HIGH TOUGHNESS TEXTURED DENTAL GLASS CERAMICS

牙科陶瓷具有化学耐用性，生物相容性，并具有实现卓越美学的最大潜力。随着金属基修复产品逐渐从口腔环境中被淘汰，它们目前正获得新的兴趣。在过去的五年里，一种新的技术被引入到牙科领域，用于制造全陶瓷牙科修复体：热压。然而，目前大多数可压陶瓷具有较低的断裂韧性，这意味着全陶瓷修复可能失败。提出的研究的总体目标是开发用于热压全陶瓷修复的高韧性织构微晶玻璃。在对有核玻璃进行热压加工的过程中，会得到这种纹理。这种独特的微观结构将与断裂韧性的各向异性增加有关，这是由于板状晶体在挤压方向上的排列。该策略是研究氧化镁对li20 - na20 - k20 - cao - mgo - sio2 - f体系中玻璃陶瓷的热性能和力学性能的影响。要测试的假设是，镁浓度的增加会增加玻璃的流动性及其工作范围。用x射线衍射、扫描和透射电子显微镜以及核磁共振波谱研究了玻璃的成核和结晶行为。热性能将通过差热分析和膨胀法进行分析。双轴弯曲强度和断裂韧性也将进行研究。热性能和机械性能的研究将为热压材料的选择提供依据。热压研究将分为两个步骤，首先，研究的玻璃陶瓷材料的简化，低熔点版本将被热压作为控制。其次，玻璃陶瓷材料本身将被热压。光学散射和吸收系数将由反射率测量计算。在挤压方向和法向方向测试两种材料的力学性能，用SEM表征织构程度。最后研究了退火对所制备的微晶玻璃裂纹愈合行为和抗弯强度的影响。

Dental ceramics are chemically durable, biocompatible and have the greatest potential for achieving superior esthetics. They are currently gaining new interest while metal-based restorative products are progressively being eliminated from the oral environment. During the past five years, a novel technique has been introduced in dentistry for fabricating all-ceramic dental restorations: hot-pressing. However, most of the currently available pressable ceramics have low fracture toughness, implying possible failure of all-ceramic restorations. The overall objective of the proposed research is to develop high-toughness textured glass-ceramics for hot-pressed all- ceramic restorations. The texture will be obtained during hot-pressing of the nucleated glass. This unique microstructure will be associated with an anisotropic increase in fracture toughness, due to the alignment of the plate-shaped crystals in the direction of pressing. The strategy is to investigate the effect of magnesium oxide on the thermal and mechanical properties of a glass-ceramic in the system Li2O-Na2O-K2O-CaO-MgO-SiO2-F. The hypothesis to be tested is that increasing concentrations of magnesium will increase the fluidity of the glass and its working range. The nucleation and crystallization behavior of the glasses will be studied by x-ray diffraction, scanning and transmission electron microscopy and nuclear magnetic resonance spectroscopy. The thermal properties will be analyzed by differential thermal analysis and dilatometry. The biaxial flexural strength and fracture toughness will also be investigated. The study of thermal and mechanical properties will allow material selection for hot-pressing. Hot-pressing studies will be divided in two steps, first a simplified, low fusing version of the glass-ceramic material studied will be hot-pressed as control. Second, the glass ceramic material itself will be hot-pressed. The optical scattering and absorption coefficients will be calculated from reflectance measurements. The mechanical properties of both materials will be tested in both the direction of pressing and the normal direction, the degree of texture will be characterized by SEM. The effect of annealing on the crack healing behavior and flexural strength of the glass-ceramic developed will be investigated last.