Effect of LED curing on the microleakage, shear bond strength and surface hardness of a resin-based composite restoration

Abstract

To determine the effect of Light emitting diode (LED) curing on dental resins, microleakage, shear bond strength and surface hardness of a dental composite cured with different LEDs were determined and compared with conventional halogen curing. For microleakage, Class V cavities were restored with Esthet-X, divided into groups, and exposed to one of the curing protocols (Elipar Freelight in soft start and standard modes; Ultra-Lume 2; Spectrum 800). Standard dye penetration tests were performed and the data summarised in a 2-way contingency table of observed frequencies. The Chi-square test was used ( p < 0.05 ) to test for significant differences between the lights. For surface hardness, samples of Esthet-X were exposed to the light-curing units (LCUs). Vickers hardness was determined on the upper and the bottom surfaces. Data was subjected to statistical analysis using ANOVA ( p < 0.05 ). Shear bond strength was determined using a push out method. Comparisons (ANOVA, p < 0.05 ) were made between the different curing protocols. No significant difference in microleakage could be demonstrated between the different LCUs at the enamel side ( p = 0.60 ). At the dentin side only the Elipar Freelight (soft start), could significantly reduce microleakage ( p < 0.01 ). The hardness score for the halogen light was significantly lower than for the LED lights ( p < 0.01 ). The Spectrum 800 and the Elipar Freelight (soft start) have significantly higher shear bond strengths than the others ( p < 0.01 ). It was concluded that the LED source is more efficient for a comparable overall power output.