Comparative evaluation of the bond strength of orthodontic brackets to monolithic zirconia surfaces prepared by conventional and laser-assisted surface roughening methods using a self-priming one-step adhesive system

Objective: To compare the shear bond strength (SBS) of Transbond XT and a self-priming one-step adhesive (GC Ortho Connect), used with and without an additional primer, on glazed monolithic zirconia after conventional and laser-based conditioning; and to evaluate zirconia findings in comparison to enamel. Method: On glaze-coated zirconia, six surface protocols [HF; HF+silane; mechanical pretreatment (sandblasting or diamond bur)+HF+silane; Er,Cr:YSGG laser+silane; sandblasting+laser+silane] were tested with three adhesive strategies (18 groups). Three enamel control groups were prepared. Brackets were bonded per instructions. SBS was measured with a universal testing machine. Failure mode was scored by modified ARI; selected specimens underwent SEM. Statistics: one-way ANOVA or Kruskal–Wallis (α=0.05). Results: HF alone and laser+silane gave the lowest SBS. HF+silane and mechanical pretreatment followed by HF+silane produced significantly higher values. GC Ortho Connect without an extra primer matched or exceeded Transbond XT, particularly with mechanical pretreatment+HF+silane; adding primer showed no consistent benefit. Sandblasting+laser+silane ranked mid-to-high; laser+silane alone was low across adhesives. Enamel controls exceeded zirconia groups. ARI indicated adhesive-dominant failures at low SBS and mixed failures at higher SBS. Conclusion: On glazed monolithic zirconia, chemically supported conventional protocols-especially HF+silane and mechanical pretreatment+HF+silane—outperform laser-only approaches. A 10-MDP self-priming one-step adhesive (GC Ortho Connect) without an additional primer is an effective alternative to Transbond XT when paired with appropriate surface preparation; adding a primer confers no extra gain. Combining mechanical and chemical conditioning with MDP-based systems appears clinically preferable. Keywords: monolithic zirconia, shear bond strength, self-priming one-step adhesive