When over half of the tooth’s biting surface is damaged, a dentist will often use an onlay.

What Are Inlays & Onlays?

Inlays and onlays can be made of porcelain, gold, or composite resin. For your information, an inlay (which is similar to a filling) is used inside the cusp tips of the tooth. An onlay is a more substantial reconstruction, similar to the inlay, but extending out over one or more of the cusps of the tooth. The choice between a composite onlay and a porcelain onlay is generally made by the Dentist depending on the size, location, and desires of the patient. Generally we do not make as many inlays any longer because this restoration can be made with a composite filling at a lot less cost to you. An onlay is used when extra strength is needed over a large filling, warrants the additional cost. These precision restorations are bonded to the damaged area of the tooth.

Traditionally, gold has been the material of choice for inlays and onlays. In recent years, however, porcelain has become increasingly popular due to its strength and color that can potentially match the natural color of your teeth. Gold is still the standard for strength and durability. The only limitation of gold is the color.

How Are They Applied?

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 a proper fit and good bite, an impression of the tooth will be taken and sent to a lab for fabrication. One of the Doctors will then apply a temporary restoration on the tooth and schedule the next appointment.

At the second appointment, the temporary restoration is removed. We will then make sure that the inlay or onlay fits correctly. If the fit is satisfactory, the inlay or onlay will be bonded to the tooth with a strong resin and polished to a smooth finish.


Traditional fillings can reduce the strength of a natural tooth by up to 50 percent. As an alternative, since inlays and onlays are bonded directly onto the tooth using special high-strength resins, they can actually increase the strength to near the value of a non restored tooth. In some cases where the damage to the tooth is not extensive enough to merit an entire crown, onlays can provide a very good alternative.