Brushite in fibrous dysplasia of the jaw bone

Crystals associated with the maxillary bone in a case of fibrous dysplasia were investigated histopathologically, crystallo-graphically and by infrared absorption spectroscopy. Light microscopically, the crystals showed a transparent and plate-like appearance, and were revealed to be piled, incomplete monoclinic structures up to 250 micron in size by scanning electron microscopy. These crystals were identified as brushite, dicalcium phosphate dihydrate CaHPO4.2H2O, by X-ray microdiffraction and infrared absorption spectroscopic analysis. From consideration of the equilibrium of brushite, it was assumed in this case that inflammation had occurred initially and that the tissue fluid conditions at the site of the lesion had deviated from normal, eventually resulting in the deposition of brushite crystals on the bone apatite. From a crystallographic view point, the mode of occurrence of brushite suggested that the bone at the lesion site would not recover through normal healing.