Influence of surface treatments on highly translucent zirconia: Mechanical, optical properties and bonding performance.

Objectives: Highly translucent yttria-stabilized zirconia (YSZ) has become more popular due to its enhanced aesthetics. This study aimed to evaluate the influence of traditional air abrasion and a new etching and cleaning agent, Multi Etchant, on the mechanical performance, optical properties, and bond strength of highly translucent zirconia.

Methods: Specimens of 6YSZ, 5YSZ, 4YSZ&5YSZ, and conventional 3YSZ were fabricated and underwent different surface treatments, including as milled, air abrasion, and Multi Etchant. The chemical, phase, and microstructural characterization of zirconia were analyzed by X-ray fluorescence, X-ray diffraction, scanning electron microscope, and optical profilometer. Furthermore, flexural strength, optical properties, and bond strength of zirconia with resin composite cement before and after three-month water storage were measured.

Results: Highly translucent zirconia contained more c-ZrO and larger grain sizes (up to 1.85 μm), resulting in higher translucency but lower flexural strength compared to 3YSZ. Air abrasion substantially increased the flexural strength of 3YSZ and improved the bond strength of all zirconia types, with bond strength remaining stable after artificial aging. Multi Etchant did not significantly alter the mechanical or optical properties but enhanced the bond strength of UTML (6YSZ), TT-MT-ML (5YSZ), EZneer (5YSZ), and CER (3YSZ), particularly after water storage.

Conclusions: Yttria content variations between highly translucent and conventional zirconia affected mechanical and optical properties but not bond performance. The bonding strategy of air abrasion pretreatment can be effectively extended to highly translucent zirconia. Using an etchant containing adhesive monomer shows clinical potential, as it enhances long-term bond strength without compromising zirconia's durability.

Clinical Significance: The air abrasion parameter of 0.2 MPa for 10 s can be extended from 3YSZ to highly translucent zirconia without impairing its properties. Air abrasion improves the bond strength of highly translucent zirconia.