OBJECTIVES 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). METHODS Two types of tungsten-carbide burs (TC), 6-blade (TC1) and 8-blade (TC2) were used to grind 3Y-TZP, in a dental air-turbine handpiece with water-cooling and were also subjected to air-particle abrasion (APA): TC1 + APA and TC2 + APA; and rubber polishing (RP): TC1 + RP and TC2 + RP; one group received only rubber-polishing RP. The control group received no treatment. Surface characterization was examined by surface roughness (Ra) 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. RESULTS Groups TC1 and TC2 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 TC2 grinding had significant higher mean BFS than those following TC1 grinding respectively (p < 0.05). SEM revealed distinct micro-cracks after tungsten-carbide grinding. SIGNIFICANCE 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.

中文翻译：

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碳化钨磨削对牙科氧化锆强度的不利影响。

目的本研究研究了碳化钨磨削对牙科用3 mol％氧化钇稳定的氧化锆（3Y-TZP）的表面特性和机械强度的影响。方法在水冷式牙科手机中，使用6刀片（TC1）和8刀片（TC2）两种硬质合金车针磨削3Y-TZP，并对它们进行空气处理-颗粒磨损（APA）：TC1 + APA和TC2 + APA；橡胶抛光（RP）：TC1 + RP和TC2 + RP；一组仅接受橡胶抛光RP。对照组未接受治疗。通过表面粗糙度（Ra）和原子力显微镜检查表面表征。还通过扫描电子显微镜（SEM）和X射线衍射（XRD）观察了样品的微观结构和晶相。每组15个样品进行了三球活塞双轴弯曲强度（BFS）测试，并在SEM下观察了断裂的样品，以研究断裂的起源模式。在α= 0.05时进行单向方差分析，Kruskal-Wallis检验和Weibull分析。结果TC1和TC2组的平均BFS最低（p <0.05），强度降低了74％。碳化钨研磨后，APA和RP均显着提高了平均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均显着降低（p <0.05）。TC2研磨后的APA和橡胶抛光的平均BFS分别高于TC1研磨后的平均BFS（p <0.05）。SEM显示碳化钨研磨后有明显的微裂纹。