The weight of wastes generated by removal of dental amalgam restorations and the concentration of mercury in dental wastewater.

OBJECTIVE To determine the amount of amalgam entering the waste stream during removal of dental amalgam restorations. METHODS Dental amalgam restorations were removed from anatomic replica teeth and natural teeth by means of a tungsten carbide bur, a high-speed handpiece and a conventional suction system. The weight of amalgam particles trapped in the primary and secondary solids separators was determined. Amalgam particles were filtered from wastewater with 15-microm filter paper and weighed. The concentration of total mercury in the effluent collected (by instantaneous flow-through) during the removal of amalgams, with and without an ISO-certified separator, was measured by means of cold-vapour atomic absorption spectrophotometry. RESULTS About 60% by weight of the amalgam removed was found in the effluent, about a third was retained in the primary solids separator and less than 10% was retained in the secondary solids separator. The ISO-compliant separator reduced the concentration of mercury in the instantaneous flow-through discharge by 99.4%, from 31.2973 mg/L to 0.1800 mg/L. CONCLUSIONS About 60% of the waste generated during the removal of amalgams escaped the primary and secondary solids collectors and was released into the wastewater. An ISO-certified amalgam particle separator was effective in removing the amalgam from the wastewater.