下颌骨牵张成骨对下牙槽神经影响的实验研究

Effects of Mandibular Distraction Osteogenesis on Inferior Alveolar Nerve

目的 观察狗双侧下颌骨牵张成骨术中不同时间点的下牙槽神经的电生理功能及组织学结构的变化。方法 实验组 :12只狗行保留下牙槽神经的双侧下颌骨截断术 ,装上自制的口内牵张器 ,于术后第 8天开始牵张 ,1mm/d ,共 10d ,牵张长度约 10mm。分别在牵张中第 6天、牵张完毕后固定 2周及 8周时各处死 4只动物。分别在术前及术后的不同时期用电生理方法检测双侧下牙槽神经的传导功能 ,并于处死前取出双侧下牙槽神经进行组织病理学及超微结构组织学检查。对照组 :4只狗 ,其中 2只狗作为对照组 ,未行手术 ;另 2只狗为手术对照组 ,进行与实验组相同的骨切开截断术 ,上牵张器 ,但未行牵张和固定 ,于操作完毕时取出双侧下牙槽神经作为术后的组织学结构标本。结果 实验组动物的下牙槽神经在光镜下显示部分神经纤维稍肿胀变粗 ;电镜下显示部分神经纤维髓鞘的板层松解及脱髓鞘现象 ;电生理结果显示 ,神经传导的速度于截断术后的不同时期均低于术前 ,但仅术后第 8天 (即牵张前 )的传导速度与术前的传导速度差异有显著性 (P <0 .0 1)。结论 对狗的双侧下颌骨进行牵张成骨时 ,可一过性引起下牙槽神经损伤。其损伤的主要原因是手术过程所致。在适当的牵张速率、牵张长度和牢固的固定条件下 。

Objective To study the changes of electrophysiology and structure of the inferior alveolar nerve (IAN) at different times of dog mandibular distraction osteogenesis. Methods 12 healthy adult dogs underwent mandibular osteotomy with reserving IAN. After a 7-day latency period,the mandibles were bilaterally distracted at a rate of 1MM per day using a custom-made intraoral distractor. The bilateral inferior alveolar nerve specimens were harvested respectively at the 6th day (n=4) of distraction, 2(n=4) and 8weeks(n=4) after completion of distraction and processed for histological and ultrastructural evaluation. Another 4 dogs were regarded as control group (2 without operations, 2 with identical operations). The function of IAN was assessed at different times. Results The nerve fiber was slightly swelled and thicker under light microscope, and myelin sheath of nerve fiber was disrupted and tore under electron microscope.The speed of nerve conduction were lower after distraction than that before distraction, but there was not notable discrepancy between them except for the comparison between pre-distraction and pre-surgery. Conclusion Slight degenerative changes of IAN occur in distraction osteogenesis, and the changes are reversible. The osteotomy is the main process which has led to the damage of IAN.