Methods: Two lights were evaluated (Kerr Demi, Kerr LEDemetronII). Five composites (Premise Body, Herculite XRV Enamel, Filtek Supreme Plus, Spectrum TPH3, Esthet-X) were prepared for depth of cure (DOC; n=10/composite) and Vickers microhardness (VHN; n=4/composite) measurements. Complete groups were tested for each of two curing times (5 and 10s). DOC was determined by scrape test (ISO 4049), and reported as absolute values. VHN measurement (disks, 2.0mm thick, top and bottom surface) was evaluated using a diamond indenter. Curing unit output was monitored using a handheld radiometer, with consistent output of approximately 1000 mW/m2 for Demi light and 800 mW/m2 for LEDemetronII. All groups were analyzed for means and standard deviations, and compared within test sub-groups using ANOVA and post-hoc t-tests (P<0.05).
Results: DOC (mm±SD) ranged from 5.3±0.2 to 6.7±0.2 (5s) and 6.3±0.2 to 8.2±0.4 (10s) for LEDemetronII, and 5.5±0.3 to 7.4±0.3 (5s) and 6.5±0.3 to 8.7±0.4 (10s) for the Demi light. Vickers hardness measurements for the top surface were reported as VHN±SD. Values ranged from 40.5±3.5 to 55.1±1.5 (5s) and 42.9±1.1 to 64.2±2.2 (10s) for the LEDemetronII light, and values for the Demi light ranged from 43.7±2.1 to 64.4±3.4 (5s) and 48.1±1.7 to 68.7±2.0 (10s). Bottom surface samples showed ranges of 22.8±4.0 to 31.7±5.4 (5s) and 33.7±1.9 to 46.4±2.3 (10s) for LEDemetron II, and 25.8±3.1 to 38.1±1.8 (5s) and 36.9±3.0 to 52.1±1.9 (10s) for the Demi light. Samples cured for 10 seconds showed statistically significant differences compared to those cured for 5 seconds.
Conclusion: A second generation light(Demi) yielded similar results to the first generation light (LEDemetronII). In cases where significant differences occurred, values for VHN and DOC were higher for the Demi light.(Supported in part by Kerr)