Influence of cantilever position and implant connection in a zirconia custom implant-supported fixed partial prosthesis: in silico analysis

Abstract Introduction A better tension distribution on implants and abutments in implant-supported fixed partial prosthesis is essential in the rehabilitation of posterior mandible area. Objective: To evaluate the influence of cantilever position and implant connection in a zircônia custom implant-supported fixed partial prosthesis using the 3-D finite element method. Material and method: Four models were made based on tomographic slices of the posterior mandible with a zirconia custom three-fixed screw-retained partial prosthesis. The investigated factors of the in silico study were: cantilever position (mesial or distal) and implant connection (external hexagon or morse taper). 100 N vertical load to premolar and 300 N to molar were used to simulate the occlusal force in each model to evaluate the distribution of stresses in implants, abutments, screws and cortical and cancellous bone. Result: The external hexagon (EH) connection showed higher cortical compression stress when compared to the morse taper (MT). For both connections, the molar cantilever position had the highest cortical compression. The maximum stress peak concentration was located at the cervical bone in contact with the threads of the first implant. The prosthetic and abutment screws associated with the molar cantilevers showed the highest stress concentration, especially with the EH connection. Conclusion: Morse taper implant connetions associated with a mesial cantilever showed a more favorable treatment option for posterior mandible rehabilitation.

摘要 引言：在下颌后区牙列缺损的种植支持式固定局部义齿（implant-supported fixed partial prosthesis）修复中，实现种植体与基台的合理应力分布至关重要。研究目的：采用三维有限元法，评估悬臂位置与种植体连接方式对定制氧化锆（zirconia）种植支持式固定局部义齿的影响。材料与方法：基于下颌后区的断层扫描影像构建4个模型，每个模型均搭载定制氧化锆种植支持式三单位固位螺钉型固定局部义齿。本虚拟（in silico）研究的考察因素包括：悬臂位置（近中或远中）以及种植体连接方式（外六角（external hexagon）或莫氏锥度（morse taper））。对每个模型分别施加前磨牙区100N的垂直载荷、磨牙区300N的垂直载荷以模拟咬合应力，以此评估种植体、基台、螺钉以及皮质骨与松质骨内的应力分布情况。结果：与莫氏锥度（morse taper）连接方式相比，外六角（external hexagon）连接的皮质骨压应力水平更高。两种连接方式下，悬臂置于磨牙区时的皮质骨压应力均为最高。最大应力峰值集中于与第一枚种植体螺纹接触的颈缘骨区域。与磨牙区悬臂匹配的修复体螺钉及基台螺钉的应力集中程度最高，尤其在外六角连接方式下更为显著。结论：搭配近中悬臂的莫氏锥度种植体连接方案，可为下颌后区牙列缺损修复提供更优的治疗选择。