不同皮质骨厚度区域的加载正畸微种植体骨整合的组织形态学和生物力学分析

目的研究皮质骨厚度(CBT)对正畸微种植体骨整合的影响。方法选择四川大学实验动物中心的健康雄性成年Beagle犬12只,依据种植钉植入区皮质骨厚度分为厚CBT组与薄CBT组,将48枚微种植体植入12只Beagle犬两侧胫骨,厚CBT组与薄CBT组微种植体分别在距近中干骺端4 cm和2 cm处植入。术后1、3、5、7周处死,作力学拉拔测试和组织形态学研究。结果薄CBT组和厚CBT组1、3、5、7周CBT比较差异均有统计学意义(P<0.05);在第1、3、5周,厚CBT组骨整合、皮质骨体积密度(骨体积/总体积)、相交表面(与骨表面接触的微种植体)均显著高于薄CBT组,第7周时两组间差异无统计学意义;厚CBT组最大拉拔力在1周达顶峰,3周降到最低点,薄CBT组则随时间延长持续上升。结论较大CBT对微种植体初期稳定性有益,而较薄皮质骨更有利于二期稳定性的获得。

Histomorphometric and Biomechanical Analysis on the Osseointegration of Loaded Orthodontic Microscrews Inserted at Different Cortical Bone Thickness Sites

Objective To evaluate the influence of different cortical bone thickness（CBT） sites on the osseointegration of loaded orthodontic microscrews. Methods A total of 12 healthy male adult beagles from Experimental Animal Center of Siehuan University were chosen. Forty-eight microscrews were inserted bilaterally in the tibias of 12 beagles, and divided into thick and thin CBT group. The distance between insertion site and proximal metaphyses of the thick CBT group was 4 cm, and that of the thin CBT group was 2 cm. After 1,3,5, and 7 weeks, the dogs were killed and their bone-screw specimens were prepared for microscopic computerized tomography（μCT） analysis and biomechanical pull-out testing. Results The CBT data was significantly different between the thick CBT and thin CBT group in week 1,3,5,7 （ P 〈 0. 05 ）. In the thick CBT group,the indexes of OI,BV/TV ,IS were all significantly higher than those in thin CBT group in week 1,3,5 ,but the difference was not significant in week 7 after insertion. Fmax of microscrews in the thick CBT sites reached a peak in week 1 ,but dropped to the lowest level in week 3. And Fmax of the thin CBT group increased with the prolongation of time. Conclusion Relatively larger CBT is beneficial to the primary stability of the microserews,whereas thinner CBT is more appropriate for achieving long-term stability.