下顎枝垂直骨延長術後 1 年間の咀嚼機能回復の筋電図学的観察 : 口内法サルと口外法サルにおけるリズム咀嚼, 咬合力および咬筋 H 波の比較

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Intraoral vertical ramus osteotomy of the mandible (IVRO) is a most frequently used method for correction of the facial asymmetry by lengthening the mandible vertically mandible. Postoperative relapse of elongated mandibular ramus following IVRO is more likely to result from excessive tension of the masseter-medial pterygoid muscle sling. It is also more likely to be lightened of such muscular tension in the case of extraoral vertical ramus osteotomy (EVRO) in which the masseter-medial pterygoid muscle sling is cut off. The purpose of the present study was to compare postoperative recovery process of masticatory motor function between the monkeys given IVRO and EVRO. Three adult Japanese monkeys were used. In two monkeys, the right mandibular rami were cut with IVRO, whereas the left ramus was cut with IVRO (IVRO Monkey) or with EVRO (EVRO Monkey). After splitting of the rami, metal splints were cemented to the left lower molars for the unilateral ramal elongation. In a Sham Monkey, the right and left rami were cut with IVRO and EVRO, respectively, and no treatment was given for the unilateral ramal elongation. In the Sham-and EVRO Monkeys, the masseter-medial pterygoid muscle sling was separated, and remained unsutured on the side received EVRO. The intermaxillary fixation was applied for three weeks in all monkeys. Concerning masticatory motor function such as natural chewing, producibility of a biting force of 20kg, and the Hoffman (H)-reflex activity in the masseter muscle, follow-up recordings were carried out bilaterally at an interval of about one month for more than one year postoperatively. The results obtained were as follows : 1. Voluntary chewing of raw sweet potato appeared 24 days postoperatively in the Sham Monkey, while the IVRO and EVRO Monkeys recovered it on the postoperative 64 and 68 days, respectively. 2. On the left side with EVRO and right side with IVRO in the Sham Monkey, forced chewing of a silicone tube started on the postoperative 24 and 66 days, respectively. 3. Recovery of 20 kg-biting force in the Sham Monkey occurred 35 and 167 days postoperatively on the left side with EVRO and right side with IVRO, respectively. On the other hand, recoveries of the biting force were observed 200 and 267 days postoperatively on both sides of the EVRO and IVRO Monkeys, respectively. 4. Masseteric H-reflex activity was first restored 66 days postoperatively on both sides of the Sham Monkey. In the EVRO Monkey, the left side with EVRO and right side with IVRO recovered on the postoperative 68 and 200 days, respectively. In the IVRO Monkey, the H-reflex was restored on neither sides over a year postoperatively. From these results, it is concluded that EVRO is superior in less operative invasion of the neuromuscular mechanisms to IVRO probably due to the former method eminent for the separation of the masseter-medial pterygoid muscle sling.
九州歯科学会の論文
1999-02-25

下顎枝垂直骨延長術後 1 年間の咀嚼機能回復の筋電図学的観察 : 口内法サルと口外法サルにおけるリズム咀嚼, 咬合力および咬筋 H 波の比較

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