Factors Influencing the Creep of Dental Amalgam

Abstract

The purpose of this study was to investigate the influence of relevant microstructural and compositional factors on the creep of 12 representative dental amalgams by means of stepwise multiple linear regression. The independent variables accepted by the regression were volume percent of the eta' (Cu6Sn5) phase, grain size of the gamma 1 (Ag2Hg3) phase, volume percent of the gamma (Ag3Sn) plus epsilon (Cu3Sn) phases, number of very small eta' crystals (less than 1.5 microns) per mm, and weight percent of Hg. The results of this regression showed an adjusted R2 of 0.949, significant at p = 0.002.

Setting Reactions in Dental Amalgam Part 1. Phases and Microstructures Between One Hour and One Week

“…Moreover, some HCA amalgams, particularly those whose alloy powders contain less copper than other HCA powders, showed 7 2 -to -7 Ag-Sn x-ray peak ratios indicative of the presence of considerable 7 2 (Malhotra and Asgar, 1981). Workers using metallographic techniques (Abbott and Makinson, 1979;Okabe et al, 1985;Mahler and Adey, 1991) have detected as much as 7.3 vol% 7 2 in one-to 14-day-old HCA amalgams. Similarly, using x-ray diffraction, Jensen and lorgensen (1981) calculated that a two-day-old HCA amalgam contained 3.6 wt% 7 2 .…”

“…The 7, grains are equi-axial and between 1.0 and 2.0 (xm across (Mahler and Adey, 1991). The y ] grain size seems to depend on the composition and microstructure of the alloy particles; however, the factors influencing grain size are not understood.…”

“…The y ] grain size seems to depend on the composition and microstructure of the alloy particles; however, the factors influencing grain size are not understood. A better understanding of grain size would be desirable, since grain size influences creep resistance, which in turn affects an amalgam's clinical performance (Mahler and Adey, 1991).…”

“…For example, Mahler and Adey (1991), using lineal analysis of x-ray line profiles, found that the compositions of four HCA amalgams fell within the following ranges: 41 to 46 vol% unconsumed alloy particles, 53-56 vol% 7,, 0 to 3.6 vol% y 2 SnHg, and 5.4 to 9.1 vol% r\' Cu-Sn. These volume percentages are in good agreement with weight percentages determined for an HCA amalgam from x-ray diffraction peak height data (Jensen and Jorgensen, 1981).…”

“…Like HCA amalgams, the matrix of these amalgams contains 7, AgHg and TJ' Cu-Sn, but much less 7 2 Sn-Hg than low-copper amalgams. For example, when Mahler and Adey (1991) analyzed three HCSC amalgams by lineal analysis of x-ray line profiles, they found compositions that ranged as follows: from 47 to 58 vol% unconsumed alloy particles, from 46 to 53 vol% 7, Ag-Hg, and from 16 to 24 vol% T]' Cu-Sn. In these 14-day-old amalgams, they detected no y 2 Sn-Hg.…”