Graded Zirconia Structures for Resistance to Chipping, Delamination, and Fatigue

说明(申请人提供)：陶瓷因其美学价值和化学惰性而被广泛应用于牙科和整形外科。然而，陶瓷很容易破裂，每年的更换成本高达数百万美元，可能会导致患者严重不适，失去有效的生活方式。尽管材料性能有所改善，但全瓷修复体的性能仍然比不上金属陶瓷修复体的黄金标准。我们以前的研究已经建立了失效模式与修复体厚度、表面条件、陶瓷性能和加载条件之间的关系。这些结果表明，单块微晶玻璃和贴面氧化铝修复体容易受到咬合滑动接触损伤和粘结块状断裂的影响，而氧化锆贴面修复体容易发生贴面剥落和剥离。这些发现与临床报告一致。我们目前由NIDCR支持的项目在理论和实验工作方面的最新进展表明，修复层内可控的成分梯度可以显著缓解贴面破坏和整体断裂。与均匀结构相比，这种梯度结构表现出更高的抗滑动接触损伤和弯曲整体断裂的能力。在这一竞争性的更新应用中，我们建议阐明在平板模型结构和解剖正确的几何形状中，具有和不具有薄贴面(0.3 mm)的渐变玻璃-氧化锆材料具有更强的抗碎屑、贴面/芯层剥离和口腔运动疲劳的能力。这将使我们更接近一个临床问题的解决方案-陶瓷修复体的碎屑、分层和断裂。此外，我们建议建立一种简单但功能强大的边缘压痕技术来评估分级层合板的韧性属性，这一问题超出了当前断裂测试协议的范围。我们建议通过三个具体目标来实现这些目标：1.使用一种新的边缘压痕技术来量化渐变氧化锆结构的抗切边性能；2.使用一种新的裂纹扩展技术和传统的剪切粘结测试来阐明渐变氧化锆结构的裂纹-界面相互作用；以及3.在潮湿环境中使用口腔运动模拟器来确定解剖学上正确的玻璃/氧化锆/玻璃梯度结构加或不加薄瓷贴面的渐变结构相对于商用贴面和整体式氧化锆系统的抗疲劳损伤能力。从这项研究中获得的知识将促进用于下一代牙科和矫形假体的智能玻璃-氧化锆分级结构的开发，该结构具有更好的损伤容忍度、美观和粘接性能。这些改善措施将会减低牙科修复者的发病率和市民的更换费用。

DESCRIPTION (provided by applicant): Ceramics are widely used in dental and orthopedic applications because of their esthetic value and chemical inertness. However, ceramics are vulnerable to fracture which accounts for millions of dollars annually in replacement costs and can cause significant patient discomfort and loss of productive lifestyle. Despite improvements in material properties, the performance of all-ceramic restorations still fails to match the 'gold standard' of metal-ceramic restorations. Our previous investigations have established relations between failure modes and restoration thickness, surface conditions, ceramic properties, and loading conditions. These findings indicate that monolithic glass-ceramic and veneered-alumina restorations are vulnerable to both occlusal sliding-contact damage and cementation bulk fracture, while the veneered zirconia restorations are prone to veneer chipping and delamination. These findings are consistent with clinical reports. Recent advances in theoretical and experimental work from our current NIDCR-supported project have demonstrated that veneer failure and bulk fracture may be substantially mitigated by controlled compositional gradients within the restoration layer. Such graded structures exhibit significantly higher resistance to sliding- contact damage and flexural bulk fracture relative to their homogeneous counterparts. In this competing renewal application we propose to elucidate enhanced resistance to chipping, veneer/core delamination, and mouth-motion fatigue of graded glass-zirconia materials with and without a thin veneer (0.3 mm) in both flat model structures and anatomically-correct geometries. This will bring us closer to a solution of a clinical problem-chipping, delamination, and fracture of ceramic restorations. Additionally, we propose to establish a simple but powerful edge-indentation technique to assess the toughness properties of graded laminates, a problem area that lies beyond the scope of current fracture testing protocols. We propose to achieve these objectives through three specific aims: 1. Quantify increased resistance to edge-chipping of graded zirconia structures using a novel edge-indentation technique; 2. Elucidate crack-interface interaction of graded zirconia structures using a novel crack growth technique and a conventional shear bond test; and 3. Determine resistance to fatigue damage of anatomically-correct glass/zirconia/glass graded structures with or without a thin porcelain veneer relative to commercial veneered and monolithic zirconia systems using a mouth-motion simulator in wet environments. Knowledge generated from this investigation will facilitate the development of smart glass-zirconia graded structures for next-generation dental and orthopedic prostheses with improved damage-tolerance, esthetics, and cementation properties. These improvements will lead to reduced morbidity of dental prostheses and cost of replacement to the public.