Evaluation of Bond Strength, Nanoleakage, and Marginal Adaptation of Bulk-fill Composites Submitted to Thermomechanical Aging

Purpose: To evaluate the bond strength (BS), nanoleakage, and marginal adaptation (MA) of three bulk-fill and one conventional composite, submitted or not to mechanical and thermal cycling. Materials and Methods: Ninety-six molars were selected and 4-mm-deep class I cavities were prepared and restored. Half of the teeth were submitted to mechanical and thermal cycling (MTC). Teeth were divided into 8 groups (n = 12), according to the composite used - Filtek Z350 XT (Z350), Tetric N-Ceram Bulk Fill (TET), Filtek Bulk Fill Posterior Restorative (FBF) and SonicFill (SF) - and aging, submitted or not to MTC. Fifty-six teeth (n = 7) were used for bond-strength testing, which was performed on stick-shaped specimens obtained from the restored area. Two sticks per tooth were selected to assess nanoleakage. For MA analysis, 40 teeth (n = 5) were sectioned parallel and perpendicular to the occlusal surface and resin-based replicas from the obtained surfaces were prepared. Fracture pattern, nanoleakage, and MA were evaluated using SEM. Quantitative analysis of nanoleakage and MA were performed with ImageJ software. Data obtained were submitted to two-way ANOVA and Tukey's test (ɑ = 0.05). Results: TET presented good MA and higher values of BS when compared to SF. Z350 and FBF presented poorer MA and lower BS, which was statically similar to the other groups. SF obtained the best MA values. Regarding nanoleakage, the highest values were obtained for TET, which differed significantly from the other groups, which presented similar results among themselves. Aging by MTC solely affected MA. Conclusion: Bulk-fill composites presented similar performance to the conventional nanocomposite and remained stable when aged. Keywords: bond strength, bulk-fill composites, composite resins, marginal adaptation, nanoleakage