Mitochondrial granule distribution in tooth germ cells.

Incisor and molar tooth germs of albino rats sacrificed at the eighteenth and twentieth days in utero and one to seven days after birth were studied with light and electron microscopy. Observations of the various stages of tooth development in molars established that intramitochondrial granules in odontoblasts were comparable to the intramitochondrial granules of other hard tissue cells. These electron-dense deposits appeared in mitochondria in an appreciable number only when odontoblasts become engaged in dentin mineralization. When dentin mineralization was advanced the odontoblast mitochondria appeared devoid of these deposits. Mesenchymal cells and preodontoblasts of the pulp were not involved in this activity.