Influence of crown and hybrid abutment ceramic materials on the stress distribution of implant-supported prosthesis

Abstract Introduction A new dental implant-abutment design is available with the possibility of improving aesthetic with no compromise of mechanical strength, using perforated CAD/CAM ceramic blocks. Objective This study evaluated the influence of crown and hybrid abutment ceramic materials combination on the stress distribution of external hexagon implant supported prosthesis. Method Zirconia, lithium disilicate and hybrid ceramic were evaluated, totaling 9 combinations of crown and mesostructure materials. For finite element analysis, a monolithic crown cemented over a hybrid abutment (mesostructure + titanium base) was modeled and screwed onto an external hexagon implant. Models were then exported in STEP format to analysis software, and the materials were considered isotropic, linear, elastic and homogeneous. An oblique load (30°, 300N) was applied to the central fossa bottom and the system’s fixation occurred on the bone’s base. Result For crown structure, flexible materials concentrate less stress than rigid ones. In analyzing the hybrid abutment, it presented higher stress values when it was made with zirconia combined with a hybrid ceramic crown. The stress distribution was similar regarding all combinations for the fixation screw and implant. Conclusion For external hexagon implant, the higher elastic modulus of the ceramic crowns associated with lower elastic modulus of the hybrid abutment shows a better stress distribution on the set, suggesting a promising mechanical behavior.

摘要 引言 本研究提出一种新型牙科种植体-基台设计方案，可在不牺牲机械强度的前提下改善美学效果，其采用带孔的计算机辅助设计/计算机辅助制造（CAD/CAM）陶瓷块加工而成。研究目的 本研究旨在评估牙冠与混合基台陶瓷材料的组合对外六角种植体支持式修复体的应力分布的影响。研究方法 本研究选取氧化锆、二硅酸锂及混合陶瓷三种材料，共计9种牙冠与中间结构（mesostructure）材料组合方案。采用有限元分析（finite element analysis）方法，建模将一体化牙冠粘接于混合基台（中间结构+钛基底）之上，再通过螺钉固位至外六角种植体。将模型以产品模型数据交换标准（STEP）格式导出至分析软件，且设定材料为各向同性、线弹性且均质的材料。在牙冠中央窝底部施加30°斜向载荷（300N），系统固定于骨基底部。研究结果 就牙冠结构而言，柔性材料的应力集中程度低于刚性材料。针对混合基台的分析显示，当混合基台采用氧化锆且搭配混合陶瓷牙冠时，其应力值更高。而固位螺钉与种植体的应力分布在所有组合方案中均较为相似。研究结论 对于外六角种植体而言，陶瓷牙冠较高的弹性模量搭配混合基台较低的弹性模量，可使整个修复体系统获得更优的应力分布，展现出良好的力学性能表现。