Effect of sodium hypochlorite and EDTA on mercury released from amalgam.

OBJECTIVES

The effect of sodium hypochlorite (NaOCl) and EDTA on mercury released from dental amalgam was assessed in vitro.

STUDY DESIGN

Fifty-six samples of dental amalgam of similar size were prepared and exposed to a 10-mL solution of either 1% NaOCl, 3% NaOCl, 10% EDTA in 1% NaOCl, or 10% EDTA in 3% NaOCl for periods of 20, 40, and 60 minutes. Mercury concentrations in the solutions were measured by using a cold-vapor atomic absorption Mercury Analyzer System, and the differences between the groups were statistically analyzed.

RESULTS

All amalgam samples exposed to 1% NaOCl and 3% NaOCl-either alone or in combination with EDTA-released mercury into the solutions. Mercury release was significantly higher in the test groups than in the EDTA, distilled water, or phosphate buffer controls (P <.001). Increase in the mean concentration levels of mercury in solution was time-dependent and directly related to NaOCl concentration. The addition of EDTA caused a reduction in mercury levels detected in solution, which was more significant in amalgam samples exposed to 1% NaOCl combined with EDTA (P <.001).

CONCLUSIONS

NaOCl solutions commonly used for root canal cleaning and shaping cause mercury release from dental amalgam and may alter its chemo-physical properties as a sealant for root perforations.