A dental inlay or onlay is bigger than a filling and smaller than a crown. It is bonded or cemented into place. An inlay is similar to a filling, but it lies within the cusps (bumps) on the chewing surface of your tooth. An onlay is larger than an inlay. It covers one or more cusps.
Inlays or onlays can be made of gold, composite resin (plastic) or ceramics. They can last for decades.