Liu Guanqi, Deng Shudan, Chen Xiaoyan, Lin Jiahui, Liu Runheng
Hospital of Stomatology, Guanghua School of Stomatology, Sun Yat-Sen University and Guangdong Provincial Clinical Research Center of Oral Diseases, Guangzhou, China.
Front Bioeng Biotechnol. 2025 Feb 25;13:1546656. doi: 10.3389/fbioe.2025.1546656. eCollection 2025.
This study aims to investigate the stress distribution in bone tissue, implant, abutment, screw, and bridge restoration when the mesial implant is placed axially and the distal implant is inserted at varying angles in the posterior maxillary region with free-end partial dentition defects, using three-dimensional finite element analysis.
Cone-beam computed-tomography were utilized to create 3D reconstruction models of the maxilla. Stereolithography data of dental implants and accessories were used to design a three-unit full zirconia bridge for the maxillary model. The 3D models were imported into ANSYS Workbench 23.0 software for mesh generation and material property definition. Five different distal implant implantation directions were designed: Inner Tilting 30° group, Inner Tilting 17° group, Parallel group, External Tilting 17° group, and External Tilting 30° group. The models consisted of cortical bone, trabecular bone, implants, abutments, central screws, prosthesis screws, and prostheses. Material properties were assumed to be isotropic, homogeneous, and linearly elastic. The maxillary models were subjected to strict fixation restrictions, and the implants were considered fully osseointegrated. Two loading types were set in ANSYS Workbench 23.0: a vertical load of 300N and a lateral load of 300N at a 45°angle to the implant.
Under vertical loading, the parallel group exhibited the lowest maximum stress across all implants, crowns, abutments and screws. Greater tilt angles increased abutment stress, with the external tilting 30° group reaching 1,426 MPa (close to titanium alloy's yield strength). Smaller angles of both external tilting and inner tilting shifted stress to implants from abutment and screw. During lateral loading, the external tilting 30° group showed catastrophic stress escalation (abutment: 8,612 MPa), exceeding titanium's yield limit. Bone stress remained physiological except for the internal tilting 30° group under lateral loading (142 MPa).
The parallel group demonstrated the least stress accumulation in all components and bone tissues. Internal tilting of the distal implant is biomechanically preferable to external tilting, and a smaller tilt angle is recommended when external tilting is necessary. This study provides valuable reference data for optimizing implant angulation in patients with the loss of three posterior maxillary teeth, potentially reducing long-term complications associated with implant-fixed bridges.
本研究旨在通过三维有限元分析，探讨在上颌后牙区游离端部分牙列缺损时，近中种植体轴向植入，远中种植体以不同角度植入时，骨组织、种植体、基台、螺钉和桥修复体中的应力分布情况。
利用锥形束计算机断层扫描技术创建上颌骨的三维重建模型。使用牙种植体及配件的立体光刻数据为上颌模型设计一个三单位全锆桥。将三维模型导入ANSYS Workbench 23.0软件进行网格划分和材料属性定义。设计了五种不同的远中种植体植入方向：向内倾斜30°组、向内倾斜17°组、平行组、向外倾斜17°组和向外倾斜30°组。模型包括皮质骨、松质骨、种植体、基台、中央螺钉、修复体螺钉和修复体。假定材料属性为各向同性、均匀且线弹性。对上颌模型施加严格的固定约束，并认为种植体完全骨结合。在ANSYS Workbench 23.0中设置了两种加载类型：垂直载荷300N和与种植体成45°角的侧向载荷300N。
在垂直加载下，平行组在所有种植体、牙冠、基台和螺钉上的最大应力最低。更大的倾斜角度会增加基台应力，向外倾斜30°组的应力达到1426MPa（接近钛合金的屈服强度）。向外倾斜和向内倾斜角度较小时，应力从基台和螺钉转移到种植体。在侧向加载期间，向外倾斜30°组显示出灾难性的应力增加（基台：8612MPa），超过了钛的屈服极限。除侧向加载下的向内倾斜30°组（142MPa）外，骨应力仍保持在生理范围内。
平行组在所有部件和骨组织中的应力积累最少。远中种植体向内倾斜在生物力学上优于向外倾斜，如需向外倾斜，建议采用较小的倾斜角度。本研究为优化上颌后牙三颗缺失患者的种植体角度提供了有价值的参考数据，可能减少与种植固定桥相关的长期并发症。
