Amalgam — Hazards In Your Teeth

Amalgam has, ever since its introduction 150 years ago, been the subject of recurrent controversies because of its mercury content. Amalgam is an unstable alloy and continuously gives off mercury (Hg) in the form of gas, ions and abraded particles (Stock, 1939 a, Radics et al., 1970, Mocke, 1971, Till and Wagner, 1973, Svare et al., 1981). Amalgam contains an especially cor-rodible gamma-2-phase of tin and mercury. There is also a small phase of fluid mercury with dissolved tin (Brecht-Bergen, 1933). Tin dissolves continuously in surrounding fluids and also forms weakly soluble but not insoluble compounds which are easily abraded in vivo. When tin (also zinc and copper if present) dissolves, mercury is set free and will evaporate and ionize. The Hg vapor pressure over silver amalgam amounts to 10-25 percent of that over pure mercury; at a Hg content of 54 percent in the amalgam the vapor pressure is 25 percent (Brecht-Bergen, 1933). The actual rate of evaporation depends on the air movement over the fillings (Stock, 1939 a).