Crowns or "caps" as they are sometimes called, are protective covers placed over a vulnerable tooth. The tooth becomes vulnerable for a number of reasons, including following heavy restoration (filling), root canal therapy or being cracked. All of these processes weaken a tooth and leave it vulnerable to a catastrophic fracture or split of the tooth. In this instance the tooth would need to be extracted (opening up a whole new dilemma of whether to fill the gap left by the missing tooth - think dentures, bridges or implants).
These days crowns are usually made of hard ceramic or porcelain, but in some cases they can also incorporate a metal alloy into their design, with gold still being a strong and viable option. To accommodate a crown over the top of a tooth, the tooth must first be assessed, and then shaved down and shaped appropriately. An impression of this preparation is then taken and the crown is cemented at a subsequent appointment.
