Department of Prosthodontics, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R. China.
Shanghai Key Laboratory of Stomatology & Shanghai Research Institute of Stomatology, National Clinical Research Center of Stomatology, Shanghai, P.R. China.
J Prosthodont. 2019 Jan;28(1):e404-e410. doi: 10.1111/jopr.12946. Epub 2018 Jul 20.
To evaluate the influence of specimen thickness and low-temperature degradation (LTD) on yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP).
Thin discs of Y-TZP from four manufacturers were sintered according to each manufacturer's recommendations, cut into 23 mm (length) × 4 mm (width) × 0.8 mm/1.5 mm (thickness) specimens, artificially aged under standard autoclave sterilization conditions (34°C at 0.2 MPa for 10 and 20 hours), and finally ground and polished. Tetragonal to monoclinic transformation was confirmed by X-ray diffraction (XRD) analysis. Flexural strength was measured by 3-point bending tests and Vickers hardness measurements. Fracture surfaces were examined by scanning electron microscopy (SEM).
SEM investigation revealed that with increasing aging time, the surface defects and grain size increased, particularly in the 20-hour group. Compared with the 1.5 mm group, the 0.8 mm group showed more significant defects, irrespective of aging time. The flexural strengths of Y-TZP materials decreased with a decrease in the thickness. Moreover, LTD of Y-TZP can cause significant tetragonal to monoclinic transformation, which also results in a statistically significant decrease in the flexural strength.
A thinner Y-TZP specimen was likely to present surface defects and microcracks after aging. In addition, the flexural strengths decreased with a decrease in the thickness, a notable fact for further studies.
评估标本厚度和低温降解（LTD）对钇稳定四方氧化锆多晶（Y-TZP）的影响。
根据各制造商的建议，将来自四个制造商的 Y-TZP 薄片烧结，切割成 23mm（长度）×4mm（宽度）×0.8mm/1.5mm（厚度）的标本，在标准高压灭菌条件下（34°C 时 0.2MPa 下 10 和 20 小时）进行人工老化，并最终研磨和抛光。通过 X 射线衍射（XRD）分析确认四方相到单斜相的转变。通过三点弯曲试验和维氏硬度测量来测量弯曲强度。通过扫描电子显微镜（SEM）检查断裂面。
SEM 研究表明，随着老化时间的增加，表面缺陷和晶粒尺寸增加，尤其是在 20 小时组中。与 1.5mm 组相比，0.8mm 组在任何老化时间下均显示出更明显的缺陷。Y-TZP 材料的弯曲强度随厚度的减小而降低。此外，Y-TZP 的 LTD 会导致明显的四方相到单斜相转变，这也会导致弯曲强度的显著下降。
经过老化后，较薄的 Y-TZP 标本可能会出现表面缺陷和微裂纹。此外，随着厚度的减小，弯曲强度降低，这是进一步研究的重要事实。
