Microhardness of molar teeth in cattle with fluorosis.

Cattle were fed forage containing fluoride at a yearly average of 40 mg of fluoride/kg of forage for 5 or 6 years from the time they were 4 months of age. A significant (P < 0.05) negative correlation was observed between the average microhardness of the 3rd premolar and 3rd molar enamel and the fluorosis score of the 2nd incisor. The microhardness of fluorotic outer molar enamel was only 41% of the microhardness values of enamel from control teeth not exposed to long-term fluoride, and electron probe microanalysis indicated increased fluoride concentrations in the molar coronal cementum, enamel, and dentin. Increased incisor fluorosis scores were diagnostic of softer molar enamel. When severe, such changes may have a detrimental effect on the proper mastication and subsequent nutrition of cattle with fluorosis.