Objective: To evaluate the cervical marginal and internal adaptation of posterior bulk fill resin composites of different viscosities, before and after thermo-cycling (TMC).
Materials and methods: Eighty box-only class II cavities were prepared in 40 extracted human premolars with the distal proximal box beneath the enamel-cementum junction (CEJ). The teeth in the experimental groups were restored with bulk fill resin composite restorations (Gr. I- Sonic Fill, Gr. II- SDR, Gr. III- Tetric N Ceram Bulk Fill or a conventional composite designed for 2-mm increments (Gr. IV- Tetric N Flow along with Tetric N Ceram). Before and after thermal cycling, the gap-free marginal length was analyzed using SEM of epoxy resin replicas. After thermal cycling, specimens were cut longitudinally in order to investigate internal dentine adaptation by epoxy replicas under SEM (500 × magnification).
Results: Statistical analysis was performed using the ANOVA and Tukey Post Hoc tests (P < 0.05). In enamel, high percentages of gap-free margins were initially identified for all the groups, which declined after thermal cycling. However, no significant differences were identified among any of the groups (P > 0.05). In dentine, bulk fill groups performed at par with the incremental placement; for both marginal and internal adaptation (P < 0.05), for all materials except Tetric N Ceram Bulk Fill.
Conclusions: Viscosity of the bulk fill restorative material influenced the proportion of gap-free marginal interface and the internal adaptation in dentin.
Keywords: Bulk fill; composites; flowables; margin adaptation.