Bond Strength of a Flowable Bulk-fill Resin Composite in Class II MOD Cavities.

PURPOSE: To evaluate the microtensile bond strength (μTBS) of a bulk-fill low-stress resin-based composite to dentin from gingival walls of Class II MOD cavities.

MATERIALS AND METHODS: Class II MOD cavities were prepared in 44 human molars with the distal and mesial proximal boxes 4 and 6 mm deep, respectively. Eight experimental groups (n = 11) were obtained by a factorial design including 1. "composite" in two levels: a bulk-fill low-stress composite (SureFil SDR Flow, Dentsply Caulk) and a conventional composite (Filtek Z350 XT, 3M ESPE); 2. "filling technique" in two levels: bulk-fill (Bf) and incremental (In); and 3. "depth" in two levels: 4 mm and 6 mm in order to create different polymerization conditions. Twenty-four hours after placement of restorations, teeth were sectioned into beams with a cross-sectional bonded area of approximately 1 mm2. Bonded beams obtained from the gingival walls of the proximal boxes were tested in tension at a crosshead speed of 1 mm/min. Data were submitted to a 3-way ANOVA followed by a post-hoc Tukey's test (p < 0.05).

RESULTS: ANOVA failed to identify significant differences for the triple and double interaction between factors. However, significant differences were observed for the factors "composite" and "filling technique" (p < 0.05). SDR presented significantly higher μTBS values for bulk and incremental filling techniques (p < 0.05), and the incremental filling technique presented significantly higher μTBS values for both composites (p < 0.05).

CONCLUSION: It can be concluded that the bulk-fill flowable composite SDR may improve the bond strength to the gingival walls of Class II MOD cavities.