Investigating the effect of surface and heat treatment on mechanical properties of zirconia based ceramicsand evaluating by X-ray difractometer surface analyses

In dentistry zirconia based ceramics are frequently used because of their high mechanical properties. However, different surface and heat treatment methods are believed effect their mechanical properties . In this in-vitro study, the effect of surface and heat treatment on mean surface roughness, phase transformation analysis and biaxial flexural strength of two zirconia based core materials were investigated.In this study 40 discs specimens of the materials were fabricated with a diameter of 15 mm and 1.2±0.2 mm. Fourty discs from each material were randomly divided into four groups (control, sandblasting, etching with laser energy, firing process).Surface roughness was measured by using profilometer. Surface topographic analysis was examined by scanning electron microscopy (SEM). X-ray diffraction analysis was performed to characterize the crystalline phases for all specimens.All spicemen?s flexural strength were examined by biaxial flexural strength test (piston on 3 balls).The data were analyzed by using the Kruskal Wallis H Test and Mann Whitney U Test for multiple comparison. Spearman?s rho (?) coefficient was usedto investigate relationshipbetween surface roughness roughness and biaxial flexural strength, relative amount of monoclinic zirconia and biaxial flexural strength, surface roughness and relative amount of monoclinic zirconia. Heat and surface treatments effect the surface roughness of two zirconia based core materials but the diffrences are not significantly important. X-ray diffraction analysis revealed that in all materials, transformation from tetragonal to monoclinic phases was decreased by heat treatments. Firing significantly decreased the strength values of two materials. The mean biaxial flexural strength of laser and sandblasted group were significantly different. A liner correlation was found between the roughness of the surface and strength for all groups. However, significant correlation was found only in firing DC-Zirkon specimens.