Innervation of the dental pulp during tooth succession in the cat.

The possibility that axons branch to supply the pulps of both the upper deciduous canine tooth and its permanent successor has been investigated by stimulating the pulp of one tooth and recording from the pulp of the other. In cats less than about 14 weeks of age, the permanent canine was too poorly developed to allow electrodes to be applied to it satisfactorily. In 5 of 14 preparations in cats aged 14-23 weeks, compound action potentials were recorded in one canine during stimulation of the other. These responses were not abolished by sectioning the infraorbital nerve or its canine branch in the floor of the orbit or by paralysing the animal, but they were abolished by sectioning the pulp of the permanent canine, indicating that they were due to branched axons. In preparations in which there was no tooth-to-tooth response, there was usually evidence that the pulp of one or other of the teeth did not have a functional innervation. The results indicate that at least some of the nerves which supply the pulp of a deciduous tooth are retained to supply its permanent successor.