Patient came in with an defective old amalgam filling on his lower molar. Marginal leakage with undermine secondary caries. We decided to replace the silver coloured amalgam with tooth-coloured resin composite, which is more aesthetic than amalgam. In this case, we used sonic energy activated resin composite, SonicFill® from Kerr USA. It deliver by using an ultrasonic handpiece to enhance the adaptation of the filling material to the cavity wall.