Autoradiographic demonstration of ipsilateral and contralateral sensory nerve endings in cat dentin, pulp, and periodontium.

In order to determine the location of sensory nerve ending in cat teeth, 3H-proline and 3H-leucine were injected into the left trigeminal ganglion of eight cats aged 6.5-10 months; 24 hours was allowed for axonal transport of radioactive protein to dental nerve endings, and the endings were then detected by autoradiography. The pulps of most ipsilateral (left) teeth contained some labeled axons. These axons ended in the odontoblastic layer and predentin of roots and crown; at the tip of the pulp horn of each cusp, nerve endings also extended as far as 150 micrometer into dentinal tubules. Labeled nerve endings were extremely rare in contralateral (right) teeth; only one tooth of 83 studied (eight cats) contained heavily labeled axons, and one other had faintly labeled axons. Both labeled contralateral teeth were central maxillary incisors. Their labeled axons were unbranched in the root and arborized in the crown to end among odontoblasts and many adjacent dentinal tubules. Labeled periodontal nerve endings were most numerous in the apical one-third of the ligament, with some endings extending as far as the gingiva. The nerve endings in the periodontal ligament were often clustered and appeared to end freely between the collagen bundles; their radioactivity varied in the same way as that of pulp nerves in the adjacent root.