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In vitro tarnish of dental amalgams
In vitro tarnish of dental amalgams T. K. Vaidyanathan, Ph.D.,* R. Gowda, D.D.S.,** and A. Schulman, D.D.S., M.S.*** New York University
Dental Center, College of Dentistry,
New York, N. Y.
M
any interesting articles describing in vitro tarnish on dental casting alloys have been published.‘-” However, there have been few in vitro tarnish studies on dental amalgams. Previous investigations on amalgams have largely relied on continuous immersion of the amalgams in sulfide or chloride solutions for several days6, ’ Tuccillo and Nielsen’ suggested the use of an alternate immersion and wiping technique to depict tarnish in dental casting alloys. The tarnish tendencies of dental amalgams using this technique have not been reported. This article reports the results of tarnish tests on conventional and high-copper amalgams using the Tuccillo-Nielsen apparatus.
MATERIALS AND METHODS The study was conducted on conventional and high-copper amalgams. New True Dentalloy? and Spheralloyt represented the conventional amalgams. In addition, high-copper alloys which used the single-composition mode of copper alloying (Tytin,? Aristaloy CR,$ Sybralloyx, and Indiloyjl) as well as those which used the additive mode of copper Cupralloy,# Optaloy II,** alloying (Dispersalloy, and Micro II**) were tested (Table I). All the single-composition alloys are made using the atomization techniques so that Tytin, Sybralloy,
Presented at the 56th General Session of IADR, Washington, D. C., March 1978. *Associate Professor, Department of Dental Materials Science. **Private Practice, Los Angeles, Calif. ***Associate Professor and Chairman, Department of Dental Materials Science. tS. S. White Dental Mfg. Co., Philadelphia, Pa. $Kerr Mfg. Co., Romulus, Mich. $Baker Dental Co., Carteret, N. J. //Shofu Dental Corp , Menlo Park, Calif. 1 Johnson and Johnson, East Windsor, N. J. e Weber Consumable Products, Mount Vernon, N. Y. **L. D. Caulk Co., Milford, Del.
0022-3913/81/010063
+ 11$01.10/00
1981 The C. V. Moshy Co.
Fig. 1. Tuccillo-Nielsen
tarnish test equipment.
and Indiloy consist of spherical alloy particles. Aristaloy CR, however, is atomized with water so that the alloy particles are both spherical and irregular. The additive high-copper amalgam alloys use a mixture of conventional lathe-cut, copper-deficient particles to which copper-rich, spherical silvercopper or silver-copper-tin particles are added. The testing apparatus used is shown in Fig. 1. It consisted of a vertically rotating plastic wheel with eight holes, 1 inch in diameter along its periphery, in which standard metallographic mounts with the specimens can be clamped. The wheel rotates at 1 rpm. Such an arrangement allows each specimen to be alternately immersed in the testing solution for 15 seconds and withdrawn for 45 seconds per revolution. As each specimen is withdrawn from the medium, it is mechanically wiped with a cloth to
THE JOURNAL
OF PROSTHETIC
DENTISTRY
63
VAIDYANATHAN,
GOWDA,
AND
SCHULMAk
Fig. 2. Microstructures of 2-hour conventional amalgams after 10 minutes of testing. A, NPW True Dentalloy. B, Spheralloy. The y phase (larger dark regians) and y2 phase (smaller dark regions/ tarnished more.
Table I. Amalgam
Mode of copper alloying
Alloy Conventional New True Dentalloy Spheralloy High-copper
-
tested % Copper in alloy
(6
9
Micro II
Additive
9
Cupralloy
Additive
21
Dispersalloy
Additive Single-composition Single-composition Single-cornposition SingIe-composition
12
Aristaloy Tytin Indiloy Sybralloy
II
Particle shapes
Irregular Spherical
(6
Additive
Optaloy
64
alloys
13
Irregular and spherical Irregular and spherical Irregular and spherical Irregular and spherical Irregular and spherical
13 13
Spherical
(5 Indium)
Spherical
29
Spherical
remove any nonadherent deposit. This usually leaves a thin tarnish layer intact. The amalgam specimens were condensed by hand into 4 mm holes drilled into the mounts. One batch of amalgams was allowed to set for 2 hours, metallographically polished, and then subjected to testing. Another batch was tested after 8 days. The initial stages of tarnish were microstructurally examined after 10 minutes of testing. Similarly, advanced states were also examined after 16 hours. The medium used for the test was 0.5% Na!S solution at a pH of 12.
RESULTS The unreacted amalgam particles are metallographically referred to as the gamma (y) phase and consist of a silver-tin compound. Once this material has reacted with mercury, it forms a silver mercury or gamma-l (yl) phase and a tin-mercury or gamma2 (y.J phase. Fig. 2 shows the tarnish microstructures of the 2 hour conventional amalgams, New True Dentalloy and Spheralloy, subjected to 10 minutes of testing.
JANUARY
1981
VOLUME
45
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
0B
Fig. 3. Microstructures minute test. A, Aristaloy
THE JOURNAL
OF PROSTHETIC
DENTISTRY
.
of z-hour high-copper amalgams (single-composition) CR; B, Sybralloy; C, Indiloy; and D, Tytin.
after
IO-
65
VAIDYANATHAN,
GOWDA,
AND
SCHULMAN
45
NUMBER
Fig. 4. Microstructures of Z-hour high-copper amalgams (additive type of copper alloying) after lo-minute test. A, Micro II; B, Optaloy II; C, Dispersalby; and D, Cupralloy. Additive particles [dark areas) tarnished more.
66
JANUARY
1981
VOLUME
1
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
Fin. 5. Microstructures A,-New True Dentalloy
of S-day conventional and B, Spheralloy
The tarnish initiation occured primarily in the y and ya phases. The y1 phase appeared to be less tarnish prone. The wiping action may physically remove the soft y2 phase, making it difficult to discriminate this phase from the porosities in the tarnish test. It appears, however, that the y phase is electrochemitally more active than the y1 phase. This has also occurred in the single-composition high-copper amalgams (Fig. 3). The tarnish originated in discrete points or regions in the y and y, phases. These points or regions may indeed be the copper-rich regions in the amalgam. The rate of tarnish attack appeared to be highest in Indiloy. The remaining amalgams, Tytin, Aristaloy CR, and Sybraloy, appeared less tarnished at this stage. The tarnished microstructures of the additive amalgams are shown in Fig. 4. The tarnish initiation is in the copper-rich additive phase (shown as the dark spherical particles in Fig. 4). Interestingly, tarnish attack appeared less severe in the y phase of the copper-rich additive phase amalgams. The Micro II and Optaloy II additive phase was less tarnished. Dispersalloy additive particles were more severly attacked, but the severest attack was on the Cupralloy additive phase. Figs. 5 to 7 show the tarnished microstructures of 8-day old conventional and high-copper amalgams
THE JOURNAL
OF PROSTHETIC
DENTISTRY
amalgams subjected to lo-minute
tarnish test.
subjected to 10 minutes of tarnish tests. The attack was similar but less severe than that described for the 2-hour specimens. The older amalgams were relatively less tarnished except for the single-composition alloys. In these, the increased amounts of copper-tin reaction products resulted in more localized tarnish in these regions. Fig. 8 shows the 8-day conventional amalgams subjected to 16 hours of tarnish. The tarnish was more intense at both the unreacted y and y, phases. Fig. 9 shows the tarnished microstructures of 8-day high-copper amalgams from single-composition alloys. The tarnish is essentially similar to that of the conventional amalgams. Sybralloy and Indiloy appeared to be more severely tarnished than Aristaloy CR and Tytin. Fig. 10 shows the tarnished microstructures of high-copper amalgams from the additive alloys. Interestingly, the severely attacked microstructures revealed copper-tin halos surrounding the copperrich additive. The peripheries of the unreacted additive particles were less severely attacked, but the core of each particle was severely attacked. In addition, these amalgams showed a spotty, tarnished appearance on gross examination, compared to a more uniform tarnish appearance of the amalgams from single-composition alloys.
67
VAIDYANATHAN.
Fig. 6. Microstructures of &day high-copper amalgams (single-composition) tarnish test. A, Aristaloy CR; B, Sybralloy; C, Indiloy; and D, Tytin.
68
IANUARY
GOWDA.
AND SCHULMJN
after IO-minute
1981
VOLUME
4.5
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
Fig. 7. Microstructures of S-day high-copper amalgams (additive type) after lo-minute tarnish test. A, Micro II; B, Optaloy II; C, Dispersalloy; and D, Cupralloy.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
69
Fig. 8. Microstructures of S-day conventional New True Dentalloy and B, Spheralloy. Park
DISCUSSION The selectivity of the points or regions where tarnish originates clearly indicates the electrochemical nature of the origin of tarnish. Amalgams constitute a multiphase system where individual phases necessarily undergo anodic oxidation at a rate controlled by the electrochemical activity of the individual phases. Comparison of the tarnished microstructures subjected to the lo-minute test with those tested for 16 hours clearly indicated that the tarnish began at discrete points in electrochemically active phases with subsequent growth into a continuous film through lateral spread. Alternating immersion and wiping probably removed any nonadhering deposit on the surface of the amalgam, leaving only the more tenaciously adherent films to accrue. Under these conditions, the copper-rich phases appear to tarnish most; the y phase is less tarnish prone than copperrich phases but more tarnish prone than the y1 phase. In addition, the tarnish tendency of the y phase is reduced in the presence of copper-rich phases. This may be seen by comparing the tarnished microstructures of high-copper amalgams from additive alloys with those of conventional amalgams and single-
70
amalgams subjected to 16-hour tarnish rqions are the y phase and y. phace.
test.
~1,
composition amalgams after 10 minutes of tarnish. Such changes may be expected in multielectrode systems. Another interesting feature of tarnish in amalgams from the additive systems is that the higher the copper content in the additive phase, the more intense is the tarnish. Thus Micro II and Optaloy II (9% copper in the additive phase) had less intense tarnish. Dispersalloy (28% copper in the additive phase) showed more intense tarnish, and Cupralloy (52% copper) showed the severest tarnish in the additive phase. From a tarnish point of view, therefore, additive systems using higher copper content in the additive are less desirable. Another interesting aspect of the amalgams from additive systems is the appearance of halos surrounding the additive phase, especially in the older amalgams. These regions clearly represent the copper-tin reaction products surrounding the additive phase, as has been demonstrated in Dispersalloy. In addition to the halos, there appears to be a peripheral region and core in each particle which have distinct differences in tarnish properties. This is probably because the particles have a silver-tin outer periphery and a tin or copper-rich core more sensitive to sulfide
JANUARY
1981
VOLU‘ME
55
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
Fig. 9. Microstructures of B-day high-copper amalgams (single-composition) after 16-hour tarnish test. A, Aristaloy CR; B, Sybralloy; C, Indiloy; and D, Tytin. Scratch marks are due to the wiping action over a prolonged period.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
71
VAIDYANATHAN,
GOWDA,
AND
SCHULMAN
Fig. 10. Microstructures of d-day high-copper amalgams (additive types) after 16-hour tarnish test. A, Micro II; B, Optaloy 11;C, Dispersalloy; and D, Cupralloy. Durk regions are the additive particles.
72
JANUARY
1981
VOLUME
45
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
tarnish. Thus, the heterogeneity in the composition across a single particle is reflected in the microstructures. CONCLUSIONS
REFERENCES Tuccillo, J. J., and Nielsen, J. P.: Observation of the onset of sulfide tarnish on gold base alloys. J PROSTHET DENT 25:629, 1971.
THE JOURNAL
OF PROSTHETIC
Nielsen, J. P.: Microprobe analysis of an in viva tion. J PROSTHET DENT 31:285, 1974.
3.
Burse, 4. B., Swartz, M. C., and Phillips, R. W.: Comparison of the in vitro and in viva tarnish of three gold base alloys. J Biomed Mater Res 6:267, 1972. Vaidyanathan. T. K., and Prasad, A.: Corrosion and tarnish properties of the Ag-Pd binary system. Transactions of the 4th Annual Meeting of the Society for Biomaterials and the 10th Annual International Biomaterials Symposium, ~012, p 127, 1978. Hodges, R. J.: The corrosion resistance of gold and base metal alloys. In Valega, T. M., editor: Alternatives to Gold Alloys in Dentistry. Proceedings of a conference held at the NIH, Bethesda, Maryland, 1977, DHEW publication (NIH) No. 77-1227, p 106. Sarkar, N. K., Fuys, Jr., R. A., and Stanford, J. W.: The effect of copper on the sulfide tarnish resistance of dental amalgams. IADR Programs and Abstracts, 1976. (Abstr No.
4.
Tuccillo-Nielsen tarnish test is an effective screening device for dental amalgams. The y phase appears to he more tarnish prone in conventional dental amalgams than y, phase. Although y2 appeared to be tarnish prone, it was difficult to discriminate this phase because of the porosity in the amalgams. The copper-rich phases are the most tarnish prone in high-copper amalgams. Gross examinations of amalgam from additive systems show spotty tarnish, whereas more uniform tarnish appearance is observed in amalgams from single-composition alloys. The amalgams can be graded for in vitro tarnish performance in selected groups like the additive systems and the single-composition alloys.
1.
2.
DENTISTRY
5.
6.
7.
discolora-
895). Averette, D. F., Hochman, R. F., and Marek, M.: The effects of corrosion in vitro on the structure and properties of dental amalgam. IADR Programs and Abstracts, 1978, p 165.
Reprint requeststo: DR. T. K. VAIDYANATHAN NEW YORK UNIVERSITY DENTAL CEN?.ER COLLEGE OF DEKTISTRY
345 E. 24~~ ST. NEW YORK, N. Y. 10010
73
Dental Center, College of Dentistry,
New York, N. Y.
M
any interesting articles describing in vitro tarnish on dental casting alloys have been published.‘-” However, there have been few in vitro tarnish studies on dental amalgams. Previous investigations on amalgams have largely relied on continuous immersion of the amalgams in sulfide or chloride solutions for several days6, ’ Tuccillo and Nielsen’ suggested the use of an alternate immersion and wiping technique to depict tarnish in dental casting alloys. The tarnish tendencies of dental amalgams using this technique have not been reported. This article reports the results of tarnish tests on conventional and high-copper amalgams using the Tuccillo-Nielsen apparatus.
MATERIALS AND METHODS The study was conducted on conventional and high-copper amalgams. New True Dentalloy? and Spheralloyt represented the conventional amalgams. In addition, high-copper alloys which used the single-composition mode of copper alloying (Tytin,? Aristaloy CR,$ Sybralloyx, and Indiloyjl) as well as those which used the additive mode of copper Cupralloy,# Optaloy II,** alloying (Dispersalloy, and Micro II**) were tested (Table I). All the single-composition alloys are made using the atomization techniques so that Tytin, Sybralloy,
Presented at the 56th General Session of IADR, Washington, D. C., March 1978. *Associate Professor, Department of Dental Materials Science. **Private Practice, Los Angeles, Calif. ***Associate Professor and Chairman, Department of Dental Materials Science. tS. S. White Dental Mfg. Co., Philadelphia, Pa. $Kerr Mfg. Co., Romulus, Mich. $Baker Dental Co., Carteret, N. J. //Shofu Dental Corp , Menlo Park, Calif. 1 Johnson and Johnson, East Windsor, N. J. e Weber Consumable Products, Mount Vernon, N. Y. **L. D. Caulk Co., Milford, Del.
0022-3913/81/010063
+ 11$01.10/00
1981 The C. V. Moshy Co.
Fig. 1. Tuccillo-Nielsen
tarnish test equipment.
and Indiloy consist of spherical alloy particles. Aristaloy CR, however, is atomized with water so that the alloy particles are both spherical and irregular. The additive high-copper amalgam alloys use a mixture of conventional lathe-cut, copper-deficient particles to which copper-rich, spherical silvercopper or silver-copper-tin particles are added. The testing apparatus used is shown in Fig. 1. It consisted of a vertically rotating plastic wheel with eight holes, 1 inch in diameter along its periphery, in which standard metallographic mounts with the specimens can be clamped. The wheel rotates at 1 rpm. Such an arrangement allows each specimen to be alternately immersed in the testing solution for 15 seconds and withdrawn for 45 seconds per revolution. As each specimen is withdrawn from the medium, it is mechanically wiped with a cloth to
THE JOURNAL
OF PROSTHETIC
DENTISTRY
63
VAIDYANATHAN,
GOWDA,
AND
SCHULMAk
Fig. 2. Microstructures of 2-hour conventional amalgams after 10 minutes of testing. A, NPW True Dentalloy. B, Spheralloy. The y phase (larger dark regians) and y2 phase (smaller dark regions/ tarnished more.
Table I. Amalgam
Mode of copper alloying
Alloy Conventional New True Dentalloy Spheralloy High-copper
-
tested % Copper in alloy
(6
9
Micro II
Additive
9
Cupralloy
Additive
21
Dispersalloy
Additive Single-composition Single-composition Single-cornposition SingIe-composition
12
Aristaloy Tytin Indiloy Sybralloy
II
Particle shapes
Irregular Spherical
(6
Additive
Optaloy
64
alloys
13
Irregular and spherical Irregular and spherical Irregular and spherical Irregular and spherical Irregular and spherical
13 13
Spherical
(5 Indium)
Spherical
29
Spherical
remove any nonadherent deposit. This usually leaves a thin tarnish layer intact. The amalgam specimens were condensed by hand into 4 mm holes drilled into the mounts. One batch of amalgams was allowed to set for 2 hours, metallographically polished, and then subjected to testing. Another batch was tested after 8 days. The initial stages of tarnish were microstructurally examined after 10 minutes of testing. Similarly, advanced states were also examined after 16 hours. The medium used for the test was 0.5% Na!S solution at a pH of 12.
RESULTS The unreacted amalgam particles are metallographically referred to as the gamma (y) phase and consist of a silver-tin compound. Once this material has reacted with mercury, it forms a silver mercury or gamma-l (yl) phase and a tin-mercury or gamma2 (y.J phase. Fig. 2 shows the tarnish microstructures of the 2 hour conventional amalgams, New True Dentalloy and Spheralloy, subjected to 10 minutes of testing.
JANUARY
1981
VOLUME
45
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
0B
Fig. 3. Microstructures minute test. A, Aristaloy
THE JOURNAL
OF PROSTHETIC
DENTISTRY
.
of z-hour high-copper amalgams (single-composition) CR; B, Sybralloy; C, Indiloy; and D, Tytin.
after
IO-
65
VAIDYANATHAN,
GOWDA,
AND
SCHULMAN
45
NUMBER
Fig. 4. Microstructures of Z-hour high-copper amalgams (additive type of copper alloying) after lo-minute test. A, Micro II; B, Optaloy II; C, Dispersalby; and D, Cupralloy. Additive particles [dark areas) tarnished more.
66
JANUARY
1981
VOLUME
1
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
Fin. 5. Microstructures A,-New True Dentalloy
of S-day conventional and B, Spheralloy
The tarnish initiation occured primarily in the y and ya phases. The y1 phase appeared to be less tarnish prone. The wiping action may physically remove the soft y2 phase, making it difficult to discriminate this phase from the porosities in the tarnish test. It appears, however, that the y phase is electrochemitally more active than the y1 phase. This has also occurred in the single-composition high-copper amalgams (Fig. 3). The tarnish originated in discrete points or regions in the y and y, phases. These points or regions may indeed be the copper-rich regions in the amalgam. The rate of tarnish attack appeared to be highest in Indiloy. The remaining amalgams, Tytin, Aristaloy CR, and Sybraloy, appeared less tarnished at this stage. The tarnished microstructures of the additive amalgams are shown in Fig. 4. The tarnish initiation is in the copper-rich additive phase (shown as the dark spherical particles in Fig. 4). Interestingly, tarnish attack appeared less severe in the y phase of the copper-rich additive phase amalgams. The Micro II and Optaloy II additive phase was less tarnished. Dispersalloy additive particles were more severly attacked, but the severest attack was on the Cupralloy additive phase. Figs. 5 to 7 show the tarnished microstructures of 8-day old conventional and high-copper amalgams
THE JOURNAL
OF PROSTHETIC
DENTISTRY
amalgams subjected to lo-minute
tarnish test.
subjected to 10 minutes of tarnish tests. The attack was similar but less severe than that described for the 2-hour specimens. The older amalgams were relatively less tarnished except for the single-composition alloys. In these, the increased amounts of copper-tin reaction products resulted in more localized tarnish in these regions. Fig. 8 shows the 8-day conventional amalgams subjected to 16 hours of tarnish. The tarnish was more intense at both the unreacted y and y, phases. Fig. 9 shows the tarnished microstructures of 8-day high-copper amalgams from single-composition alloys. The tarnish is essentially similar to that of the conventional amalgams. Sybralloy and Indiloy appeared to be more severely tarnished than Aristaloy CR and Tytin. Fig. 10 shows the tarnished microstructures of high-copper amalgams from the additive alloys. Interestingly, the severely attacked microstructures revealed copper-tin halos surrounding the copperrich additive. The peripheries of the unreacted additive particles were less severely attacked, but the core of each particle was severely attacked. In addition, these amalgams showed a spotty, tarnished appearance on gross examination, compared to a more uniform tarnish appearance of the amalgams from single-composition alloys.
67
VAIDYANATHAN.
Fig. 6. Microstructures of &day high-copper amalgams (single-composition) tarnish test. A, Aristaloy CR; B, Sybralloy; C, Indiloy; and D, Tytin.
68
IANUARY
GOWDA.
AND SCHULMJN
after IO-minute
1981
VOLUME
4.5
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
Fig. 7. Microstructures of S-day high-copper amalgams (additive type) after lo-minute tarnish test. A, Micro II; B, Optaloy II; C, Dispersalloy; and D, Cupralloy.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
69
Fig. 8. Microstructures of S-day conventional New True Dentalloy and B, Spheralloy. Park
DISCUSSION The selectivity of the points or regions where tarnish originates clearly indicates the electrochemical nature of the origin of tarnish. Amalgams constitute a multiphase system where individual phases necessarily undergo anodic oxidation at a rate controlled by the electrochemical activity of the individual phases. Comparison of the tarnished microstructures subjected to the lo-minute test with those tested for 16 hours clearly indicated that the tarnish began at discrete points in electrochemically active phases with subsequent growth into a continuous film through lateral spread. Alternating immersion and wiping probably removed any nonadhering deposit on the surface of the amalgam, leaving only the more tenaciously adherent films to accrue. Under these conditions, the copper-rich phases appear to tarnish most; the y phase is less tarnish prone than copperrich phases but more tarnish prone than the y1 phase. In addition, the tarnish tendency of the y phase is reduced in the presence of copper-rich phases. This may be seen by comparing the tarnished microstructures of high-copper amalgams from additive alloys with those of conventional amalgams and single-
70
amalgams subjected to 16-hour tarnish rqions are the y phase and y. phace.
test.
~1,
composition amalgams after 10 minutes of tarnish. Such changes may be expected in multielectrode systems. Another interesting feature of tarnish in amalgams from the additive systems is that the higher the copper content in the additive phase, the more intense is the tarnish. Thus Micro II and Optaloy II (9% copper in the additive phase) had less intense tarnish. Dispersalloy (28% copper in the additive phase) showed more intense tarnish, and Cupralloy (52% copper) showed the severest tarnish in the additive phase. From a tarnish point of view, therefore, additive systems using higher copper content in the additive are less desirable. Another interesting aspect of the amalgams from additive systems is the appearance of halos surrounding the additive phase, especially in the older amalgams. These regions clearly represent the copper-tin reaction products surrounding the additive phase, as has been demonstrated in Dispersalloy. In addition to the halos, there appears to be a peripheral region and core in each particle which have distinct differences in tarnish properties. This is probably because the particles have a silver-tin outer periphery and a tin or copper-rich core more sensitive to sulfide
JANUARY
1981
VOLU‘ME
55
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
Fig. 9. Microstructures of B-day high-copper amalgams (single-composition) after 16-hour tarnish test. A, Aristaloy CR; B, Sybralloy; C, Indiloy; and D, Tytin. Scratch marks are due to the wiping action over a prolonged period.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
71
VAIDYANATHAN,
GOWDA,
AND
SCHULMAN
Fig. 10. Microstructures of d-day high-copper amalgams (additive types) after 16-hour tarnish test. A, Micro II; B, Optaloy 11;C, Dispersalloy; and D, Cupralloy. Durk regions are the additive particles.
72
JANUARY
1981
VOLUME
45
NUMBER
I
IN VITRO
TARNISH
OF DENTAL
AMALGAMS
tarnish. Thus, the heterogeneity in the composition across a single particle is reflected in the microstructures. CONCLUSIONS
REFERENCES Tuccillo, J. J., and Nielsen, J. P.: Observation of the onset of sulfide tarnish on gold base alloys. J PROSTHET DENT 25:629, 1971.
THE JOURNAL
OF PROSTHETIC
Nielsen, J. P.: Microprobe analysis of an in viva tion. J PROSTHET DENT 31:285, 1974.
3.
Burse, 4. B., Swartz, M. C., and Phillips, R. W.: Comparison of the in vitro and in viva tarnish of three gold base alloys. J Biomed Mater Res 6:267, 1972. Vaidyanathan. T. K., and Prasad, A.: Corrosion and tarnish properties of the Ag-Pd binary system. Transactions of the 4th Annual Meeting of the Society for Biomaterials and the 10th Annual International Biomaterials Symposium, ~012, p 127, 1978. Hodges, R. J.: The corrosion resistance of gold and base metal alloys. In Valega, T. M., editor: Alternatives to Gold Alloys in Dentistry. Proceedings of a conference held at the NIH, Bethesda, Maryland, 1977, DHEW publication (NIH) No. 77-1227, p 106. Sarkar, N. K., Fuys, Jr., R. A., and Stanford, J. W.: The effect of copper on the sulfide tarnish resistance of dental amalgams. IADR Programs and Abstracts, 1976. (Abstr No.
4.
Tuccillo-Nielsen tarnish test is an effective screening device for dental amalgams. The y phase appears to he more tarnish prone in conventional dental amalgams than y, phase. Although y2 appeared to be tarnish prone, it was difficult to discriminate this phase because of the porosity in the amalgams. The copper-rich phases are the most tarnish prone in high-copper amalgams. Gross examinations of amalgam from additive systems show spotty tarnish, whereas more uniform tarnish appearance is observed in amalgams from single-composition alloys. The amalgams can be graded for in vitro tarnish performance in selected groups like the additive systems and the single-composition alloys.
1.
2.
DENTISTRY
5.
6.
7.
discolora-
895). Averette, D. F., Hochman, R. F., and Marek, M.: The effects of corrosion in vitro on the structure and properties of dental amalgam. IADR Programs and Abstracts, 1978, p 165.
Reprint requeststo: DR. T. K. VAIDYANATHAN NEW YORK UNIVERSITY DENTAL CEN?.ER COLLEGE OF DEKTISTRY
345 E. 24~~ ST. NEW YORK, N. Y. 10010
73