Calcium fluoride in demineralized bones from rats with experimental chronic fluorosis

Thirteen male rats, 7 or 10 months old, were given 0.005% NaF in the diet or 0.025 NaF in the drinking water fro periods of 3 to 20 weeks. Femur/tibia bones were demineralized in 3.25% HNO3, the process being watched on radiographs. As soon as all radiopaque material representing mineralized bone had disappeared, demineralization was discontinued. In some instances the process was stopped while some radiopaque material was still present. Hematoxylin-eosin stained paraffin sections from all bones showed deep blue granules, fluoride granules. Transmission electron microscopy and selected area diffraction revealed that the fluoride granules contain microcrystalline CaF2. X-ray diffraction of hydrazine-deproteinated, demineralized fluorotic bones revealed the presence of CaF2 and a minor unidentified component. The results are discussed in relation to (1) the identity of the fluoride granules, and (2) their inconsistent presence in demineralized hard tissues.