Scanning electron microscopic observations of tooth germ in tissue culture with special reference to the migration of epithelial cells.

Tooth germ derived from the mandible of newborn mice was used in this study. The enamel organs were dissected and attached directly to coverslips without using the plasma clot. By this method it was possible, for the first time as far as is known, to attain preparations in which the major part of the outgrowth from the explant consisted purely of epithelial-like cells which probably were aneloblasts. Abundant desmosomes and tonofilaments were confirmed by transmission electron microscopy. Under the scanning electron microscope this outgrowth of epithelial cells revealed characteristic intercellular connections which were divided into four types. 1)In the part nearest to the explant, cell boundaries were indicated with a large number of short microvilli. 2)In the zone beyond the first type, the intercellular connection was represented by bridge-like processes firmly combined with each other. 3)In a still further zone, the tips of bridge-like processes were free from the cell connection and extended to the adjacent cells with the advance of cell migration. 4)In the most peripheral part of the explant, the cytoplasmic processes were capable of further expansion. These cells were soon separated from the adjacent cells to migrate as free cells.