Color stability and hardness of a composite-resin lightactivated by LEDs

Objectives:The purpose of this study was to evaluate color stability and microhardness Vickers of composite resin Charisma (Heraeus Kulzer) shades A2 and SL photo-activated with two different curing light units (Halogen light bulb - 522mW/s2 ; LEDs – Optilight LD III- 450 mW/s2). Methods: Sixty specimens (17mm in diameter and 1mm in thickness) were built in metallic moulds and divided in four groups (G1, G2, G3 and G4) according to the shade and curing unit (G1: A2/ halogen; G2: SL/ halogen; G3: A2/ LEDs; G4: SL/ LEDs). The specimens were immersed in deionized water at 60ºC for 30 days and at dark. Two color measurements have been done, one initial (baseline), before experimental treatment, and a final one, after 30 days of immersion. Reflectance spectrophotometry (Spectrophotometer Cary-Varian 100) were used in wavelenght range 360 to 720 nm, with CIE-Lab color space and DE were calculated. Then the sample was submitted to Vickers microhardness test (Microdurometer digital Mmt3 HMV-Shimadzu), with 30gF during 30 seconds. Data was submitted to ANOVA two criteria and, if there were significant statistical difference, to Tukey test. Results:Concerning color stability, there was no statistical difference between groups, with the biggest DE within accetable values. However, results of microhardness test showed significant statistical difference for G2. Conclusions:It was concluded that halogen light unit showed the best results for microhardness in both shades, while SL showed better color stability than A2 for both light curing units. Finally, LEDs curing light unit was able to keep color stability for both shades.(This study has been supported by CAPES/ Fundação Araucária)