Zirconia surface modification by various chemical treatments after silica coating by sandblasting was investigated in this study. The surface of silica-coated dental zirconia was hydroxylated by treatment with different acids at room temperature for 4 h, rinsed with deionized water and air-dried. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Shifts in binding energies for Zr 3d(5/2) and Si 2p peaks were observed after treatment with acids, thereby showing a change in the chemical states of zirconium and silicon on the surface layer of silica-coated zirconia. The XPS analysis revealed that the silica-coated zirconia (SiO2-ZrO2) surfaces had changed to hydrous silica-coated zirconia (SiO2-ZrO2 center dot nH(2)O). One-way ANOVA analysis revealed there was significant difference in both surface roughness parameters of silica-coated zirconia after chemical treatments and the surface topography varied depending on the acid treatment. (C) 2010 Elsevier B. V. All rights reserved.