When more than half of the tooth’s biting surface is damaged a dentist will often use an inlay or onlay.

Porcelain inlays or onlays are recommended when a filling is not enough and a crown is not needed. Inlays and onlays are made from porcelain, rather than metal amalgam or white composite. Porcelain is nearly impossible to distinguish between the filling and the tooth because of its astonishingly natural appearance.

Difference Between Inlays and Onlays

The overlying difference between onlays and inlays is that they differ in size. Inlays are smaller, filling cavities that reside inside the tooth’s cusps. Onlays are larger and will extend to the outer surface of a tooth. Onlays are generally needed when there is a more severe level of decay. After an initial appointment, your dentist will be able to conclude if you are in need of an inlay or an onlay based on the decay that has taken place.

What are inlays & onlays?

Inlays and onlays can be made of porcelain, gold, or composite resin. These pieces are bonded to the damaged area of the tooth. 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.

Traditionally, gold has been the material of choice for these. In recent years, however, porcelain has become increasingly popular due to its strength and color, which can potentially match the natural color of your teeth.

How are inlays & onlays applied?

Two appointments are necessary 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 by the dentist, and sent to a lab for fabrication. The dentist will then apply a temporary sealant on the tooth and schedule the next appointment.

At the second appointment, the temporary sealant is removed. Dr. Sorber 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, inlays and onlays, which are bonded directly onto the tooth using special high-strength resins, can actually increase the strength of a tooth by up to 75 percent. As a result, they can last from 10 to 30 years. 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.