The differences in calcium distribution pattern between preodontoblasts and preameloblasts in developing rat molar tooth germs.

Ultrastructural localization of calcium in preodontoblasts and preameloblasts was investigated using the potassium pyroantimonate technique, and it was confirmed that there were clear differences in calcium distribution pattern between preodontoblasts and preameloblasts. In preodontoblasts, pyroantimonate reaction products were mainly observed in the Golgi region, lateral intercellular spaces, and secretory granules, especially in the distal portion of cell body; however, few were found in mitochondria and on the plasma membrane. In preameloblasts, on the other hand, the precipitates were located in mitochondria, nuclei, and on the inner face of the plasma membrane; however, few reaction products were observed in the intercellular spaces, lysosomelike granules, secretory granules, and stippled materials. Granular reaction product approximately 20-40 nm in diameter adhered preferentially to the growing end of needlelike crystals in the initial enamel matrix.