Mechanical and microstructural properties of ultra-translucent dental zirconia ceramic stabilized with 5 mol% yttria
Mechanical and microstructural properties of ultra-translucent dental zirconia ceramic stabilized with 5 mol% yttria
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DOI：
10.1016/j.jmbbm.2020.103974
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发表时间：
2020-11-01
影响因子：
3.9
通讯作者：
Nakamura, Keisuke
中科院分区：
文献类型：
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作者：
Harada, Akio;Shishido, Shunichi;Nakamura, Keisuke
由3 mol.%氧化钇稳定的氧化锆（3YZ）变得越来越流行。最近，5 mol.%制备了氧化钇稳定的氧化锆（5YZ），它显著改善了3YZ的透光性。然而，其机械和微观结构性能，特别是那些受低温降解（LTD），尚未完全阐明。本研究的目的是建立之间的关系5YZ的弯曲强度与或不与高压灭菌诱导LTD和其微观结构性能。为此，从5YZ和3YZ块上切下总共320个条形试样，每组中的一半试样在134 ℃下高压灭菌50小时。通过三点弯曲试验测定了它们的弯曲强度，并用威布尔统计方法对所得结果进行了分析。通过扫描电镜（SEM）和X射线衍射分析了试样的晶粒尺寸和晶体结构。此外，通过拉曼显微镜和横截面表面分析来检查LTD诱导的相变。5YZ和3YZ的特征强度分别为约620和950 MPa，并且发现5YZ在相变方面比3YZ更耐LTD。然而，少量的单斜相检测，即使在5YZ高压灭菌50小时后，这显着降低其弯曲强度和可靠性。SEM分析的结果表明，5YZ是由两个不同的区域：一个占主导地位的大颗粒（中值尺寸：0.8 μ m）和分散的小颗粒（中值尺寸：0.4 μ m）的区域矩阵。相变分析和断口分析数据表明，小晶粒区域受到LTD的强烈影响，可能代表了断裂起源。在临床应用5YZ整体式义齿时，应考虑上述性能。
Monolithic dental prostheses fabricated from 3 mol.% yttria-stabilized zirconia (3YZ) are becoming increasingly popular. Recently, 5 mol.% yttria-stabilized zirconia (5YZ) which significantly improves the translucency of 3YZ has been prepared. However, its mechanical and microstructural properties, especially those affected by low-temperature degradation (LTD), have not been fully elucidated yet. The objective of the present study was to establish the relationship between the flexural strength of 5YZ with or without autoclave-induced LTD and its microstructural properties. For this purpose, a total of 320 bar-shaped specimens were cut from 5YZ and 3YZ blocks, and half of the specimens in each group were autoclaved at 134 degrees C for 50 h. Their flexural strengths were determined by conducting three-point bending tests, and the obtained results were analyzed by the Weibull statistical method. Grain sizes and crystalline structures of the specimens were analyzed by scanning electron microscopy (SEM) and X-ray diffraction, respectively. Additionally, the LTD-induced phase transformation was examined by Raman microscopy and cross-sectional surface analysis. The characteristic strengths of 5YZ and 3YZ were approximately 620 and 950 MPa, respectively, and 5YZ was found to be more resistant to LTD in terms of phase transformation than 3YZ. However, a low amount of the monoclinic phase was detected even in 5YZ after 50 h of autoclaving, which significantly decreased its flexural strength and reliability. The results of SEM analysis revealed that 5YZ was composed of two distinct regions: a dominant matrix with large grains (median size: 0.8 mu m) and scattered areas with small grains (median size: 0.4 mu m). Phase transformation analysis and fractography data indicated that the small-grain region was strongly affected by LTD and likely represented a fracture origin. The described properties should be considered during the clinical application of monolithic 5YZ dental prostheses.