An inlay is similar to a filling and lies inside the cusp tips of the tooth. They are custom-made to fit the prepared cavity and are then cemented into place. An on-lay is a more extensive reconstruction that covers one or more cusps of a tooth. On-lays are indicated in situations where a substantial reconstruction is required. However, more of the tooth structure can be conserved compared to the placement of a crown.

To repair damage to the tooth's biting surface, rather than using a simple filling, or a crown, a dentist will often use an inlay, or an on-lay. Inlays and on-lays can be made from porcelain, gold, or composite resin, although porcelain is now becoming the material of choice because of its strength and potential to match the natural color of your tooth.