THERMALLY INDUCED CHANGES IN DENTAL PORCELAIN EXPANSION

描述：拟议研究的总体目标是 确定热致变化的机制 出现在牙科陶瓷的热膨胀系数中 由于多次烧制、缓慢冷却和后焊接 运营 陶瓷热膨胀的这些变化是 有害的，并产生裂纹的瓷器融合到金属陶瓷 (PFM)要么是在开火后不久，要么是在开火后不久 任一种情况 导致额外的成本和可能对患者造成的额外创伤。 有六个具体目标。 第一个是解释热 白钨矿和透长石基瓷器的膨胀行为 体积分数，微裂纹密度，白榴石颗粒表面 地区 二是确定局部冷却速率的影响 牙科陶瓷热不稳定性的差异 多次烧制、冷却和等温退火。 三是 确定H2O作为玻璃改性剂在牙科陶瓷中的作用， 特别是在白榴石和透长石的结晶中。 第四 是为各种陶瓷-金属系统制定烧制时间表， 最大限度地减少热诱导的微观结构变化， 热膨胀的变化。第五是修改瓷器渲染 它们更能抵抗热膨胀变化。 第六，发展 求解热膨胀的原型专家系统计算机程序 不匹配问题。为实现这些目标而使用的技术包括 定量X射线衍射，扫描电子显微镜与能量 色散X射线光谱，定量体视学，和常规 和激光测径法。

DESCRIPTION: The overall objective of the proposed research is to determine the mechanisms responsible for the thermally induced changes that occur in the coefficients of thermal expansion of dental porcelains as a result of multiple firings, slow cooling and post-soldering operations. These changes in porcelain thermal expansion are detrimental and produce cracks in porcelain fused to metal restorations (PFM) either shortly after firing or sometime later. Either event causes additional costs and possibly additional trauma to the patient. There are six Specific Aims. The first is to explain the thermal expansion behavior of porcelains on the basis of leucite and sanidine volume fractions, microcrack densities, an leucite particle surface areas. The second is to determine the effect of localized cooling rate differences on the thermal instability of dental porcelain during multiple firing, cooling, and isothermal anneals. The third is to determine the role of H2O as a glass modifier in dental porcelain and specifically in the crystallization of leucite and sanidine. The fourth is to develop firing schedules for various porcelain-metal systems to minimize the thermally induced microstructural changes that lead to thermal expansion changes.The fifth is to modify porcelains to render them more resistant to thermal expansion changes. The sixth to develop a prototype expert system computer program for solving thermal expansion mismatch problems. Techniques used in pursuit of these aims include quantitative X-Ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, quantitative stereology, and conventional and laser dilatometry.