Cuspal Deflection and Marginal Integrity of Class II Cavities Restored with Bulk-fill Resin Composites

This laboratory study aims to assess the cuspal deflection, adaptation, and marginal sealing of premolars restored with bulk-fill resin composites.

Fourty-four premolars received class II preparations (distal and mesial boxes located 1 mm above and 1 mm below the cementoenamel junction, respectively). The teeth were distributed into four groups according to the resin composite used for restoration (n=11): G1 (control): Filtek Z250 XT; G2: Filtek Bulk-Fill; G3: Tetric N-Ceram Bulk-Fill; G4: Aura Bulk-Fill. A digital micrometer was used to measure the cuspal deflection before and after the restorative procedures. Replicas in epoxy resin of the restored teeth were achieved before and after thermal cycles. The cervical margins were observed by SEM at 200x magnification to obtain the percentage of continuous margins (%CM). After thermal cycles, the samples were immersed in a silver nitrate solution, and the microleakage was analyzed in the cervical margins.

ANOVA showed no significant differences in the cuspal deflection and %CM among the resin composites. Student’s t-test showed a significant decrease in the %CM after thermal cycles for all resin composites at the cervical margin in dentin. There was higher microleakage at the dentin margin for all the resin composites.

Bulk-fill resin composites had comparable behavior to a conventional composite in regard to the cuspal deflection, adaptation, and marginal sealing parameters.