Qualitative and quantitative evaluations of topography for CAD/CAM all ceramic zirconia after different surface treatments

Abstract

Background and objectives: The purpose of this in vitro study was to evaluate the effect of grinding, reglazing and polishing procedures on the surface roughness of monolithic zirconia qualitatively and quantitatively. Materials and methods: Thirty-six disc-shaped yttrium-stabilized zirconium oxide specimens were milled from pre-sintered zirconia blanks using CAD-CAM machine with a diameter of 12mm and thickness of 1.4mm for twenty-seven discs while 12mm and 1.2mm for nine discs as a control group. After that, they were sintered and overglazed. The control group (GA) left untouched while the other twenty-seven specimens were subjected to standardized wet grinded with a coarse diamond rotary instrument. Then they were randomly divided into three groups (nine specimens for each): grinded group (GB) without any additional surface treatment; reglazed group (GC) by adding galze material; polished group (GD) polishing with an intraoral zirconia polishing kit Kenda in a 2-step procedure. Then specimens were evaluated under a stereomicroscope. The surface roughness values were measured with a profilometer for all groups. The mean of surface roughness values was calculated and analyzed using one-way ANOVA and using LSD significant difference tests for comparison between groups (a = 0.05). Results: Stereomicroscopic images revealed that the grinded specimen showed grooves and scratches, reglazed surface showed the same criteria as control with a little bit more evidence of irregularities. While polished specimen appeared smoother and more homogeneity. Statistically significant differences were noted among the experimental groups, in which GB resulted in the highest roughness, GD with the lowest roughness. While GC was close to GA. Conclusions: Roughness significantly increased after grinding, but polishing decreased roughness significantly while glazing restores the smoothness.