Olea's Response

Considerable concerns about bisphenol A (BPA) as a potential endocrine disruptor remain controversial among dentists and patients due to the study of Olea et al. (1). Their study has frequently been mentioned in scientific papers as well as in the mass media, popular journals, and books. When I read the paper, I was shocked to find unscientific data related to high performance liquid chromatography (HPLC) analysis. I am concerned about continued reference to this study. Ashby (2) commented on the study in a letter in EHP titled "Bisphenol-A Dental Sealants: The Inappropriateness of Continued Reference to a Single Female Patient," but I feel his comments are insufficient. Olea et al. (1) reported that 90-931 pg of BPA was identified in saliva collected from 18 subjects treated with 50 mg of a bisphenol A diglycidyl methacrylate (bis-GMA)-based sealant on molars during a 1-hr period after treatment. However, based on data presented in their Table 1, this is unlikely. According to Table 1 (1), 50 mg of the sealant should contain 3.7 pg of BPA or 78.7 pg of a mixture of bis-GMA, bisphenol A diglycidyl ether (BADGE), bisphenol A dimethacrylate (BPDMA), and BPA. This mixture (78.7 pg) is equivalent to 48.2 pg of BPA. Assuming that all the components of the mixture leached into the saliva uncured and were degraded completely to BPA within 1 hr, the amount of BPA collected from the saliva should be 48.2 pg. However, their Table 2 (1) showed 1.9-19.3-fold higher values than expected (89.9-931.0 pg). In the "Results," Olea et al. (1) reported that A subject initially selected for treatment had been treated with tooth sealant 2 years earlier; chro-matograms demonstrated the presence of bisphe-nol-A (66.4 pg) and bisphenol-A dimethacrylate (49.2 pg) in her saliva before the second treatment. The results from this subject were excluded from analysis. This finding suggested that 66 pg/hr of BPA may be continually released over 2 years. This is unlikely because the treatment would have been practically impossible. Assuming that 66 pg of BPA leached into the saliva daily, leaching of BPA would have constituted 48.2 mg over 2 years. The BPA content in the sealant was 0.0074% according to their data. Therefore, the original amount of sealant used would have been about 650 g. Even if BPDMA, which is easily hydrolyzed to BPA, is included in the calculation, it would have been approximately 200 g. In their Table …