Cytotoxicity of intracanal bleaching agents on periodontal ligament cells in vitro

Intracoronal bleaching of nonvital teeth is a simple and conservative proce dure for esthetic restoration of discolored teeth. However it is possible t hat damage to the periodontal ligament may occur if the bleaching agents co ntact this tissue. The purpose of this study was to examine the cytotoxicit y of intracanal bleaching agents on human periodontal ligament (PDL) cells in vitro. Three bleaching agents, 30% hydrogen peroxide (H2O2), 2.0 g/ml so dium perborate (SP) solution, and 2.0 g/ml SP in H2O2, were diluted from 10 (-3) to 10(-7) with Eagle's minimal essential medium and incubated with PDL cells isolated and cultured from extracted teeth. Cytotoxicity was assesse d quantitatively by determining the amount of lactic dehydrogenase activity released from the cells after exposure to the agents for 24 or 72 h. Dose- response curves were plotted, and TD50 values (dilution causing the release of 50% of control lactate dehydrogenase activity) and 95% confidence limit s determined. The rank order of the TD50 values after exposure for 24 h was SP in H2O2 (Most toxic) >H2O2 > SP solution (least toxic). After 72 h SP i n H2O2 Still produced the greatest cytotoxic effect. However the SP solutio n was more cytotoxic than H2O2 at this time point. It is concluded that the mixture of SP with H2O2 was the most toxic to the PDL cells in vitro.