Quality of curing in relation to different light sources by measuring hardness, degree of conversion and depth of cure

Abstract

This study was to determine the quality of curing of second generation light emitting diode (LED-II) compared to a first generation LED (LED-I) and conventional halogen (quartz tungsten halogen) light curing unity by measuring depth of cure, degree of polymerisation and surface hardness. Filtek Z-250 hybrid composite resin (3M-ESPE, Germany), with shade A2, was used in this study. One quartz tungsten halogen/light curing unit (LCU) (Hilux, Benlioglu Dental, Turkey), one LED-I-LCU unit (Elipar Freelight 3M-ESPE, Germany) and one LED-II-LCU (Elipar Freelight, 3M-ESPE, Germany) were used for polymerisation of the composite resin. The depth of cure was obtained with scrape test, degree of cure was measured with Fourier transform infrared spectrometer (Spectrum-One, Perkin-Elmer, USA) and surface hardness was calculated with surface hardness tester (Micromet-2001, Buehler, Dusseldorf, Germany). The data were analysed by Kruskal Wallis and Mann Whitney-U. The polymerisation depth of LED-I-LCU was significantly lower than that of the other LCUs (p<0.05). However, no significant differences were obtained among all tested systems in point of degree of cure and surface hardness at 2 mm depth. Within the limitations of this study, although LED-I showed lower depth of cure, all tested systems appear suitable for routine clinical practice for polymerisation of the composite resin.