Effects of bicarbonate on remineralization of enamel.

Enamel surfaces were demineralized in acetic acid and remineralized in solutions that contained 1.5 mM calcium, 1.0 mM phosphate, and 0.0, 5, 15, and 25 mM NaHCO3, and 0.00 or 5.0 mM Naf at pH 7.0. NaF in CO2-free solutions increased the rates of calcium and phosphate uptake during remineralization. Bicarbonate in NaF-free solutions caused small increases of calcium and phosphate uptake. Bicarbonate with NaF in solutions synergistically increased calcium uptake, but did not affect phosphate uptake. Bicarbonate reduced fluoride uptake by about 50% during remineralization, and increased the Ca/P ratios of deposited minerals from about 1 (dicalcium phosphate) to approach and exceed the ratios of apatites.