Department of Prosthodontics, Heidelberg University Hospital, University of Heidelberg, Heidelberg, Germany.
Department of Prosthodontics, Heidelberg University Hospital, University of Heidelberg, Heidelberg, Germany.
Dent Mater. 2019 Mar;35(3):e53-e62. doi: 10.1016/j.dental.2019.01.017. Epub 2019 Jan 25.
In the past, discrepancies between laboratory results and clinical behavior have been observed for all-ceramic restorations. This analysis of fracture resistance of zirconia-based inlay-retained fixed partial dentures (IRFPDs) aimed at identifying correlations between an in-vitro test setup and the clinical situation. The effects of tooth material, tooth mobility, restoration design, load direction, and different cements were taken into account.
The in-vitro test model and IRFPD were reverse engineered (Geomagic DesignX) and meshed predominantly with hexahedral elements (approx. 230,000 elements). Homogenous, linear-elastic behavior was assumed for all materials. On the basis of the calculated stresses (ANSYS 18.2) and already known strength distributions for the restorative materials fracture resistance of the complete restoration and force at initial damage (fracture within the veneer) was estimated on the basis of the principal stress hypothesis. Differences depending on the assumed clinical situation and effects of different variables on fracture resistance were evaluated.
All variables tested in the finite element analysis affected the calculated fracture resistance of the IRFPD. Use of resin teeth led to an underestimation of fracture resistance by up to -57%, whereas fracture resistance of IRFPDs on metal abutment teeth was close to the clinical reference (-6% to +15%). Good correlation between the clinical scenario and that using metal teeth could only be achieved when the natural resilience of the abutment teeth was simulated.
When testing fracture resistance of zirconia-based IRFPDs, metal abutment teeth in combination with simulated tooth resilience can reflect the clinical situation accurately.
过去，全瓷修复体的实验室结果与临床行为之间存在差异。本分析旨在确定体外测试设置与临床情况之间的相关性，研究氧化锆基嵌体固位固定局部义齿（IRFPD）的抗断裂能力。考虑了牙体材料、牙动度、修复设计、载荷方向和不同水门汀的影响。
采用逆向工程（Geomagic DesignX）对体外测试模型和 IRFPD 进行反向工程设计，并主要采用六面体单元（约 230,000 个单元）进行网格划分。所有材料均假定为均匀、线弹性行为。基于计算出的应力（ANSYS 18.2）和已知的修复材料强度分布，基于主应力假设，估算了完整修复体的抗断裂能力和初始损伤时的力（贴面内断裂）。评估了取决于假设的临床情况和不同变量对抗断裂能力的影响。
有限元分析中测试的所有变量都影响了 IRFPD 的计算抗断裂能力。使用树脂牙会导致抗断裂能力低估高达-57%，而金属基牙上的 IRFPD 抗断裂能力接近临床参考值（-6%至+15%）。只有当模拟基牙的自然弹性时，才能在金属牙的临床场景和使用金属牙的场景之间实现良好的相关性。
在测试氧化锆基 IRFPD 的抗断裂能力时，金属基牙与模拟牙弹性相结合可以准确反映临床情况。
