Membrane junctions between odontoblasts and associated cells. A freeze-fracture study of the human odontoblastic cell...

The relationship between odontoblasts and adjacent cell structures within the odontoblastic cell layer was analyzed by means of the freeze-fracturing technique. Two principal forms of interodontoblastic cell structures were found. The first was tubular or thread-like in appearance, having a general diameter around 0.1-1.0 micron. From morphological criteria these were believed to represent small, unmyelinated nerve fibers. The second type of cell structure found between odontoblasts was more irregular and heterogeneous in outline, and often lamellar or branched. These slender formations sometimes proved to constitute cellular projections from adjacent odontoblasts or neighboring, subodontoblastic fibroblasts. Both the nerve-like fibers and the irregular branched cells between the odontoblasts showed morphological contact areas with odontoblastic cell bodies. At these sites the intracellular distances were reduced, and characteristic gap junctional complexes occurred. Nerve ending specialization or membrane structures indicating the presence of chemical synapses on the odontoblastic cell surface were not observed.