单侧完全性唇腭裂植骨患者上颌前牵引矫治的有限元分析

Biomechanics of craniofacial skeleton with cleft lip and palate on maxillary protraction: three-dimensional finite element analysis

目的:探讨唇腭裂患者牙槽突裂植骨前、后上颌骨前牵引的生物力学变化特点,研究植骨前、后以及植骨区吸收时前牵引对唇腭裂颅上颌复合体的影响,为临床上应用前牵引治疗唇腭裂患者上颌发育不足提供理论依据。方法:采用三维有限元方法,在已建立的唇腭裂上颌复合体有限元模型中模拟植骨及植骨吸收,利用Ansys12.0软件,分别对各个模型在双侧上颌尖牙牙槽骨处施加与平面呈30°的牵引力,大小为每侧5N(约500g),模拟临床上的上颌前牵引,分析其生物力学变化情况。结果:相同加载条件下,植骨前患侧的水平位移显著大于健侧,且患侧与健侧骨缝的应力分布不均匀。植骨后,患侧与健侧的位移差值减小,患侧与健侧骨缝的应力分布趋于更均匀。在所观察的骨缝中,应力最大值出现在翼腭缝,其次为颧颞缝、颧颌缝和颧额缝。结论:植骨前对上颌骨进行前牵引,裂隙有扩大化趋势;植骨有利于上颌前牵引矫治力分布更均匀,健、患侧位移变化趋于接近;且植骨不吸收时,上颌前牵引效果最佳。在模拟植骨发生吸收的几种情况中,植骨区上方发生吸收的上颌前牵引效果比植骨区下方发生吸收的前牵引效果差。

PURPOSE： To explore the biomechanical effects of maxillary protraction on the craniofacial skeleton with cleft lip and palate after a alveolar bone graft（ABG）,and to provide a theoretical basis for clinical application of maxillary protraction which can improve the facial deformity of the cleft patients.METHODS： A finite element model of a patient with unilateral cleft lip and palate（UCLP） was constructed to simulate ABG and resorption of ABG.Then a orthopedic force（30° downward and forward to the occlusal plane,500 g/side） was loaded on the region of alveolus of maxillary canine.Three-dimensional features of displacement and stress distribution were analyzed after loading by using Ansys 12.0 software.RESULTS： Before ABG,the cleft side showed larger horizontal displacement than the non-cleft side,when it came to the stress distribution in the craniofacial suture,it showed an asymmetric pattern.After ABG,the horizontal displacement difference between the cleft side and the non-cleft side decreased,and the stress distribution in the craniofacial suture showed more symmetric before ABG.Among the observed sutures,the pterygopalatine suture obtained the largest value,followed by zygomatico-temporal,zygomatico-maxillary,zygomatico-frontal sutures.CONCLUSIONS： Maxillary protraction after ABG had a more favorable outcome.Among the ABG models,non-resorption showed the best effect after loading maxillary protraction force,resorption in the lower region of the grafted bone showed a better effect than resorption in the upper region of the grafted bone.