Investigation of the effect of different application techniques on microhardness in bulk-fill composite resins

Abstract

Aim: The aim of this study was to investigate the effect of different application techniques on microhardness in one universal resin material and three different bulk-fill composite resin materials. Materials and Methods: In this study, one universal composite resin (Universal Restorative 200 [U], 3M-ESPE, USA) and three different bulk-fill composite resins (Filtek-One Bulk-Fill Restorative [F]; 3M-ESPE, USA: Tetric Evo-Ceram Bulk-Fill [E]; and Ivoclar-Vivadent, Liechtenstein; Tetric NCeram Bulk-Fill [N], Ivoclar-Vivadent, Liechtenstein) materials were used. A total of 60 disk-shaped samples, including 20 samples from each bulk-fill composite resin group, were prepared. The polymerization of the bulk-fill composite resins in one group was completed using a 2 mm (40 sec) + 2 mm (40 sec) incremental technique, and in the other group, it was completed using a 4 mm bulk technique (40 sec). The U composite resin (control group) polymerization was completed using a 2 mm + 2 mm (40 sec) incremental technique (n = 10). The Vickers microhardness (VHN) values of the samples were calculated. The data were analyzed with Kruskal–Wallis and Mann–Whitney U tests (p < 0.05). Results: Higher VHN values were found in the U composite resin compared to those in the bulk-fill composite resins (p 0.05). A lower N bulk-fill composite resin was observed in the groups in which the incremental technique was applied than in the control group (p < 0.05). When the techniques applied to the bulk-fill composite resins were evaluated within themselves, higher VHN values were observed in the E composite resin in the group in which the incremental technique was applied but not in the group in which the bulk was applied. Conclusion: It was observed that the content differences of composite resins were effective at different VHN values. The U composite resin (control) group showed higher VHN values than all the bulk-fill composite groups. Keywor