A porcelain or resin inlay or onlay is used in place of a normal filling, when the cavity is  big. Inlays are subtle tooth-coloured restoration which can fill large cavities and repair damaged teeth. They are virtually indistinguishable from natural teeth, thanks to their natural coloring. Onlays will overlay one or more cusps in order to protect and strengthen the tooth. For even bigger cavities, a crown may be required.