An onlay is a type of indirect dental restoration that repairs a tooth with extensive decay or damage, particularly when the damage is too significant for a filling but not severe enough to require a full crown. Sometimes referred to as “partial crowns” because they cover one or more cusps (the raised points) of the tooth.
Unlike traditional fillings, which are applied directly to the tooth, onlays are fabricated outside the mouth—typically from materials such as porcelain, composite resin, or gold—before being bonded onto the affected tooth.