Method: Two bulk fill composites, Tetric EvoCeram Bulk Fill (TBF) and Sonic Fill (SF) and a conventional composite, Filtek Supreme Ultra (FSU) were evaluated. Samples (n=10) were made using 2 shades (Light, Dark), 2 thicknesses (2mm, 4mm) and 2 exposure times (20s, 40s). Using a Tukon testing instrument, three Knoop Hardness Numbers (KHN) were obtained at the top and bottom of each sample. Depth of cure (DOC) was calculated as a B/T ratio of the means. Multiple T-tests were used for comparisons between groups; Bonferroni correction of p<0.004.
Result: Top hardness values were similar within materials; 79.8–85.1 (FSU), 69.5–91.6 (SF), 51.0-57.8 (TBF). Bottom KHNs ranged from 23.5–73.2 (FSU), 45.7–77.1 (SF), 36.9–52.5 (TBF). At 2mm thickness, DOC did not increase with additional exposure time and was greater than 80% for all materials and both shades (.84-.93%). At 4mm thickness, DOC increased significantly with additional exposure by 6% (SF), 10% (TBF), 20% (FSU) for Light shades and 19% (SF), 8% (SF), 27% (FSU) for darker shades. For lighter shades at 4mm, only SF (.82) had 80% cure after 20s exposure, but both SF (.88) and TBF (.83) had 80% cure after 40 seconds. For a darker shade at 4 mm, only SF (.81) had 80% DOC after 40s exposure.
Conclusion: Increasing the exposure time from 20s to 40s did not have a significant effect on DOC at 2mm but did increase the DOC for all materials at 4mm. DOC was also significantly greater for lighter shades compared to darker shades at 4 mm for all materials.