A comparative study of the 5 mm-layer Vickers hardness model with bulk-fill resin-based composites

Aim: The aim of this study was to compare the Vickers hardness numbers (VHNs) of two bulk-fill resin-based composites (BFRBC) and a conventional hybrid resin-based composite (RBC) through the layers of a 5mm thickness model with two different light-curing time intervals. Methodology: In the present study, a sonic-activated and dual-cure BFRBC, and a conventional hybrid RBC were used. Semi-cylindrical specimens 4 mm in radius and 5 mm in height were prepared using a two-piece stainless-steel mold (n=10). The BFRBCs allowed a single 5mm increment to be introduced into the molds, whereas hybrid RBC was incremented (2+2+1 mm). Two different time intervals were applied for the light-curing (irradiance of 1200 mW/cm2) of each material (hybrid-sonic-activated bulk-fill, 20 s and 40 s; dual-cure bulk-fill, 7 s and 15 s). VHN measurements were carried out from top to bottom at every 1 mm of the specimen thickness. Data were analyzed using three-way and two-way ANOVA for the VHN and bottom/top ratios and Bonferroni correction for multiple comparisons (p=0.05). Results: For each layer and time interval groups, there was a significant difference between the materials. The highest VHN was found within hybrid groups, whereas dual-cure bulk-fill groups showed the lowest results. Sonic-activated bulk-fill had the lowest bottom/top ratios, which were significantly different from those of the other materials. There was no significant difference between the different time intervals for bottom/top ratios within each material. Conclusion: Increased irradiation intervals positively affected the VHN of hybrid and dual-cure bulk-fill. BFRBCs showed clinically acceptable bottom/top hardness ratios.   How to cite this article: Aytaç Bal F, Ağaccıoğlu M, Demir O. A comparative study of the 5 mm-layer Vickers hardness model with bulk-fill resin-based composites. Int Dent Res 2021;11(2):172-9. https://doi.org/10.5577/intdentres.2021.vol11.no3.6   Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.