Some Physical Properties of Silver-Tin Amalgams

¹ Department of Dental Materials, Loyola University and Northwestern University, Chicago, Illinois

The amalgams formed with silver-tin alloys in the composition range of 4 to 31 percent tin have been studied as to the effect of the silver-tin content and the trituration time on the compressive strength, dimensional change, and cohesion time of the amalgam. All other experimental variables were constant.

In general, the compressive strength increased with increase in trituration time, although in certain instances a maximum strength was obtained that was not changed by further trituration. Such an increase in strength was considered to be a result of increased amalgamation and bond strength with increased trituration.

A composite alloy that contained both the and , phases resulted in a slow amalgamation rate with a consequent reduction in bond strength. The strength was less than that of either the or phases alone.

XWhen the and phases were combined in the same alloy, the strength increased with (but not in proportion to) the addition of . Also, the addition of produced more rapid rates of amalgamation and crystallization; these rates were greater than those of either the or phases alone.

The -phase alloy resulted in the strongest amalgam, probably because of less volume of matrix and a greater bond strength, as indicated by the reduction in mercury content of the amalgam.

The dimensional change was reduced with increases in trituration time and silver content of the alloys, as predicted by existing theories.

With exception of the amalgam from the -phase alloy, the composition and manipulation did not affect the residual mercury content of the amalgam.