Tsukada Gakuji, Sueyoshi Hidekazu, Kamibayashi Hiroki, Tokuda Masayuki, Torii Mitsuo
Department of Restorative Dentistry and Endodontology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima, Japan.
Department of Mechanical Engineering, Graduate School of Science and Engineering, Kagoshima University, Korimoto, Kagoshima, Japan.
J Dent. 2014 Dec;42(12):1569-76. doi: 10.1016/j.jdent.2014.09.012. Epub 2014 Oct 2.
The purpose of this study was to fabricate functionally graded materials (FGMs) consisting of yttria-stabilised tetragonal zirconia polycrystal (Y-TZP) and porcelain using spark plasma sintering (SPS) and examine the influence of their microstructures and thermal stress on their bending strengths.
Two types of four-layered Y-TZP/porcelain FGMs having a constant layer thickness and a varying layer thickness, Y-TZP/porcelain composite materials having a microstructure corresponding to each layer in FGMs and monolithic materials of Y-TZP and porcelain were fabricated by SPS. The Y-TZP/porcelain volume fraction of each layer in FGMs was varied over 100/0-70/30. Three-point bending test, X-ray diffraction, density measurement, microstructure observation, and thermal stress estimation were performed to characterise the materials.
The bending strength of the Y-TZP/porcelain composite materials decreased with the volume fraction of the porcelain. About FGMs, when the 100%Y-TZP layer was on the tensile stress side during the bending test, the bending strength was almost the same as that of the 100%Y-TZP monolithic material. On the other hand, when the 100%Y-TZP layer was on the compressive stress side, the bending strength of FGM having a constant layer thickness was almost the same as that of the 70%Y-TZP+30%porcelain composite material, while the bending strength of FGM with a varying layer thickness was significantly higher than that of the 70%Y-TZP+30%porcelain composite material.
The FGMs prepared and analyzed in this research can potentially be used for crowns and bridges as well as for inlays and onlays.
The SPS method could effectively fabricate the Y-TZP/porcelain FGMs, and the bending strength results revealed that the graded structure was very efficient to raise the bending strength.
本研究旨在使用放电等离子烧结（SPS）制备由氧化钇稳定的四方氧化锆多晶体（Y-TZP）和陶瓷组成的功能梯度材料（FGM），并研究其微观结构和热应力对弯曲强度的影响。
通过SPS制备了两种具有恒定层厚和可变层厚的四层Y-TZP/陶瓷FGM、具有与FGM中各层相对应微观结构的Y-TZP/陶瓷复合材料以及Y-TZP和陶瓷的整体材料。FGM中各层的Y-TZP/陶瓷体积分数在100/0至70/30之间变化。进行了三点弯曲试验、X射线衍射、密度测量、微观结构观察和热应力估计以表征材料。
Y-TZP/陶瓷复合材料的弯曲强度随陶瓷体积分数的增加而降低。关于FGM，在弯曲试验中当100%Y-TZP层处于拉应力侧时，其弯曲强度与100%Y-TZP整体材料几乎相同。另一方面，当100%Y-TZP层处于压应力侧时，具有恒定层厚的FGM的弯曲强度与70%Y-TZP + 30%陶瓷复合材料几乎相同，而具有可变层厚的FGM的弯曲强度显著高于70%Y-TZP + 30%陶瓷复合材料。
本研究中制备和分析的FGM有潜力用于制作冠桥以及嵌体和高嵌体。
SPS方法可有效制备Y-TZP/陶瓷FGM，弯曲强度结果表明梯度结构能非常有效地提高弯曲强度。
