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 Sixty-four 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 ≈ 0.8mm ² ) 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 and 5YG groups, 1-step SE and 2-step ER approaches yielded the highest µTBS values, while the 1YR group performed consistently across all adhesive systems. Overall, the 1YR group achieved the lowest nanoleakage (p < 0.01). Consistently, the 3-step ER strategy resulted in the highest nanoleakage values regardless of operator experience, reinforcing the high technique sensitivity often associated with multi-step systems. 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.