The effect of noble metals on the mechanical properties of dispersed phase dental amalgam

The effects of noble metals added as part of a Ag-Cu dispersant on the compressive strength and creep of dental amalgams was determined. The Ag-Cu eutectic used in high copper dispersant alloy L(0), was altered by adding 15 per cent by weight (wt%) of noble metal in place of Ag. In L(1) the noble metal was Pd. In L(2), Au and Pd were combined in equal proportions. In L(3), the noble metal content was Pd and Pt in equal proportions. A low copper lathe-cut amalgam, Aristalloy® was used as the matrix. Amalgams S(0) and S(1) had the same composition as L(0) and L(1) except that the the low copper alloy matrix was Spheralloy®, a low copper spherical amalgam. The compressive strength and creep were measured according to American Dental Association specification No. 1 and the results analysed by ANOVA. The addition of noble metals to the dispersant significantly lowered the 1-h compressive strength of amalgams. Compared to the control amalgam L(0), the 24-h compressive strength was increased for L(1) and L(2) but lowered for L(3). The ADA creep values were significantly lowered by addition of all combinations of noble metals. Reported microstructural changes such as an increase in unreacted particles, and a slowed setting reaction may account for the findings.