MICRO-RADIOGRAPHY OF THE EFFECT OF ACUTE AND CHRONIC ADMINISTRATION OF FLUORIDE ON HUMAN AND RAT DENTIN AND ENAMEL

The effects of water-borne and single injections of fluoride on developing enamel and dentine were examined in human teeth and the continuously-growing incisors of rats by microradiography. Single injections produced hypermineralized zones followed by hypomineralized zones in both enamel and dentine in both species. Water-borne fluoride produced extensive hypomineralization of enamel and an accentuation of the incremental pattern in dentine in both species. Thus, dental fluorosis is an abnormality of both enamel and dentine. The nearly simultaneous development of hyper- and hypo-mineralized zones in the acute response in enamel and dentine may be explained by a hastening of crystal growth concomitant to an inhibition of apatite nucleation by fluoride. The pathogenesis of the lesions resulting from the chronic administration of fluoride is obscure, but the mechanisms may be of a generalized nature as both enamel and dentine react in a similar way, i.e. an inhibition of mineralization. © 1979.