ABSTRACT
Background: Bulk-fill resin composite material gains popularity due to its simple and time-efficient application. However, some dentists question whether the no-light cure side is fully polymerized and the hardness of that side. Objective: This study investigated the microhardness of flowable bulk-fill resin composites on the light-cured/top side and no light-cured/bottom side immediately and after 24 hours immersed in artificial saliva. Methods: Three flowable bulk-fill resin composites were tested: Tetric N-Flow Bulk Fill (TBF), Filtek Bulk Fill (FBF), and Palfique Bulk Flow (PBF). A Vickers microhardness tester was used to determine the microhardness at each cylindrical sample's top and bottom sides. Thirty samples were divided into two groups, Group 1 was tested immediately, and Group 2 was tested after 24 hours of immersion in artificial saliva. Results: The highest microhardness mean value was 47.52 VHN for the PBF top side tested immediately, while the lowest was 25.20 VHN for FBF on the bottom side tested after 24 hours of storage. Two-way ANOVA showed significant differences among the groups (p<0.05). There were significant differences (p<0.05) between immediate and 24 hours on the top and bottom sides of TBF and the bottom side of the FBF group. There was no significant difference between the immediate PBF group and 24 hours at the top and bottom sides, and the top side of the FBF group. All groups’ bottom/top ratio was 0.78 or above. Conclusion: The Vickers microhardness has a tendency to decrease on both sides after 24 hours of immersion in artificial saliva.
