Protective effect of Copalite surface coating on mercury release from dental amalgam following treatment with carbamide peroxide

The effect of Copalite coating on mercury release from dental amalgam follo wing treatment with 10%, 20%, 30% and 40% carbamide peroxide was assessed i n vitro, using a cold-vapour atomic absorption Mercury Analyzer System. Eig hty samples of dental amalgam were automatically mixed in a dental amalgama tor and condensed into silicon embedding molds. Forty amalgam samples were coated with three uniform layers of Copalite intermediary varnish and the o ther 40 samples were left uncoated. The coated and non-coated amalgam sampl es were exposed for 24 h to 10%, 20%, 30% or 40% carbamide peroxide prepara tions and compared with samples exposed to phosphate buffer. In the noncoat ed samples a significant increase of mercury concentration in solution was found following exposure to all carbamide peroxide preparations tested. Mer cury concentration was directly related to carbamide peroxide concentration . In the Copalite-coated samples, significantly lo lower concentrations of mercury in solution were found as compared to the non-coated samples (P<0.0 1). In conclusion, exposure of amalgam restorations to 10%-40% carbamide pe roxide-based bleaching agents increased the mercury release. Pre-coating of the external amalgam surfaces with Copalite significantly reduced the rele ase of mercury.