The effect of disinfectants and line cleaners on the release of mercury from amalgam.

BACKGROUND: Dental practices use disinfectants or line cleaners to flush dental unit wastewater lines to minimize odor generation, remove solid waste particles and remove biofilms in dental unit water lines (DUWLs). METHODS: The authors evaluated 47 disinfectants or line cleaners for their potential to release mercury from amalgam waste. They prepared each product concentration according to the manufacturer's recommendations and gently agitated it along with one amalgam specimen for 24 hours. They filtered the combined decanted liquid and rinse and analyzed it for mercury using modified U.S. Environmental Protection Agency method 245.1. RESULTS: Six preparations released significantly more mercury from amalgam (about 17 to 340 times) than did the deionized water control (P < .001). The amount of mercury released by the other disinfectants/line cleaners was not statistically different from that released by the control. The pH values of all preparations ranged from 1.76 to 12.35. CONCLUSION AND CLINICAL IMPLICATIONS: This study and other published reports have demonstrated that preparations containing chlorine release more mercury from amalgam than did some other products and the deionized water control. As a result, the use of these products is not recommended for treating dental office wastewater lines or DUWLs.

Evaluating amalgam separators using an international standard.

BACKGROUND: Most amalgam particles generated during placement and removal of amalgam restorations are captured by chair-side traps and suction system traps and filters. Particles not captured can end up in the wastewater discharged from the dental office. Environmental initiatives to reduce the discharge of mercury-containing products such as dental amalgam waste into the environment have sparked interest in the use of amalgam separators. METHODS: The authors used International Organization for Standardization (ISO) Standard 11,143 for Amalgam Separators in a laboratory test to evaluate the amalgam removal efficiency of 13 commercially available amalgam separators and two commercially available filtration devices not marketed as amalgam separators but that have the potential to be used as such. RESULTS: All 13 amalgam separators and the two filtration devices exceeded the ISO Standard 11,143 requirement of 95 percent amalgam removal efficiency. The authors found statistical differences in the efficiency of the separators and filtration devices. No differences were found between the "empty" and "full" conditions for each separator. CONCLUSION AND CLINICAL IMPLICATIONS: This laboratory evaluation shows that amalgam separators and the filtration devices removed at least 97.05 percent of the amalgam in samples with particle-size distribution as specified in ISO Standard 11,143.

Laboratory evaluation of amalgam separators.

BACKGROUND: Amalgam in dental wastewater is receiving increasing scrutiny from regulators because of national, state and local initiatives to reduce or virtually eliminate the discharge of mercury and mercury-containing items into the environment. Amalgam separators are considered to be one means of reducing the amount of amalgam that dental offices discharge into sewers. The purpose of this study was to evaluate the amalgam removal efficiency of commercially available amalgam separators and the total mercury concentration in the effluent from laboratory testing. METHODS: The authors evaluated the amalgam removal efficiency of 12 amalgam separators according to International Organization for Standardization, or ISO, Standard 11143 for Amalgam Separators. Total mercury concentration in the effluent was calculated using the mass of amalgam particles larger than 1.2 micrometers and the volume of effluent, together with U.S. Environmental Protection Agency, or EPA, Method 245.1 for amalgam particles smaller than 1.2 microm. Total dissolved mercury also was determined. RESULTS: The results show that all 12 amalgam separators exceeded the ISO 11143 requirement of 95 percent amalgam removal efficiency. Statistical differences were found in the efficiencies of the separators. Both the total mercury concentration and total dissolved mercury concentration in the effluent demonstrated large variations. CONCLUSIONS AND CLINICAL IMPLICATIONS: This laboratory evaluation shows that amalgam separators removed at least 96.09 percent of the amalgam in samples with particle-size distribution as specified in ISO 11143. Total mercury concentration and total dissolved mercury concentration in the effluent varied widely for each amalgam separator. Additional research is needed to develop test methods to evaluate the efficiency of amalgam separators in removing small amalgam particles, colloidal amalgam particles and ionic mercury in solution.