Evidence for the persistence of axons at the apex of the cat's lower canine tooth after section of the inferior alveolar nerve.

The aim of this investigation was to establish the degree of denervation produced by inferior alveolar nerve section and to provide histological evidence for the presence of pulpal nerve fibres supplying the teeth which do not travel with the inferior alveolar nerve. Four adult cats were used. Each stage of the experiment was carried out under general anesthesia. The left inferior alveolar nerve was exposed and sectioned near the mandibular foramen. After 56 hours and 7 days, respectively, the jaw opening reflex to electrical stimulation of each lower canine was tested. Recordings were made from the left canine during electrical stimulation of the ipsilateral inferior alveolar nerve central and peripheral to the site of section as well as from the ipsilateral and contralateral inferior alveolar nerve during electrical stimulation of the left canine. Recordings were also made from the lingual nerve. After the recordings were completed two animals were perfused 56 hours after inferior alveolar nerve section, two more 7 days after section. Ultrathin sections of the apices of the lower canine teeth were examined in the electron microscope and each nerve fibre photographed. Each axon was examined to determine whether it was degenerating or normal. A jaw-opening reflex could not be elicited by stimulation of the left canine either 2 or 7 days after nerve section, whereas a normal response was evoked by stimulation of the right, control canine. At 2 days small responses could be recorded from the left canine teeth during stimulation of the left inferior alveolar nerve peripheral to the point of section. In one 2-day animal, responses could be recorded in the lingual nerve during stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)