OPTIMIZED STRESS STATES IN CERAMIC-BASED RESTORATIONS

今天制造的固定假体约有90%是超陶瓷的 修复。最新的基于瓷质的金属陶瓷修复体 边缘，更薄的金属覆盖件，树脂粘结，支撑性植入物，以及 悬臂设计与增加的结构风险有关 失败了。此外，目前还没有建立可靠的方法来确定 评估简单生物材料的热收缩相容性状态 或三种材料的金属-陶瓷带材或更复杂的单单元或 多单元假体。尽管有许多关于热能的研究 金属-陶瓷系统的收缩兼容性，目前还没有模型 开发用于预测临床假体中的残余应力 组成属性，如热收缩系数、弹性 模数和粘滞值。此外，目前还没有研究分析 潜在破坏性拉应力的相对大小或位置 金属-陶瓷收缩引起的差异在临床上的相关性 假体的设计使潜在故障的关键区域可以 已确认身份。这项为期五年的研究计划的最初重点是 建立实用的筛查测试，区分不同的体温 从不兼容的系统兼容，并确定 所选材料热不相容引起的残余拉应力 假体设计。此外，潜在的故障机制将是 增强陶瓷基修复体的研究和方法 基于对冷却速度变化的分析，热回火 治疗和离子交换治疗，以诱导保护性压迫 提醒陶瓷中残余应力分布的应力 在放置到口腔中之前，请先检查口腔内的结构。四部小说 将利用技术发展来进行拟议的分析： 1)用于有限元分析的三维粘弹性单元 不相容应力，2)液体介质中的热回火 改变残余应力分布并降低拉应力 金属烤瓷修复体和全瓷修复体的关键风险区域，3) 单、双离子交换强化处理的研究 低烧富钾和富Rb的浆料 短时间内的温度，以及4)微型 半导体应变片(长度约100亩) 与产生光弹应力的光应力涂层相结合 实际尺寸模型的加载假体表面内的图案 或放大模型设计，以验证有限元预测的应力分布 元素分析。拟议的研究将旨在 评估热收缩引起的瞬时和残余应力状态 不亲和性，将实验不亲和性日期与 那些从粘弹性模型获得的结果已经发展到 预测不相容应力，并开发热加工 协议，以优化产生的应力分布在这些 假肢。拟议研究的总体目标是开发 预测模型，用于分析金属陶瓷和陶瓷的失效危险因素 基于分析和实验模型的微晶玻璃修复体， 并改变残余应力分布，以提高边际 通过控制全瓷和金属烤瓷修复体的安全性 热处理、回火、离子交换、化学蚀刻和设计 各种因素。

Approximately 90% of the fixed prostheses made today are meta-ceramic restoration. Recent metal-ceramic prostheses that are based on porcelain margins, thinner metal copings, resin bonding, supporting implants, and cantilever designs are associated with an increased risk of structural failure. In addition, no method has yet been established to reliably assess the thermal contraction compatibility status of simple biomaterial or trimaterial metal-ceramic strips or more complex, single-unit or multiple-unit protheses. In spite of numerous studies on the thermal contraction compatibility of metal-ceramic systems, no model has yet been developed to predict residual stresses in clinical prostheses based on constituent properties such as thermal contraction coefficients, elastic moduli, and viscosity values. Furthermore, no study has yet analyzed the relative magnitudes or locations of potentially damaging tensile stresses caused by metal-ceramic contraction differences in clinically relevant prosthesis designs so that critical zones of potential failure can be identified. The initial focus of this five-year research program will be to establish practical screening tests that differentiate thermally compatible from incompatible systems and to identify critical zones of residual tensile stress caused by thermal incompatibility in selected prosthesis designs. In addition, potential failure mechanisms will be investigated as well as methods of strengthening ceramic-based prostheses based on analysis of cooling rate variations, thermal tempering treatment, and ion exchange treatment to induce protective compressive stresses that alert the residual stress profiles in the ceramic structures prior to their placement in the oral cavity. Four novel technological developments will be employed for the analyses proposed: 1) a three-dimensional visco-elastic element for finite element analysis of incompatibility stresses, 2) thermal tempering in liquid media to alter residual stress profiles and to reduce tensile stresses in critical-risk areas of metal-ceramic and all-ceramic prostheses, 3) single and double ion-exchange strengthening treatments based on potassium-enriched and rubidium-enriched slurries that are fired at low temperatures over short time periods, and 4) micro-miniature semiconductor strain gages (gage length approximately 100 mu) in combination with PhotoStress coatings that produce photoelastic stress patterns within the surface of loaded prostheses of actual-size models or enlarged-model designs to validate stress profiles predicted by finite element analysis. The proposed research studies will be designed to assess transient and residual stress states caused by thermal contraction incompatibility, to correlate experimental incompatibility date with those obtained from visco-elastic models that have been developed to predict incompatibility stresses, and to develop thermal processing protocols to optimize the resulting stress distributions in these protheses. The overall objective of the proposed research is to develop a predictive model, to analyze failure risk factors for metal-ceramic and glass-ceramic restorations based on analytical and experimental models, and to alter residual stress distributions that will enhance the margin of safety for all-ceramic and metal-ceramic prostheses by control of thermal processing, tempering, ion exchange, chemical etching, and design factors.