[An experimental study on regeneration of periodontal mecanoreceptors after alveolar segmental osteotomy in the cat].

This study demonstrates the electrophysiological and morphological characteristics of the nerve fibers and its endings in the cat periodontal ligament. Furthermore, it shows regeneration of periodontal nerves after alveolar segmental osteotomy of two groups: the repositioned group and the group in which the segment was moved. Electrophysiological investigation were made by applying various stimuli to the mandibular canine and recording changes in response from the canine periodontal branch of the inferior alveolar nerve. For the sake of morphological investigations, changes in the nerve fiber and its endings were observed by means of the silver stain and histochemical method. Results 1. Both fast-adapting and slow-adapting responses were obtained from normal cats. Latency was short 0.45 +/- 0.07 msec, and mean conduction velocity was about 30m/sec. Vibratory stimulation demonstrated a 1:1 response from 10Hz to 250Hz, with no decrease in amplitude observed during stimulation. Pressure stimulation caused a small-continuous amplitude. 2. Nerve fibers distributed in the periodontal ligament entered from the bottom, together with the pulpal nerve and through some holes in the lateral wall of the bony socket. Scarcely, nerve fibers relating with those running from the gingiva were observed in the cervical region. 3. Both free nerve endings and encapsulated endings occurred in the periodontal membrane. Most free nerve endings were especially numerous in the apical 2/3 and these types were simple and sharp, though a few of them were bumplike, spindlelike or clublike. These latter types were especially numerous in the cervical 1/3, and especially in the area between the canine and the third incisor. 4. In both groups, it was possible to record nerve action potential 4 weeks after the osteotomy. Mean conduction velocity was 6.16 +/- 0.63 m/sec in the repositioned group and 5.41 +/- 0.15 m/sec in the moved-segment group. Mean conduction velocity recovered rapidly 6 weeks after osteotomy to reach 15.85 +/- 1.81 m/sec in the repositioned group and 13.71 +/- 1.91 m/sec in the moved-segment group. Thereafter increase was gradual; 48 weeks after osteotomy, the values were 21.60 m/sec for the repositioned group and 20.00 m/sec for the moved-segment group. Regeneration rates were 71.3% for the repositioned group and 66.0% for the moved-segment group. 5. In both group, fast-adapting responses had recovered 4 weeks after the osteotomy; and slow-adapting responses were clearly recorded 6 weeks after the osteotomy.(ABSTRACT TRUNCATED AT 400 WORDS)