Influence of fluoride and carbonate on in vitro remineralization of bovine enamel.

The influence of fluoride, carbonate, and fluoride in combination with carbonate on the in vitro remineralization of bovine enamel was investigated with the use of a sandwich technique. After demineralization, enamel slices were subjected for 610 h to remineralizing solutions with 0.03 or 1.0 ppm fluoride. At each fluoride level, either 0, 1, 10, 20, or 25 mmol/L carbonate was tested. After 0, 22, 62, 126, 192, 329, and 610 h of remineralization, contact microradiographs were made by Cu K alpha-radiation. At 0.03 ppm fluoride, carbonate had an inhibiting influence on remineralization. At 1.0 ppm fluoride, the inhibiting influence of carbonate changed into a stimulation of remineralizatization at 20 and 25 mmol/L carbonate. At 0, 1, and 10 mmol/L carbonate, fluoride had an inhibiting influence on remineralization. The differences in remineralization between the groups were explained by events concerning crystal growth, i.e., different types of minerals might have precipitated with differences in precipitation rates, and retardation of a precipitation step might have occurred under the various remineralization conditions. There was a mutual influence of fluoride and carbonate on the remineralization process. We conclude that the composition of the remineralizing solution with respect to fluoride and carbonate concentrations is important for the remineralization process.