Thin Film Surface Coatings for Toughened Dental Ceramics

说明(申请人提供)：陶瓷是替代金属基修复体材料的理想候选者。陶瓷具有优异的化学耐久性、耐磨性、生物兼容性、环境友好性和美观性。然而，全瓷修复体的广泛应用受到了与边缘抗折能力和临床寿命相关的担忧的阻碍。这项正在进行的研究的总体目标是开发一种实用的方法，通过溅射沉积的薄膜表面涂层进行修改，生产出更坚韧、更耐疲劳的牙科全瓷修复体。在美国国立卫生研究院资助的为期6年的项目(一旦续签)内进行的研究重点是沉积薄膜的微观结构控制，评估薄膜对改性陶瓷衬底的机械行为的影响，以及影响薄膜应力和衬底行为的薄膜/环境相互作用的表征。在最初的3年时间里，氧化钇稳定的氧化锆(YSZ)被确定为建议应用的最佳薄膜陶瓷涂层材料。研究表明，YSZ薄膜不会对牙科陶瓷表面的粘结或半透明陶瓷的美观产生不良影响。在第二个3年期间，沉积的YSZ薄膜与环境湿度之间的独特相互作用被识别和表征。对这些薄膜的电子显微镜分析表明，在内部缺陷附近发生了明确的、可控的四方单斜相转变。这些都可以被操纵以适应电影的压力。延性/脆性聚合物/YSZ层压薄膜的初步研究表明，通过控制YSZ/水蒸气的相互作用机制，有望提高脆性牙科基材的抗断裂性能。对这些结构的模拟表明，可以创建特定的薄膜结构以在不同的环境中提供最佳效益。这项继续研究的具体目标是：1)验证这样的假设，即结合结构和应力状态信息的YSZ薄膜演变的有限元分析(FEA)可以预测纳米和微维缺陷的集中/分布，2)测试具有交替的延性/脆性、低/高模数(对二甲苯/YSZ)层的薄膜叠层将允许对薄膜和薄膜/衬底界面应力进行精细控制的假设，允许这些应力的方向(拉伸、压缩或零应力)和大小可重复地控制，以及薄膜与局部环境的相互作用，3)测试具有延性/脆性、低/高模量层交替的薄膜层压板将显著提高传统商用牙科陶瓷的耐久性的假设，以及4)展示一种实用的实验室加工YSZ和对二甲苯/YSZ薄膜不同排列的可行技术(开发实用的台式原型沉积系统)。相信这项研究将对现有的牙科陶瓷技术产生直接、积极的影响，扩大瓷器等低强度材料的潜在应用范围，并提高长期临床疗效。由于生物兼容性问题和与金属废物和处置相关的环境问题，开发非金属(例如，汞合金替代品)修复材料是一个高度优先的研究重点。陶瓷材料提供了生物相容性和环境友好性的最佳组合，但它们传统上存在长期临床性能差的问题。这项研究中正在研究的技术有可能显着提高现有牙科陶瓷的功效是一种相对简单的方式。

DESCRIPTION (provided by applicant): Ceramics are an ideal candidate for replacing metal-based restorative materials. Ceramics provide excellent chemical durability, wear resistance, biocompatibility, environmental friendliness, and esthetics. Nevertheless, widespread all-ceramic restoration use has been hindered by concerns related to marginal fracture resistance and clinical longevity. The overall goal of this ongoing research is to develop a practical method to produce tougher, more fatigue-resistant all-ceramic Dental restorations by modification with sputter-deposited thin-film surface coatings. Research conducted within the funded 6-year NIH project (once renewed) has focused on microstructural control of deposited films, assessing film effects on mechanical behavior of modified ceramic substrates, and characterization of film/environment interactions which affect film stress and substrate behavior. In the initial 3-year period yttria-stabilized zirconia (YSZ) was identified as the best thin-film ceramic coating material for the proposed application. It was demonstrated that YSZ thin-films produce no deleterious effect on bonding to a modified Dental ceramic surface, or on the esthetics of a translucent ceramic. In the second 3-year period, a unique interaction between deposited YSZ thin-films and environmental moisture was identified and characterized. TEM analyses of these films produced evidence of well defined and controllable tetragonal monoclinic phase transitions adjacent to internal defects. These can be manipulated to tailor film stress. Initial study of ductile/brittle polymer/YSZ laminate thin-films demonstrated promise for enhancement of fracture resistance of a brittle Dental substrate with control of the YSZ/water vapor interaction mechanism. Modeling of these structures indicates that specific thin-film structures can be created to provide optimal benefit in different environments. The proposed Specific Aims of this continued research are to: 1) Test the hypothesis that finite element analysis (FEA) of evolving YSZ thin-films, incorporating structural and stress state information, can predict the concentration/distribution of nano- and micro-dimensional defects, 2) Test the hypothesis that thin-film laminates with alternating ductile/brittle, low/high modulus (parylene/YSZ) layers will allow fine control of thin-film and film/substrate interfacial stress, allowing the direction (tensile, compressive, or zero) and magnitude of these stresses, and the interaction of the thin-film with the local environment to be controlled reproducibly, 3) Test the hypothesis that thin-film laminates with alternating ductile/brittle, low/high modulus layers will significantly enhance durability of traditional commercially available Dental ceramics, and 4) Demonstrate a viable technology for practical lab processing of varying permutations of YSZ and parylene/YSZ thin-films (development of a practical bench-top prototype deposition system). It is believed that this research will have a direct, positive impact on existing Dental ceramic technologies, enhancing the range of potential applications for low strength materials such as porcelain, and improving long term clinical efficacy. Development of non-metallic (e.g., amalgam-substitute) restorative materials is a high research priority due to biocompatibility issues and environmental concerns associated with metals waste and disposal. Ceramics offer the best combination of biocompatibility and environmental friendliness, but they have traditionally suffered from poor long-term clinical performance. The technology being investigated in this study has the potential to significantly improve the efficacy of existing Dental ceramics is a relatively simple manner.