A crown, also called a cap, entirely covers a damaged tooth that is too broken down to be fixed with a filling. A crown not only strengthens the tooth, but it can also dramatically improve the tooth's appearance, shape, and alignment.
When a tooth is cracked, a crown can be used to bind the sides together so the crack doesn’t continue to propagate down into the tooth.
Crowns are also used to protect teeth that are at high risk of fracture. This is especially important when a back tooth has had a root canal, since root canal treatment involves hollowing out the inside of the tooth to remove an infection, and leaves the tooth likely to crack if it isn’t protected.
Since back teeth with root canal treatment need crowns, people often ask if the reverse is also true: do crowned teeth need root canals? The answer: they definitely don’t. In fact, if a tooth is alive, the purpose of a crown is to protect the nerve and prevent a root canal.
Finally, crowns are also used to cover dental implants to replace missing teeth. In this case, the crown connects with the underlying implant through a specially-made connector called an “implant abutment.”