Cytotoxicity of amalgams, alloys, and their elements and phases

The purpose of this study was to compare the relative cytotoxicity of amalgams, alloys, and their constituent elements and phases, by means of a rapid and sensitive in vitro cell culture test. Pure copper and zinc showed intensive cytotoxicity, significantly greater than that of pure silver and mercury. Pure tin was non-cytotoxic. The gamma-one phase (Ag₂Hg₃) revealed moderate cytotoxicity, which was significantly decreased by the additioon of 1.5% and 5% Sn. However, the addition of 1.5% Zn to γ₁ containing 1.5% Sn dramatically increased the cytotoxicity of γ₁ to the same level as that of pure zinc. Whenever zinc was present in amalgams, higher cytotoxicity was revealed. High-copper amalgams showed the same cytotoxicity as a zinc-free low-copper amalgam. The addition of selenium did not reduce the cytotoxicity of amalgam. The cytotoxicity of amalgams was reduced after 24 h. The results of this study suggest that the major contributor to the cytotoxicity of alloy for amalgam is probably copper, while that for amalgam is zinc.