[Effects of pulpal inflammation on the activities of periodontal mechanoreceptive afferent fibers].

Response properties of periodontal single afferents were investigated in cats with inflammatory irritant-induced pulpitis. A deep dentin cavity was prepared on the right mandibular canine in order to apply an inflammatory agent and small fiber excitant, allyl-isothiocyanate (mustard oil: MO), and single afferents innervating the canine periodontal mechanoreceptor were dissected from the mandibular nerve bundle by examining impulse responses while applying mechanical stimuli to the tip of the crown. Evoked impulses by mechanical stimuli were increased in number for 15 minutes with MO application to the pulp when compared with those with mineral oil. The mechanoreceptive thresholds of single nerve fibers were decreased after the MO application to the pulp when compared with those with mineral oil. These results suggest that the alteration of responses in the periodontal afferent fiber, or the peripheral sensitization, can be produced by MO-induced pulpal inflammation probably due to the axon reflex mechanism in the furcating branches of nerve fibers innervating both the tooth pulp and periodontal ligament.