Effect of primer composition on zirconia surface properties and bond strength

This study investigated the effects of different surface treatments on surface roughness, wettability, and shear bond strength of 3Y-TZP (yttria-stabilized tetragonal zirconia polycrystal). A total of 180 specimens (6 × 6 × 2 mm) underwent sandblasting with 50 µm Al₂O₃ and were divided into six groups: (i) control (no treatment), (ii) 10-MDP + silane primer, (iii) universal adhesive with 10-MDP and HEMA, (iv) silane-based primer with phosphate methacrylate, (v) methacrylate-based primer with ethanol, and (vi) PMDM primer. Surface roughness and wettability were measured before and after treatment. For shear bond strength evaluation, each group was subdivided by type of resin cement. After 10,000 thermal cycles, shear bond strength and adhesive remnant index were measured. Surface treatments increased roughness and wettability. Primers with 10-MDP and silane had the highest bond strength, followed by silane-based primer and universal adhesive. Primers with other functional monomers showed intermediate performance, while the control and PMDM primer had the lowest values. Adhesive remnant index analysis revealed predominantly type 1 failures for 10-MDP + silane and silane-based primers, whereas universal adhesive and other primers showed mixed failures. These results indicate that combining sandblasting with functional surface agents improves zirconia adhesion, with primer composition influencing long-term bonding effectiveness.