Depth of cure of dual- and light-cure bulk-fill resin composites

To evaluate the degree of conversion (DC), Vickers microhardness (VMH), and depth of cure of dual-cure and light-cure bulk-fill resin composites (BFRCs).

One dual-cure (Fill-Up) and two light-cure (QuiXfil and Tetric N-Ceram Bulk Fill) BFRCs were investigated. For each tested BFRC, 11 cylindrical specimens (5 mm diameter, 4 mm height) were prepared, and light cured for 10 seconds (n= 11). DC was obtained by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and VMH was obtained using a VMH tester. The specimens were measured for DC and VMH at top and bottom surfaces. Statistical analysis was performed using two-way ANOVA, Tukey's post-hoc, and Pearson correlation tests (P< 0.05).

Fill-Up and Tetric N-Ceram Bulk Fill revealed significantly higher DC and VMH values on the top surfaces than that on the bottom surfaces, whereas QuiXfil revealed no significant difference between top and bottom surfaces for DC and VMH. All tested BFRCs showed bottom/top ratios >80% for both DC and VMH. Each tested BFRC showed a significant positive correlation between DC and VMH. All tested BFRCs had adequate depth of cure, but only QuiXfil had a uniform depth of cure. Both DC and VMH bottom/top ratios were effective for depth of cure evaluation.

QuiXfil, Tetric N-Ceram Bulk Fill, and Fill-Up BFRCs were well cured up to a 4 mm depth. Although Fill-Up (dual-cure) can be used with its chemical-curing mode, light curing improved DC and VMH values of the top layer. Distinct variance in DC and VMH among the three tested BFRCs may affect their clinical performance.