Is rabbit dentine innervated? A fine-structural study of the pulpal innervation in the cheek teeth of the rabbit.

The pulpal innervation of rabbit premolars and molars has been studied in transverse sections of perfusion-fixed, demineralised specimens using light microscopy and transmission electron microscopy. A mixed population of small myelinated and unmyelinated axons enters the apical foramen to supply the mesial and distal laminae of these continuously growing teeth. The nerve fibres are remote from the preodontoblasts and odontoblasts near the apical end, but in their passage to the occlusal end the pulp becomes progressively narrower and nerve fibres come to lie subjacent to the odontoblasts and postodontoblasts. Counts of myelinated fibres near the apical end and in the occlusal pulp suggested that the myelin is shed near the occlusal end. Most of the dentine in these teeth is tubular and migrates occlusally with supporting odontoblasts. Near the occlusal end, postodontoblasts deposit an atubular tissue which closes the pulpal ends of the tubules. Nearer the occlusal tip the pulpal contents degenerate and become embedded in the forming atubular tissue. Evidence of axon profiles was found near the occlusal end in the pulp, passing through the odontoblast layer and in the dentine tubules adjacent to odontoblast processes. However, many of the tubules contained an odontoblast process only and the atubular tissue was not innervated. Since innervated tubules eventually become closed by atubular tissue it is assumed that the nerve fibres retract from the tubules before their closure. In common with other teeth the function of the pulpal nerve supply is likely to be mostly nociceptive.(ABSTRACT TRUNCATED AT 250 WORDS)