Effect of surface treatments with acid solutions on the surface roughness of an Yttrium-Tetragonal Zirconia Polycrystal

BACKGROUND: The purpose of this in vitro study was to evaluate the effect of conventional surface treatment with acid solutions on the surface roughness of a zirconia-based ceramic. MATERIAL AND METHODS: Specimens of yttrium-tetragonal zirconia polycrystal (Y-TZP) -based ceramic were fabricated (5.0 x 5.0 x 2.0 mm, n=40). The specimens were submitted to the tested surface treatment method and divided into 4 groups (n=10): no treatment-control (GI), airborne 110 µm aluminum oxide particle abrasion for 1 minute-conventional method (GII); etching with 48% hydrofluoric acid for 2 minutes (GIII), and nitric acid/hydrofluoric acid etching for 2 minutes (GIV). The surface roughness (Ra) test was performed, followed by AFM analysis. The results were analyzed by ANOVA and the Tukey test, with the level of significance set at a=.05. RESULTS: The surface treatment with acid solutions (0.16 ± 0.02-GIII; 0.11 ± 0.01-GIV) promoted a significant increase in roughness, with higher mean Ra values of Y-TZP (μm) compared to control (0.06 ± 0.01-GI) (p >.05), and lower values compared to the conventional method (0.21 ± 0.06-GII). The aluminum oxide particle treatment resulted in deep microretentions forming sharp Y-TZP peaks compared to only microretentions with acid solution treatments. CONCLUSIONS: All Y-TZP treatments effectively promoted microretention in the ceramic. Hydrofluoric acid (48%) proved to be more effective in increasing the Ra of Y-TZP than the nitric acid/hydrofluoric acid treatment. Atomic force microscopy images revealed that both acid solutions modified the surface of the Y-TZP in a uniform manner. Key words:Zirconia, surface modification, roughness, yttria-stabilized tetragonal zirconia polycrystal.