The effect of fluoride treatment on bone mineral in rabbits

Fluoride therapy has been used clinically for many years, but its use remai ns controversial and many basic questions remain unanswered. Accordingly, t his study returns to an animal model to study the effects of high doses of fluoride on bone mineral in rabbits. Twelve rabbits, aged 3 1/2 months at t he start of the study, received drinking water fluoridated at 100 ppm while their 12 control counterparts drank distilled water. All rabbits were sacr ificed after 6 months. Fluoride was readily incorporated into femoral corti cal bone (7473 +/- 966 ppm F versus 1228 +/- 57 ppm in controls; P < 0.0000 5). Fluoride therapy led to increased mineralization, as measured by densit y fractionation (P < 0.0005 for the distributions). The bone mineral itself was altered, with a significant increase in the width of crystals (66.2 +/ - 2.0 Angstrom versus 61.2 +/- 0.9 Angstrom; P < 0.01). The microhardness o f both cortical and cancellous bone in the femoral head of fluoride-treated rabbits was greater than that in the controls (P < 0.05). The phosphate, c alcium, and carbonate contents in the bone was the same in both groups. Fin ally, fluoride administration did not affect the architecture or connectivi ty of cancellous bone in the femoral head. Previously published data [1] in dicated that the mechanical properties of bone were adversely affected; thi s suggests that the effect of high doses of fluoride on the strength and st iffness of bone may be mediated by its effect on bone mineral.