Pulse activation: reducing resin-based composite contraction stresses at the enamel cavosurface margins.

The surface hardnesses of both the 40 s@600 mW/cm2 group and the 40 s@100 mW/cm2 group developed at nearly the same rate. The surface hardness of the pulse activated group developed appreciably slower. The diametral tensile strengths of all three groups were not significantly different. There was significantly less dye penetration with the use of the lower power density but there was very little leakage noted with the pulse-activated group. It is believed that this is the result of a prolonged gel state, which allowed flow to occur in the resin-based composite. There is significant clinical potential for the use of pulse activation of light-cured resin-based composite materials.