Effect of low levels of fluoride on calcium uptake by demineralized human enamel

The effect of fluoride (ca. 0.1 parts/106) on calcium uptake by enamel was examined under alternating remineralizing and demineralizing conditions. The remineralizing solutions contained either 0, 0.058, 0.104 or 0.138 parts/106 fluoride (ex NaF), while the demineralizing solutions contained no added fluoride. During the demineralization periods, calcium loss was similar for all groups. However, during the remineralizing periods, all levels of added fluoride were found to promote calcium uptake. Calcium levels taken up by the artificial lesions were found to increase with increasing fluoride concentration in solution, and were independent of surface area of exposed enamel. In the absence of fluoride, even under conditions that are considered to be remineralizing, further demineralization took place.