Some teeth need greater strength and support than can be provided by fillings alone. Inlays and onlays are tooth-coloured restorations that can fill large cavities and repair damaged teeth. When more than half of the tooth's biting surface is damaged, we may use an inlay or onlay. Inlays and onlays can be made of porcelain, gold, or composite resin.

An inlay or onlay is 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 tooth cusps.

Porcelain is the material of choice due to its natural colour and strength. Traditional amalgam fillings can reduce the strength of a natural tooth by up to 50 percent. Inlays and onlays are bonded directly to the tooth using special high-strength resins and can actually increase the strength of a tooth by up to 75 percent. As a result, they can potentially 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.