种植钉辅助扩弓后腭中缝断裂的有限元模型建立

Establishing the Finite Element Model of Mid-Palatal Suture Fracture by Microimplant-Assisted Palatal Expansion

目的用三维有限元方法分析扩弓时上颌复合体应力蓄积至腭中缝完全断裂过程的力学特点,并验证模型有效性。方法建立包含种植钉的上颌复合体有限元模型。设定腭中缝屈服强度,以每5 ms加载0.25 mm水平横向位移为载荷,加载至腭中缝完全断裂,同时以临床1例种植钉辅助扩弓患者扩弓前后CT影像结果进行对比验证。结果 0~17 ms,腭中缝应力主要蓄积于腭骨水平板、种植钉周围、腭中缝中后方及颧颌缝;18~60 ms,腭中缝中后部出现裂纹并向前后扩展;61~71 ms,腭中缝中后部、前部、后部依次发生断裂。结论基于断裂力学的种植钉辅助扩弓的三维有限元模型有效,其计算的断裂过程结果更符合临床实际。研究结果为今后更有效研究种植钉辅助扩弓提供力学参考模型。

Objective To analyze mechanical characteristics for stress accumulation of the maxillary complex during expansion until complete fracture of the mid-palatal suture by using the three-dimensional (3D) finite element method, and verify validity of the model. Methods The finite element maxillary complex model containing the microimplants was established. The yield strength of the mid-palatal suture was set,and the transverse displacement of 0. 25 mm was loaded every 5 ms as the load until the suture was completely fractured.The CT images of one clinical patient before and after expansion were compared and verified. Results During 0-17 ms,the stress was mainly concentrated around the microimplants,the middle of the mid-palatal suture and the zygomatico-maxillary sutures. During 18-60 ms,cracks began to occur in the mid-palatal suture, and expanded forward and backward. During 61-71 ms,the rupture path was followed by posterior part of the mid,palatal suture-the front part and the back part. Conclusions The 3D finite element model of microimplant-assisted expansion based on fracture mechanics was effective and the calculated fracture process result were more consistent with clinical practice. The research findings provide the mechanical reference model for more effective research on microimplant-assisted palatal expansion in the future.