Is Ammonium Hydrogen Difluoride a Solution for Zirconia Surface Conditioning?

Introduction: This research investigated the topographical features and phase transformation of high-translucent monolithic zirconia after different surface conditioning methods.

Methods: Zirconia slabs were divided into six groups according to surface treatment method. Group I: etched with hydrofluoric acid (HF); Group II: etched with an experimental acid solution (EAS); Group III: melt-etched with ammonium hydrogen difluoride (AHD); Group IV: air abrasion (AB); Group V: etched with EAS after air abrasion (AB+EAS); Group VI: melt-etched with AHD after air abrasion (AB+AHD). Surface topographies of specimens were documented by scanning electron microscopy (SEM). Tetragonal-to-monoclinic phase transformation was detected by X-ray diffraction and surface evaluation of zirconia specimens; surface roughness and contact angle measurements were performed. The data were statistically analyzed by the Kruskal- Wallis test and post hoc tests (P⟨0.05).

Results: The acid-etched zirconia groups (Group I, II, and III) showed the lowest contact angle and surface roughness values (P⟨0.05), while the air abrasion groups (Group IV, V, VI) showed the highest. The SEM images also supported these results.

Conclusion: Within the limitations of this in vitro study, treating the monolithic zirconia surfaces with EAS or AHD after air abrasion may be recommended to alter the zirconia surfaces.