Objectives: The purpose of this study was to determine the amount of leachable bisphenol A(BPA), p-t-butylphenol(p-t-BuP) and p-cumylphenol(p-CP) from brackets immersed in human saliva for 6 and 12 months and also that of the residual BPA, p-t-BuP and p-CP in brackets. Methods: Brackets used were Clear Bracket(Sankin), Plastic Bracket(Tomy), Bondable Plastic Light Wire Bracket(TP), Plastic Edgewise Central Bracket(Ortho), Miura Medium Single Standard Edgewise(RMO) and Mitsuba(MOS). Each bracket made of polycarbonate(PC) was immersed in human saliva at 37°C. The determination of BPA, p-t-BuP and p-CP was performed using HPLC with a fluorescence detector. Results: Before the saliva-immersion, levels of residual BPA, p-t-BuP and p-CP were 3-14mg/g resin, 0.1-49mg/g resin and 0-47mg/g resin, respectively, depending on kinds of the brackets. Leaching of BPA, p-t-BuP and p-CP occurred in different amounts and at different rates, depending on kinds of the brackets. After the immersion for 12 months, the levels of leached BPA ranged from 6 to 69mg/g resin, while those of leached p-t-BuP and p-CP did from 0.1 to 0.9 and 0-3mg/g resin, respectively. The level of residual BPA significantly increased by about 140 times that of the original value (p<0.05), suggesting that PC is hydrolyzed into its components under the simulated oral environment. Conclusions: These results suggest that BPA, p-t-BuP and p-CP are migrated from the bracket into the oral environment during the orthodontic therapy. Though the levels of leached BPA, p-t-BuP and p-CP were very low, those of residual BPA, p-t-BuP and p-CP increased duration-dependently, suggesting that it is desirable to avoid the long-term use of orthodontic bracket made of PC. This study was supported by Health Sciences Research Grants from the Ministry of Health, Labour(H13-IYAKU-004) and Welfare of Japan and by Grand-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan(14370627).

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