Barcoll hardness of different resin-based composites cured by halogen or light emitting diode (LED)

The clinical performance of light curing resin composites is greatly influenced by the quality of the light-curing unit (LCU). Halogen LCUs are commonly used for curing composite materials. However, they have some drawbacks. The development of new, blue, super bright light emitting diodes (LED LCU) of 470-nm wavelength with high light irradiance comes as an alternative to standard halogen LCUs of 450-470-nm wavelengths. This study evaluated the surface hardness of the different resin-based composites (flowable, hybrid and packable resin composites) cured by LED LCU or halogen LCU. A Teflon mold 10-mm in diameter and 2-mm in depth was made to obtain five disk-shaped specimens for each experimental group. Then, the specimens were cured by an LED LCU or halogen LCU for 40 seconds. The hardness of the upper and lower surfaces was measured with a Barcoll hardness-measuring instrument. The statistical analysis was performed using one-way analysis of variance (ANOVA) and Duncan test at a p=0.05 significance level. The results of the hardness test indicated that the hardness of resin composites cured by an LED LCU were greater than those cured by a halogen LCU. Additionally, for all resin-based composites, the hardness values for the upper surfaces were higher than the lower surfaces. However, for both results no statistically significant differences were observed (p>0.05).