Degree of conversion in dental resins polymerized by Argon laser, halogen lamp and LED: a Raman study

Abstract

ABSTRACT Raman Spectroscopy was used in the present investigation to evaluate the degree of conversion of composite resin, photoactivated by the Halogen lamp, the Argon Laser beam and by the Light Emitting Diode. Eighteen circular blocks of resin (7mm X 2,5mm) were cured by the Halogen light source (n = 9, = 400-500nm, Power density = 478 mW/cm 2 ), by the Argon laser beam (n = 9, = 488nm, Power density = 625 mW/cm 2 ) and nine blocks (6mm X 3mm) by the LED (n = 9, = 475 15nm, Power density = 190mW/cm 2 ) using the same irradiation time (20, 40 and 60 seconds). The resin surfaces were analyzed immediately after curing by Raman and FT-Raman Spectroscopy. The Raman results show changes of the relative intensities between the peaks at 1610 and the 1640cm -1 , as a function of irradiation time. After 60s of irradiation time, the maximum degree of conversion reached for the samples cured either by the Argon laser, the Halogen lamp and LED were 66,4%, 62,2% and 52%, respectively. The Argon laser was more effective and shown a better biocompatibility, with less residual monomer in the bottom. Keywords: Raman spectroscopy, FT-Raman Spectroscopy, Degree of conversion, Composite resin, Halogen lamp, Argon laser, LED.