HEAT-TREATMENT OF AMALGAM ALLOY VERSUS CREEP OF AMALGAM

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 degree C, respectively, for 2 or 4 weeks. The steady-state creep rate was determined at a compressive stress of 116 MN/m**2 and at a temperature of 22. 5 degree C. On the average the results are as follows. Creep is unaffected by the annealing temperature in the region 100 to 225 degree C. Between 225 and 315 degree C the creep decreases as the annealing temperature increases. No major differences are detected between 315, 319, and 382 degree C specimens. In the range 382 to 435 degree 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 homogenizing and aging lathe cut alloys. Probably the homogenizing treatement contributes more to creep than the aging treatment. Powders tested included Ag-Sn-Cu alloys and amalgams, and Ag-Sn-Cu-Zn alloys and amalgams.