A crown, sometimes known as dental cap, 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. While inarguably beneficial to dental health, the procedure and materials can be relatively expensive.
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. Using this indirect method of tooth restoration allows use of strong restorative materials requiring time-consuming fabrication methods requiring intense heat, such as casting metal or firing porcelain which would not be possible to complete inside the mouth. As new technology and materials science has evolved, computers are increasingly becoming a part of crown fabrication, such as in CAD/CAM dentistry.
Crowns are normally used to:
- Restore the form, function and appearance of badly broken down, worn or fractured teeth, where other simpler forms of restorations are unsuitable or have been found to fail clinically.
- Improve the aesthetics of unsightly teeth which cannot be managed by simpler cosmetic procedures.
- Maintain the structural stability and reduce the risk of fractures of extensively restored teeth including like teeth which have been root filled as in Root Canal Treatment, especially posterior teeth which are subjected to higher occlusal forces.
- Restore a dental implant
Dental ceramics or porcelains are used for crowns manufacture primarily for their aesthetic properties compared to all metal restorations. Many classifications have been used to categorise dental ceramics, with the simplest, based on the material from which they are made, i.e. silica, alumina or zirconia.