Influence of operator experience on the bond strength of etch-and-rinse, self-etch, and universal adhesive systems to dentin.

OBJECTIVE: To evaluate the influence of operator experience on the bonding performance of four adhesive strategies: three- and two-step etch-and-rinse (ER), and two- and one-step self-etch (SE) systems to dentin. MATERIALS AND METHODS: Ninety-six caries-free molars were divided according to the operator experience (3YG: third-year undergraduate students; 5YG: fifth-year undergraduate students; 1YR: first-year residents in Operative and Restorative Dentistry) and four adhesive systems. The occlusal third of each crown was removed to obtain a flat, mid-coronal dentin surface, which was standardized using 600-grit silicon carbide paper. Adhesives were applied following the manufacturer's recommendations, and a 4-mm-thick composite resin build-up was placed. Specimens were sectioned into resin-dentin beams (cross-sectional area ≈ 0.8mm2) for microtensile bond strength (µTBS) and nanoleakage (NL) evaluation. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (α = 0.05). RESULTS: The less experienced group (3YG) generally showed significantly lower µTBS and higher NL compared to more experienced operators (p < 0.05), with the exception of the 1-step SE strategy, where experience did not influence bond strength. Within the 3YG group, the 1-step SE approach yielded the highest µTBS values, whereas in the 5YG group, 1-step SE and 2-step ER showed the highest values; the 1YR group performed consistently across all adhesive systems. For NL, the 3YG group generally showed higher values than the more experienced groups, although 5YG and 1YR did not differ for the 1-step SE strategy. In the 3YG and 5YG groups, the 3-step ER strategy resulted in the highest NL values, whereas no significant differences among adhesive strategies were observed within the 1YR group. CONCLUSIONS: Two-step etch-and-rinse and one-step self-etch adhesives showed higher µTBS values and demonstrated lower sensitivity to operator experience compared with more technique-dependent multi-step systems. CLINICAL RELEVANCE: Simplified adhesive protocols may provide more predictable bonding outcomes in teaching environments and for clinicians with limited clinical experience.