Though crowns can be used to improve the appearance of a tooth, they are not primarily cosmetic devices. Dentists recommend crowns to protect or strengthen weakened teeth, or to restore a disfigured tooth to its original shape. "Capping" a tooth requires buffing away part of a tooth to make room for the crown, so dentists often discourage it as a cosmetic method unless the teeth are damaged.
Crowns strengthen teeth by binding the sides of the weakened tooth together, much the way a splint holds together a broken bone. Large fillings taking up over a third of the tooth may weaken that tooth over time; crowns are often used in cases where such weakened teeth threaten to break.
The "capping" procedure takes place under anaesthetic. Because the crown is about two millimeters thick, the dentist first shaves this same amount off your existing tooth to avoid awkward-looking, oversized teeth. The dentist will also re-shape your tooth into a form upon which a cap can easily sit. He or she will then make a replica of your tooth. Usually, this replica will be a putty mold. This mold is then sent to a laboratory, where the crown will be made based on this mold. In the case of a porcelain crown, the dentist will choose a shade close to the colour of the surrounding teeth. You will return about two weeks later to have the crown fitted and, once both you and your dentist are satisfied with the "look and feel" of the crown, cemented over your original tooth.
