The effect of fluoride treatment on bone mineral crystals in the rat.

In order to investigate the effect of fluoride on bone mineral crystals, we gave groups of female rats 8 mM NaF/L water and distilled water to control groups. The rats were sacrificed at six weeks, three months, and six months. The fluor content of the bone was determined by neutron activation. X-ray diffraction showed no difference in bone crystal size/strain with fluoride treatment. Fourier transform Infrared Spectroscopy (FTIR) showed an increased crystallinity in fluoride-fed animals, which seems to be associated with a decrease of labile phosphate environment. Three carbonate bands have been found in fluoridated and normal bone samples. The distribution of carbonate ions on type A and B sites is strongly affected by fluoride. Type A carbonate is always present in bone, but decreases with increasing bone fluoride content. A carbonate band found at 866 cm-1 may correspond to a fluoride interaction with type B carbonate ions. Lastly, phosphate bands have been found to be shifted towards high wave number, which is probably related to the change in unit cell size induced by the fluoride ion. All these changes induced by fluoride reduce the solubility of bone crystals by direct incorporation of fluoride ions in the apatite lattice and by decreasing the labile phosphate environments.