Bond strength in class V cavities: an in vitro study on beveling, universal adhesive strategy, and composite type

Abstract

Cervical Class V lesions present restorative challenges due to their multifactorial etiology and complex bonding substrates. Objectives: This study evaluated the influence of marginal bevel, bonding using a universal adhesive (etch-and-rinse or self-etch), and the resin composite type (conventional or bulk-fill) on the bond strength of simulated Class V cavities. Methodology: A total of 80 dental fragments (7mm×7 mm×2 mm) were obtained from bovine incisors. Cylindrical cavities with enamel margins and internal dentin walls were prepared centrally in each specimen. Samples were randomly assigned to groups based on three factors: presence or absence of bevel, bonding strategy (etch-and-rinse or self-etch), and resin composite type (conventional or bulk-fill). Groups with bevel received a 1 mm enamel bevel along the preparation margins using a conical diamond bur. Adhesive and restorative procedures were performed following the manufacturer's recommendations. Bond strength was assessed using a push-out test on a universal testing machine. Data were analyzed using three-way ANOVA and Tukey's post-hoc test (α=5%). Results: Presence of a marginal bevel did not significantly influence bond strength. The etch-and-rinse bonding strategy resulted in significantly higher bond strength than the self-etch approach, and bulk-fill composites presented superior performance compared with conventional composites. Conclusions: Combining a universal adhesive applied with the etch-and-rinse strategy and a bulk-fill composite proved to be an effective approach for enhancing bond strength with enamel and dentin substrates. Beveling of enamel margins did not improve the bond strength of Class V restorations, suggesting that this procedure may be unnecessary when margins are in enamel. Avoiding beveling in such situations contributes to preserve sound tooth structure and supports a more conservative restorative approach.