Effect of acid-etching solution on surface properties, crystallography, and shear bond strength of ultra-translucent zirconia to enamel

Ultra-translucent zirconia has gained popularity in restorative dentistry due to its excellent esthetic properties and high strength. Surface treatment methods play a crucial role in optimizing the bond between zirconia and enamel. This laboratory study aimed to investigate the influence of acid-etching solution on the surface properties of ultra-translucent zirconia and its subsequent shear bond strength to enamel. Thirty-six ultra-translucent zirconia disks were divided into three groups (n = 12): as-sintered (C) as the control group, airborne-particle-abraded (AB), and acid-etched with Zircos-E^™ etching solution (ZE). Surface topography, roughness, and phase composition were assessed using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and X-Ray diffraction analysis (XRD), respectively. The remaining disks were bonded to enamel using resin cement, and shear bond strength (SBS) was tested after 10,000 thermo-cycles between 5℃ and 55℃. Data were statistically analyzed using one-way ANOVA (α = 0.05). ZE induced higher surface roughness compared to AB, with a more stable crystalline structure. ZE group exhibited the highest SBS (22.48 ± 2.97 MPa), followed by AB (16.72 ± 2.52 MPa), while C group had the lowest SBS (7.55 ± 2.73 MPa). ZE solution demonstrated enhanced surface properties and higher shear bond strengths to human enamel compared to conventional airborne-particle abrasion. This finding highlights the potential of acid-etching solutions in improving the bond between ultra-translucent zirconia and enamel in restorative dentistry applications.