后牙种植体支持单冠面高度的三维有限元力学分析

Three-dimensional finite element analysis of influence of occlusal surface height on stress distribution around posterior implant-supported single crown

目的:评价下颌后牙区种植支持单冠(种植单冠)的面高度对种植体周围骨内应力分布的影响。方法:建立右下第二前磨牙种植单冠、近远中天然邻牙、牙周膜、牙槽骨、加载用刚体及模拟杏仁食物的三维有限元模型。采用国际牙科联合会系统(Federation Dentaire International system,FDI)命名法,以44、45、46分别代表右下第一前磨牙、右下第二前磨牙及右下第一磨牙。分别进行单牙最大力(44加载280 N,45加载360 N,46加载480 N)及平均力(44加载140 N,45加载180 N,46加载240 N)独立加载、联合加载(各牙位最大力之和转换为3.7 MPa,均布载荷加载于刚体上表面,刚体与各牙冠部接触点确定关系)及模拟杏仁的食物加载(各牙位平均力之和转换为1.67 MPa,均布载荷加载于模拟杏仁的食物上表面,食物与各牙冠部接触点确定关系),研究种植单冠3种不同面高度(正常高度、低15μm及低30μm)对于种植体周围骨内应力分布的影响。结果:在最大力独立加载时,46、45、44周围骨组织内Von Mises应力峰值分别为82.57 MPa、45.26 MPa、27.79 MPa;在平均力独立加载时,Von Mises应力峰值分别为41.28 MPa、22.63 MPa、13.89 MPa。在联合加载时,种植单冠低30μm与正常高度组相比,45应力峰值降幅为4.6 MPa,降低了0.84%;46应力峰值增幅为7.52 MPa,增加了20.04%;44应力峰值降幅为1.8 MPa,降低了5.84%。在模拟杏仁食物加载时,种植单冠低30μm与正常高度组相比,45应力峰值降幅为0.34MPa,降低了1.62%;46处应力峰值增幅为1.11 MPa,增加了2.66%;44处应力峰值增幅为0.06 MPa,增加了0.54%。结论:在本研究条件下,降低种植单冠面高度30μm范围内,种植体周围骨内应力峰值没有明显的变化。

Objective：To evaluate the effect of the occlusal surface height of a mandibular posterior implant-supported single crown on stress in bone tissues. Methods： Three-dimensional finite element models of the implant-supported single crown replacing the missing fight lower second premolar, mesial and distal natural teeth, periodontal membrane, alveolar bone, loaded rigid body and analog food of almond were established. Using the Federation Dentaire International （FDI） system, the first premolar, the second premolar and the first molar were represented with 44, 45,46. Three occlusal surface heights of the crown were studied： （1） normal height; （2） 15 μm reduction in height; （3） 30 μm reduction in height. The models were loaded by independent loading with maximal occlusal force （44 by 280 N, 45 by 360 N, and 46 by 480 N）and average occlusal force（44 by 140 N, 45 by 180 N, and 46 by 240 N）on the single crown ; combined loading （ maximal occlusal force transformed into uniform load of 3.7 MPa on top of rigid body, in contact with points on the occlusal surface） , and analog almond-like food loading （ average occlusal force transformed into uniform load of 1.67 MPa in simulated food chewing, in contact with points on the occlusal surface）. Results： For maximal biting force under independent loading, Von Mises stress peak values in bone tissues around 44, 45, and 46 were 82.57 MPa, 45.26 MPa and 27.79 MPa; For average biting force, peak values were 41.28 MPa, 22.63 MPa and 13.89 MPa. Under com- bined loading, compared with the normal occlusal surface height group, Von Mises stress peak values decreased 4.6 MPa, by 0.84% ; increased 7.52 MPa, by 20.04% , and decreased 1.8 MPa, by 5.84% , for 45, 46, and 44 in the 30 μm infra-occlusion group, respectively. Under food loading, Von Misesstress peak values decreased 0. 34 MPa, by 1.62% ; increased 1.11 MPa, by 2.66% ; and increased 0.06 MPa, by 0.54% , and for 45, 46, and 44 in the 30 p.m infra-ocelusion group, respectively. Conclusion：Within the limitation of this study, within 30 p.m reduction of the occlusal surface height of im- plant-supported single crown, no significant difference of the peak values was observed.