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目的:对上颌第一磨牙远中移动时牙周膜的应力分布进行非线性有限元分析,并与线性分析结果比较,为临床提供生物力学依据。方法:采用Mimics、Geomagic、Pro E、Ansys Workbench等软件相结合的方法,建立包含上颌第一磨牙、牙周膜、牙槽骨、骨松质、骨皮质、颊面管的三维有限元模型,分别将牙周膜材料设定为非线性材料和线弹性材料,模拟临床远移上颌第一磨牙的操作,使用不同组合的负荷方式进行加载。结果:非线性模型中,牙周膜Von Mises等效应力峰值分布和压应力峰值分布均存在低应力通道:当符合条件Mt/F-Mr/F≈2时,等效应力峰值处于较低水平;当符合条件Mt/F≈Mr/F时,压应力峰值处于较低水平。线性模型中,牙周膜相关应力值均较高且变化剧烈,无低应力通道。结论:牙周膜应力分布存在低应力通道,远中移动上颌第一磨牙时,应尽量使施加的力偶矩与力比值满足低应力条件。
OBJECTIVE: To analyze the stress distribution of periodontal ligament during distal movement of the maxillary first molar by nonlinear finite element analysis and compare with the results of linear analysis to provide biomechanical basis for clinical practice. Methods: The three-dimensional finite element model of maxillary first molar, periodontal ligament, alveolar bone, cancellous bone, cortical bone and buccal canal was established by combining the softwares of Mimics, Geomagic, Pro E and Ansys Workbench. The periodontal ligament material was set as non-linear material and linear elastic material to simulate the clinical operation of distal maxillary first molars. Different loading methods were used to load the periodontal ligament. Results: In the non-linear model, the distributions of Von Mises equivalent stress peak and compressive stress peak in the periodontal ligament both have low stress path: when the condition Mt / F-Mr / F≈2 is satisfied, the peak value of equivalent stress is at a low level ; When the condition Mt / F ≈Mr / F is satisfied, the compressive stress peak is at a low level. In the linear model, the stress values of periodontal ligament were both higher and more violent, with no low stress channel. CONCLUSIONS: There is a low stress path in the stress distribution of the periodontal ligament. When the maxillary first mover is moved distally, the ratio of moment of force to force to be applied should meet the condition of low stress.