Effect Of Polishing And Glazing On Cyclic Fatigue Properties Of Y-TZP Zirconia

Objectives Yttrium-stabilized zirconia was widely used as restoration material because of its excellent performance.But there were still cyclic fatigue failure phenomena during use.In addition to its own characteristics,the fatigue characteristic was also influenced by incorrect clinical operation.It was very important to study the effect of polishing and glazing on the cyclic fatigue performance of yttrium-stabilized zirconia.Methods Two types of zirconia specimens were prepared: the control group（20mm ×4mm × 2.0mm,10 specimens）and the experimental group（20mm × 4mm × 2.4mm,50specimens）.The experimental group was randomly divided into 5 groups according different treatments（a: grinding,b: polishing,c: polishing paste,d: glazing,e: polishing and glazing）.The specimens of each group were randomly divided into two groups.One group was loaded on the fatigue test machine for 2×106 cycles,and the other group was directly tested.X-ray diffraction was used to analyze the crystal phase before and after loading,and the contents of monoclinal phase was calculated.The surface morphology was observed by scanning electron microscope.Three-point bending strength was detected by the universal experimental machine.The Weibull modulus m and Weibull characteristic strength value σ₀ were obtained by Weibull analysis.The data were analyzed by SPSS22.0 software,and the test standard was set as 0.05.Results 1 Results of XRD: Before cyclic loading,there were no monoclinal phase contents in the specimens of control group,group d and group e,while those in group a,b and c were 15.419%,13.450% and 7.994% respectively.After cyclic loading,monoclinal phase contents were 29.392%,12.923%,6.257%,5.602%,61.372% and 50.480% respectively.2Results of SEM: Before cyclic loading,the surface of control specimen was smooth and dense.The surface of group a was rough,irregular and had some scratches.The surface of group b and c was smoother.The surface of group d,e was smooth and uniform without obvious flaws.After cyclic loading,the surface morphology showed no significant changes in control group and group c.Flaky stripping and obvious stripping particle belts appeared at group a.Scattered exfoliating particles and narrow shallow pits were seen in group b.A large number of stripping particles scattered at the surface of group d and group e.3Results of three-point bending strength: Before cyclic loading,there were no significant differences among all groups.After cyclic loading,the three-point bending strength of group b and c were higher than other groups.There were statistical differences between groups d and e（P<0.05）.4 Results of Weibull analysis: Before cyclic loading,there was no significant change in Weibull modulus and characteristic strength in each group.After cyclic loading,the Weibull modulus and characteristic strength were all decreased.The value of group b and group c were higher than that of group d.There were no significant differences among the other groups.Conclusions Under this experimental condition,the zirconia surface was ground and subjected to various treatments.After certain times of cyclic loading,its bending strength was significantly different.The bending strength of polished zirconia was significantly higher.In addition,the bending strength of the glazed group after polishing was better than that of the direct glazed group after grinding.It could be concluded that polishing can effectively improve the fatigue resistance of the material.Therefore,after grinding,the surface of zirconia must be polished completely.If glazing was necessary,it must be polished before glazing in order to minimize the side effects.Figure17;Table4;Reference 106...