Risk assessment of root canal disinfectants in terms of endocrine-disruption and development of their substitutes

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In this study, estrogenic activities of four root canal disinfectants; Formalin/Cresol (FC), Formalin/Guaiacol (FG), p-Chlorophenol/Guaiacol (Methocol^【R!○】), and Guaiacol (Creodon^【R!○】), and their components were investigated in vitro and in vivo.By in vitro reporter gene assay, Methocol was found to demonstrate estrogenic activity at 10μg/mL or greater, and p-Chlorophenol and p-Cresol were estrogenic at 50 μM and over. For FC and FG, the activity could not be determined as the cells were killed due to the toxicity of the specimens even at the least concentration tested. The estrogenicity shown by Methocol is considered to be dependent upon p-Chlorophenol, and it is possible that FC exhibits estrogenic activity as it contains p-Cresol.In vivo estrogenicities of the four disinfectants and the components were studied by uterotrophic assay using ovariectomized rats. Disinfectants were administered at 15 μL/kg/day and, the componentsat 50 mg/kg/day. For any of the specimens, no change in the weight or morphology of ovary was observed, indicating that these chemicals were not estrogenic in vivo.These results indicate that estrogenicities of root canal disinfectants tested were negligible under in vivo condition, although some of their components showed estrogenic-activity by in vitro assays.