The effect of surface treatment of 3 different zirconia based full ceramics on mean surface roughness and flexural strength and the determination of the effects of surface treatment of the zirconia systems by X-ray difractometer surface analyse

Zirconia ceramics have been recently introduced in dentistry for fabrication of crowns and fixed partial dentures in order to have remarkable mechanical properties compared to other substructure ceramics. However, mechanical properties of zirconia can be directly influenced by different surface treatment methods. The aim of this study was to evaluate and compare the effect of surface grinding and sandblasting on surface roughness, phase chances and flexural strength of three yttria stabilized tetragonal zirconia (Y-TZP) core materials.Specimens of three Y-TZP core materials (Cercon, DentaCad, Zirkonzahn) were fabricated with a diameter of 14 mm and 1.3 ± 0.2 mm. Thirty discs from each material were randomly divided into three groups of ten. For each group, a different surface treatment was applied: grinding, grinding followed by sandblasting and a control group. Surface roughness was measured by using profilometer and X-ray diffraction analysis was performed to characterize the crystalline phases for all specimens. Finally, biaxial flexural strength (piston on 3 balls) was determined. The data were analyzed by using the 2-way ANOVA test (?. 0.01) Multiple comparison was performed with the Duncan test. Weibull statistics was used to analyze the variability of flexural strength. To determine the influence of the surface treatments on the Y-TZP core materials, Pearson correlations between surface roughness and biaxial flexural strength and relative amount of monoclinic zirconia were calculated.Control groups of three materials had different surface roughness. The surface treatments were significantly effected the surface roughness of the materials (p<0.01). Grinding and sandblasting were increased surface roughness of Cercon whereas decreased surface roughness of Zirkonzahn. Surface roughness of DentaCAD specimens were decreased by grinding and increased by sandb X-ray diffraction analysis revealed that control groups of Cercon and Zirkonzahn specimens composed of tetragonal zirconia. DentaCADcontrol group which was machined from fully sinterized Y-TZP blocks was contained monoclinic zirconia. In all materials, transformation from tetragonal to monoclinic phases occurred after surface treatments. Grinding significantly decreased the strength values of control groups in all materials (p<0.01). The mean biaxial flexural strength of control and sandblasted group were not significantly different (p>0.01). A liner correlation was found between the roughness of the surface and strength for all groups. However, significant correlation (r:-0.75, p<0.01) was found in ground Zirkonzahn specimens.