The anatomy of a tooth can be divided into two parts - the root and the crown. The crown is the part of the tooth that is visible in the mouth, above the gumline. A crown is a type of dental restoration which completely caps or encircles a tooth or dental implant. Crowns are often needed when a large cavity threatens the ongoing health of a tooth. They are typically bonded to the tooth using a dental cement. Crowns can be made from many materials, which are usually fabricated using indirect methods. Crowns are often used to improve the strength or appearance of teeth. The most common method of crowning a tooth involves using a dental impression of a prepared tooth by a dentist to fabricate the crown outside of the mouth. The crown can then be inserted at a subsequent dental appointment.