Internal and marginal adaptation of high-viscosity bulk-fill composites in class II cavities placed with different adhesive strategies

The aim of this study was toevaluate internal and marginal adaptation of high-viscosity bulk-fill composites to enamel and dentin with a self-etch (SE) and an etch-and-rinse adhesive (ER) without and with artificial aging. 128 MOD cavities in extracted human molars were prepared, randomly assigned to 8 groups (n=16), bonded with either OptiBond FL (OFL, ER) or Xeno V+ (X, SE), and restored in 4mm horizontal bulk layers with SonicFill (SF), Tetric EvoCeram Bulk fill (TEC), and x-tra fil (XF). Incremental layering technique with Premise (P) served as control. Half of the specimens each (n=8) were subjected either to water storage (1day, 37 degrees C) or prolonged storage (180days) and thereafter thermocycling. Replicas were analyzed for marginal gap formation. After sectioning, interfacial adhesive defects were assessed. Results were statistical analyzed. (1) Internal adaptation: Except for TEC/OFL at enamel without artificial aging, no significant differences between bulk-fill composites and the control were observed. All groups at dentin with OFL showed less internal adhesive defects than that with X (p<0.05). (2) Marginal adaptation: Nosignificant differences were observed between bulk-fill composites and controlexcept for P after artificial aging (p>0.05). All other composites, regardless of artificial aging, formed significantly more marginal gaps at enamel with X compared to with OFL (p0.05). Simplified restorations with high-viscosity bulk-fill composite showed comparable internal and marginal adaptation to incrementally placed fillings. A superiority of the 3-step ER approach was seen compared to the 1-step SE adhesive irrespective of the bulk-fill composite used.