Department of Materials Science and Technology, Faculty of Odontology, Malmö University, Malmö, Sweden.
Department of Restorative Dentistry, Faculty of Dentistry, Umm Al-Qura University, Makkah, Saudi Arabia.
J Prosthodont. 2020 Apr;29(4):315-322. doi: 10.1111/jopr.13146. Epub 2020 Feb 5.
To evaluate the influence of the framework designs on the stress distribution within tooth-supported partially veneered fixed dental prostheses (FDPs) made of translucent zirconia under simulated loads using a three-dimensional finite element analysis (3D-FEA).
For a linear 3D-FEA, simplified 3D solid models of prepared abutment teeth (first premolar and first molar) with different 3-unit FDPs were created. The models with different FDP designs-monolithic zirconia (control); semi-monolithic zirconia with 0.3 mm veneer thickness (SM0.3); semi-monolithic zirconia with 0.5 mm veneer thickness (SM0.5); semi-monolithic zirconia with 0.5 mm veneer thickness supported with cap design (SMC), and semi-monolithic zirconia with 0.5 mm veneer thickness supported with wave design (SMW)-were analyzed using 3D-FEA. The elastic properties of the components (bone, dentine, cement, translucent zirconia, and veneering porcelain) were obtained from the published data for FEA. Simulated static loading forces (300 N) were applied at 10° oblique direction over six points in the occlusal surfaces of the FDPs. Maximum principal stress, shear stress, and safety factor were calculated and analyzed among the different models.
Semi-monolithic with cap design showed the smallest maximum principal stress levels in the veneering porcelain compared to all other models (SM0.3, SM0.5, SMW). The SM0.3 had lower maximum principal stress levels in the veneering porcelain compared to SM0.5. Regarding stresses in the zirconia framework, all models had comparable results in maximum principal tensile stresses, except SMW had a lower value. Maximum principal stress levels were located in the veneer component of SM0.3, SM0.5, and SMW, whereas, such levels were observed in the cervical areas of the zirconia frameworks of SMC and control. The SM0.3 had the highest maximum shear stress levels at the zirconia-veneer interface, while SMW had the lowest shear values. The 3D-FEA models with different FDP designs showed different minimum safety factor levels.
Framework and veneer designs play a significant role in the stress distribution of the partially veneered zirconia FDPs under loading. The FDPs with zirconia frameworks with cap design minimize the maximum principal tensile stress in the veneering porcelain. The FDPs with 0.3-mm-veneering porcelain show low maximum principal tensile stress in the veneering porcelain, but highest maximum shear stress at the zirconia-veneer interface. The FDPs with wave design of zirconia frameworks minimize the maximum shear stress considerably.
通过三维有限元分析（3D-FEA）评估不同框架设计对透光氧化锆全瓷覆盖式固定修复体（FDP）在模拟负载下基牙内应力分布的影响。
对于线性 3D-FEA，制作了具有不同 3 单位 FDP 的预备基牙（第一前磨牙和第一磨牙）的简化 3D 实体模型。通过 3D-FEA 分析了具有不同 FDP 设计的模型-整体氧化锆（对照）；0.3mm 饰瓷厚度的半整体氧化锆（SM0.3）；0.5mm 饰瓷厚度的半整体氧化锆（SM0.5）；带有帽设计的 0.5mm 饰瓷厚度的半整体氧化锆（SMC）和带有波设计的 0.5mm 饰瓷厚度的半整体氧化锆（SMW）。使用 3D-FEA 分析了具有不同 FDP 设计的模型-整体氧化锆（对照）；0.3mm 饰瓷厚度的半整体氧化锆（SM0.3）；0.5mm 饰瓷厚度的半整体氧化锆（SM0.5）；带有帽设计的 0.5mm 饰瓷厚度的半整体氧化锆（SMC）和带有波设计的 0.5mm 饰瓷厚度的半整体氧化锆（SMW）。组件（骨、牙本质、粘结剂、透光氧化锆和饰瓷）的弹性特性从 FEA 的已发表数据中获得。在 FDP 的咬合面以 10°斜向施加模拟静态加载力（300N）。在不同模型之间计算并分析了最大主应力、剪切应力和安全系数。
与所有其他模型相比（SM0.3、SM0.5、SMW），带帽设计的半整体氧化锆显示出饰瓷中最小的最大主应力水平。与 SM0.5 相比，SM0.3 的饰瓷中具有更低的最大主应力水平。关于氧化锆框架内的应力，除了 SMW 具有较低的值外，所有模型的最大主拉伸应力都具有可比的结果。最大主应力水平位于 SM0.3、SM0.5 和 SMW 的饰瓷组件中，而在 SMC 和对照的氧化锆框架的颈部区域观察到这种水平。SM0.3 在氧化锆-饰瓷界面处具有最高的最大剪切应力水平，而 SMW 具有最低的剪切值。不同 FDP 设计的 3D-FEA 模型显示出不同的最小安全系数水平。
框架和饰瓷设计在负载下部分饰瓷氧化锆 FDP 的应力分布中起着重要作用。带有帽设计的氧化锆框架 FDP 可最大程度地减少饰瓷中的最大主拉伸应力。具有 0.3mm 饰瓷的 FDP 在饰瓷中表现出低的最大主拉伸应力，但在氧化锆-饰瓷界面处具有最高的最大剪切应力。具有氧化锆框架波设计的 FDP 可大大减少最大剪切应力。
