishing.

As before stated all good and bad procedures are deductions from data derived from laboratory tests which are

conventional, artificial and of short duration. Consider

for instance the test for solubility which was just

(5) • • • described. Here disk-shaped specimens were immersed m

distilled water for 24 hours, which is radically different

from service test conditions in the mouth for several years.
-9-

Likewise, the laboraotry test for strength is a static test

in compression as several minutes are used in crushing the

specimen. On the other hand, in the mouth the silicate

cement restoration is subjected to a quickly applied and

released load during mastication. Nevertheless a correlation

between research findings and clinical practice has been

( 6 ) demonstrated.

Another demonstration is shown in Figure 5 v/here two

restorations side by side show about the same condition

after h/2 years of service. The restoration in the larger

tooth (the central incisor) was made from a cement having

a water solubility of 0.5% and the restoration in the smaller

tooth, the lateral incisor on the right, was made from a cement having a water solubility of 1.1%. Figure 6 shows

the same restorations after 4 years and 8 months without any

apparent difference. This same patient, however, had

restorations made of a cement with very high water solubility

(3 to 5%) . The condition of restorations made with such a cement is shown in Figure 7 and portrays again a considerable

degree of correlation between laboratory and clinical findings.

Color stability of dental resins

Hard rubber dominated the organic denture base field

from the 1850's to the late 1930's when acrylic resins were

first used. Since then, nothing has displaced acrylic resin

because nothing has been developed with better properties.

In the late 1860 ' s celluloid was invented and found its

way into denture bases. Then came phenol-formaldehyde dentures in 1924, the vinyls in 1932 and finally the acrylic

resins in the 1930' s.
- 10 -

One always learns as much or more from failures than from

successes. Consider the old celluloid material in Figure

(7) . 8. Notice the shrinkage and discoloration. This also

occurred in the mouth. Figures 9 and 10 are two phenolformaldehyde dentures, Luxene 37 and Aldenol . The Luxene 37

turned orange in the mouth and the Aldenol turned black and

they both shrank.

What was needed was an abusive laboratory test that

would simulate such discoloration quickly. The old color

stability test for plastics of the American Society for

Testing Materials, as illustrated in Figure 11, was adopted.

This test has had a 100% clinical correlation for thirty

years. Every denture base polymer that discolored in service

in the mouth after many months or years of use likewise

discolored about an equal amount in this test for color

stability in 24 hours, and vice-versa every denture base

polymer that did not discolor in service in the mouth after

years of service did not discolor under this sun lamp.

When the cold-curing, sometimes called the self-curing

acrylic polymers, were introduced they were tested under

this sun lamp and discolored. They likewise discolored in

service as can be seen in Figure 12 where the self-curing

polymer was used as a repair material on a denture, the main

base of which did not discolor in the mouth or during the

laboratory testing. Later the self-curing denture base

polymers were formulated that did not discolor under the

test in the laboratory or in service.

Strength of denture base resins

As previously stated^, in the late 1930's the acrylic

resins made all of the other organic denture base materials

obsolete so it was necessary to characterize the denture

base acrylic polymers and formulate a standard for them.
- 11 -

Here we shall treat only one aspect--strength. What

type of strength should be used —compressive, shear, tensile,

transverse, impact, fatigue, etc. The transverse test was

selected because it probably simulates best the actual loading

conditions in the mouth.

The specimen size and apparatus used in determining

properties in transverse bending is shown in Figure 13.

Notice that the tolerance on the dimensions of the specimen

is fairly close on the thickness and on the width. The data

obtained from such testing is shown graphically in Figure 14.

The values for the transverse deflection in the original

specification were based on such data because the acrylic

resins in use in 1940 were certainly reasonably satisfactory

in service. The data in Figure 14 are much later 1965,

including other kinds of polymers which are or were used as

denture bases. These data show definite differences in

stiffness and strength. Naturally there is an inclination

to select an organic denture base on the basis of high

strength and low deflection values. However, clinical

experience has shown that polymers with low strength and

large deflection, like the self-curing acrylic resins, may

hold up better in service than bases with high strength and

( 11 ) low deflection. This presents a good example of how

physical data on symmetrical specimens may be misleading

when applied to a fabricated appliance. In this instance

the denture is the fabricated appliance. It is composed of

the base polymer and porcelain or polymer teeth. The

porcelain and the denture base do not adhere and their

thermal expansivity is vastly different. Methods of processing

also affect the polymers. These considerations really make

it necessary to do some physical testing on the denture and

make it imperative to do clinical testing with dentures also.
- 12 -

But one cannot do all of this testing immediately.

Adequate testing of dentures in the mouth takes several

years. So at first one must resort to a physical and

chemical characterization of the available materials,

select what properties are pertinent to their use in the

mouth and make some arbitrary decisions on limiting values

for the selected pertinent physical properties. Then as

more extant knowledge becomes available and as new materials

are developed or the old ones improved the specification or

standard should be revised. All of the foregoing holds

principally when one is attempting to formulate a standard

for materials that have been in clinical use for some time.

There are available some good impressions of the clinical

behavior of the materials —dental amalgam being a good

example

.

Much of the foregoing holds true when a new material

is introduced as happened in the case of the acrylic resins.

A common mistake is to use unreservedly test methods

developed for one material in the evaluation of another

material. Many examples exist where this has been done.

One will be cited. When epoxy resins were introduced as

denture base materials they were evaluated by the same test

procedures which had been developed for the acrylic resins.

Sometimes this was acceptable. In other instances it was not.

In the test for water absorption on acrylic resin denture base

materials, the thin specimens (0.5 ± 0.1 mm thick) came into

equilibrium with water in about 24 hours. Both the acrylic

and the epoxy denture base resins had about 1.6% gain in

weight in hours. If the test was continued for 65 days

there was little or no increase in the absorption of water
-13-

by the acrylic resin denture base materials but the epoxy

resin denture base material had absorbed about 4% by weight

of water in sixty-five days as shown in Table 3. (10 ^

Water absorption is usually accompanied by expansion

( 12 ) of the resin. This did occur in dentures m the mouth.

This expansion was determined on dentures fitted with

stainless steel pins (Figure 15) on which reference lines

were ruled. The linear changes in dimension were measured

on a toolmaker's microscope (Figure 16) . With such a procedure the data on the graph (Figure 17) were obtained.

It would appear from this dimensional history that from the

time the dentures were wax models in the flask until they

had been used for seven years, that the epoxy resin dentures

gradually expanded. Dentures made of hard rubber continuously

shrank and warped to a much greater extent than did the epoxy

dentures. Warpage was measured by determining the difference

between the percentage of linear change on the molar-to-molar

and on the flange-to-flange distances.

These linear changes on the dentures occurred gradually.

Neither the patients or the researchers, dentists in this

instance, could detect the changes clinically. This is just

another way of saying that the tissues followed the changes

so there was little or no difference in serviceability.

Summary

Research is always needed in designing tests for

characterizing biomaterials. These tests should simulate

conditions of use as much as is practicable, must often

be conducted when the material is subject to exaggerated

service conditions, that is, be abusive, and must have satisfactory reliability and validity.
14-

The formulation of standards or specifications for

new materials is usually more difficult than the preparation

of such standards for materials that have been used for

several years largely because of the uncertainty about the

biocompatibility of the new material and its service

performance over an extended time.

Sources of information

Those interested in learning of the sources of extant

information in biomaterials in general but with special

reference to dental materials may find references 13 to 20

helpful

.
-15-

Table 1

Solubility and Disintegration of Silicate Cements

in Distilled water

(percentage loss in weight)

Time in rater at 37 °C in weeks

CEMENT 1 2 3 4 5 Total

% % % % % Loss

A 3.0 0.6 0.4 0.4 0.3 4.7

B 0.6 0.2 0.1 0.1 0.1 1.1

C 2.4 0.3 0.2 o « K) 0.1 3.2

D +i CO

• CM 0.5 0.3 0.3 0.2 4.1

E 1.3 0.4 0.3 0.3 0.2 2.5

± Other values on different batches ranged

from 1.5 to 0.9%.

These data or Solubility and Disintegration of

Silicate Cements in Distilled Water are from

Reference (4) .
Effects of Different Immersion Media on the , > Compressive Strength of Silicate Cement with Time '

I m m e r s ion M e d i a Distilled

Water Saliva Oil

A g e of £ p e c i mens

CEMENT

1

week

6

months

14

months

6

months

14

months

6

months

14

months

A * 19, 500 25,000 23,000 26,000 23, 500 30,000 34,000

B 19, 500 22,500 24, 000 24,000 24,500 29,000 28, 500

C 19, 000 20,500 19, 500 23,000 22,000 29,500 32,000

D 21,500 21,000 19, 500 24,000 25,000 23, 500 24, 500

E 19,500 23, 500 19, 500 27,000 21,000 29, 000 33,000
Water sorption at 37 °C ( 10 )

Sorption

Material

24 hours 65 days Difference

Self-curing acrylic resin

Acralite 88

%

1.60

%

1.68

%

0.08

Heat curing acrylic resin

Duraflow 1.54 1.60 0.06

Epoxy denture base resin

Epoxolon 1.57 3.98 2.41
- 18 -

References

1. Guide to Dental Materials and Devices, 1970-1971.

5th Ed. American Dental Association, 211 E. Chicago

Avenue, Chicago, 111. 60611.

2. Charpy, Georges. Les cahiers des charges pour la

reception des matieres metalliques. Revue de Metallurgie

Memoires 4:1041, 1907.

3. Paf fenbarger , G. C. Silicate cement: an investigation

by a group of practicing dentists under the direction

of the A. D. A. Research Fellowship at the National

Bureau of Standards, JADA 27: 1611 Oct. 1940.

4. Paffenbarger , G. C., Schoonover, I. C. and Souder, W.

Dental silicate cements: physical and chemical

properties and a specification. JADA 25:32 Jan 1938.

5. Paf fenbarger , G. C., Swaney, A. C., Schoonover, I. C.

and Dickson, G. American Dental Association Specification No. 9 for dental silicate cements, first revision,

effective July 1950, JADA 40:186 Feb. 1950.

6. Paf fenbarger , G. C. Some clinical applications of

research findings in dental materials. Ohio Dental

J. 33:218 Sept. 1959.

7. Souder, W. and Paffenbarger , G. C. Physical properties

of dental materials. Circular C433, National Bureau of

Standards, 1942. Superintendent of Documents (now out

of print)

.

8. ASTM Designation D620-576. Tentative method of test

for color fastness of plastics to light. Volume 27,

ASTM Standards 1964. American Society for Testing

Materials, 1916 Race Street, Philadelphia, Pa.

9. Sweeney, W. T. and Paf fenbarger , G. C. Tentative

American Dental Association Specification No. 12 for

denture base material, acrylic resin or mixtures of

acrylic or other resins. JADA 28:325 Feb. 1941.

Woelfel, J. B. , Paf fenbarger , G. C. and Sweeney, W. T.

Some physical properties of organic denture base

materials. JADA 67:489 Oct. 1963.

10 .
-19-

11. Woelfel, J. B., Paffenbarger , G. C. and Sweeney, W. T.

Clinical evaluation of complete dentures made of

11 different types of denture base materials. JADA 70:

1170 May 1965.

12. Woelfel, J. B. and Paffenbarger , G. C. Expanding and

shrinking 7-year old dentures: report of cases. JADA

81:1342 Dec. 1970.

13. Journal of Dental Research, the bimonthly Journal of

the International Association for Dental Research,

211 E. Chicago Ave. , Chicago, 111. 60611.

14. Philips, R. W. and Ryge, G. Adhesive Restorative

Dental Materials. (Proceedings from a workshop

sponsored by the Dental Study Section, National

Institutes of Health, and supported by a grant from

the National Institute of Dental Research.) Owens

Litho Service, Spencer, Indiana. Published 1961.

15. Adhesive Restorative Materials II. (Proceedings from

the second workshop sponsored by the Biomaterials

Research Advisory Committee, National Institute of

Dental Research.) Public Health Service Publication

No. 1494 (1966) . For sale by the Supt. of Documents,

U. S. Government Printing Office, Washington, D. C.

20402. Price $1.00.

16. National Institute of Dental Research, Research Contracts

Office, Room 403 Westwood Building, Bethesda, Md . 20014

will furnish a list of Clearinghouse numbers of the

Reports of Research Contractors with N.I.D.R. Copies

of these reports may be obtained from the National

Technical Information Service, Springfield, Va. 22151.

17. Science Information Exchange, Smithsonian Institution,

300 Madison National Bank Building, 1730 M Street N. W.

,

Washington, D. C. 20036. This is a National Registry

of Research in Progress where retrieval service for

queries is available.

18. Gilmore, H. W. Text book of operative dentistry. The

C. V. Mosby Co., St. Louis, Mo. 1967.

19. Schultz, L. G. et al . Operative dentistry. Lea &

Febiger, Philadelphia, Pa. 1966.
- 20 -

20. Paf f enbarger , G. C. Dental Cements, Direct Filling

Resins, Composite and Adhesive Restorative Materials

A Resume. To be published in Journal of Biomedical

Materials Research.

* * *
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in

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co

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tn •H

It

but

after

4

2

/3

years

of

service.
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rG >1

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rd •H -H

Oh > i—

1

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33 G

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1

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|iFigure

8.

A

celluloid-type

denture

(Hecolite)

showing

shrinkage

on

cast

of

plaster-of-paris

.

The

discoloration

does

not

show

in

this

black

and

white

illustration

but

the

denture

turned

from

pink

to

brown.

(7)
and

white

illustration

but

the

from

pink

to

orange.

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sals • . A

as tPPG C Eh •Hso • ,G

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Sh'-'

as rd • Sh CP,y i a

Mh rd 0 i

1 1 Sh

as -P a, us >1 <d a: •pH a

o,-h

as cp

'a 4h >i o e

•G o

-P ‘ G4-> g

as TS

as oP

as T3

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rtf E

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as & -H 4

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as

G

G

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as -p Cn

rd as G H

as

tr> •H


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fta

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•r-1 u CD g <y P > <d

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g

ft £

CD rd <DCO ft cd C ft •H Q

•H 03

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CD

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U < rC o m

CDs

•H

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TjuJ
0

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2

3

4

5

6

1

a

a

so

ft &

Graphs showing the strength and stiffness of

various organic denture base materials in

trarisverse bending.,

e 14
Figure 15 Experimental clinical denture with stainless

steel reference pins used as reference points

in measuring dimensional changes over AB (molarto-molar) and CD ( flange-to-flange) distances.

c
Figure 16 Toolmaker's microscope used in measuring

dentures illustrated in Figure 15.
< -

C/) C3 =5 = ^ d

- u 5 - oe, Z *— LU Q to

LU LO 3 v: iu ^ oo LJ 5<o

> -i a: > u_ a_

in

<

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LL. O Q UJ yj

> X

O ^2

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Q£ Q_

DIMENSIONAL HISTORY OF

UPPER AND LOWER DENTURES

MADE OF VULCANITE AND EPOXOLON

TIME IN MONTHS

ON CO

LUu

O'UJQ_

• 1.0

0 8

0.6

•0 4

0.2

0.0

O

z

<

X

u

I <

0.2

- 0.4

MOLAR-TO-MOLAR

C D FLANGE-TO-FLANGE

^ ° O CN °° o L " in n co

i r

o o cn oo N’N’iO'O'ONNOO

ffiW//

-p/\j

m

- 0.6

1 VULCANITE ^ M M .

0.8 V—V UPPER A B (5 6.2 6 ) 0—

0

UPPER C 0 (67 9 2 )

V—

V

LOWER A B (5 0.7 4 )

- 1.0 0—0 LOWER C D (7 129 ) EPOXOLON :

-

1 , L E —E UPPER A B <5 4 44 ) ©—

@

UPPER C 0 (6 9.3 7 )

E —E LOWER A B (5 0.1 2 )

- 1.4 LOWER C 0 (6 0 3 9 )

v —-.v

Figure 17 Dimensional history of expanding and contracting

dentures after 7 years of service.
'