An electrophysiological study of the reinnervation of reimplanted and autotransplanted teeth in the cat.

There is evidence to suggest that some reimplanted and autotransplanted teeth are reinnervated, but the time-course of reinnervation and the properties and source of the reinnervating axons are not known. This reinnervation has been investigated using electrophysiological techniques in 6 adult cats. In each cat, one lower canine and three incisor teeth were extracted and immediately reimplanted. Three other lower incisor teeth were transplanted into an edentulous area. The teeth were splinted in position for 6 weeks. Bipolar electrical stimulation of 22 of the 38 successfully reimplanted or autotransplanted teeth evoked a jaw-opening reflex within 9-24 weeks of the surgery. The reflex had a raised threshold and increased latency. Twenty-four weeks after reimplantation or autotransplantation, 32 of the 38 teeth contained nerve fibres travelling in the ipsilateral inferior alveolar nerve but, compared with normal, the fibres had decreased conduction velocities and produced small amplitude compound action potentials in the teeth when stimulated. Seven of the reimplanted teeth contained nerve fibres travelling in the contralateral inferior alveolar nerve. These results suggest that reimplanted and autotransplanted teeth may be reinnervated but the axons are small in diameter, and either few in number or mainly located near to the apices of the teeth. Reimplanted teeth may be reinnervated by axons from the nerve which supplied them originally or by sprouting and ingrowth of axons from nerves supplying adjacent tissues.