Effect of Light-Curing in the Microhardness of Resin Cements of Dual Polymerization

AbstractObjectiveThe aim of this study was to evaluate the influence of the type of the light curing unit, exposure time and absence of light-curing in the microhardness of two resin cements of dual polymerization.Materials and MethodsDisc-shaped samples were prepared for each resin cement. The samples were light-cured with Visilux 2500 or with Elipar FreeLight 2 for 20 or 40 seconds. In addition, samples that had not been light cured were prepared for each cement studied. Measurements of Knoop microhardness were made after 15 minutes and 24 hours. The average value of Knoop microhardness was determined to each group and the results were submitted to analysis of variance ANOVA and Tukey test (α=0.05).ResultsDifferences have been detected between light-cured and non light-cured samples, with these showing significantly lower results. Samples with 20 seconds exposure time and measurements undertaken 15 minutes post-exposure showed statistically significant lower values, compared to samples with 40 seconds exposure time and measurements made 24 hours post-exposure time. No statistically significant difference was found between the results obtained with the two light-curing units.ConclusionsLight-curing with second generation LED systems did not show higher results, comparatively to conventional Halogen light units. For both cements, microhardness was significantly higher when light-curing was undertaken and there was a significant increase in microhardness after light exposure. Dental practitioners should consider that a LED whit high intensity doesn’t mean a short polymerization time nor a better polymerization in regard to a conventional halogen