Review of fluoride research since 1959.

The evidence for the two main hypotheses proposed for the mode of action of F in reducing caries is reviewed. The current conclusion is that low concentrations of F in plaque, which need frequent renewal, favour remineralization of dental tissue (i.e. a net reduction of demineralization) in the later stages of a cariogenic episode. This replaces the other view that a high concentration of F in the tooth mineral reduces its solubility.