Shear bond strength of different bulk fill composite systems to dentin with or without preheating

Purpose investigate shear bond strength of different bulk-fill composite systems to the dentin with or without preheating. Material and methods This in vitro study was performed on sixty sounds extracted periodontally affected human molars. The enamel of the occlusal surfaces was removed to expose the superficial dentin. The samples with flat occlusal dentin surfaces were randomly divided into two groups of thirty teeth each (n = 30) according to the type of restoration material used, each group is then subdivided into two subgroups (A and B) each (15 specimens), corresponding to the modified technique of application with or without preheating using transparent polymer tubes 4 × 4mm. Group I: X-tra fill bulk fill composite and Group II: Tetric®N-Ceram Nano hybrid Bulk fill composite (compules). All specimens were subjected to thermocycling and were tested in shear mode. The debonded surfaces of the samples were inspected to determine the mode of failure for each specimen. All data was collected, tabulated, and statistically analyzed. Results There were no significant differences between the shear bond strength of two studied groups (X-tra fill and Tetric N-ceram bulk-fill) and their subgroups (A and B), considering with preheating modality recorded slightly higher insignificant statistically mean values in MPa. The most observed mode of failures in composite resin were of mixed mode. The type of composite resin material has no statistically significant difference effect of shear bond strength. On the other hand, it was found that there is a significant effect of the thermal treatment modality on the bond strength regardless the type of composite material used. Conclusion within the limits of the present study, the preheated bulk fill composite resin had a superior significant bond strength to dentin compared to unheated one.