Effect of stopping fluoride administration on the distribution profiles of fluoride in three different kinds of rat bones.

The aim of this work was to explore the reduction of fluoride concentrations in the skeleton after stopping experimental fluoride administration. Fluoride was administered to the rats at varying doses (0, 50, 100 ppm in drinking water) and for different lengths of time (4, 13, 25 weeks). A series of fluoride concentrations across the full thickness of humerus, parietal bone, and vertebra arch in rats were measured by means of an abrasive micro-sampling technique. The distribution profiles of fluoride from periosteal to endosteal surfaces, which were apparently related to the histological structure of these bones, were U shaped in the humerus, V shaped in the parietal bone, and W shaped in the vertebra arch. The average fluoride concentrations in the bones increased significantly with each increasing dose and length of fluoride administration. The relative increments were similar between the different regions or the different bones. After stopping fluoride administration, on the other hand, the relative reduction of the average fluoride concentrations in the bones were 30-100%. They were greatly related to the length after stopping fluoride administration and the dose and length of fluoride administration, but also dependent upon the type of bone and the region examined.