Enamel demineralization under driving forces found in dental plaque fluid

The present study was carried out to examine the kinetics of enamel deminer alization in vitro under driving forces for demineralization (i.e., the deg ree of saturation with respect to enamel, DSEn) similar to those found in d ental plaque fluid, Thin sections of human enamel were exposed at 25 degree s C to lactic acid solutions with DSEn values (DSEn = [(Ca2+)(5)(OH-)(PO43- )(3)/K-En](1/9). K-En = 5.5 x 10(-55)) ranging from 0.28 to 0.79, Lesion de velopment was monitored by quantitative microradiography, Enamel mineral lo ss in solutions with DSEn values of 0.28, 0.32 and 0.36 was first detected after 3, 3, and 7 wk of continuous exposure, respectively. Consistent with previous findings, subsurface demineralization was observed and rates of mi neral loss increased significantly with decreasing DSEn values. However, no mineral loss was observed in sections of enamel exposed to solutions with DSEn values of 0.41 and 0.79, even after 11 months. These results suggest t hat (outer) enamel mineral behaves as a mineral phase that is less soluble than that dictated by the solubility product constant (K-En) used in this s tudy, Furthermore, these results indicate that the kinetics and general fea tures of the demineralization process are maintained over a wide range of D SEn values, including conditions that better reflect those found in the ora l cavity. These findings are particularly relevant to the assessment of the cariogenic potential of dental plaque fluids.