"Let us always meet each other with a smile, for the smile is the beginning of love." - Mother Theresa
Inlays and onlays are used to reinforce an existing tooth that is too damaged to support a filling, but not damaged enough to require a crown. These restorations are usually made from composite resin material, porcelain, or gold. An inlay is placed on the chewing surface between the grooves (cusps) of a tooth, while an onlay covers one or more of the cusps. Once in place, they are virtually undetectable, and they conserve much of your natural tooth structure. For an illustration, visit http://yourtotalhealth.ivillage.com/inlays-onlays.html
Both inlays and onlays are prepared outside your mouth and then cemented or bonded to the teeth, and fit much like a puzzle piece. They are intended to rebuild a larger surface area of a tooth, whereas fillings only fill a small hole. Inlays and onlays are not as extensive as crowns, which cover most of the tooth.
For an inlay to be successful, it is best if the cavity involves only the occlusal surface (chewing surface) and one proximal surface (surface in between the teeth). The other proximal surface should be free of decay. An onlay, which is similar to an inlay, covers the entire proximal surface and protects the cusps from fracture. Treatment involves isolation of the tooth and removal of the old fillings under local anesthesia. Once your dentist makes an impression, the inlay/onlay is created from porcelain, gold, or composite resin material. The inlay/onlay is then cemented securely into place. Inlays and onlays usually take two to three appointments to complete. The onlay is the best alternative for covering larger surface restorations. An inlay/onlay looks exactly like the rest of the tooth, and is so durable that it doesn't need to be replaced for years.
Materials such as gold, composite resin, or ceramics may be used to create inlays and onlays. Which material is chosen may be influenced by aesthetic appeal, strength, durability and cost. The material used plays a major role in determining how long these restorations will last, as some substances are tougher and better tolerated than others. Other factors that influence the longevity of an inlay or onlay include the strength of the tooth that is treated, the amount of chewing that occurs on the restoration, and a patient's willingness to maintain oral hygiene and to have regular dental examinations.