An inlay is a lab made filling fitted into the grooves of a tooth and do not extend over the cusps of tooth. This is one of the restorations used to repair a tooth after it sustains harm from injury or decay that does not affect the cusps of the tooth. The dentist removes the decay in the tooth and takes an impression and sends it to a laboratory where the inlay is made. The dentist will place a temporary inlay at the same appointment. At the next appointment the inlay will be bonded or cemented to the tooth. Inlays are made from porcelain or gold material. A porcelain inlay matches the color of the tooth and provides almost invisible restoration while repairing the chewing surface. Dental inlays are usually more durable than fillings made from composite or amalgam.
An onlay is used to repair a tooth that has more extensive damage affecting the cusp or tips of the tooth and the biting surface. The dentist will clean out the cavity, remove any decayed tooth structure and insert a temporary dental onlay, while sending off the onlay impression to the laboratory. At the next visit (a couple of weeks later) the dentist removes the temporary onlay and bonds or cements the dental onlay in its place