Department of Prosthodontics and Periodontology, University of São Paulo, Bauru School of Dentistry, Bauru, SP, Brazil.
Department of Prosthodontics and Periodontology, University of São Paulo, Bauru School of Dentistry, Bauru, SP, Brazil.
J Mech Behav Biomed Mater. 2020 Dec;112:104021. doi: 10.1016/j.jmbbm.2020.104021. Epub 2020 Aug 18.
To characterize the optical and mechanical properties of a commercial and in-house translucent Y-TZP before and after aging in autoclave or hydrothermal reactor.
In-house experimental discs were obtained through uniaxial and isostatic pressing a translucent Y-TZP powder and sintering at 1,550 °C/1 h. Commercial discs were milled from pre-sintered blocks fabricated with the same powder through uniaxial and isostatic pressing and sintering. Discs were allocated into three groups according to aging condition: immediate, aged via autoclave, or reactor (134 °C, 20 h, 2.2 bar). Crystalline content and microstructure were evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Residual compressive stress (CS) was determined by Raman spectroscopy. Optical properties were determined by the contrast ratio (CR) and translucency parameter (TP) using reflectance data. Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength tests.
XRD and SEM revealed a typical Y-TZP crystalline content, chiefly tetragonal phase, and a dense crystalline matrix for both processing protocols. Reactor aging triggered a more pronounced t-m transformation relative to autoclave. In-house and commercial Y-TZPs demonstrated similar CR and TP, with reactor aging significantly increasing their translucency. Similarly, reactor aging influenced Vickers hardness and fracture toughness. In-house processed Y-TZP clearly demonstrated the presence of CS, whereas commercial Y-TZP showed no presence of CS. Non-aged in-house Y-TZP resulted in significantly lower characteristic strength relative to commercial Y-TZP. While aging protocols significantly increased the characteristic strength of in-house Y-TZP, reactor significantly decreased commercial Y-TZP characteristic strength. Both Y-TZP processing protocols demonstrated high reliability at high-stress missions, with no detrimental effect of aging.
Laboratory aging methodology significantly influenced optical and mechanical properties of a commercial and in-house translucent Y-TZP.
在高压釜或水热反应堆中老化前后，对一种商业和内部半透明 Y-TZP 的光学和机械性能进行特征描述。
通过单向和等静压将半透明 Y-TZP 粉末成型并在 1,550°C/1 小时下烧结，获得内部实验用圆盘。商业圆盘通过单向和等静压以及预烧结块的烧结从预制烧结块中铣削而成，使用相同的粉末。根据老化条件将圆盘分为三组：立即老化、高压釜老化或反应堆老化（134°C，20 小时，2.2 巴）。使用 X 射线衍射（XRD）和扫描电子显微镜（SEM）评估晶体含量和微观结构。通过拉曼光谱确定残余压缩应力（CS）。通过反射率数据确定光学性质，包括对比率（CR）和透光率参数（TP）。通过维氏硬度、断裂韧性和双轴弯曲强度测试评估机械性能。
XRD 和 SEM 显示两种加工方案均具有典型的 Y-TZP 晶体含量，主要为四方相和致密的晶体基质。与高压釜老化相比，反应堆老化引发了更明显的 t-m 转变。与商业 Y-TZP 相比，内部和商业 Y-TZP 具有相似的 CR 和 TP，但反应堆老化显著提高了它们的透光率。同样，反应堆老化影响了维氏硬度和断裂韧性。内部加工的 Y-TZP 明显表现出 CS 的存在，而商业 Y-TZP 则没有 CS 的存在。与商业 Y-TZP 相比，未经老化的内部 Y-TZP 的特征强度明显较低。虽然老化方案显著提高了内部 Y-TZP 的特征强度，但反应堆显著降低了商业 Y-TZP 的特征强度。两种 Y-TZP 加工方案在高应力任务下均表现出高可靠性，且老化无不利影响。
实验室老化方法显著影响商业和内部半透明 Y-TZP 的光学和机械性能。
