Marginal Adaptation of Different Bulk-fill Composites: A Microcomputed Tomography Evaluation

OBJECTIVES: In the last decade, bulk-fill materials were introduced to allow resin-based composites (RBC) in one layer (up to 4-5 mm thick) with optimum polymerization. We sought to evaluate the adaptation ability of different bulk-fill composites resin (CRs)and restoration marginal integrity. METHODS: A total of 28 caries-free and crack-free human molars underwent mesio-occlusal-distal cavity preparation. Each sample prepared the mesial margins on enamel, and the distal margins were extended into dentin. Teeth were then randomly distributed into four groups (n = 7 per group) according to the CR used to restore the cavity. Three bulk-fill CRs—Smart Dentin Replacement Flow+, 3M™ Filtek™ One Bulk Fill (FBF), and Tetric® N-Ceram Bulk Fill (TBF)—and one conventional CR (CC)—Filtek™ Z350—were used. The teeth were then subjected to aging via thermocycling, followed by cyclic loading. Finally, the volumetric width of the interfacial gap at the tooth-restoration interface was measured using a microcomputed tomography (µ-CT) analysis. RESULTS: SDR demonstrated the smallest gap volume among all tested CRs, 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 > 0.050). CONCLUSIONS: It is safe to suggest using bulk-fill RBC in deep class II cavities instead of conventional layered RBC when dealing with dentin margins. However, further clinical investigation is required.