Where there is damage to more than half of the tooth's biting surface, an inlay or onlay is recommended instead of a simple filling. These are more durable than a filling since they are fabricated in a lab under high temperature and pressure that increase their hardness and hence their strength. Porcelain is becoming the material of choice because of it's strength and eshthetics. Onlays provide more conservative treatment than crowns since they require only the damaged area of the tooth to be restored. Typically fillings can reduce the strength of the tooth by up to 50%. Since inlays and onlays are bonded to the tooth with special resins, they can increase the strength of the tooth by up to 75%.

Two visits are required for the treatment. During the first visit, the old filling and all the decay is removed and the tooth is prepared for the inlay/onlay. An impression is taken and then a temporary inlay/onlay is placed. The impression is send to the laboratory for the fabrication of inlay/onlay that will fit exactly to the tooth prepration.

During the second visit, the inlay/onlay is bonded to the tooth using high strength bonding resins and polished.