Discipline of Biomaterials, Faculty of Dentistry, The University of Sydney, New South Wales.
Aust Dent J. 2013 Jun;58(2):141-7. doi: 10.1111/adj.12040.
In the previous three papers, the authors sought to conduct a thorough analysis of the feasibility for the use of zirconia in inlay supported, fixed partial dentures via finite element analysis (FEA). Correlating the response of the numerical model against the experimental model has never been satisfactorily performed for an anatomically accurate ceramic bridge; such validation is crucial if the results from the FEA are to be confidently relied upon. Part 4 of this series is a detailed fractographic analysis of the zirconia bridge that was the model for the experimental validation, performed in order to confirm the fracture origin/s and fracture trajectory as predicted from the FEA.
Established fractographic techniques involving optical examination followed by examination with scanning electron microscopy were conducted. The porous, granular surface of zirconia (both partially and fully sintered) does not lend itself to easy surface analysis but the classic fractographic signs (hackle lines, wake hackle lines and compression curl) are present. Use of linear fracture elastic mechanics allowed the calculation of theoretical critical flaw size and a comparison to two defects or inclusions found at the primary origin of fracture.
Excellent agreement between the fracture sites and paths of travel as predicted in the numerical analysis exist with fractographic analysis. Furthermore, the calculated critical flaw size of 30 μm to 40 μm equates very well with defects seen at the general vicinity of the primary fracture origin and the general observed size of critical flaws in machined ceramics which range between 20 μm to 50 μm, thus providing further confirmation.
The fractographic analysis detailed in this study provides validation of the 'zones of failure' as predicted in our FEA. Additionally, the excellent correlation between the calculated critical flaw size and the defects observed at the primary fracture site demonstrates that field of experimental mechanics is a powerful predictive tool.
在前三篇论文中，作者试图通过有限元分析（FEA）对氧化锆在嵌体支持的固定局部义齿中的应用进行全面分析。从未对解剖学上准确的陶瓷桥进行过令人满意的数值模型与实验模型的相关性研究；如果要可靠地依赖 FEA 的结果，则这种验证至关重要。本系列的第 4 部分是对实验验证模型的氧化锆桥进行的详细断口分析，目的是确认从 FEA 预测的断裂起源和断裂轨迹。
采用光学检查和扫描电子显微镜检查相结合的方法进行了已建立的断口分析技术。氧化锆（部分和完全烧结）的多孔、颗粒状表面不便于进行表面分析，但存在经典的断口分析特征（拔模线、后拔模线和压缩卷曲）。使用线性断裂弹性力学允许计算理论临界缺陷尺寸，并将其与在断裂初始源处发现的两个缺陷或夹杂物进行比较。
在数值分析中预测的断裂部位和传播路径与断口分析之间存在极好的一致性。此外，计算出的临界缺陷尺寸为 30μm 至 40μm，与在初级断裂起源附近观察到的缺陷以及在加工陶瓷中观察到的临界缺陷的一般尺寸非常吻合，范围在 20μm 至 50μm 之间，从而提供了进一步的确认。
本研究中详细的断口分析为我们的 FEA 预测的“失效区”提供了验证。此外，计算出的临界缺陷尺寸与在初级断裂部位观察到的缺陷之间的极好相关性表明，实验力学领域是一种强大的预测工具。
