An inlay is done when the tooth structure replaced is within the cusp tips of the tooth. If the damage is more extensive and the new structure covers the entire chewing surface, including one or more tooth cusps, the procedure is called an onlay. Like a crown, an onlay covers and protects the tooth’s biting surface. While a crown covers the entire tooth, an onlay fits inside the tooth cusps and covers only the biting surfaces. Because an inlay or onlay is fabricated in a dental laboratory, it takes two or more appointments to complete the restoration.

More conservative than a full crown, inlays and onlays are two methods of restoring tooth structure after decay or other damage. Inlays and onlays are known as indirect fillings because unlike a standard filling, both are made in a laboratory and cemented or bonded to the surface of the tooth during a second visit. Inlays and onlays make the most of the remaining tooth structure, protecting the tooth from fracture. After the procedure, the tooth can bear up to 50 to 75% more chewing force.