The Effect of Tin on the Corrosion Behavior of the Ag-Hg Phase of Dental Amalgam and Dissolution of Mercury

Abstract

The anodic polarization behavior of the Ag-Hg matrix phase of dental amalgam (γ1) and the rate of mercury dissolution were examined as a function of the tin content. The objectives were to determine the effect of tin on the electrochemical behavior and dissolution of mercury and to provide evidence on whether tin dissolves in the γ1 phase or precipitates as a tin-rich phase. Anodic polarization curves were recorded for specimens of the γ1 phase containing 0-1.5% Sn and for the γ2 phase and a γ2-containing dental amalgam, in synthetic saliva. Mercury dissolved in synthetic saliva in 24 h was determined for the γ1 phase containing 0-1.0% Sn, with cold-vapor Atomic Absorption Spectrophotometry used for mercury analysis. Tin induced passive behavior of the γ1 phase and suppressed mercury dissolution. The passive γ 1 phase did not exhibit a breakdown of passivity occurring at the γ 2 phase. The results were consistent with the tin presence in γ 1 in a solid solution, rather than in tin-rich precipitates, and indicated that at least 1.5% Sn can be dissolved in γ1 at 37°C.