Inlays and onlays can be made of porcelain, gold, or resin. Traditionally, gold has been the material of choice, but porcelain has become more popular due to its strength and color, which can be matched to the natural color of teeth. An inlay, which is similar to a filling, is used inside the cusp (the pointed, projecting, or elevated feature) tips of the tooth. An onlay is a more substantial reconstruction, similar to an inlay, but extends out and over one or more of the cusps of the tooth. In cases where the damage of the tooth is not extensive enough to merit an entire crown, onlays can provide a good alternative and therefore, are sometimes referred to as “partial crowns”.
Inlays and onlays require two appointments to complete the procedure. During the first visit, the filling being replaced or the damaged or decaying area of the tooth is removed and the tooth is prepared for the inlay or onlay. To ensure proper fit and bite, an impression of the tooth is made and between the two visits, a temporary restoration is worn while the permanent inlay or onlay is being fabricated. During the second visit, the temporary restoration is removed and if the fit is satisfactory, the permanent inlay or onlay will be bonded to the tooth and polished to a smooth finish.