Effects of small-grit grinding and glazing on mechanical behaviors and ageing resistance of a super-translucent dental zirconia

Objectives: The purpose of this study is to elucidate the effects of small-grit grinding on the mechanical behaviors and ageing resistance of a super-translucent dental zirconia and to investigate the necessity of glazing for the small-grit ground zirconia.Methods: Small-grit grinding was performed using two kinds of silicon carbide abrasive papers. The control group received no grinding. The unground surfaces and the ground surfaces were glazed by an experienced dental technician. Finally, the zirconia materials were thermally aged in water at 134 degrees C for 5 h. After aforementioned treatments, we observed the surface topography and the microstructures, and measured the extent of monoclinic phase, the nano-hardness and nano-modulus of the possible transformed zone and the flexural strength.Results: Small-grit grinding changed the surface topography. The zirconia microstructure did not change obviously after surface treatments and thermal ageing; however, the glaze in contact with zirconia showed cracks after thermal ageing. Small-grit grinding did not induce a phase transformation but improved the flexural strength and ageing resistance. Glazing prevented zirconia from thermal ageing but severely diminished the flexural strength. The nano-hardness and nano-modulus of the surface layer were increased by ultrafine grinding.Conclusions: The results suggest that small-grit grinding is beneficial to the strength and ageing resistance of the super-translucent dental zirconia; however, glazing is not necessary and even impairs the strength for the supertranslucent dental zirconia. Clinical significance: This study is helpful to the researches about dental grinding tools and maybe useful for dentists to choose reasonable zirconia surface treatments.

目的：本研究旨在阐明小粒度研磨对超透明白榴石增强牙科氧化锆的力学行为和抗老化性能的影响，并探讨对小粒度研磨后的氧化锆进行上釉的必要性。 方法：使用两种碳化硅砂纸进行小粒度研磨。对照组不进行研磨。未研磨表面和研磨表面由经验丰富的牙科技师进行上釉。最后，将氧化锆材料在134℃的水中热老化5小时。经过上述处理后，我们观察表面形貌和微观结构，并测量单斜相的程度、可能转变区域的纳米硬度和纳米模量以及弯曲强度。 结果：小粒度研磨改变了表面形貌。表面处理和热老化后，氧化锆的微观结构没有明显变化；然而，与氧化锆接触的釉层在热老化后出现裂纹。小粒度研磨没有引起相变，但提高了弯曲强度和抗老化性能。上釉防止了氧化锆的热老化，但严重降低了弯曲强度。超细研磨提高了表面层的纳米硬度和纳米模量。 结论：结果表明，小粒度研磨有利于超透明白榴石增强牙科氧化锆的强度和抗老化性能；然而，对于超透明白榴石增强牙科氧化锆来说，上釉是不必要的，甚至会损害其强度。 临床意义：本研究有助于牙科研磨工具的研究，可能对牙医选择合理的氧化锆表面处理方法有用。