Effects of Different Surface Treatments on Flexural Strength of Zirconium Oxide Cores

Abstract

Objective: The aim of this study was to investigate the effect of different surface treatments on the biaxial flexural strength of zirconia and to determine phase transformation before and after sintering. Materials and Methods: 150 cylindrical specimens with the dimensions 15 mm diameter and 1,3 mm height were obtained from semi-sintered Y-TZP blocks. These specimens were randomly separated into subgroups; sandblasting, Er:YAG laser, Nd:YAG laser, Er:YAG laser+sandblasting, Nd:YAG laser+sandblasting, fine grain bur, coarse grain bur. Half of the semi-sintered Y-TZP samples were treated before sintering and the others were treated after the sintering procedures. No treatment was performed in control group. Biaxial flexural strength test was performed to all samples. X-ray diffraction analysis (XRD) were performed to identify transformed monoclinic phase. The data were analyzed by Kruskal-Wallis, Man Whitney U test and Wilcoxon test (p<0,05). Results: Specimens that were treated before sintering had lower biaxial flexural strength. The highest biaxial flexural strength values in all groups were seen in sandblasting groups and the lowest in grinding groups. According to the XRD analysis the highest phase transforme was determined in sandblasting groups. Sandblasting, Er-YAG laser+sandblasting and Nd-YAG laser+sandblasting were greatly increased the biaxial flexural strength of all the surface treatments after sintering. All the sandblasting treatments were found more monoclinic phase was found than other groups. Conclusions: Surface treatments were found to affect both the mechanical properties and phase changes of zirconia.