Even after more than six decades of dental composite invention (1962), there is still controversial information about the time in which composite restorations should be polished in order to avoid marginal gap formation at the tooth-composite interface. The aim of the present study was to analyze the influence of adhesive strategy, the type of dental composite, and polishing time on marginal gap formation (%MG) at the tooth-composite interface. Class I-like cavities were hybridized with a universal adhesive system (Single Bond Universal) through two strategies: selective enamel etching (SEE) or self-etching mode (SEM). Cavities were filled with two types of dental composites: nanofilled (Z350) or bulk fill (Filtek One Bulk Fill-ONE), and polishing was performed immediately or delayed for 7 days (n = 5). %MG was evaluated by using a 3D laser confocal microscope. As flexural modulus (FM) and degree of conversion (DC%) are determinants of marginal integrity in dental composite restorations, these properties were evaluated for both composites. Data were analyzed by ANOVA and Tukey's HSD test (α = 0.05). Cavities hybridized following the SEE strategy presented lower %MG (p < 0.05). Z350 showed higher %MG than ONE (p < 0.05). There was no difference in %MG between the polishing times when the SEE strategy was used (p > 0.05). Z350 presented higher FM than ONE (p < 0.05). DC% was found to be not significant (p > 0.05). The results suggest that selective enamel etching (SEE) is a better strategy for producing less %MG in composite restorations with enamel margins irrespective of the time in which the restoration is polished.
Keywords: bond strategy; dental composite; dental polishing; gap formation; permanent restorations.