Bond-strength of a Bulk-fill Base and Restorative Composite to Dentin
Objectives: The aim of this study was to evaluate the effect of a bulk-fill composite as base and/or restorative material on the microtensile bond strength (μTBS) to dentin. Methods: Twenty intact third molars were sectioned with a precision low-speed diamond saw to expose midcoronal dentin. Specimens were randomly assigned into four experimental groups (n=5) according to the restorative technique (Dentsply products, A2 shade): 4mm restoration of Esthet X HD in the incremental technique (EX); 2mm base of SureFil SDR flow + 2mm restoration of Esthet X HD (BEX); 2mm base of SureFil SDR flow + 2mm restoration of SureFil SDR flow (BSF); and 4mm restoration of SureFil SDR flow in the bulk-fill technique (SF). All specimens were etched with 34% phosphoric acid for 15 seconds prior to Prime & Bond Elect Universal bonding agent following the etch-and-rinse mode. After 24h in distilled water at 37°C, all specimens were sectioned to obtain sticks with a cross-section of 0.8±0.1mm2. The μTBS test was performed at a crosshead speed of 1mm/min and the failures were classified as adhesive, cohesive, mixed or debonded. The data was evaluated statistically by one-way ANOVA and Games Howell post-hoc test (α=.05). Results: The lowest bond strength was obtained with the EX group (22.43 MPa). No significant statistical difference was observed among BEX, BSF and SF groups (P>.05). The adhesive failure was predominant in all experimental groups. Conclusions: The bulk-fill composite increased the bond strength to dentin when used as base and/or restorative material.