Purpose: To compare different concepts of direct composite restorations in class-II cavities using bulk-fill composites and a conventional composite with different layer thicknesses in a clinical study over a period of 2 years.
Materials and Methods: A low-viscosity (SDR), a high-viscosity bulk-fill (Tetric EvoCeram Bulk Fill) and a conventional nanohybrid composite (Tetric EvoCeram) were randomly assigned and placed in different layer thicknesses up to 4 mm in 160 class-II cavities in 94 patients. Restorations were clinically examined at baseline (n = 160), after 12 (n = 150) and 24 months (n = 148) and evaluated according to eight selected FDI criteria. In case of complete loss of the restoration or irreversible pulpitic symptoms, the restoration was rated as failure; repair was considered as relative failure.
Results: The materials investigated showed no significant differences regarding the FDI scores and failure rate during the entire follow-up. After 12 months, 7 failures and after 24 months a total of 8 failures were observed. After 2 years, Tetric EvoCeram Bulk Fill with a 4-mm layer thickness and SDR in combination with Tetric EvoCeram Bulk Fill with a 2-mm layer thickness exhibited a non-significant tendency towards increased hypersensitivity (FDI score 5) as compared to the reference material Tetric EvoCeram with a 2-mm layer thickness (p = 0.051; Kruskal-Wallis test).
Conclusion: The clinical stability of bulk-fill materials in layers up to 4 mm is comparable to nanohybrid composites after 2 years.