When a tooth is damaged but not sufficiently damaged to require a full crown, dental onlays often are used to restore it. Dental onlays generally are made of porcelain or resin that matches the natural color of the teeth. Sometimes a dental gold onlay is used depending on the needs and preferences of the patient.
Dental onlays can be used to help restore teeth that are cracked or fractured, as well as teeth that suffer from decay. Dentists also use dental inlays for this type of repair, depending on where the tooth is damaged. Dental inlays and onlays both correct the same type of problem in teeth. A dental inlay is used when damage to the tooth lies between the cusps of the teeth or in the center of the tooth; a dental onlay is placed over the cusps, or covers part or all of the chewing surface of the tooth. Essentially, inlays and onlays are the same type of restoration, and the name merely describes where they are placed.
A dental onlay procedure is relatively simple and typically occurs in two stages. The first visit usually involves an examination of the tooth and the removal of decay, if applicable. A dentist then takes an impression of the tooth to be treated. Temporary fillings can be placed on the tooth to protect it. The dentist usually sends the impression to an off-site lab where the final, custom-made onlay is produced. On a return visit, the permanent onlay usually is affixed.
Typically, dental onlays are made of materials that match the existing teeth so many patients prefer them to traditional amalgam fillings or metal crowns. Dental onlays have other advantages, as well. Because very little restructuring to the original tooth is required, the majority of the tooth structure usually can be preserved, helping reduce the need for additional work later.
The material used to make dental onlays also can help strengthen the tooth, and onlays typically last longer than traditional amalgam fillings. Onlays also do not expand or contract with temperature changes, a problem that is associated with amalgam fillings that can lead to eventual cracking of the surrounding tooth. By contrast, dental onlays remain stable in changes of temperature, helping protect the tooth.
Using dental onlays instead of fillings also can provide an additional option to those who wish to avoid dental amalgam due to health concerns. While controversy exists regarding the safety of dental amalgam, onlays made of porcelain or other composite materials contain no mercury. No identifiable hazardous materials have been associated with onlays.