骨内型镁合金牵引器在犬牙槽骨垂直骨增量中的应用

Application of intraosseous magnesium alloy distractor in vertical bone augmentation of dog alveolar bone

背景:牙槽骨牵张成骨由于治疗周期长、二次手术创伤等限制了临床的广泛应用,镁合金作为可降解的生物金属材料可以制作成牵引器解决牙槽骨的软硬组织缺损问题。目的:探讨运用自行研制的骨内型镁合金牵引器垂直牵引犬下颌牙槽骨的可行性。方法:选取9只犬,拔除犬双侧下颌前磨牙,形成萎缩牙槽嵴模型。选取右侧下颌骨为实验侧,左侧为对照侧。3个月后选取右侧下颌骨行骨切开术形成输送盘,并植入1枚牵引器,1周后开始牵张,2次/d,每次0.5 mm,共6 d。固定期3个月后将犬麻醉处死并解剖下颌骨进行大体、X射线片、Micro-CT和组织学观察,并与对照侧进行比较。结果与结论:①9只犬除1只中途死亡并补足后,均成功完成牙槽骨的垂直增高,游标卡尺测量实验侧较对照侧增高4.94 mm;②X射线片检查发现牵张间隙消失,新骨密度增加;取出牵引器可见表面出现腐蚀、降解;③组织学检查可见实验侧活跃的成骨细胞和骨小梁结构,以及部分成熟的骨组织;④Micro-CT检查可见实验侧比对照侧骨小梁与牵张方向更一致(P<0.05);实验侧和对照侧相比骨小梁数目、厚度少量增加但无显著差异(P>0.05),分离度减少(P<0.05),新生骨的骨体积百分比(P<0.05)和矿物质密度(P>0.05)增加;⑤提示自行研制的骨内型镁合金牵引器可以成功增高萎缩的下颌骨,并且骨质愈合良好,可为将来牵引器的研制和临床应用提供参考。

BACKGROUND:Long course of treatment and second operation limit the extensive application of alveolar distraction osteogenesis,and the distra ctor made by magnesium alloy as a biodegradable metal mate rial can solve the problem of soft and hard tissue defects of alveolar bone.OBJECTIVE:To explore the feasibility of establishing an expe rimental dog model of vertical alveolar distraction osteogenesis using the custom-made intraosseous distra ctor made by magnesium alloy.METHODS:Nine adult mongrel dogs were provided.The bilateral mandibular premolars were extra cted from expe rimental dogs to form models of atrophic alveolar ridge.The right mandible was selected as the experimental side and the left side as the control side.After 3 months,an alveolar segmental osteoto my was carried out in the right mandible and one intraosseous vertical distra ctor was placed.After a 7-day latency period,the alveolar bone was augmented at a rate of 0.5 mm per times,twice a day for 6 days.After a consolidation of 3 months,the dogs were sacrificed to dissect the mandibles for clinical,X-ray,micro-CT and histological examination.The expe rimental side was compared with the control side.RESULTS AND CONCLUSION:(1)Of the nine dogs,one dog died and was replaced.The rest of the expe rimental dogs obtained the predicted height and the average alveolar ridge was vertically increased for 4.94 mm measured by a vernier caliper as compared with the control side.(2)The X-ray showed that the distraction gap disappeared and the bone density increased.There were obvious cracks on surfa ces of the distractor.(3)Histological examination revealed active osteoblasts and trabecular bone structures,as well as pa rtially mature bone tissue.(4)Micro-CT showed that most of trabecular bone had the same distraction direction(P<0.05);the trabecular thickness and trabecular number slightly increased(P>0.05),trabecular separation decreased(P<0.05)and percentage of bone volume(P<0.05)and bone mineral density increased(P>0.05)in the expe rimental side compared with the control side.(5)It is concluded that the custom-made intra osseous distra ctor made by magnesium alloy can increase the height of atrophy alveolar and obtain a mature new bone,which provides a good theoretical reference for development of alveolar distra ctor and clinical practice of the technique.