A crown is a shell that fits over a tooth. The tooth must first be prepared, requiring around 1mm to be shaved off all around the circumference and from the biting surface of the tooth, leaving the core intact. The crown is custom made by a dental technician and is cemented in place over the core.
Crowns are primarily designed to improve the structural integrity of teeth that have been significantly weakened by large cavities, fractures, cracks, heavy wear or large fillings. Often, a tooth which has required a root canal filling will be rendered weak and will require a crown. If a crown is recommended, the tooth will usually be too weak to support a filling. Having the crown fit over and around the core of the tooth helps to hold the tooth intact.
In some cases, crowns are used to improve the appearance of a tooth which is relatively healthy but unsightly. However, in some cases alternative treatments such as porcelain or composite veneers, or teeth whitening may be more suitable.
Unless the tooth has had the nerve removed for a root canal filling, it will usually be necessary to numb the tooth with a local anaesthetic. Any diseased or damaged tooth tissue or unsound filling will be removed from the tooth, which will then be prepared from the crown. This involves shaving 1mm thickness off the tooth around the circumference and the biting surface, leaving the core intact. For any tooth which already has a large filling, most of that which is shaved off may well be filling material rather than tooth. Impressions of the teeth will be taken which will allow the dental technician to construct the crown. A temporary crown will be fitted. At the second appointment, the temporary crown will be removed, and the custom-made crown cemented in place.
A crown placed on a suitable tooth in good conditions will last an average of 12-15 years. This is not a minimum – it means 50% of crowns will last less than this time. However, crowns are sometimes placed on significantly damaged teeth as a last resort, with a reduced life expectancy. If this is the case, your dentist will inform you. A crown may fail by becoming decemented from the tooth, by the tooth decaying under the crown, a dental abscess forming, or by the tooth breaking off inside the crown. Further treatment to save the tooth is not always possible.
The tooth preparation (shaving down) required cuts away some healthy tooth, which will slightly increase the risk of the tooth developing an abscess as a result. For structural crowns, this is usually outweighed by the increased strength the crown provides, but with crowns for cosmetic purposes, it is a risk that must be considered before consenting to treatment.
|Best way to improve structural integrity of weakened teeth||Slight increased risk of abscess|
|Prolongs life of weakened teeth||2 appointments required|
|Excellent aesthetics can be achieved|
|For weakened teeth, significantly stronger than filling|
Barry broke his front tooth when eating. The tooth has been restored with an Emax porcelain crown which has achieved a very life-like appearance.