Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany.
Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany.
J Mech Behav Biomed Mater. 2022 Sep;133:105309. doi: 10.1016/j.jmbbm.2022.105309. Epub 2022 Jun 7.
Although endocrown is a successful restorative approach for endodontically treated molars, its survival rate in endodontically treated premolars with extensive loss of coronal structure has been debated. The aim of this study was to evaluate the biomechanical behavior of endodontically treated maxillary premolars restored with different lithium disilicate endocrown designs.
Based on cone-beam computed tomography (CBCT) of an intact maxillary premolar, five models were designed. Model A: fiber post, core, and crown; Model B: endocrown, 5 mm pulpal extension and butt margin; Model C: endocrown, 5 mm pulpal extension and axial extension; Model D: Endocrown, 3 mm pulpal extension and butt margin; Model E: Endocrown, 3 mm pulpal extension and axial extension. The bone geometry was simplified as a cylinder of compact and trabecular bone. All models were imported into finite element analysis (FEA) software, where the base of the bone cylinder was chosen as fixed support. Axial and oblique loads of 100 N each were applied separately to each model, and static structural analysis was performed.
Regardless of the design of the endocrown, the resulting von Mises stresses were far below the yield strength of the tooth structure and the flexural strength of the ceramic material. The generated von Mises stresses on the restoration decreased by 15% in the models with 3 mm pulp extension (D and E) compared to the 5-mm pulpal extension models. In addition, the resulting von Mises stresses on the tooth structure decreased also by 15% in models C and E with the axial extension compared to models B and D with the butt margin.
Endocrown is a suitable restoration for endodontically treated maxillary premolars. Furthermore, reducing the depth of the pulpal extension to 3 mm with the addition of an axial extension resulted in a more favorable stress distribution within the tooth-restoration interface.
尽管全瓷嵌体是治疗牙髓病的磨牙成功的修复方法，但对于牙冠结构广泛缺损的牙髓病治疗的前磨牙，其存活率仍存在争议。本研究旨在评估不同二硅酸锂全瓷嵌体设计用于牙髓病治疗的上颌前磨牙的生物力学行为。
基于完整上颌前磨牙的锥形束 CT（CBCT），设计了 5 种模型。模型 A：纤维桩、核和牙冠；模型 B：全瓷嵌体，5mm 牙髓延伸和肩台边缘；模型 C：全瓷嵌体，5mm 牙髓延伸和轴面延伸；模型 D：全瓷嵌体，3mm 牙髓延伸和肩台边缘；模型 E：全瓷嵌体，3mm 牙髓延伸和轴面延伸。骨几何形状简化为密质骨和松质骨的圆柱体。将所有模型导入有限元分析（FEA）软件中，选择骨圆柱体的底部作为固定支撑。分别向每个模型施加 100N 的轴向和斜向载荷，并进行静态结构分析。
无论全瓷嵌体的设计如何，产生的 von Mises 应力远低于牙体结构的屈服强度和陶瓷材料的弯曲强度。与 5mm 牙髓延伸模型相比，牙髓延伸 3mm（D 和 E 模型）的模型中，修复体上产生的 von Mises 应力降低了 15%。此外，与肩台边缘模型 B 和 D 相比，轴向延伸模型 C 和 E 中牙体结构上产生的 von Mises 应力也降低了 15%。
全瓷嵌体是治疗牙髓病的上颌前磨牙的一种合适的修复体。此外，将牙髓延伸深度减少到 3mm，并增加轴向延伸，可使牙-修复体界面内的应力分布更有利。
