A survey of the elemental composition of alloy for dental amalgam

Analyses of 51 alloys (conventional, 41, and high-copper, 10) currently available in Australia were made. A rapid and precise procedure was developed that relied on wet-way methods for silver and tin while copper, zinc, mercury, indium and low-level constituents, such as lead, cadmium and antimony, were determined by atomic absorption spectroscopy. The conventional alloys, with two minor exceptions, all complied with the compositional requirements of modern standards and little quantitative variations was noted when the range of the major component was compared with the values obtained in two surveys made over thirty years ago. The high-copper contained, among other factors, an average copper concentration about four times that of conventional alloys. Rather surprising were the contents of mercury, indium, and cadmium found in some of the alloys as well as the low-level concentration of lead, and in a few cases antimony. Other elements were not detected by the sensitive technique used. It is justifiable to recommend that the maximum zinc content to be permitted in zinc-free type alloys should not be greater than 0.01%, and this value was subsequently incorporated in the revised Australian standard 2110-1977: Alloy for Dental Amalgam.