Decreasing in sintering temperature and improvement in abrasion properties of dental porcelains

采用X射线衍射仪（XRD）分析了三种商品牙本质瓷和切缘瓷的晶相组成。结果表明，冷却条件对白榴石晶体的微观结构变化影响不大，因为白榴石晶体的形成温度高于烧成和冷却温度，并通过在晶格中加入添加剂而稳定。Ba和Sb取代了白钨矿中5 ~ 50at%的K。根据白钨矿的（400）和（004）衍射峰的衍射角，分别计算了它们的a轴和c轴晶格参数。结果表明，阳离子的掺入使白榴石的晶格发生了畸变 关于我们 取代的K和它们的变化主要取决于阳离子的种类，即离子的大小和在lattice.Thermal膨胀系数测定商业牙科瓷，化学计量的tetraorbicleucite，铯添加立方白榴石，三种玻璃，和白榴石和玻璃的混合物。利用高温X射线衍射法计算了白榴石的热膨胀系数。结果表明，由于白榴石颗粒周围的玻璃基体中仍存在较高的应力，因此要求白榴石颗粒周围的玻璃具有高于650℃的玻璃转变温度，并研究了不同白榴石含量、颗粒尺寸和烧成条件对玻璃性能的影响研究了牙科陶瓷的双轴弯曲强度、维氏硬度、热膨胀和人牙釉质的磨损。FE-SEM和XRD分析表明，烧结过程中，在立方白榴石颗粒与玻璃基体的界面处，立方白榴石转变为四方白榴石。不同立方白榴石含量的瓷的双轴弯曲强度无显著性差异（p<0.05）。结果表明，立方晶系白榴石的分散度对瓷的抗弯强度影响不大，而与四方晶系白榴石的分散度有关。含立方白榴石的烧结试样的维氏硬度值随立方白榴石粒度的增大而增大。含有立方白榴石的烧结试样的热膨胀系数随其含量的增加而增加。立方白榴石含量对磨损率影响不大。少

X-ray diffractometry (XRD) was used to analyze the crystal phases of three commercial dentin and incisal porcelains prepared by normal cooling, quenching in water, and controlled slow annealing after normal firing. The results suggest that the cooling condition has little effect on the microstructural changes of leucite crystals in the dental porcelains, since the leucite crystals were formed at a higher temperature range than the firing - and cooling- temperature range and were stabilized by incorporation of additives into the lattice.The leucite crystals having modified compositions from stoichiometric one were prepared by the incorporation of Na, Rb, Cs, Ca, Ba, and Sb substituted for 5 -50 at% of K in the leucite. The lattice parameters of a- and c-axes of these tetragonal leucite were derived from the diffraction angles of (400) and (004) peaks due to tetragonal leucite, respectively. It is concluded that the crystal lattice of leucite was deformed by the incorporation of cations … More substituted for K and their variations mainly depend upon the kind of cation, namely ionic size and substitution site in the lattice.Thermal expansion coefficients were determined using a dilatometer on commercial dental porcelains, stoichiometric tetragonal leucite, cesium added cubic leucite, three kinds of glasses, and mixtures of leucite and glass. Thermal expansion coefficients of leucite were also derived from the lattice parameter changes using high temperature X-ray diffractometry. The results suggested that the glass surrounded around leucite particles is required to have a high glass transformation temperature than 650℃ because of the remains of high stress in the surrounded matrix glass.The influences of cubic leucite having various contents, particle sizes, and firing conditions on various properties (biaxial flexure strength, Vicker's hardness, thermal expansion, and abrasion of human enamel) of dental porcelains were investigated. FE-SEM and XRD analyzes revealed that cubic leucite was changed to tetragonal leucite on the boundary between cublic leucite particle and glass matrix by firing. There were no significant differences in the biaxial flexure strengths of the experimental porcelains containing different content of cubic leucite (p<0.05). It is concluded that the flexure strength of feldspathic dental porcelains was independent on the dispersion of cubic leucite, but depended on the dispersion of tetragonal leucite. Vicker's hardness values of the fired specimens containing cubic leucite increased with the particle size of cubic leucite. Thermal expansion coefficient of the fired specimens containing cubic leucite increased with their contents. Contents of cubic leucite had little effect on abrasion rate. Less