Degree of cure of composite resins polymerized by diode laser: an FT-raman study

Abstract

The degree of conversion (DC) of Z100 (3M) composite resin photoactivated by both Light-Emitting Diode and halogen lamp was evaluated by FT-Raman Spectroscopy. Eighteen circular blocks of resin (Φ 6mm X 3mm) were cured either by the LED (λ = 470nm, 190mW/cm2,Φ = 8mm) and by the halogen lamp (λ = 400-500nm, 600mW/cm2,Φ = 7mm) varying the irradiation time (20, 40 and 60s). The resin surfaces were analyzed immediately after curing by FT-Raman Spectroscopy. The FT-Raman results showed the reduction in monomer trough changes in the intensity of the peak at 1640cm-1 as a function of irradiation time. The samples that were cured by 60s with LED source reached the maximum degree of conversion of 52% and 50% for the irradiated and non-irradiated surface, respectively. Whereas the samples cured by the same irradiation time, but with halogen lamp, those values were around only 4% higher for each surface with no statistically significant difference. It was observed no statistically significant differences in the DC values between both light sources used with 40s of irradiation. Therefore we conclude that, despite of their reduced irradiance, LEDs can cure composite resin ensuring a DC without statistically significant differences from the halogen lamp.