不同速率牵张下颌后下齿槽神经的组织学和超微结构改变

目的 研究不同速率牵张延长下颌骨后下齿槽神经的组织学和超微结构改变，为临床上确立合理而安全的牵张速率提供实验依据。方法 ８只山羊随机分为Ａ、Ｂ、Ｃ三组，Ａ、Ｂ组各３只，Ａ组１ｍｍ／ｄ，Ｂ组以２ｍｍ／ｄ牵张，Ｃ组２只动物为对照。牵张延长下颌骨１０ｍｍ，固定２ｗ处死。取下齿槽神经行组织学，透射电镜观察。结果 牵张动物的下齿槽神经均发生了Ｗａｌｌｅｒ变性，以２ ｍｍ／ｄ牵张组神经退行性病变严重而广泛。超微结构病变主要发生于粗大的有髓神经纤维，而细小的有髓神经及无髓神经纤维未见异常。结论 ２ｍｍ／ｄ牵张会对下齿槽神经造成严重损伤，而１ｍｍ／ｄ牵张速率为较适宜而安全的下颌牵张速率。

Changes of histology and ultrastracture in the inferior alveolar nerve after mandibular lengthening with different rates of distraction

Objective To study the changes of histology and ultrastructure in the inferior alveolar nerve (IAN) after mandibular lengthening with different rates of distractioin, and thus determine the safe rate of mandibular osteodistraction. Methods 8 goats were involved in this study. The mandibles were lengthened with a rate of 1 mm/day for 10 days (3 goats) and 2 mm/day for 5 days) 3 goats) respectively, se the final length of distraction was 10 mm in distracted mandibles. The other 2 goats served as control. Specimens of IAN from all animals were evaluated with histok4c and electron microscopic technique. Results Signs of Wallerian degeneration were observed in all distracted animals. The degeneration was mainly occured in the large myelinated fibers. However, the decrease in unmber of axon were more extensive and Prominent in those nerves distracted at a rate of 2 mm/day. Conclusion Wallerian degeneration are found in IAN after mandibular lengthening. However the rate of 2 mm/day distraction causes serious degeneratoin in IAN. This study suggestes that a rate of 1 mm/dav should be a proper and safe distraction rate for INA during mandibular osteodistraction.