Specialized Cells in the Inner Dental Epithelium

¹ Georgetown University, Schools of Medicine and Dentistry, Department of Anatomy, Washington, D.C.

This investigation was designed to extend our knowledge concerning the significance and role of a slender type of cell visualized in the inner dental epithelial layer. Serial undecalcified sections of developing rat molars (birth-10 days) were stained with Gomori's cobalt technique for alkaline phosphatase. A slender type of cell was consistently observed in the inner dental epithelium. The outstanding characteristic of these cells was a marked alkaline-phosphatase-positive reaction. Apparently originating from the stratum intermedium, they were observed singly and in small groups at irregular intervals. They started to appear just prior to and during differentiation of odontoblasts, and were no longer observed after enamel matrix production began. Since these cells do not seem to participate in the production of enamel matrix in the way that ameloblasts do, the question arose whether they were left included in the matrix. Thin homogeneously stained areas consistently observed between forming enamel rods were suggested as residual protoplasm of the original slender cells observed in the inner dental epithelium. Two possible roles were assigned to the slender cells: (1) stimulating cell differentiation (odontoblasts), and (2) serving as pathways for diffusion of elements to the forming enamel rods (interrod substance).