Using Bulk-Fill Composite and High-Intensity Curing When Light Tip Placement Is Compromised

Purpose: To evaluate whether reduced curing performance due to compromised light tip placement can be mitigated by bulk-fill composite and/or high-intensity curing light. Methods: Plastic discs with 2.5-mm deep cavities were filled with a conventional (Mosaic™) or bulk-fill (Tetric® PowerFill) composite and cured with a BluePhase® PowerCure curing light at normal and high-power settings, with light tip placement at distance and/or 45 degree angle. Curing time and irradiance were three, five, or 10 seconds at 1,200, 2,000, or 3,000 mW/cm2 (10 samples). After 24 hours, Vickers hardness on top and bottom surfaces was measured and analyzed using analysis of variance and pairwise comparisons (α<0.05). Results: All top surfaces had higher hardness than bottom surfaces. Cure (bottom-to-top hardness ratio) was significantly affected by material, distance/angle, and curing regimen (P<0.001), and generally decreased when tip distance and angle increased. Bottom-to-top hardness ratios of bulk-fill composite (0.42 to 0.66) were significantly higher than those of conventional composite (0.20 to 0.31). High-power curing significantly increased bulk-fill's curing performance as it was specifically formulated for this curing light. Conclusions: Increased light tip distance and angle compromised composite curing. Bulk-fill composite cured better at the bottom of the restoration than conventional composite regardless of light tip distance/angle. High-power light curing improved curing performance only in bulk-fill composite. Nevertheless, due to low bottom-to-top ratios (0.20 to 0.66) across all samples, even under ideal light tip placement, both composites should be cured in increments of less than 2.5 mm.