Influence of Cavity Design, Bonding‐Banding Sequence, and Thermomechanical Loading on the Marginal Adaptation of Class II Resin Composite Restorations

OBJECTIVE: To evaluate whether differences exist in marginal adaptation among beveled and non-beveled cavity designs, different bonding-banding sequences, and before and after thermomechanical loading. METHODS: Forty molars received occluso-mesial preparations and were assigned to two groups: box-shaped cavities (n = 20) and cavities with buccal and palatal bevels (n = 20). Each group was subdivided based on whether adhesive was applied before or after matrix band placement. Restorations were replicated in epoxy, and marginal adaptation at proximal buccal, palatal, and gingival interfaces was examined by scanning electron microscopy (SEM) at ×200 magnification, using percentage of continuous margin (%CM) and by World Dental Federation (FDI) criteria after 24 h and after thermomechanical loading. RESULTS: Cavity design did not significantly influence marginal adaptation. Bonding before banding improved immediate %CM at buccal-palatal margins. Thermomechanical loading significantly reduced %CM in all groups, while none of the tested variables influenced FDI scores. CONCLUSIONS: Proximal beveling had no effect on adaptation. Bonding before banding enhanced immediate %CM values, with no significant effect after aging. Aging reduced %CM across all margins. SEM was more sensitive than FDI criteria in detecting marginal discrepancies. CLINICAL SIGNIFICANCE: Bonding before banding may improve immediate margins, though aging compromises adaptation.