Promotion of bone dissolution by excessive fluoride in acidic buffer solution.

Abstract

In order to quantitatively examine fluoride uptake by bone and the effect on its chemical and physical properties, rat bone was incubated in acidic buffer solutions (pH 5) with fluoride concentrations of 0-1000 ppm F. After 1 wk incubation, there was a substantial increase in the crystallinity of the bone mineral with increasing fluoride concentration in the solution. The calcium concentration in the solutions used for incubation decreased dramatically, with increased levels of fluoride in the solution, approaching a plateau. The phosphate concentration initially decreased, with increasing levels of fluoride in proportion to the decrease of calcium concentration, and then increased when the fluoride concentration of the solution was above 200-300 ppm. These phenomena, when considered with X-ray diffraction data, reflected the formation of CaF2. The increase of the phosphate concentration in the solution suggests that the presence of excessive fluoride in the acidic buffer solution may promote the dissolution of soluble bone apatites, in spite of the dissolution-preventive activity of fluoride.