Although
pit and fissure sealants have been utilized extensively in dentistry as a way of preventing occlusal caries, results described by Olea et al. (1996) raised concerns about the safety of sealants and other resin-based
dental materials due to the reported presence of
bisphenol A (BPA) and its dimethacrylate
ester (BPA-DM). Although the release of these compounds from
dental materials has not been substantiated by two subsequent studies, we believed it was important to confirm or refute the report that BPA and BPA-DM have estrogenic activity in vitro. We grew
breast cancer cells (MCF-7, T-47D, ZR-75-1) known to proliferate under estrogenic stimulation in
phenol red-free DMEM containing human serum and concentrations of BPA or BPA-DM ranging from 10(-8)M to 5 x 10(-6)M. After 1 week, plates were harvested for
crystal violet or
sulforhodamine-B assays, and the optical densities of groups of treated cells were compared with values from control cells. At concentrations at or above 10(-6)M, both BPA and BPA-DM significantly increased cell proliferation (p < 0.05), comparable to the increase seen with 10(-9)M of
estrogen. Flow cytometric methods demonstrated that these mitogenic effects occurred within 24 h of exposure to
estrogen, BPA, or BPA-DM. The increase in
DNA synthesis was analogous to that seen with
estrogen stimulation. Thus, we confirmed that BPA and BPA-DM cause cell proliferation at micromolar concentrations that exceed the effective concentrations of
estrogen by 1 to 10,000-fold.