目的 比较植体不同植入深度时Ⅱ类和Ⅲ类骨质中种植体周围牙槽骨应力分布特征，指导临床选择合适的种植方案以均衡应力分布。 方法 利用Abaqus 6.13分别绘制下颌后牙区牙槽骨骨块与Straumann骨水平种植体模型以及下颌第一磨牙的牙冠简化模型。分别加载垂直向200 N、水平向20 N的载荷，观察不同植入深度下种植体周围骨皮质的最大应力和应力分布特征。 结果 当平台转换种植体上表面与骨皮质上表面相平时，可以观察到种植体周围骨组织最大von Mises应力(MVMS)位于骨皮质表面，随着种植体植入深度的增加，骨皮质内MVMS也随之移动，基本保持在种植体上表面周围的骨皮质内，并在种植体上表面位于骨皮质一半厚度时达到MVMS的最低值。 结论 Ⅱ类和Ⅲ类骨质平台转换种植体周围骨MVMS出现于种植体周围皮质骨内，皮质骨的应力集中则主要位于与颈部平台接触区，调整种植体植入深度可以改变皮质骨中应力集中位置。种植体上表面位于牙槽嵴下水平时，有利于减轻牙槽嵴顶皮质骨的应力。

Objective To analyze the Platform Switching implant-supported denture in posterior mandibular area, to compare the maximal stress value of the bone around the implant with the implant depth, and to use the stress distribution around the implants to guide the clinical selection of appropriate planting program. Methods A simplified model of the alveolar bone in the posterior region of the mandible was drawn using Abaqus 6.13. The simplified model of the straight crown of the mandibular first molar was obtained with the Straumann bone-level implant. Abaqus CAE 6.13 was used to perform finite element analysis to observe the maximal stress of the cortical bone around the implant in different implant depths. The maximal stress of the cortical bone around the implant was measured at different implant depths. Results The maximal Von Mises stress (MVMS) of the bone around the implant was observed on the surface of the cortical bone when the upper surface of the implant was shifted to the upper surface of the cortical bone. With the increase of implant depth, the MVMS in the cortical bone moved along the cortical bone around the upper surface of the implant and reached the minimum value of MVMS when the upper surface of the implant was located a half thickness of the cortical bone. Conclusion Bone stress around the platform switching implant MVMS appeared in the peri-implant cortical bone. The stress concentration of the cortical bone was mainly located in the contact area with the neck platform. Adjusting the implant depth could change the stress concentration in the cortical bone. The upper surface of the implant is located below the level of the alveolar ridge, which helps to relieve the stress of the alveolar crest cortical bone.