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.
