Effect of fluoride ingestion on dental fluorosis in sheep

The effects of fluoride ingestion (3.5 mg/kg of body weight) were evaluated in 9 ewes at 6 through 9, 10 through 13, or 14 through 17 months of age (3 ewes/age group). In the 3 groups, the plasma fluoride concentration rapidly increased to 0.45, 0.46, and 0.50 microgram/ml, respectively, and decreased rapidly to 0.1 microgram/ml after fluoride was removed from the ration. In 5 of the 9 ewes, this short-term exposure caused symmetrical, moderate damage to the molars, which is characteristic of fluorosis in sheep. In 7 of the 9 ewes, abnormal gaps were found between incisors, which are not characteristic of fluorosis in sheep. Fluoride accumulation was higher in the roots of the incisors and in the dentine of the molars and was particularly evident in teeth that were developing when fluoride was administered; however, the fully developed teeth and teeth that developed several months after administration of fluoride also were affected. The increase in fluoride concentration in the enamel was confined to a maximum of 2 molars. The abnormal wear of the molars was not directly linked to fluoride accumulation.