Microstructure, Composition, and Etching Topography of Dental Ceramics

Purpose: Topographic analysis of etched ceramics provides qualitative surface structure information that affects micromechanical retention mechanisms. This study tested the hypothesis that the etching mechanism changes according to the type of etchant and the ceramic microstructure and composition. Materials and Methods: Quantitative and qualitative analyses of 15 dental ceramics were performed using scanning electron microscopy, back-scattered imaging, X-ray diffraction, optical profilometry, and wavelength dispersive spectroscopy based on Phi-Rho-Z correction. All ceramic specimens were polished to 1 µm with diamond compound, and the following etchants and etching times were used: ammonium bifluoride (ABF) for 1 minute, 9.6% hydrofluoric acid (HF) for 2 minutes, and 4% acidulated phosphate fluoride (APF) for 2 minutes. Results: HF produced an irregular etching pattern in which pores were the characteristic topographic feature. ABF-etched ceramic surfaces showed mostly grooves, and APF etchant caused a buildup of surface precipitate. Core ceramics showed less topographic change after etching because of their high alumina content and low chemical reactivity. Conclusion: The observations suggest that the etching mechanism is different for the three etchants, with HF producing the most prominent etching pattern on all dental ceramics examined.