Objectives: Because BPA is a chemical substance suspected as one of endocrine disruptors, the level of leachable bisphenol A (BPA) in orthodontic bracket made of polycarbonate(PC) has become serious problems from the point of view of the clinical treatment. The purpose of this study was to determine the amount of leachable BPA and p-t-butylphenol(p-t-BuP) from the brackets immersed in human saliva for 4 and 12 weeks and that of residual BPA and p-t-BuP in brackets. Methods: Brackets used were Clear Bracket(Sankin), Plastic Bracket(Tomy), Bondable Plastic Light Wire Bracket(TP) and Plastic Edgewise Central Bracket(Ortho). Each bracket was immersed in human saliva at 37°C. The determination of BPA and p-t-BuP was performed using HPLC with a fluorescence and electrochemical detector. Results: Before the saliva-immersion, levels of residual BPA and p-t-BuP were 15-84mg/g resin and 3-64mg/g resin, respectively, depending on kinds of the brackets. Leaching of BPA occurred in different amounts and at different rates, depending on kinds of the brackets. After the immersion for 12 weeks, the levels of leached BPA ranged from 5 to 35mg/g resin, while those of leached p-t-BuP did from 0.3 to 0.7mg/g resin. The levels of residual BPA significantly increased several times the original value (p<0.05), suggesting that PC is decomposed into its components under the simulated oral environment. Conclusions: These results suggest that BPA and p-t-BuP are migrated from the bracket into the oral environment during the orthodontic therapy. As the levels of leached BPA and p-t-BuP were very low, its levels may not affect human health presently. This study was supported by Health Sciences Research Grants from the Ministry of Health and Welfare of Japan and by Grand-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.

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