MICA-BASED LITHIUM CONTAINING MACHINABLE GLASS-CERAMICS

近年来，对美学的耐心需求刺激了 牙科全瓷修复体新材料的开发。玻璃- 陶瓷属于这一类，比起陶瓷有许多优点。 用于牙科应用的传统长石陶瓷。然而， 有几个因素限制了它们的使用：1)牙齿的断裂强度 目前可用的微晶玻璃系统不允许 固定局部义齿的制作2)微晶玻璃工艺是时间 消耗和需要昂贵的设备，3)结晶缺陷 经常出现，使修复变得麻木。 拟议研究的总体目标是开发一种新的可加工 微晶玻璃材料牙科应用。这种材料将会是 在较低的温度和比目前可用的更短的时间内进行处理 牙科微晶玻璃。它将改善同质性和机械性 与目前可用的牙科微晶玻璃的性能进行比较。 该策略是评估CaF2，AlPO4和Zr02添加剂对 基本微晶玻璃的热性能、光学性能和力学性能 Li2O-MgO-K2O-SiO_2-F系的组成。需要检验的假设 添加剂如CaF2或AlPO4会导致相分离和 促进玻璃中云母晶体的成核和生长- 陶瓷器。四方氧化锆纳米粒子将诱导出独特的 不影响纳米粒子嵌入云母晶体的微观结构 微晶玻璃的半透明性，因为它们的尺寸小于 光的波长。散射系数和吸收系数将为 通过使用双光束的反射率测量计算得到的 分光光度计。用差热分析法研究了其热性能。这个 晶相和微观结构将通过x射线进行表征。 衍射和扫描电子显微镜。 弹性常数、弯曲强度、断裂韧性和赫兹系数 将评估五种微晶玻璃材料的压痕响应。 在第二部分提出了研究建议。需要检验的假设 都是首先认为存在的是黄铁矿，一种含有锂的 四硅氟云母以致密致密的晶体为特征，将 确保基础组成材料具有良好的机械性能。 其次，添加CaF2或AIPO4将有助于形成均一的 相对于基座具有改进的机械性能的微观结构 合成材料。第三，氧化锆将保留在四方晶系中。 晶化后形成，并通过强化微晶玻璃 相变增韧。

In recent years, patient demand for esthetics has stimulated the development of new materials for all ceramic dental restorations. Glass- ceramics belong to this category and offer many advantages over conventional feldspathic porcelain for dental applications. However, several factors limit their use: 1) the fracture strength of the dental glass-ceramic systems presently available does not allow for the fabrication of fixed partial dentures, 2) the glass-ceramic process is time consuming and requires expensive equipment, 3) crystallization defects are frequent and render the restoration unesthetic. The overall objective of the proposed research to develop a new machinable glass-ceramic material dental applications. This material will be processed at lower temperature and in less time that currently available dental glass-ceramics. It will have improved homogeneity and mechanical properties compared to currently available dental glass-ceramics. The strategy is to evaluate the effect of CaF2, A1PO4 and Zr02 additives on the thermal, optical and mechanical properties of a basic glass-ceramic composition in the system Li2O-MgO-K2O-SiO2-F. The hypotheses to be tested are that additives such as CaF2 or A1PO4 will induce phase separation and promote the nucleation and growth of mica crystals within the glass- ceramic. Tetragonal zirconia nanoparticles will induce a unique microstructure of nanoparticles embedded in mica crystals without effecting the translucency of the glass-ceramic since their size is less than the wavelength of light. The scattering and absorption coefficients will be calculated from reflectance measurements using a dual-beam spectrophotometer. The thermal properties will be studied by DTA. The crystalline phases and microstructure will be characterized by x-ray diffraction and Scanning Electron Microscopy. The elastic constants, flexural strength, fracture toughness and Hertzian indentation response of the five glass-ceramic materials will be evaluated in the second part of the proposed research. The hypotheses to be tested are first that the presence of taeniolite, a lithium containing tetrasilicic fluormica characterized by dense and compact crystals, will insure favorable mechanical properties for the base composition material. Secondly, the addition of CaF2 or AIPO4 will help develop an homogeneous microstructure with improved mechanical properties with regard to the base composition material. Thirdly, zirconia will be retained in the tetragonal form after crystallization and strengthen the glass-ceramic via transformation toughening.