Inlays and onlays are restorations used to repair rear teeth with mild to moderate decay or cracked and fractured teeth that are not sufficiently damaged to need a crown. Inlay is an indirect restoration (filling) consisting of a solid substance (as gold, porcelain or less often a cured composite resin) fitted to a cavity in a tooth and cemented into place. This technique involves fabricating the restoration outside of the mouth using the dental impressions of the prepared tooth, rather than placing a soft filling into the prepared tooth before the material sets hard. Onlay is the same as an inlay, except that it incorporates a replacement for a tooth cusp by covering the area where the missing cusp would be. Crowns are onlays that completely cover all surfaces of a tooth.