Ultrastructure of nerves in the dentinal-pulp border zone after sensory and autonomic nerve transection in the cat

Abstract

In order to investigate the origin of intradentinal nerve-like structures, unilateral transection of the sensory (inferior alveolar nerve) and/or the autonomic (cranial cervical sympathetic ganglion) supply was performed in 6 cats. After 2—4 weeks, when degenerative change was expected in the cut nerves, electrophysiological recordings from the dentin showed total absence of impulse activity in teeth subjected to sensory denervation regardless of whether or not the autonomic innervation was intact. Control teeth, on the other hand, responded to different local pain stimuli. Electron microscopic study of predentin and inner dentin in control teeth showed intratubular nerve-like structures similar to «associate cells» earlier described in human teeth. In teeth subjected to sensory nerve resection, however, the intradentinal «associate cells» showed advanced degenerative change or were absent. Resection of the sympathetic nerve supply did not influence the appearance of these intratubular structures.

The present results indicate that intratubular nerves are present in predentin and the inner dentin in the cat and that these nerves are of sensory origin. It is further suggested that the intradentinal «associate cells» earlier described in human teeth are sensory neurons.