The incidence and distribution of branched pulpal axons in the adult ferret.

Previous laboratory studies have revealed that some axons branch to supply the pulps of two teeth, but the incidence of such fibres in different regions of the jaws has not been investigated. The present study has used electrophysiological techniques to determine the incidence and distribution of branched pulpal axons in ferret maxillary and mandibular teeth. Under anaesthesia, pairs of Ag/AgCl electrodes were inserted into cavities in the left mandibular (10 animals) or maxillary (seven animals) teeth. Using these electrodes, electrical stimuli were applied to each tooth in turn, and averaged responses were recorded individually from the other teeth. The responses revealed 14 axons that branched to supply two mandibular teeth and for 13 of these the teeth were adjacent. The responses had latencies of 1-9.8 ms (mean 3.8 ms) and amplitudes of 4-320 microV (mean 49 microV). These axons most commonly branched to supply the second and third premolars, and the canine and third incisor, and the branching point was always within the mandibular canal. Thirty-four branched axons supplying maxillary teeth were found (latency, 1.4-18.8 ms, mean 5.9 ms; amplitude; 5-210 microV, mean 36 microV); 14 of these supplied adjacent teeth and they most commonly innervated the canine and incisors.