Depth Of Cure And Microhardness Of Bulk-Fill Composites

This study aimed to compare a self-cured composite with three light-cure bulk-fill composites by assessing top and bottom surface microhardness values, and the depth of cure calculated through the bottom/top microhardness ratio (B/T ratio). Forty disc-shaped samples (4 mmx5 mm) were prepared using a self-cured composite (STL) and light-cure bulk-fill composites [one-shade flowable (OMN), multi-shade flowable (ESTL), and multi-shade restorative (BLK)]. The Vickers microhardness was measured on the top and bottom surfaces, and the B/T ratio was calculated. The Kruskal-Wallis test and Bonferroni-corrected Mann-Whitney U test were used for multiple-group and pairwise comparisons, respectively (p<0.05) A statistically significant difference was found among the materials regarding the B/T ratio (p = 0.001). The highest B/T ratios were observed in the STL (1.08±0.21) and OMN (0.96±0.23). In terms of the top surface microhardness, BLK exhibited the highest values (121.33±27.5). Additioanlly, the ESTL and STL showed significantly higher top surface microhardness values than OMN (p=0.000). Regarding the bottom surface microhardness, BLK (87.73±30.93) and STL (71.02±14.14) demonstrated higher values (p=0.002), while ESTL (58.98±7.89) and OMN (55.02±11.53) exhibited lower values. Depth of cure, as reflected by the B/T ratio, may be influenced by the materials' chemical composition. Additionally, the microhardness of top and bottom surfaces is material-dependent.