Effectiveness of composite cure associated with different curing modes of LED lights

This study compared the effectiveness of cure of two LED (light-emitting diodes) lights (Elipar FreeLight [FL], 3M-ESPE; GC e-Light [EL], GC) to conventional (Max [MX], Dentsply-Caulk [control]), high intensity (Elipar TriLight [TL], 3M-ESPE) and very high intensity (Astralis 10 [AS], Ivoclar Vivadent) halogen lights. The 10 light-curing regimens investigated were: FL1 400 mW/cm2 [40 seconds], FL2 0-400 mW/cm2 [12 seconds] --> 400 mW/cm2 [28 seconds], EL1 750 mW/cm2 [10 pulses x 2 seconds], EL2 350 mW/cm2 [40 seconds], EL3 600 mW/cm2 [20 seconds], EL4 0-600 mW/cm2 [20 seconds] --> 600 mW/cm2 [20 seconds], TL1 800 mW/cm2 [40 seconds], TL2 100-800 mW/cm2 [15 seconds] --> 800 mW/cm2 [25 seconds], AS1 1200 mW/cm2 [10 seconds], MX 400 mW/cm2 [40 seconds]. Effectiveness of cure with the different modes was determined by measuring the top and bottom surface hardness (KHN) of 2-mm thick composite (Z100, [3M-ESPE]) specimens using a digital microhardness tester (n=5, load=500 g; dwell time=15 seconds). Results were analyzed using one-way ANOVA/Scheffe's post-hoc test and Independent Samples t-test (p<0.05). At the top surface, the mean KHN observed with LED lights ranged from 55.42 +/- 1.47 to 68.54 +/- 1.46, while that of halogen lights was 62.64 +/- 1.87 to 73.14 +/- 0.97. At the bottom surface, the mean KHN observed with LED and halogen lights ranged from 46.90 +/- 1.73 to 66.46 +/- 1.18 and 62.26 +/- 1.93 to 70.50 +/- 0.87, respectively. Significant differences in top and bottom KHN values were observed between different curing regimens for the same light, and between LED and halogen lights. Although curing with most modes of EL resulted in significantly lower top and bottom KHN values than the control, no significant difference was observed for the different modes of FL. Hence, the effectiveness of composite cure with LED LCUs is product dependent.