Factors affecting mercury release from dental amalgam exposed to carbamide peroxide bleaching agent

Purpose: To assess, in vitro, the effects of aging and surface polishing on mercury release from dental amalgams exposed to 10% carbamide peroxide at two pH levels. Methods: Samples of fresh and aged amalgam, polished and unpolished, were treated with 10% carbamide peroxide at pH 4.5 and at pH 6.5 for periods of 1, 4, 7, 10 and 13 days. At each time period, mercury concentrations in solution were measured using a cold-vapor atomic absorption mercury analyzer system and compared to control samples treated with phosphate buffer. Results: Amalgam samples exposed to 10% carbamide peroxide released significantly more mercury in solution than samples exposed to phosphate buffer controls. Mercury release was time-dependent and significantly higher in aged amalgam than in fresh amalgam (P<0.001). Mercury release was also pH-dependent and higher in unpolished amalgam.