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 (gamma 1) 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 gamma 1 phase or precipitates as a tin-rich phase. Anodic polarization curves were recorded for specimens of the gamma 1 phase containing 0-1.5% Sn and for the gamma 2 phase and a gamma 2-containing dental amalgam, in synthetic saliva. Mercury dissolved in synthetic saliva in 24 h was determined for the gamma 1 phase containing 0-1.0% Sn, with cold-vapor Atomic Absorption Spectrophotometry used for mercury analysis. Tin induced passive behavior of the gamma 1 phase and suppressed mercury dissolution. The passive gamma 1 phase did not exhibit a breakdown of passivity occurring at the gamma 2 phase. The results were consistent with the tin presence in gamma 1 in a solid solution, rather than in tin-rich precipitates, and indicated that at least 1.5% Sn can be dissolved in gamma 1 at 37 degrees C.