A crown, or full-coverage restoration (sometimes incorrectly called a cap) is a prosthetic tooth designed by a dentist and usually created by a lab technician (or more recently, a CAD-CAM machine). Crowns can be either metal, porcelain fused to metal (PFM), or all porcelain/ceramic. Metals can either be noble metals or base metals, noble metals having higher content of gold, platinum or palladium. Noble metals are typically more accurate when they are cast by the lab technician and offer a better bond with porcelain. Noble alloys in PFMs have a much lower incidence of allergic reactions as they do not contain nickel. All porcelain restorations can be made from feldspathic (traditional) porcelain, lithium disilicates, aluminous porcelains, or zirconia. All ceramic restorations typically are not as strong as those with metal substructures and can cause increased wear of the opposing teeth.

Why use a crown?

A damaged tooth may be difficult or impossible to restore to correct form and function using a direct dental restorative material such as amalgam or dental composite, since these materials are placed in the damaged tooth and carved to shape by the dentist in the mouth, and thus have limited strength. In such cases, the tooth may require an indirect restoration made outside the mouth by a dental technician, who can work to produce a customized tooth shape in the chosen material that will fit the patient’s damaged tooth exactly, somewhat like a thimble fits over a finger to protect it. Crowns can also be used to support bridgework which replaces missing teeth adjacent to the crowned teeth and may be required in cases of very severe staining or where the visible form of teeth need to be realigned without the use of orthodontics. Makeover shows such as Extreme Makeover use crowns extensively, as the timeframe of the makeover is not long enough to allow up to 18 months for orthodontic treatment. Finally, crowns can also provide a suitable form for a removable partial coverage denture to link with for added denture retention.