[Microhardness of resins as a function of color and halogen light]

The aim of this study was to evaluate the influence of light intensity and the influence of the color of a composite resin on Knoop hardness. Samples were confected utilizing polyester matrices with 6 mm of diameter and 2 mm of depth. The matrices were filled with composite resin (Fill Magic - Vigodent), colors A3, B3, C3, D3 and I, and light-cured by means of an Elipar light-curing unit in three different light intensities: 450 mW/cm2, 800 mW/cm2 and an increasing intensity setup of 100 mW/cm2 to 800 mW/cm2. Ninety test specimens were confected, with the standard curing time of 40 seconds. The specimens were stored at 37 +/- 1 degrees C and immersed in distillate water. The Knoop test was carried out in superficial and deep areas of the specimens. The results revealed that there was no statistical difference (Tukey) between the tested colors. However, there was statistical difference between different light intensities. The authors concluded that the color of the composite resin did not influence Knoop hardness and that the progressive intensity setup led to the best Knoop hardness.