Effect of fluoride on ion exchange, remineralization and acid resistance of surface enamel.

In a system of constant ion activities the rates of F- exchange in enamel, under conditions of exchange alone and remineralization, depended on the concentration of F- in solutions. Acid resistance of surface minerals resulted from exchange of F- for OH- in the enamel at pH 7.0 and 4.5. The level of 0.5 mM NaF, compared to 0.05 and 6.0 mM, caused maximum rates of isotopic exchange of 45Ca and maximum acid resistance of enamel. Similarly low levels of F- may be feasible for use in caries prevention in the absence and presence of remineralization.