Heat treatment of amalgam alloy versus creep of amalgam

Abstract

The influence of a heat treatment of the alloy powder upon the creep of dental amalgams was investigated. Only commercially available conventional composition amalgam alloys were used. Alloy powders were heat treated at 100, 150, 225, 315, 319, 382, and 435°C, respectively, for 2 or 4 weeks. The steady-state creep rate was determined at a compressive stress of 116 MN/m² and at a temperture of 22.5°C. On the average the results are as follows. Creep is unaffected by the annealing temperature in the region 100 to 225°C. Between 225 and 315°C the creep decreases as the annealing temperature increases. No major differences are detected between 315, 319, and 382°C specimens. In the range 382 to 435°C, creep increases with increasing annealing temperature. It is hypothesized that the actual combination of the homogenizing and aging heat treatment gives minimum creep for a majority of the commercial la the cut alloys. Probably the homogenizing treatment contributes more to creep than the aging treatment. The time of the aging heat treatment probably is too short to contribute to creep. As far as the spherical alloys are concerned, the extrapolation to heat treatments is difficult because of their more complicated thermal history which might include quenching.