NATIONAL BUREAU OF STANDARDS REPORT

9879

Progress Report

on

AN EVALUATION OF A GALLIUM-PALLADIUM-TIN ALLOY

FOR RESTORATIVE DENTISTRY

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

311.05-11-3110560 July 17, 1968 9879

Progress Report

on AN EVALUATION OF A GALLIUM-PALLADIUM-TIN ALLOY

FOR RESTORATIVE DENTISTRY

by

R. M. Waterstrat*

* Research Associate from the American Dental Association in the Dental Research Section, National Bureau of Standards,

Washington, D. C. 20234.

This investigation was supported in part by Research Grants

D E—00949 to the American Dental Association from 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 Council on Dental Research of the American Dental

Association; the Army Dental Corps; the Dental Sciences Division

of the School of Aerospace Medicine, USAF; and the Veterans

Administration.

IMPORTANT NOTICE 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 specitical

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

ess accounting documents intended

s subjected to additional evaluation

re listing of this Report, either in he 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
*
AN EVALUATION OF A GALLIUM-PALLADIUM-TIN

ALLOY FOR RESTORATIVE DENTISTRY

by

R. M. Waterstrat

1. Introduction

The use of gallium metal as a replacement for mercury

in dental alloys was suggested at le&st as long ago as

1928* *" 4’ but subsequent attempts to develop satisfactory

alloys for this application were unsuccessful® Further research on gallium dental alloys was conducted by the Aluminum

Company of America® and their studies led to the development

of at least two promising alloys, one of which was patented

in 195211 A systematic study of gallium alloys as possible

dental restorative materials was begun at the National Bureau

of Standards in 1952 and this study revealed several other

alloy systems with potentially useful properties® * 9 • 1 0 8 1

None of these alloys have been subjected to an extensive

biological and clinical investigation. They were selected

primarily on the basis of their mechanical and physical

properties which compared favorably with those of ordinary
-2

dental amalgam. The present study summarizes research at

the National Bureau of Standards and presents experimental

data for one of the more promising gallium alloys. Much

more work remains to be done, however, mainly in the biological and clinical testing of these alloys before they can

be recommended for general use.

The selection of a gallium-palladium-tin alloy as

offering unusual potential for use in restorative dentistry

was based on an exhaustive study of many alternative binary

and ternary alloys. The basis for this selection included

a comparison of mechanical and physical properties together

with a consideration of possible reactions with oral fluids

and tissues. Alloys of nickel, for example, had been reported as possessing some outstanding physical properties®” 0

but were eliminated from consideration when it was subsequently discovered that these alloys showed a pronounced

carcinogenic behavior in soft tissue implants1. 3
-3-

2. Experimental Procedures and General Observations

A primary requirement of any gallium alloy for dental

application is considered to be an ability to form a plastic mass which hardens through a diffusion reaction similar

to that which occurs in dental amalgam. The convenience of

using such an alloy is largely responsible for the widespread

use of dental amalgam in preference to gold foil or gold

alloy castings. In order to obtain hardening by such a reaction it is necessary that the alloy be capable of forming

an intermetallic compound at mouth temperature. The only

metals^which form such compounds with gallium and have

adequate resistance to corrosion in oral fluids are found

within the family of transition elements or within the triad

of copper, silver and gold.

Each of these metals was, therefore, mixed with liquid

gallium or gallium-tin eutectic alloy (gallium + 11% tin) in

order to determine which metals would harden at mouth temperature (37°C) . Many of these powder-liquid mixtures would not

harden at this temperature but would react rapidly with considerable
—4~

exothermic heating, if the mixtures were heated to about

400 °C. In these alloys, thin oxide films may prevent the

diffusion reaction at mouth temperature. The metals which

formed hardenable powder-liquid mixtures at 37 °C were cobalt,

nickel, copper, rhodium, palladium, silver, iridium, platinum and gold. In subsequent tests of compressive strength,

however, the cobalt, rhodium, iridium and silver alloys were

mechanically weak and were, therefore, eliminated from

further consideration. In addition, the rhodium, iridium,

and platinum alloys required far too much time to complete

their respective hardening reactions. Since nickel-galliumtin alloys had been eliminated from consideration by the

aforementioned carcinogenic reactions, this reduced the

remaining elements to copper, palladium and gold. These

three metals formed the basis for a more extensive explora9 tion of possible gallium dental alloys. Gold-gallium alloys

were eventually eliminated since they were generally not as

strong as similar alloys of copper or palladium, and also

because the gold-gallium alloys had an undesirable blue

colored surface after hardening.
-5

A series of tests were made using copper-gold alloy

powders having compositions of 0, 35, 50, 80 and 100% Au

by weight. The products of the hardening reaction in the

ternary Cu-Au-Ga alloys were identified by x-ray diffraction

in each case and compared with compounds reported in the

binary systems Cu-Ga and Au-Ga1

, 3 In each case the compounds

which formed were those richest in gallium even though

other binary compounds are also stable at room temperature.

The relative proportion of CuGas or AuGa2 compounds which

formed depended on the copper-gold ratio and there was no

evidence for any mutual solubility of these compounds.

The ternary alloys, however, were not appreciably stronger

than the binary Cu-Ga or Au-Ga mixtures alone and were,

therefore, discarded in favor of the stronger Pd-Ga alloys.

X-ray diffraction studies of hardened alloys of pure

palladium powder and liquid gallium-tin eutectic alloy

revealed the presence of the intermetallic compound PdGa5 and some residual palladium^ 0 The compound PdGa5 has a

tetragonal crystal structure14 which is a somewhat modified

version of the structure of the compound CuA1 2 , an important

hardening constituent in commercial aluminum alloys.
-6

Fine powders of pure palladium or pure gold produce

violent exothermic reactions when mixed with liquid galliumtin alloy at room temperature. It is, therefore, necessary

H

s to dilute the pure metals with some other element before

reacting the fine powder with gallium in order to reduce the

amount of exothermic heating. Various elements were alloyed

with palladium in a study of their effectiveness in reducing

heat evolution, but in many instances the strength of the

resulting alloy was lowered appreciably by the alloy addition.

However, a very stable compound Pds Ga exists in the binary

Pd-Ga alloy system1

5

and this compound will react with the

liquid gallium-tin eutectic alloy without excessive exothermic

heating and without reduction in strength1

. 0 The alloy Pd2 Ga

was prepared by arc-melting in a water-cooled copper crucible

under an atmosphere of inert gas such as argon or helium.

The as-cast alloy was crushed to a very fine powder; appreciably finer than is needed to pass the 325 mesh screen and

having the consistency of a fine flour. This was accomplished,

by grinding it in a hardened steel rod mill for several

hours. A very fine particle size is essential in order to
-7-

obtain such desirable properties as high strength, optimum

hardening time, moderate expansion on setting, and good

surface finish in the gallium alloy mixtures. The strength

increases while the setting time and setting expansion decrease as progressively finer alloy particle sizes are utilized.

In mixing the Pd2 Ga alloy powder with the liquid gallium-tin

eutectic, the proportions used were 0.09 ml of liquid per

gram of powder. The liquid was dispensed from a microburet.

The alloy was mixed in a Teflon® capsule without a pestle

using a mechanical mixer of the type normally employed in

dentistry. It was necessary to mix the alloy for about one

minute when using the Wig-L-Bug® mechanical mixer. The Teflon®

capsule is desirable to minimize wetting by liquid gallium.

After mixing, any excess liquid may be removed with a squeeze

cloth. The mixture can be handled and carved, using, ordinary

dental instruments. The alloy very effectively wets the

tooth structure in the mouth in contrast to the behavior

of ordinary dental amalgams1

. 6 A typical restoration is

shown in Figure 1.

»
—8—

3. Physical and Mechanical Properties

The compressive strength after one hour from the time

of mixing averaged 23,000 psi (159 MN/m2

) as compared with

values of about 10,000 psi (69 MN/m2

) obtained for dental

amalgam under identical conditions. The gallium-palladiumtin alloy has an average fully-hardened compressive strength

of about 75,000 psi (517 MN/m2

) with occasional specimens

showing strengths as high as 87,000 psi (600 MN/m2 ). This

can be compared with an average value of 55,000 psi (379

MN/m2

) for the fully-hardened compressive strength of dental

amalgam. The tensile strengths averaged 9,700 psi (67 MN/m2

)

with occasional specimens as high as 12,000 psi (83 MN/m2

)

as compared with 8,200 psi (57 MN/m2

) for dental amalgam.

Thus, the gallium alloys appear to have a higher early strength

than dental amalgam and a higher final compressive and tensile

strength. The modulus of elasticity of the alloy, measured

by ultrasonic methods, was 12.0 ± 0.6 x 106 psi (83 ± 4.1

GN/m2

) as compared with 9.1 ± 0.1 x 10® psi (63 ± 0.7 GN/m2

)

for dental amalgam measured by the same method1

. 7 These data

are summarized in Table 1.

The greater strength and rigidity of the galliumpalladium-tin alloy over that of dental amalgam may be

partially due to the higher peritectic decomposition temperature of PdGa 5 (200 °C) as compared with that of Ags Hg3
—9—

(reported as 127 °C in binary Ag-Hg alloys, but observed as

about 80 °C in dental amalgam) . It may also be due to the

virtual absence of internal voids which are a source of

weakness in dental amalgams1

. 8 ' 19 Microscopic examination

of the gallium-palladium-tin alloy reveals a dense packing

of the Pda Ga alloy particles and remarkably few voids

(Fig. 2) . The Pd2 Ga alloy particles appear to be fairly

uniform in size and somewhat spheroidal in shape.

The measured density of the gallium-palladium-tin

alloy was 8.8 g/cm3 as compared with 11.4 g/cm3 for a

dental amalgam. The thermal expansion coefficient between

25 °C and 60 °C of the gallium-palladium-tin alloy was 15 x 10"6

cm/cm/°C as compared with 25 to 27 x 10”6 cm/cm/°C for

dental amalgam and 8 to 12 x 10”6 cm/cm/ ° C for tooth structure.

The gallium-palladium-tin alloys had setting expansions

which were usually in the range of 15 to 20 urn/cm (.15 to

.20%) as compared with 0 to 15 um/cm (0 to .15%) for dental

amalgam, but the dimensional change was a sensitive function

of the alloy particle size and could be readily changed.
-10-

Creep tests on the gallium-palladium-tin alloy revealed

a remarkable resistance to flow under an applied load at

room temperature. When loaded in tension to about half its

ultimate tensile strength (4,000 psi) (27 MN/m^) the galliumpalladium-tin alloy undergoes a barely detectable flow in

two weeks, whereas dental amalgam under the same conditions

will flow to the point of probable fracture. The flow rate

for dental amalgam was about 5 x 10”5 inches/inch/minute20

while the gallium-palladium-tin alloy had a flow rate of

only 7 x 10“8 inches/inch/minute. This result may be

partially explained, since room temperature, at which the

test is conducted, is fairly close to the decomposition

temperature of dental amalgam (80 °C) whereas the galliumpalladium-tin alloy at this same testing temperature is

farther from its decomposition temperature (200 °C) . It is

likely that the higher decomposition temperature of the

gallium-palladium-tin alloy will also enable it to retain

its strength at moderately elevated temperatures as is the

case with gallium-nickel-tin alloys1

. 8
- 11-

X-ray diffraction studies reveal that the hardened alloy

contains the compound PdGa5 together with residual Pd2 Ga but

there was no evidence of any other compounds 0 This suggests

that the alloy hardens by the reaction:

Pds Ga + 9Ga-2PdGa5 Compounds containing tin were not detected either by

x-ray diffraction or metallographic examination. The

primary purpose of the tin in this alloy, however, is to

lower the melting point of gallium below room temperature

for convenience in mixing the alloy.

Corrosion tests on the gallium-palladium-tin alloy in

distilled water at room temperature have revealed the slow

formation of a gelatinous compound which ultimately crystallizes as the white gallium oxyhydroxide GaO(OH), identified

by x-ray diffraction. This reaction is accompanied by a

blackening of the surface of the alloy. The blackening is

apparently not due to another oxide but may be caused by

residual palladium or a palladium-rich intermetallic compound

The black coating was very thin and we were unable to collect

enough of this material for identification. Blackening

of the surface of these alloys was later observed after

about one week in vital rat teeth and in vital dog teeth.
-12-

but there was no indication of any blackening or corrosion

in tests in vital human teeth even when observed for two

months1

.

4

* Conditions in the human oral cavity are difficult

to reproduce in vitro and may not be satisfactorily reproduced

®v@n fey the oral environment of rats or dogs. For this reason,,

did not undertake any extensive in vitro corrosion testing

program* Actual clinical trials would presumably resolve

this question.

In view of th® pronounced tendency of gallium to wet *

tooth structure, it appeared to be of considerable interest

whether an improved marginal seal is obtained in restorations using galliuM-palladium-tin alloy. An investigation

Marginal leakage was conducted using the method described

by Pickard and Gayford?1 This method entails measuring

amounts of air pressure needed to produce marginal leakage

in restorations in extracted human teeth. The air pressure

is applied through a channel in the root canal which leads

beneath the restoration. The tooth itself is immersed in

distilled water during the test. Both ordinary dental amal”

gams and gallium^pa1Iadium-tin alloys were tested using

argon gas as the pressure medium. Pressures ranging from 3

to 19 psi (2 to 13 kN/ra3

) were required to produce leakage
-13

in dental amalgam restorations that had been allowed to harden

for 24 hours, whereas pressures of 22 to 55 psi (15 to 38 kN/m2

)

were required to produce leakage in 24-hour restorations of

the gallium-palladium-tin alloy. The amalgam restorations

after five weeks required pressures varying from 69 psi

(48 kN/m2

) to over 100 psi (69 kN/m2

) . No attempt was made

to apply pressures greater than 100 psi due to possible

explosion hazards. After 48 hours, all of the gallium-palladium'

tin restorations were leak-tight at pressures of over 100 psi

and they all remained leak-tight when retested after four weeks.

All of the restorations were made by the same operator using,

as far as possible, identical techniques. The galliumpalladium-tin alloy, therefore, seems capable of consistently

producing a more effective seal at the margins of a restoration

than is usually obtained with ordinary dental amalgam.

The gallium-palladium-tin alloy, when contaminated with

a 0.6% saline solution, did not undergo a "delayed expansion",

but did have a greatly increased initial setting expansion

of up to 420 u m/cm (4.2%) . Therefore, the gallium-palladiumtin alloy, like zinc-containing amalgam, should not be contaminated with moisture during mixing or packing.
” 14*“

4, Clinical and Biological Studies

Tests for tissue tolerance and corrosion resistance

are, of course, essential and some preliminary tests were

conducted in various laboratories. The copper-gallium

alloys were evaluated initially by means of subdermal implants in guinea pigs and were found to produce a rather severe

reaction? 2 Similar severe reactions to subdermal implants

of gold-gallium alloys and palladium-gallium alloys were

observed in rats? 3 However, in contrast to the nickel-gallium

alloys1

, 3 no carcinomas were detected.

These findings, however, may be somewhat irrelevant

since the alloys are intended for use as restorations of

«* lost tooth tissues and not as subdermal implants in soft

tissues. Studies of pulp reactions may provide a more

appropriate basis upon which to evaluate the performance of

the gallium alloy as a dental restorative material. At the

same time one can obtain information on the corrosion resistance of the material in an oral environment. Preliminary

studies were begun using vital teeth in both rats and dogs? 4

In each case the surface of the gallium alloy restorations

turned black within one week after being placed, and it

appeared that a further study of the corrosion of these alloys
-15-

was needed. Since laboratory corrosion tests were unreliable in evaluating the performance of this material, it was

suggested that the corrosion tests might be performed in an

actual oral environment using caries-free human vital teeth

that were eventually to be extracted in preparation for full

dentures. Additional information on pulp reactions could

also be obtained on the extracted teeth. These studies were

begun in 1963 by Dr. H. Swerdlow and Dr. H. R. Stanley at

the National Institute of Dental Research using the galliumpalladium-tin alloy.

In a preliminary study 20 fillings were placed in 5

patients for periods of time ranging from 1 day to 84 days,

followed by extraction and histopathological examination* 6

There was no evidence of any corrosion and the pulp reactions

were similar to those normally obtained with conventional

dental amalgam, which usually presents a small percentage

(less than 5%) of severe lesions® 6 It seemed rather surprising that the test results for corrosion using rats and dogs

were not in agreement with the tests in humans. Some of the

gallium-palladium-tin alloy used by Drs. Swerdlow and Stanley

was submitted to Drs. L. and K. Langeland at the State

University of New York at Buffalo who subsequently reported
-16-

®®v«gr® pulp r ©actions to this alloy in vital monkey teeth® 6

Much more data are needed to evaluate adequately the biological behavior of this alloy.

We have recently learned that some of the gallium-eoppertin alloys that were developed during the early stages of this

research9

’ have been subjected to clinical tests with favorably results? 8 Nevertheless, the use of gallium-copper alloys

may be premature. Even though copper amalgams have been used

in dentistry for many years, there has been little work done

on possible pulp reactions or toxicity? 9 ' 30 and their corrosion

resistance is marginal. On the other hand, palladium is

normally quite inert at mouth temperature, and both palladium

and gallium are reported to have low toxicities? 1 ” 51

5. Conclusion

Gallium-palladium-tin alloys possess many of the properties desired in a dental restorative material. When

compared with dental amalgam the gallium-palladium-tin alloys

exhibit superior strength and vastly ^superior resistance to

flow under an applied load at mouth temperature. The

gallium-palladium-tin alloys also possess thermal expansion

coefficients that more closely match those of human teeth.
- 17 -

The gallium alloys effectively wet the tooth structure and

this apparently produces a tighter marginal seal than is

usually obtained with dental amalgam.

It is concluded that the use of a gallium-palladium-tin

alloy offers several significant advantages over dental amalgam

as a restorative material and that this alloy possesses some

outstanding physical and chemical properties. Its use in

clinical dentistry, however, must await a much more extensive study of its biological properties.

References

1. Puttkammer. Mercury-free amalgam? Zahnarztl.

Runds. 35:1450 August 1928 .

2. Schwarz, L. and Decker t, W. Mercury-free amalgam?

Zahnarztl. Runds. 7:282 February 1929.

3. Poutot, H. Investigation of a low-melting metal alloy

(gallium compound) as a substitute for amalgam fillings.

Corespondezblatt Zahnartze 54:438, 454, 502, Oct .-Nov. -Dec.

1930.

4. Greth, H. Experimental investigation of a fusible

metal intended as an amalgam substitute. Stomat.

28:586 July 1930.

5. Weibke, F., and Hesse, E. On the question of replacement of mercury in dental amalgams with gallium.

Z. Elektrochem. 46:219, March 1940.

6. Lyle, J. P., Jr. Dental alloys containing gallium.

Alum. Research Lab. (ALCOA) Report #13-49-IG3, 1949.

7. Lyle, J. P., Jr. Plastic alloy which sets at room

temperature. U. S. Patent 2,585,393 1952.
8. Smith, D. L. and Caul, H. J. Alloy* of gallium with

powdered metals as possible replacement for dental

amalgam. JADA 53:315, September 1956.

9. Smith, D. L., Caul, H. J., and Sweeney, W. T. Same

physical properties of gallium-copper-tin alloya.

JADA 53:677, December 1956.

10 o Waterstrat, R. M. and Longton, R. W. Gallium4.palladium

alloys as dental filling material. Public Health

Reports 79:638, July 1964.

11. Smith, D. L. and Caul, H. J. Cobalt-gallium and nickelgallium dental alloys. U. S. Patent 2,864,695 1958.

t

12. Mitchell, D. F. , Shankwalker, G. B., and Shazer, S.

Determining the tumorgenicity of dental materials.

J. Dent. Res. 39:1023, Sept>-0ct., 1960.

13. Hansen, M. and Anderko, K. Constitution of Binary

Alloys. Second Edition. McGraw-Hill Book Co., New York.

14. Elliott, R. P. Constitution of Binary Alloys. First

Supplement 1965. McGraw-Hill Book Co., New York.

15. Schubert, K. , Lukas, H. L., Meisner, H. G., and Bhan, S.

The diagrams of the systems Co-Ga, Pd-Ga, Pd-Sn and

similar alloys. Z. Metallkunde 50:534, September 1959.
16. Swerdlow, H. and Stanley, H. R. Unpublished results

1964.

17. Dickson, G. and Oglesby, P. E. Elastic constants of

dental amalgam. J. Dent. Res. 46:1475, Nov. -Dec. 1967.

18. Jorgensen, K. D., Ebensen, A. L., and Borring-Moller , G.

The effect of porosity and mercury content upon the

strength of silver amalgam. Acta Odont. Scand. 24:535

1966.

19. Eden, G. T., Waterstrat, R. M. , and Moore, G. A. Unpublished results, 1966.

20. Oglesby, P. L. , Dickson, G. , Rodriguez, M. L. , Davenport,

R. M., and Sweeney, W. T, To be published, 1968.

21. Pickard, H. M. and Gayford, J. J. Leakage at the

margins of amalgam restorations. British Dental

Journal 119:69, July 1965.

22. Hartley, J. L. and Harris, N. 0. A comparative evaluation

of tissue tolerance to a gallium alloy. Air University

School of Aviation Medicine, USAF Report #58-148, 1958.
23. Lyon, H. W. , Waterstrat, R. M. , and Paf fenbarger, G. C.

Soft tissue response to implantsof gallium alloys

and silver amalgam alloys. JADA 72:659 March, 1966.

24. Longton, R. W. , Ostrom, C. A., Lyon, H. W. , and

Miller, C. R. Unpublished results. Dental Division,

NMRL, Washington, D. C. 1963.

25. Swerdlow, H. and Stanley, H. R. Response of the

human dental pulp to amalgam restorations. Oral

Surgery, Oral Medicine, and Oral Pathology, 15:499,

April 1962.

26. Langeland, L. K. , Yoshiki, S., and Langeland, K.

Biologica evaluation of a gallium alloy. Abstract #24 , IADR 45th General Meeting, Washington, D. C. 1967.

27. Swartz, M. L. , Phillips, R. W. , and El Tannir, M. D.

Tarnish of certain dental alloys. J. Dent. Res.

37-837 Sept. -Oct. 1958.

28. Pilipenko, L. I. Clinical tests of a mercury- free

metal filling. Stomatologiya 44:18 1965.
29. Mitchel, D. F. Irritational qualities of dental

materials. JADA 59:954, November 1959.

30. Dixon, C. M. and Rickert, U. G, Tissue tolerance to

foreign materials. JADA 20:1459, August 1933.

31. Schwartz, L. and Sieke, F. About gallium. Arch.

Hyg. 100:143 1928.

32. Levaditi, C., Bardet, J., Tcharkirian, A. and Vaisman, A.

The distribution of gallium in the system. Comp.

Rend. Acad. d. Sc. 193:117, July 1931.

33. Meek, S. F., Harrold, G. C., and McCord, G. P.

Toxicity of gallium. Industrial Medicine 12:7, 1943.

34. Dudley, H. C. Determination of gallium in biological

materials. J. Pharma, and Exp. Therap. 95:482,

April 1949.

35. Dudley, H. C. and Levine, M. D. Studies of the toxic

action of gallium. J. Pharma, and Exp. Therap. 95:487,

April 1949
43 . Lang, F. R. The use of radioactive gallium in medicine

Ann. Intern. Med. 35:1237, December 1951.

44. Sax, N. Irving. Handbook of Dangerous Materials.

Reinhold Publishing Corp. p. 183 and 288, 1951.

45. Dudley, H. C. and Friedman, L. Influence of Vitamin

D on deposition of gallium in the bone of rat.

Science 115:146, February 1952.

46. Archdeacon, J. W. , Nash, J; B., and Wilson, J. B. The

biliary excretion of gallium 72, gold 198 and hafnium

181 in the rat. Texas Reports Biol. Med. 10:281, 1952.

47. Fairhall, L. T. Toxicologie. Ann. Rev. Medic. 3:268

1952.

48. Dudley, H. C. and Marrer, H. H. Studies of the

metabolism of gallium II deposition and clearance from

bone. J. Pharma, and Exp. Therap. 106:129, October

1952.

49. Brucer, M., Andrews, G. A., and Brunner, H. D. A

study of gallium 72: Summary and Conclusions.

Radiology 61:543, October 1953.
50. Mulay, A. S. and Schlyen, S. M. Lesions induced in

C57BR mice with gallium citrate and Methylcholanthene

Am. Journal Path. 32:117, Jan. -Feb. 1956.

51. Podosinowski, V. T. The toxicity of gallium compounds.

Gigiena Truda i. Prof. Zabelsvanija 9:45, 1965.
TABLE

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Legend of Figures

Figure 1. Gallium-palladium-tin alloy restorations in

human vital teeth.

Figure 2. Photomicrograph of a fully hardened galliumpalladium-tin alloy. Particles of the alloy Pd2 Ga embedded in

a matrix of PdGas compound.

Magnification 1200x

Original Magnification 500x

USCOMM— DC— NBS




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