Influence of different light sources on the conversion of composite resins.

The purpose of this paper was to evaluate the influence of different light curing units on the conversion of four composite resins with different compositions (Durafill VS - Heraeus-Kulzer, Tetric Ceram - Ivoclar/Vivadent, Filtek Supreme XT - 3M ESPE e Aelite LS Packable - Bisco), using differential scanning calorimetry. A stainless steel matrix was used to prepare 48 cylindrical composite test samples (n=6), measuring 3 mm in diameter and 1 mm in thickness. The samples were photoactivated using a halogen lamp (Optilux 500 - Demetron/Kerr) and three different generations of light-emitting diodes (LEDs) (LEC-470 I - MMOptics, Radii Plus - SDI and Ultra-Lume LED 5 - Ultradent). After removal of the matrix, each sample was weighed and hermetically sealed in an aluminum pan and analyzed. The amount of heat liberated by thermopolymerisation of residual monomers after photoactivation was measured in Joules/gram (J/g). The data were submitted to Analysis of Variance (ANOVA) test (P ≤ 0.002) and the Tukey test (P < 0.05). The Ultra-Lume LED 5 was superior on degree of conversion for all resins. The Radii Plus was equal to the Ultra-Lume LED 5, except for the resin Tetric Ceram , were the Optilux 500 was superior. The LEC-470 I was inferior for the conversion of all resins. The study proves the importance of the compatibility of the different photoinitiators in resin composites with the different light sources.