Nature and mechanisms of dental fluorosis in animals.

Recent studies of dental fluorosis in animals have been reviewed. The aim was to describe studies which have provided information which may be relevant to explaining the mechanisms involved in human dental fluorosis. Studies on rats, sheep, and pigs have provided details of dosage regimens which produce lesions which resemble those described in human fluorosis. In the pig and rat, the plasma fluoride concentrations associated with these dental lesions are of the same order of magnitude as those which may occur in man. Three different kinds of studies in different species have shown that fluoride affects processes occurring during enamel maturation. One study on rats has indicated that fluoride may reduce matrix removal during maturation by an effect on enamel proteases. Many studies have demonstrated accumulation of fluoride in secretory enamel and that fluoride concentrations in maturation enamel are lower than in secretory enamel. This phenomenon had previously been explained by the binding of fluoride to enamel proteins, but recent studies indicate that such binding does not occur. The hypothesis that enamel fluorosis might be caused by general effects of fluoride on calcium metabolism has not been supported by more recent studies. It was concluded that, although the mechanisms involved in dental fluorosis remain obscure, recent animal studies do seem to have provided new information which may prove to be important for our understanding of mechanisms whereby fluoride causes dental fluorosis in man.