Marginal Adaptation of Different Bulk-Fill Composites: A MicrocomputedMicro-computed Tomography Evaluation

ABSTRACT
Background: In the last decade, bulk-fill materials were introduced to allow the placement of resin-based composites (RBCs) in one layer (up to 4 mm thick) with optimum polymerization. These materials reduce contraction stress and the number of restorative steps needed and may improve marginal adaptation and cuspal deflection.
Aim: The aim of this study is to in vitro evaluate in vitro the polymerization behavior of different bulk-fill composites and the impact of such behavior on marginal adaptation of restorations.
Methods and Materials: A total of 28 caries-free and crack-free human molars underwent mesio-occlusal-distal cavity preparation. The mesial margin was prepared on enamel, and the distal margin was extended into dentin. Teeth were randomly distributed into 4 groups (n = 7 per group). Three bulk-fill RBCs—Smart Dentin Replacement (SDR™), Filtek™ One Bulk Fill (FBF), and Tetric® N-Ceram Bulk Fill (TBF)—and one conventional composite (CC) — Filtek™ Z350 — were used to restore the teeth. The teeth were then subjected to aging via thermocycling and cyclic loading. To measure the volumetric width of the interfacial gap at the tooth-restoration interface, the teeth were analyzed using a microcomputedmicro-computed tomography machine.
Results: SDR demonstrated the smallest gap volume among all of the tested RBCs, followed by CC in enamel and TBF in dentin after aging. FBF showed the highest gap volume. There was no statistically significant three-way interaction between surface, aging, and material (p > 0.05).
Conclusion: Based on the results of this study, the use of bulk-fill rather than conventionally-layered RBCs in deep Class II cavities may result in a superior marginal adaptation in dentin.