Prosthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China; The Affiliated Stomatology Hospital and School of Stomatology, School of Medicine and Key Laboratory of Oral Biomedical Research of Zhejiang Province, Zhejiang University, Hangzhou, China.
Prosthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China.
Dent Mater. 2020 Apr;36(4):560-569. doi: 10.1016/j.dental.2020.02.002. Epub 2020 Feb 13.
This study investigated the effects of tungsten-carbide grinding on the surface characteristics and mechanical strength of dental 3 mol% yttria-stabilized zirconia (3Y-TZP).
Two types of tungsten-carbide burs (TC), 6-blade (TC) and 8-blade (TC) were used to grind 3Y-TZP, in a dental air-turbine handpiece with water-cooling and were also subjected to air-particle abrasion (APA): TC + APA and TC + APA; and rubber polishing (RP): TC + RP and TC + RP; one group received only rubber-polishing RP. The control group received no treatment. Surface characterization was examined by surface roughness (R) and atomic force microscopy. Specimens were also observed with scanning electron microscopy (SEM) and X-ray-diffraction (XRD) for microstructure and crystalline phases. A piston-on-three-balls biaxial-flexural strength (BFS) test was performed with 15 samples-per-group and the broken specimen were observed under SEM to investigate the fracture origin pattern. One-way ANOVA, Kruskal-Wallis test and Weibull analysis were performed at α = 0.05.
Groups TC and TC had the lowest mean BFS (p < 0.05) with up to 74 % reduction in strength. APA and RP both significantly increased the mean BFS after tungsten-carbide grinding but was still less than the control (p < 0.05). Compared to the control, the mean BFS was significantly reduced for all groups except for the RP group (p < 0.05). APA and rubber-polishing following TC grinding had significant higher mean BFS than those following TC grinding respectively (p < 0.05). SEM revealed distinct micro-cracks after tungsten-carbide grinding.
Tungsten-carbide burs (6- and 8-blade) are not recommended for zirconia grinding due to the significant reduction of biaxial-flexural strength and observed micro-structural surface and subsurface damage.
本研究旨在探讨碳化钨磨料对牙科 3 摩尔氧化钇稳定四方氧化锆（3Y-TZP）表面特性和力学强度的影响。
使用两种类型的碳化钨磨头（TC），即 6 刃（TC）和 8 刃（TC），在带水冷的牙科空气涡轮手机上研磨 3Y-TZP，并进行空气粒子喷砂（APA）：TC+APA 和 TC+APA；以及橡胶抛光（RP）：TC+RP 和 TC+RP；一组仅接受橡胶抛光 RP。对照组未接受任何处理。通过表面粗糙度（R）和原子力显微镜对表面特性进行了检测。还通过扫描电子显微镜（SEM）和 X 射线衍射（XRD）观察了微观结构和晶体相。对 15 个样本/组进行了活塞对三个球双向弯曲强度（BFS）测试，并用 SEM 观察了断裂样本，以研究断裂起源模式。采用单因素方差分析、Kruskal-Wallis 检验和威布尔分析，α 值为 0.05。
TC 和 TC 组的平均 BFS 最低（p＜0.05），强度降低高达 74%。APA 和 RP 均显著提高了碳化钨磨料研磨后的平均 BFS，但仍低于对照组（p＜0.05）。与对照组相比，除 RP 组外，所有组的平均 BFS 均显著降低（p＜0.05）。与 TC 磨料研磨后分别进行 APA 和橡胶抛光相比，研磨后进行 APA 和橡胶抛光的平均 BFS 显著更高（p＜0.05）。SEM 显示碳化钨磨料研磨后出现明显的微裂纹。
不建议使用 6 刃和 8 刃碳化钨磨头研磨氧化锆，因为其显著降低了双向弯曲强度，并观察到微观结构表面和次表面损伤。
