Lucas Thomas J, Lawson Nathaniel C, Janowski Gregg M, Burgess John O
Department of Restorative Sciences, Biomaterials Division, University of Alabama at Birmingham School of Dentistry, 1919 7th Ave S, SDB 604, Birmingham, AL 35294, United States; Department of Materials Science and Engineering, University of Alabama at Birmingham School of Engineering, Hoehn Engineering Building, HOEHN 115A, 1075 13th Street South, Birmingham, AL 35294-4440, United States.
Department of Restorative Sciences, Biomaterials Division, University of Alabama at Birmingham School of Dentistry, 1919 7th Ave S, SDB 604, Birmingham, AL 35294, United States.
Dent Mater. 2015 Dec;31(12):1487-92. doi: 10.1016/j.dental.2015.09.014. Epub 2015 Oct 17.
Low-temperature-degradation (LTD) has been reported to cause property changes in yttria-tetragonal zirconia polycrystals (Y-TZP). The current study measured monoclinic phase transformation of Y-TZP with different grain sizes and corresponding property changes due to artificial aging.
the grain size of aged Y-TZP will not influence its transformation, roughness, hardness or modulus of elasticity.
Four groups of Y-TZP were examined with differing grain sizes (n=5). The line intercept technique was used to determine grain sizes on SEM images (100,000×). Artificial aging was accomplished by autoclaving at 2 bar pressure for 5 h. X-ray diffraction (30 mA, 40 kV) was used to measure tetragonal to monoclinic transformation (t→m). Surface roughness analysis was performed using a non-contact surface-profilometer. Nano-hardness and modulus of elasticity were measured using nano-indentation.
SEM analyses showed different grain sizes for each sample group (0.350 μm, 0.372 μm, 0.428 μm, and 0.574 μm). The fraction of t→m transformation increased as grain size increased; furthermore, aging of zirconia caused increased roughness. Modulus and hardness after aging displayed no significant correlation or interaction with grain size.
Smaller grains caused less transformation, and aging caused increased roughness, but grain size did not influence the amount of increased surface roughness. Future studies are needed to determine the effects of grain size on the wear and fracture properties of dental zirconia.
据报道，低温降解（LTD）会导致氧化钇-四方相氧化锆多晶体（Y-TZP）的性能发生变化。本研究测量了不同晶粒尺寸的Y-TZP的单斜相转变以及人工时效导致的相应性能变化。
时效后的Y-TZP的晶粒尺寸不会影响其转变、粗糙度、硬度或弹性模量。
检查四组晶粒尺寸不同的Y-TZP（n = 5）。采用线截距法在扫描电子显微镜图像（100,000倍）上测定晶粒尺寸。通过在2巴压力下高压灭菌5小时来实现人工时效。使用X射线衍射（30毫安，40千伏）测量四方相向单斜相的转变（t→m）。使用非接触式表面轮廓仪进行表面粗糙度分析。使用纳米压痕测量纳米硬度和弹性模量。
扫描电子显微镜分析显示每个样品组的晶粒尺寸不同（0.350微米、0.372微米、0.428微米和0.574微米）。t→m转变的比例随着晶粒尺寸的增加而增加；此外，氧化锆的时效导致粗糙度增加。时效后的模量和硬度与晶粒尺寸没有显著的相关性或相互作用。
较小的晶粒导致较少的转变，时效导致粗糙度增加，但晶粒尺寸不影响表面粗糙度增加的量。需要进一步的研究来确定晶粒尺寸对牙科氧化锆磨损和断裂性能的影响。
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