OCCURRENCE OF ATYPICAL CRYSTALS IN HUMAN CELLULAR CEMENTUM FIXED IN PHOSPHATE-BUFFERED FIXATIVES

In some specimens of cellular cementum, atypical crystals were observed around the circumference of some of the lacunae and the large unmineralized areas close to the cemento-dentinal junction. These crystals were only observed in the specimens fixed in phosphate-buffered fixatives, and not in specimens fixed in cacodylate buffered fixatives. The number varied from a few scattered crystals to a zone 3-4 μ in width. The crystals appeared as electron-dense rods or needles and as less electron-dense plates of varying size. The largest were mostly between 1500 and 2000Å in length and were thus considerably larger than the ordinary crystals of cementum. These large crystals were considered to be artifacts brought about by the phosphate ions in the fixative which might have caused precipitation in areas of high calcium concentration. In one specimen intracellular electron-dense deposits were observed in several of the cementocytes and in cells in the unmineralized areas. The possible nature of the deposits is discussed. © 1969.