Ultrastructural relationships between the sensory nerve terminals and the odontoblast process in the human dental pulp.

Abstract

The relationships between sensory nerve fibers and odontoblast processes in the human dental pulp were investigated primarily with the scanning electron microscope. The nerve fibers in the pulpodentinal border zone ramified from the nerve plexus which formed a dense interlacing network beneath the odontoblast layer. They run along the processes of odontoblasts in the predentin and dentin. In the odontoblast layer, a few nerve fibers were observed along one odontoblast body and some of them had branches which extended to the neighboring body. Axonal varicosities of various sizes were observed not only in the odontoblast layer but also in the predentin and dentin. The diameters of the nerve fibers and varicosities were smaller in the deeper regions of the dentin. The axoplasm of the varicosities contained many mitochondria, vesicles which were 30-150 nm in diameter and glycogen granules. The number of varicosities in the deeper portion of the dentin was greater but the diameters of the varicosities were smaller about 2μm. Thus small beaded varicosities were frequently seen in close apposition to the odontoblast processes in the dentin. The function of the varicosities for sensory perception in the dentin is discussed.