Understanding the microstructural bonding mechanisms between Y-TZP and veneering ceramic

目前，牙科贴面氧化锆基牙核修复体的应用非常广泛。氧化锆核心与瓷饰面材料分层，以达到合适的美学效果。然而，基于氧化锆的修复会产生临床问题，如瓷贴面层的碎裂或断裂。先前的研究报告了单板失效的显著发生率，如分层、碎裂和开裂。这种断裂行为可归因于贴面/芯面界面结合强度差、芯材与贴面之间弹性模量不匹配、芯材与贴面之间热膨胀系数不匹配、瓷体强度弱以及热过程中由于冷却速率和/或高温烧结导致的残余应力。为了提高贴面与瓷芯界面的相容性，避免其过早失效，需要进一步了解氧化锆/瓷的界面。本研究将研究氧化锆/陶瓷界面粘合的详细机制，以开发一种可行的解决方案，以改善这两种材料之间的粘合，同时使用两种成型技术（分层技术和压制技术）。热应力也将被评估。本研究的主要目的是表征陶瓷和氧化锆之间的相互作用，然后根据结果开发新的材料或设计。因此，在全陶瓷修复体中，瓷贴面与氧化锆芯之间的结合稳定性更好。瓷贴面与氧化锆的粘附是氧化锆基修复成功的基础。在确定制作锆基修复体的新方案和/或设计后，将进行机械测试。不同的测试将仔细进行，以描述氧化锆/瓷键的微观结构机制。采用扫描电镜（SEM）、能谱仪（EDS）、电子背散射衍射（EBSD）等测试方法。此外，EBSD还将对材料的显微组织、织构、缺陷、晶粒形貌和变形进行评价。此外，聚焦离子束显微镜（FIB）将用于制备TEM和飞行时间二次离子质谱（TOF-SIMS）的薄样品。俄歇微探针将有助于以高空间分辨率确定表面上的二维和三维元素分布。氧化锆与瓷器的结合形成也将用XPS进行检测。本研究的结果为牙科实验室提供了一种新的方案来制作牙科贴面氧化锆核修复体，以提高这种类型的牙科修复体的成功率。新方案将基于从本研究结果中获得的氧化锆/陶瓷界面的详细键合机制。在5年内，我将培养3名研究生。

Dental veneered zirconia-based core restorations have been used widely to date. The zirconia core is layered with a porcelain veneer material to achieve suitable esthetics. However, zirconia-based restorations can create clinical issues such as chipping or fracture of the porcelain veneered layer. Previous studies have reported a significant incidence of veneer failures such as delaminations, chipping and cracking. This fracture behavior could be attributed to the poor veneer/core interface bond strength, elastic modulus mismatch between the core material and the veneer, coefficient of thermal expansion mismatch between the core and the veneer, weak porcelain strength and thermal procedure which could introduce residual stress induced by cooling rate and/or sintering at high temperatures. To improve the compatibility at the interface between veneer and core, and to avoid premature failure, the interface zirconia/porcelain should be better understood. The proposed research will investigate the detailed mechanism for the adhesion at the interface zirconia/porcelain to develop a feasible solution to improve the bonding between these two materials, using both molding techniques (the layering technique and the press technique). The thermal stresses will be also evaluated. The main objectives of this study are to characterize the interaction between porcelain and zirconia then, materials or new designs will be developed based on the results. Therefore, better bonding stability between porcelain veneer and zirconia core of an all-ceramic restoration can be achieved. The adhesion of porcelain veneer to zirconia is fundamental for the success of the zirconia-based restorations. After determining the new protocol and/or design to fabricate zirconia-based restorations, mechanical tests will be performed.Different tests will be carefully conducted to describe the microstructural mechanisms of zirconia/porcelain bond. The tests are SEM, EDS, Electron Backscatter Diffraction (EBSD). Furthermore, microstructures, texture, defects, grain morphology and deformation will also be evaluated by EBSD. In addition, the Focused Ion Beam microscopy (FIB) will be used to prepare thin specimens for the TEM and for Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). Auger Microprobe will contribute to the determination of 2D and 3D elemental distributions on surfaces with high spatial resolution. The bond formation of the zirconia to porcelain will also be examined by XPS.The outcome of the research is to provide the dental laboratories with a new protocol to fabricate dental veneered zirconia-based core restorations in order to improve the success rate of this type of dental restoration. The new protocol will be based on the detailed bond mechanisms at the zirconia/porcelain interface obtained from the results of this study. Over 5 years, I will train 3 graduate students.