种植体-基台连接形式对种植体周围骨组织应力分布的影响

目的分析种植体-基台连接形式对种植体周围骨组织应力分布的影响，从生物力学角度探讨平台转换连接形式防止或减少种植体周围骨吸收的可能机制。方法利用COSMOSM2．85软件包建立种植体支持的下颌第一磨牙三维有限元模型，种植体-基台的连接形式分别采用平齐对接（模型A）和平台转换（模型B）。采用垂直和斜向两种形式加载，载荷均为200N，比较两种模型种植体周围骨组织的应力分布情况以及种植体-骨界面颊舌侧相同位置的von Mises应力大小。结果不同加载条件下两种模型种植体周围骨组织应力集中在种植体颈部颊舌侧骨皮质内，斜向加载时最大von Mises应力值高于垂直加载时。模型A和模型B骨组织内最大von Mises应力值在垂直加载时，分别为11．61MPa和7．15MPa，斜向加载时分别为22．07MPa和11．87MPa。距离种植体-基台连接处越远，von Mises应力值越小，骨皮质到骨松质交界处的应力变化最明显。与模型A相比，模型B种植体-骨界面相同节点的最大von Mises应力值较小。结论与平齐对接形式相比，平台转换设计可改善种植体周围骨组织的应力分布，降低种植体颈部骨组织所受的应力。

Influence of implant-abutment connection mode on stress distribution in peri-implant bone

Objective To investigate the influence of butt joint connection and platform switching design of implant-abutment connection on the stress distribution in peri-implant bone. Methods Three- dimensional finite element models of implant-supported mandibular first molar with different implantabutment connections were computed by COSMOSM 2. 85. Traditional butt joint connection was used in model A and platform switching design in model B. Loading conditions were a vertical load of 200 N and inclined load of the same magnitude at 45 degrees to the vertical axis of the implant. Stress distribution in peri-implant bone and von Mises stresses at the same point of buccal and lingual implant-bone interfaces in two models were compared. Results Stresses concentrated in peri-implant cortical bone at the neck of implants on the buccal and lingual sides ; maximum von Mises stresses under inclined load were higher than those under vertical load. Maximum von Mises stress in bone was 11.61 MPa in model A and 7. 15 MPa in model B under vertical load, and 22. 07 MPa in model A and 11.87 MPa in model B under inclined load respectively. Von Mises stresses decreased as the distance from implant-abutment junction increased and the most obvious change occurred at the interface between cortical bone and spongy bone. Von Mises stresses at the same points of buccal and lingual implant-bone interfaces in model A were higher than those in model B. Conclusions Compared with butt joint connection, platform switching design improved the stress distribution and decreased the maximum stresses in peri-implant bone around implant cervix.