An electrophysiological study of canine, premolar and molar tooth pulp afferents and their convergence on medullary trigeminal neurons

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Abstract
This study compared the conduction velocities of tooth pulp (TP) afferents innervating the cat canine, premolar and molar teeth and determined the degree of convergence of afferent input originating in these different teeth on medullary dorsal horn (MDH) neurons. Experiments were conducted on 10 cats anesthetized with chloralose. Single unit extracellular recordings were obtained from the tooth pulp or the MDH. The distribution of conduction velocities of afferents originating in the mandibular and maxillary canines, premolars and mandibular molar were all similar except that the mean conduction velocity of canine afferents was slightly higher than the means for the other teeth. A total of 48 MDH neurons excited by TP stimulation was studied. Most MDH neurons activated by electrical stimulation of 1 of the TP could also be activated by stimulation of 1 or more of the other TP. In addition to the marked convergence from different teeth, most of the TP-activated neurons also had convergent inputs from facial skin and/or intraoral mucosa.