Effects of Fluoride on Developing Enamel and Dentin of Rat Incisors

Abstract

The effects of fluoride on the developing enamel and dentin of rat incisors were investigated. Rats were treated orally with the anti-neoplastic agents, Tegafur and ethyl t-6-butoxy-5-fluorohexahydro-2, 4-dioxopyrimi-dine-r-5-carboxylate (TAC-278), and NaF at different doses for eight weeks. These anti-neoplastic agents contain fluorine (F) and appeared to release 5-fluorouracil after the treatment. Tegafur and TAC-278 induced mottled enamel characterized by pigment-free and chalky white areas. Histo-pathologically, ameloblasts, at the secretory to maturation stage, showed degeneration and necrosis, and formed a cystic irregular array. In the dentin, there were focal or diffuse hypoplastic defects resulting from degeneration and atrophy of odontoblasts. Microradiographically, calcio-traumatic lines resulting from damage to secretory ameloblasts, and calcio-traumatic zones resulting from damage to ameloblasts at the maturation stage were observed in the enamel. These changes were essentially the same as the abnormality resulting from NaF treatment. The F concentration in the incisors was highest in the NaF treated rats, and lowest in the TAC-278 treated rats. The severity of gross lesion of the incisors and the F concentration in the incisors were well correlated. From these results, it is suggested that, like NaF, an excessive dose of Tegafur or TAC-278 affects the developing enamel and dentin of rat incisors.