Evaluation of the topographical surface changes and roughness of zirconia after different surface treatments

The purpose of this study was to investigate the surface morphology and roughness of zirconia after different surface treatments. Eighty sintered zirconia specimens were divided into four groups (n = 20) according to the surface treatments received: no treatment, erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation (400 mJ, 10 Hz, 4 W, 100 MPS, distance: 1 mm), tribochemical silica coating with 30 μm aluminum oxide (Al₂O₃) modified by silica, and air abrasion with 110 μm Al₂O₃ particles. After the surface treatments, the surface roughness (Ra in μm) of the specimens was evaluated using a surface texture measuring instrument. Surface morphology of a specimen from each group was evaluated with atomic force microscope (AFM) and scanning electron microscope (SEM) analyses. The surface roughness values were statistically analyzed by the Kruskal-Wallis and Mann-Whitney U tests (p = 0.05). All of the surface treatments produced rougher surfaces than the control group (p < 0.005). While there were no significant differences between the surface roughness of laser and silica groups (p > 0.05). SEM and AFM analyses revealed changes in surface topography after surface treatments, especially in the laser group with the formation of rare pits and in the silica and air abrasion groups with the formation of microretentive grooves. According to the results of the statistical and microscopic analyses, all of the surface treatments can be used for roughening zirconia prior to cementation; however, air abrasion is the most effective surface treatment to obtain micromechanical retention.