组合式下颌骨延长器的研制与动物实验**☆

背景：目前牵引器的发展趋势为由外置式向内置式，由手动加力向自动化加力，由一维向多维发展。 目的：研制、开发一种具有口内型及口外型下颌骨延长器优点的组合式下颌骨延长器，通过动物实验观察其骨延长效果。 设计、时间及地点：随机对照动物实验。组合式下颌骨延长器的研发于2004-10/2005-12由河北医科大学厚朴口腔种植中心与河北医科大学口腔医院口腔颌面外科共同完成。动物实验于2006-06/2007-06在白求恩国际和平医院动物实验场完成。 材料：自行设计研制的组合式单侧下颌骨延长器由固位臂、固位臂连接杆、导向杆及调节螺杆组成；组合式双侧下颌骨延长器由中心镙杆，导向杆，水平杆和固位臂组成，最大延长量35 mm。 方法：12只健康生长期山羊按牵张后稳固时间随机数字表法分为固定1周组，固定2周组，固定3周组和固定4周组，每组3只。行双侧下颌骨牵张术，以自制延长器固定。经7 d延迟期，以0.5 mm/次的速度牵张，2次/d，连续10 d。分别于固定期第1，2，3，4周处死4组动物(处死前6，12 d给予四环素口服)，摄双侧下颌骨俯位片，留取标本。 主要观察指标：大体观察动物术后牵引器稳定情况；上、下颌咬牙合关系，两侧颞下颌关节及新生骨区域各层软组织愈合情况；光镜观察不同时期新生骨组织组织学特点；四环素荧光染色观察新骨生成的速度；扫描电镜观察固定4周组动物髁状突软骨表面超微结构变化。 结果：实验研制了具有口内、口外下颌骨牵引器优点的组合式下颌骨延长器。动物实验观察下颌骨延长量为(8.90±0.52)mm；新骨由骨断端向牵张中央区域生长，颊舌侧隆起，色泽稍暗，表面稍粗糙，中央部位稍软。下颌骨侧位X射线平片显示，牵引间隙影像密度随固定时间延长逐渐增高；术后4周，牵引间隙中心可见小块锯齿状透射区。组织学观察：固定期1周时，牵引间隙内为大量排列规则的胶原纤维，截骨线两端边缘处可见少量针状新生骨小梁；随固定时间延长，骨小梁增粗、钙化；至固定期4周时，牵引间隙内可见较完整的编织骨，新生骨小梁改建活跃，排列与牵引方向一致。四环素荧光染色观察：随固定时间延长，荧光带连续性增强，亮度增高。髁状突表面被覆光滑纤维软骨组织，扫描电镜可见髁状突软骨表面有浅波纹状结构，凝胶状物覆盖完好，表面可见细小点线状结构。 结论：组合式下颌骨延长器设计合理，结构简单；具有一定的科学性、适用性和经济性；可成功延长下颌骨，成骨效果良好。

Developing of a combined mandibular distractor and its animal experiment

BACKGROUND: Current tractor is developed from external to internal installation and from manual force to automation. OBJECTIVE: To design and develop a new combined mandibular distractor, and to explore the effect bilateral mandibular distraction osteogenesis on temporomandibular joint. DESIGN, TIME AND SETTING: A randomized, controlled animal experiment. The combined mandibular distractor was developed by Houpu Oral Implant Center and Department of Oral and Maxillofacial Surgery, Hospital of Stomatology, Hebei Medical University between October 2004 and December 2005. The animal experiment was performed at the Animal Laboratory of Bethune International Peace Hospital from June 2006 to June 2007. MATERIALS: The self-made combined unilateral mandibular distractor comprised fixed arms, connector bar of fixed arms, oriented rods and turn buckle; the combined bilateral mandibular distractor comprised center worm rod, oriented rods, horizontal rods and fixed arms. The maximal distraction was 35 mm. METHODS: A total of 12 healthy goats were randomly divided into 4 groups (n=3) according to immobilization time (1, 2, 3, 4 weeks). Bilateral mandibular body osteotomy was performed, and fixed with the distractor. After held in a neutral position for 7 days, the bone was distracted at a rate of 0.5 mm per 12 hours for 10 days. The goats were sacrificed 1, 2, 3 and 4 weeks after completion of the distraction (tetracycline 0.5 mg/kg on days 6 and 12 before sacrifice), and the specimens were harvested. The radiographic examination was made. MAIN OUTCOME MEASURES: The distractor condition, occlusion, temporomandibular joint and soft tissue healing in the newly formed bone area were observed. The histological features of newly formed bone were observed by light microscopy; osteogenesis speed was observed by tetracycline fluorescence staining; the change of superficial ultra-structure was observed by using scanning electron microscopy (SEM). RESULTS: The combined mandibular distractor was developed. The average lengthen of mandibular distraction was (8.90±0.52) mm. New bone regenerated from the edge of the distraction gap toward center. The color of new bone was dark, and the surface was rough. The surface of the condyle was covered with the smooth white fibrocartilage layer. The lateral radiographic examination showed there was no new bone formation in the interspaces of the distraction gap immediately after the distraction until 2 weeks later new bone began to regenerate. At 4 weeks, the gap was replaced by the low density bone. The results of light microscopy showed as following: at 1 week group: fibrous tissue and hemorrhage were seen in the center region. Longitudinal new bone trabeculae were observed on both sides of the cut bone ends. With increasing time, the bone trabeculae was thickened and calcified. At 4 weeks, woven bone was observed in the distraction gap, and a network of the new bone had formed. With increasing time, the dispersal fluorescent zone was expanded and the brightness was increased. The surface of condyle was covered by smooth fiberocartilage. Shallow ripple substances were found on the condyle, and the underlying collagen fibers were observed by SEM observation. CONCLUSION: The combined mandibular distractor is scientific, available and economical. It can successfully extend the mandible and promote osteogenesis.