Surface hardness of light-cured composite resin cured directly or through a transparent matrix using three different...

The purpose of this study was to compare the Vickers Hardness (HV) of composite resin which was light-cured by 3 different light guides, either through or without a transparent polyester matrix band. The 3 light guides, standard Demetron (SG), Turbo Tip (TT) and a standard Demetron, with obvious accidental damage (DL) were tested with both Model 100 and Cure Rite radiometers. HV tests were done on all samples both immediately and one hour after light-curing. Results were analysed using the Anova and Student t-test. The light intensity readings in mW/cm2 were SG 600 and TT 850 with both radiometers and DL tested 350 and 380. Composite resin surfaces undergo significant surface hardening in the first hour after light-curing. A 350-380 mW/cm2 intensity gives significantly lower HV than 600 + mW/cm2 but 800 mW/cm2 does not produce significantly greater HV than 600 mW/cm2. Curing through a transparent polyester matrix gives marginally greater HV than curing directly. The output of light guides is a significant factor in the surface hardness of cured composite resin.