Optimizing Creep and Corrosion Properties in a Dispersant Amalgam Using Manganese R. M. WATERSTRAT Research Associate of the American Dental Association Health Foundation Research Unit at the National Bureau of Standards, Washington, D.C. 20234 It is shown that the creep behavior of a commercial dispersant-amalgam containing copper is improved by the addition of a manganese-containing alloy. This improvement is apparently obtained without any serious changes in corrosion resistance, provided that no more than 20% of the Mn alloy is added.
J Dent Res 57(9-10):873-875, Sept.-Oct. 1978
Introduction. The failure of dental amalgam restorations frequently begins with loss of marginal integrity. There is some evidence that this marginal deterioration may be due to an inadequate resistance to creep1,2 and perhaps also to insufficient corrosion resistance3,4 but, as yet, there is no complete and satisfactory explanation for this behavior. Several amalgam alloys now appearing on the market* utilize additions of copper to improve the creep behavior and corrosion resistance of their amalgams, and clinical evidence indicates that these amalgams are indeed more resistant to marginal deterioration.5 Much more information is needed, however, in regard to the optimum copper content and whether it is best to incorporate the copper into a single-phase alloy or to add it separately as a dispersion of copperReceived for publication December 19, 1977. Accepted for publication March 10, 1978. This investigation was supported in part by Grant DE02455 to the American Dental Association 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 Health Foundation. *Certain commercial materials are identifiled in this report in order to adequately specify the experimental procedures. In no instance does such identification imply recommendation or endorsement by the National Bureau of Standards, nor does it imply that the material identified is necessarily the best available for this purpose.
rich particles. Manganese has also been utilized to improve the creep resistance of dental amalgams,6 but some questions have been raised as to whether the corrosion resistance of these amalgams is adequate.7'8 A brown corrosion product forms on the surface of Mn-containing amalgams when they are immersed in 1% saline solutions, but it should be noted that a green corrosion product is formed on the surface of many Cucontaining amalgams under the same conditions (Fig. 1), and yet at least one of these amalgams exhibits good overall stability in clinical restorations.5 Thus, the appearance of an amalgam after exposure to a 1% saline solution may not be relevant to its appearance in the mouth. Nevertheless, corrosion tests in 1% saline solution can be useful in preliminary screening of experimental
amalgams. It is of some interest to determine whether manganese additions can be effective in improving the creep resistance of dental amalgams without seriously degrading their corrosion resistance. We have therefore investigated the effects of manganese additions on the creep and corrosion behavior of a commercial amalgamt which is reported to possess good resistance to creep and corrosion and good marginal stability in clinical restorations.5
Materials and methods. A commercial alloy powder, consisting of two-thirds lathe cut and one-third spherical particles, was utilized.tt The lathe cut portion was Ag3Sn (4% Cu) while the spher-
tDispersalloy-Johnson & Johnson Dental Products Company, East Windsor, New Jersey 08520 ttDispersalloy-American Silver and Mercury Producers, 1126 Pioneer Way, El Cajon, California 92020 873
Downloaded from jdr.sagepub.com at Univ of Connecticut / Health Center / Library on May 21, 2015 For personal use only. No other uses without permission.
874
J Dent Res September-October 19 78
WA TER STRA T
__ _-x -~
-
--
-.-
0.6
4% 8% * 12% * 20% A
Mn Mn Mn Mn
0.5 x
-
_
_
0.4 C-
x
0.3
8-1
Fig. 1. Copper-containing dental amalgams after immersion in 1% saline solutions for 9 months at room temperature. Corrosion products shown here have a bright green color. (Dispersalloy Johnson & Johnson Dental Products Co.; Sybraloy - Kerr Mfg. Co., East Windsor, N.J. 08520; Tytin S. S. White Dental Products International, Philadelphia, Pa. 19102.)
0.2 "I
Al
..
A
0.1
-.
-a -
A
- - - -
0 0
10
20
30
40
50
Wt. % Mn alloy added
ical portion was the Ag-Cu eutectic. Proportions are in weight percent. The manganesecontaining alloy powders had various Mnconcentrations (4, 8, 12 and 20% Mn) where Mn replaces the silver in the conventional binary 74% Ag, 26% Sn composition.6 These two alloy powders were thoroughly mixed in weight percentages of 10% to 50% of the manganese-containing alloy. The amalgam specimens were made from these alloy mixtures using the procedures given in ADA Specification #19 and the same mercury/alloy ratio recommended for Dispersalloy amalgams. The creep tests were conducted according to procedures recently incorporated into this Specification.10 The corrosion tests were conducted by placing a single specimen of each amalgam in an individual dish of 1% saline solution at room temperature (%200C). Each dish was covered to retard evaporation, and the solution was replenished occasionally whenever there appeared to be a loss due to evaporation.
Results and discussioni. The results of the creep measurement are shown in Fig. 2. It can be seen that the addition of the Mn-containing alloy particles to the dispersant alloy produces a significant reduction in the creep when compared with amalgams produced from the pure
Fig. 2. -Creep of dental amalgams made from a mixture of Cu-dispersant and Mn-containing alloy
powders having Mn-contents of 4, 8, 12 and 20%, respectively.
dispersant-alloy mixture. A reduction in the creep from 0.5% for the pure dispersant amalgam to about 0.1% occurs when the powder mixture contains at least 20% by weight of alloy particles containing at least 12% Mn. The addition of more than 20% of the Mn-containing alloy particles is ineffective in producing any further improvement in the creep behavior. We have produced similar reductions in creep values by adding the manganese alloy powders to other commercial amalgam alloys, including both conventional and copper-rich Ag-Sn alloys. It is obviously of interest to determine whether the addition of up to 20% of Mncontaining alloy produces any significant loss of corrosion resistance when compared with pure dispersant amalgam. We therefore prepared five amalgam specimens for mixtures of the dispersant amalgam with 10, 20, 30, 40 and 50% of the Mn-containing alloy particles (12% Mn content). These were immersed individually in the 1% saline solution for six weeks at room temperature, with the result shown in Fig. 3. Pure dispersant amalgam and mixtures of up to 20% of the manganese-containing alloy are resistant
Downloaded from jdr.sagepub.com at Univ of Connecticut / Health Center / Library on May 21, 2015 For personal use only. No other uses without permission.
Vol 7No. 9-1 0
CREEP AND CORROSION IN DISPERSANT AMALGAM
875
Conclusion. Preliminary studies indicate that the addition of manganese to a copper-containing dispersant amalgam will improve its creep resistance without serious adverse effects on the corrosion behavior if the amount of the added Mn-containing alloy is not more than 20%. Manganese additions at this level are apparently also effective in improving the creep resistance of other conventional and copper-rich amalgams. Further studies on the use of both Cu and Mn in dental amnalgam alloys should be directed toward determining the optimum Cu/Mn ratio and whether it is best to incorporate these additions into a single phase or Dental amalgarms made from mixFig. 3. to add them as a dispersion of secondture of Cu-dispersant and Mn-containing alloy powphase particles. ders after immersion in 1% saline solutions for a
6 weeks at room temperature. The samples shown contain 10, 20, 30, 40 and 50 weight % of a Mncontaining alloy (having the composition 64% Ag, 12% Mn, 24% Sn) from left to right. The dark surfaces for the 30, 40 and 50% samples are due to a brown corrosion product. The pure Cu-dispersant amalgam, under these conditons, resembles the 10 and 20% samples in retaining a clean (uncorroded) surface.
Acknowledgment. The author wishes to express his appreciation to Dr. G. C. Paffenbarger, Dr. N. W. Rupp, Mr. G. Dickson and Dr. N. Sarkar for very helpful discussions. References 1. MAHLER, D. B.; TERKLA, L. G.; VAN EYSDEN, J.; REISBICK, M. H.: Marginal Fracture vs. Mechanical Properties of Amal-
to the 1% saline solution, but a significant change occurs at 30%. Here one begins to see gam,J. Dent. Res. 49:1452-1457, 1970. a brown surface film which completely cov2. PAFFENBARGER, G. C.; RUPP, N. W. and ers the surfaces of the specimens. If this PATEL, P. R.: Dimensional Change on Amalbehavior occurs also in clinical restorations, gams m Air at 600C, AADR abstract No. one may perhaps improve the marginal sta255:B 115, 1977. bility of the dispersant amalgams by re- 3. HOLLAND, G. A., and ASGAR, K.: Some Effects of the Phases of Amalgam Induced by placing part of the copper with manganese. Corrosion, IADR abstract No. 191:1 06, 1973. However, the fraction of Mn alloy added K. D.: The Mechanism of Marwill probably have to be kept at about 20% 4. JORGENSON, Fracture of Amalgam Fillings, Acta ginal or less. Odont. Scand. 23:347-389, 1965. It may be argued that the improvement in 5. BINON, P.; PHILLIPS, R. W.; SWARTZ, creep resistance demonstrated here is miniM. L.; NORMAN, R. D. and MEHRA, R.: mal; but, since the amount of deformation Clinical Behavior of Amalgam as Related to due to both creep and corrosion is time deCertain Mechanical Properties, IADR abstract No. 509:186, 1973. pendent, it would be difficult to predict the clinical significance of this improvement un- 6. WATERSTRAT, R. M.; RUPP, N. W. and MANUSZEWSKI, R. C.: Improved Creep less studies could be conducted under Behavior and Removal of Gamma-2 Phase in clinical conditions over the 20- to 30-year Dental Amalgans Containing Manganese, period which constitutes the life span of IADR abstract No. 883:B282, 1976. many amalgam restorations. It is possible 7. ZARDIACKAS, L. D.: unpublished research, that the simultaneous presence of Cu and Univ. of Virginia, 1975. Mn together may be more effective in in- 8. SARKAR, N. K.; FUYS, R. A. and STANcreasing creep resistance than Cu alone. FORD, J. W.: Corrosion Resistance of MnContaining Dental Amalgams, IADR abstract The amount of Mn necessary to achieve the No. 238:A102, 1977. maximum reduction in creep is minimal and, at this level, need not produce serious 9. Guide to Dental Materials, 7th Edition, American Dental Association, Chicago, Ill., 1974-75. corrosion problems if the Cu/Mn ratio is 10. Revised ADA Spec. No. 1 for Alloy for Dental optimized. Amalgam, Journ. A.D.A. 95:614-617, 1977. Downloaded from jdr.sagepub.com at Univ of Connecticut / Health Center / Library on May 21, 2015 For personal use only. No other uses without permission.
J Dent Res 57(9-10):873-875, Sept.-Oct. 1978
Introduction. The failure of dental amalgam restorations frequently begins with loss of marginal integrity. There is some evidence that this marginal deterioration may be due to an inadequate resistance to creep1,2 and perhaps also to insufficient corrosion resistance3,4 but, as yet, there is no complete and satisfactory explanation for this behavior. Several amalgam alloys now appearing on the market* utilize additions of copper to improve the creep behavior and corrosion resistance of their amalgams, and clinical evidence indicates that these amalgams are indeed more resistant to marginal deterioration.5 Much more information is needed, however, in regard to the optimum copper content and whether it is best to incorporate the copper into a single-phase alloy or to add it separately as a dispersion of copperReceived for publication December 19, 1977. Accepted for publication March 10, 1978. This investigation was supported in part by Grant DE02455 to the American Dental Association 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 Health Foundation. *Certain commercial materials are identifiled in this report in order to adequately specify the experimental procedures. In no instance does such identification imply recommendation or endorsement by the National Bureau of Standards, nor does it imply that the material identified is necessarily the best available for this purpose.
rich particles. Manganese has also been utilized to improve the creep resistance of dental amalgams,6 but some questions have been raised as to whether the corrosion resistance of these amalgams is adequate.7'8 A brown corrosion product forms on the surface of Mn-containing amalgams when they are immersed in 1% saline solutions, but it should be noted that a green corrosion product is formed on the surface of many Cucontaining amalgams under the same conditions (Fig. 1), and yet at least one of these amalgams exhibits good overall stability in clinical restorations.5 Thus, the appearance of an amalgam after exposure to a 1% saline solution may not be relevant to its appearance in the mouth. Nevertheless, corrosion tests in 1% saline solution can be useful in preliminary screening of experimental
amalgams. It is of some interest to determine whether manganese additions can be effective in improving the creep resistance of dental amalgams without seriously degrading their corrosion resistance. We have therefore investigated the effects of manganese additions on the creep and corrosion behavior of a commercial amalgamt which is reported to possess good resistance to creep and corrosion and good marginal stability in clinical restorations.5
Materials and methods. A commercial alloy powder, consisting of two-thirds lathe cut and one-third spherical particles, was utilized.tt The lathe cut portion was Ag3Sn (4% Cu) while the spher-
tDispersalloy-Johnson & Johnson Dental Products Company, East Windsor, New Jersey 08520 ttDispersalloy-American Silver and Mercury Producers, 1126 Pioneer Way, El Cajon, California 92020 873
Downloaded from jdr.sagepub.com at Univ of Connecticut / Health Center / Library on May 21, 2015 For personal use only. No other uses without permission.
874
J Dent Res September-October 19 78
WA TER STRA T
__ _-x -~
-
--
-.-
0.6
4% 8% * 12% * 20% A
Mn Mn Mn Mn
0.5 x
-
_
_
0.4 C-
x
0.3
8-1
Fig. 1. Copper-containing dental amalgams after immersion in 1% saline solutions for 9 months at room temperature. Corrosion products shown here have a bright green color. (Dispersalloy Johnson & Johnson Dental Products Co.; Sybraloy - Kerr Mfg. Co., East Windsor, N.J. 08520; Tytin S. S. White Dental Products International, Philadelphia, Pa. 19102.)
0.2 "I
Al
..
A
0.1
-.
-a -
A
- - - -
0 0
10
20
30
40
50
Wt. % Mn alloy added
ical portion was the Ag-Cu eutectic. Proportions are in weight percent. The manganesecontaining alloy powders had various Mnconcentrations (4, 8, 12 and 20% Mn) where Mn replaces the silver in the conventional binary 74% Ag, 26% Sn composition.6 These two alloy powders were thoroughly mixed in weight percentages of 10% to 50% of the manganese-containing alloy. The amalgam specimens were made from these alloy mixtures using the procedures given in ADA Specification #19 and the same mercury/alloy ratio recommended for Dispersalloy amalgams. The creep tests were conducted according to procedures recently incorporated into this Specification.10 The corrosion tests were conducted by placing a single specimen of each amalgam in an individual dish of 1% saline solution at room temperature (%200C). Each dish was covered to retard evaporation, and the solution was replenished occasionally whenever there appeared to be a loss due to evaporation.
Results and discussioni. The results of the creep measurement are shown in Fig. 2. It can be seen that the addition of the Mn-containing alloy particles to the dispersant alloy produces a significant reduction in the creep when compared with amalgams produced from the pure
Fig. 2. -Creep of dental amalgams made from a mixture of Cu-dispersant and Mn-containing alloy
powders having Mn-contents of 4, 8, 12 and 20%, respectively.
dispersant-alloy mixture. A reduction in the creep from 0.5% for the pure dispersant amalgam to about 0.1% occurs when the powder mixture contains at least 20% by weight of alloy particles containing at least 12% Mn. The addition of more than 20% of the Mn-containing alloy particles is ineffective in producing any further improvement in the creep behavior. We have produced similar reductions in creep values by adding the manganese alloy powders to other commercial amalgam alloys, including both conventional and copper-rich Ag-Sn alloys. It is obviously of interest to determine whether the addition of up to 20% of Mncontaining alloy produces any significant loss of corrosion resistance when compared with pure dispersant amalgam. We therefore prepared five amalgam specimens for mixtures of the dispersant amalgam with 10, 20, 30, 40 and 50% of the Mn-containing alloy particles (12% Mn content). These were immersed individually in the 1% saline solution for six weeks at room temperature, with the result shown in Fig. 3. Pure dispersant amalgam and mixtures of up to 20% of the manganese-containing alloy are resistant
Downloaded from jdr.sagepub.com at Univ of Connecticut / Health Center / Library on May 21, 2015 For personal use only. No other uses without permission.
Vol 7No. 9-1 0
CREEP AND CORROSION IN DISPERSANT AMALGAM
875
Conclusion. Preliminary studies indicate that the addition of manganese to a copper-containing dispersant amalgam will improve its creep resistance without serious adverse effects on the corrosion behavior if the amount of the added Mn-containing alloy is not more than 20%. Manganese additions at this level are apparently also effective in improving the creep resistance of other conventional and copper-rich amalgams. Further studies on the use of both Cu and Mn in dental amnalgam alloys should be directed toward determining the optimum Cu/Mn ratio and whether it is best to incorporate these additions into a single phase or Dental amalgarms made from mixFig. 3. to add them as a dispersion of secondture of Cu-dispersant and Mn-containing alloy powphase particles. ders after immersion in 1% saline solutions for a
6 weeks at room temperature. The samples shown contain 10, 20, 30, 40 and 50 weight % of a Mncontaining alloy (having the composition 64% Ag, 12% Mn, 24% Sn) from left to right. The dark surfaces for the 30, 40 and 50% samples are due to a brown corrosion product. The pure Cu-dispersant amalgam, under these conditons, resembles the 10 and 20% samples in retaining a clean (uncorroded) surface.
Acknowledgment. The author wishes to express his appreciation to Dr. G. C. Paffenbarger, Dr. N. W. Rupp, Mr. G. Dickson and Dr. N. Sarkar for very helpful discussions. References 1. MAHLER, D. B.; TERKLA, L. G.; VAN EYSDEN, J.; REISBICK, M. H.: Marginal Fracture vs. Mechanical Properties of Amal-
to the 1% saline solution, but a significant change occurs at 30%. Here one begins to see gam,J. Dent. Res. 49:1452-1457, 1970. a brown surface film which completely cov2. PAFFENBARGER, G. C.; RUPP, N. W. and ers the surfaces of the specimens. If this PATEL, P. R.: Dimensional Change on Amalbehavior occurs also in clinical restorations, gams m Air at 600C, AADR abstract No. one may perhaps improve the marginal sta255:B 115, 1977. bility of the dispersant amalgams by re- 3. HOLLAND, G. A., and ASGAR, K.: Some Effects of the Phases of Amalgam Induced by placing part of the copper with manganese. Corrosion, IADR abstract No. 191:1 06, 1973. However, the fraction of Mn alloy added K. D.: The Mechanism of Marwill probably have to be kept at about 20% 4. JORGENSON, Fracture of Amalgam Fillings, Acta ginal or less. Odont. Scand. 23:347-389, 1965. It may be argued that the improvement in 5. BINON, P.; PHILLIPS, R. W.; SWARTZ, creep resistance demonstrated here is miniM. L.; NORMAN, R. D. and MEHRA, R.: mal; but, since the amount of deformation Clinical Behavior of Amalgam as Related to due to both creep and corrosion is time deCertain Mechanical Properties, IADR abstract No. 509:186, 1973. pendent, it would be difficult to predict the clinical significance of this improvement un- 6. WATERSTRAT, R. M.; RUPP, N. W. and MANUSZEWSKI, R. C.: Improved Creep less studies could be conducted under Behavior and Removal of Gamma-2 Phase in clinical conditions over the 20- to 30-year Dental Amalgans Containing Manganese, period which constitutes the life span of IADR abstract No. 883:B282, 1976. many amalgam restorations. It is possible 7. ZARDIACKAS, L. D.: unpublished research, that the simultaneous presence of Cu and Univ. of Virginia, 1975. Mn together may be more effective in in- 8. SARKAR, N. K.; FUYS, R. A. and STANcreasing creep resistance than Cu alone. FORD, J. W.: Corrosion Resistance of MnContaining Dental Amalgams, IADR abstract The amount of Mn necessary to achieve the No. 238:A102, 1977. maximum reduction in creep is minimal and, at this level, need not produce serious 9. Guide to Dental Materials, 7th Edition, American Dental Association, Chicago, Ill., 1974-75. corrosion problems if the Cu/Mn ratio is 10. Revised ADA Spec. No. 1 for Alloy for Dental optimized. Amalgam, Journ. A.D.A. 95:614-617, 1977. Downloaded from jdr.sagepub.com at Univ of Connecticut / Health Center / Library on May 21, 2015 For personal use only. No other uses without permission.
