Dynamic analysis of behavior of bisphenol A in dental resin and leachable compounds

双酚A的量可以通过与自由基的反应和可浸出化合物的水解来动态改变。本研究的目的是通过分析双酚A的浸出现象，考虑到双酚A的量的动态变化，为双酚A从牙科树脂中的浸出提供一个明确的指导。双酚A存在下的自由基聚合为了阐明双酚A对自由基聚合的影响，将双酚A加入甲基丙烯酸甲酯(MMA)的聚合混合物中，并对反应进行了精确的考察。结论：1.树脂聚合后，双酚A不存在于聚合混合物中，因为双酚A通常起到阻聚剂的作用，在牙科树脂聚合过程中会用完少量的化合物。为了阐明双酚A的自由基清除机理，比较了双酚A及其相关化合物在甲基丙烯酸甲酯(MMA)聚合反应中的自由基清除现象，并对结果进行了检验。双酚A的化学计量因数(N)为1.8。结果表明，具有较高缓蚀活性的双酚A在自由基作用下被氧化。过氧化苯甲酰(BPO)对牙科树脂中共存的双酚A无反应，因为与BPO反应549小时后仍未发现新的双酚A反应产物。另一方面，在树脂固化过程中，可见光固化树脂中的双酚A消耗了数十ppm。因此，当双酚A在牙科树脂中的含量为10ppm或更少时，双酚A实际上不会从固化树脂中浸出或因水解而产生双酚A。

The amount of bisphenol A can be dynamically changed by the reaction with radicals and by the hydrolysis of leachable compounds. The purposes of this study is to provide a clear instruction of possible leaching of bisphenol A from dental resins by an analysis of leaching phenomena of bisphenol A, taking into consideration of the dynamic change in the amount.1. Radical polymerization in the presence of bisphenol AIn order to clarify the effect of bisphenol A on radical polymerization, bisphenol A was added to polymerization mixture of methyl methacrylate(MMA) and the reaction was precisely examined. It was concluded that bisphenol A is unable to exist in the polymerization mixture after the polymerization of resin, since bisphenol A acted typically as an inhibitor and a minor amount of the compound in dental resins would be used up during polymerization.2. Clarification of radical-scavenging mechanism by comparing bisphenol A with its related compoundsTo elucidate the radical-scavenging mechanism of bisphenol A, its radical-scavenging phenomenon in the polymerization of MMA was compared with those of its related compounds, and the result was examined. The stoichiometric factor (n) of bisphenol A was revealed to be 1.8. It was indicated that bisphenol A with a high inhibitive activity is oxidized as a result of the radical interaction.3. Dynamic leaching phenomenon of bisphenol A and production of bisphenol A from leachable compoundsIt was demonstrated that benzoyl peroxide(BPO) is unreactive to bisphenol A coexisting in dental resins, since no reaction product of bisphenol A was newly found even after 549 hr of reaction with BPO. On the other hand, several tens ppm of bisphenol A in visible light-curing resin was consumed during the cure of resins. Therefore, it was concluded that leaching of bisphenol A out of cured resins or production of bisphenol A as a result of hydrolysis does not practically occur, when its amount in dental resins is 10 ppm or less.