A crown is an artificial restoration that fits over the remaining part of a prepared tooth, making it strong and giving it the shape of a natural tooth. A crown is sometimes known as a ‘cap’.
Crowns are an ideal way to restore teeth that have been broken, or have been weakened by decay or a very large filling. A crown could be used for a number of other reasons, for example:
Crowns can be made of a variety of different materials and new materials are being introduced all the time. Here are some of the most popular options:
Porcelain bonded to precious or non-precious metal: this is what most crowns are made from. A precious or non-precious metal base is made and then porcelain is applied in layers over it.
Porcelain crowns: these crowns are made entirely out of porcelain and are not as strong as bonded crowns, but they can look very natural and are most often used for front teeth.
All-ceramic crowns: this modern material is metal free. It can give the strength of a bonded crown and the appearance of a porcelain crown. This makes it suitable for use in all areas of the mouth.
Glass: these crowns look very natural and are used on both front and back teeth.
Gold alloy crowns: gold is one of the oldest filling materials. Today it is used with other metals to increase its strength, which makes it a very hard-wearing restoration. These crowns are silver or gold in colour.
The dentist will prepare the tooth so it is the ideal shape for the crown. This will involve removing most of the outer surface, and leaving a strong inner core. The amount of the tooth removed will be the same as the thickness of the crown. Once the tooth is shaped, the dentist will take an impression (mould) of the prepared tooth, one of the other jaw, and possibly another to mark the way you bite together.
The impressions will then be given to the dental technician, along with details of the shade to use and other information needed for the crown to be made.
If a tooth is root filled the dentist may have to insert a post before placing a crown. A post provides support and helps the crown stay in place. The weakened crown of the tooth may be shortened to gum level.
There are ready-made stainless steel posts which the dentist can fit directly into the root canal, or the dental technician can make a custom-made post to accurately fit the shape of the prepared root canal. The post is placed into the root canal and cemented in position, ready for the crown to be attached.
If a root-filled tooth is not completely broken down, it may be possible to build it up again using filling material. This ‘core’ is then prepared in the same way as a natural tooth and the impressions are taken.
The dentist will fit a temporary crown so that you can use the tooth while you wait for the crown to be made. This crown may be more noticeable but you will only have it for 1 or 2 weeks.
When you and your dentist are happy with the fit and appearance of the new crown it will be fixed in place with special dental cement or adhesive. The cement forms a seal to hold the crown in place.
You will need to have at least two visits. The first is to have the tooth prepared, the impressions taken, the shade matched and the temporary crown fitted. The second is to fit the permanent crown. There will usually be about 1 to 2 weeks in between appointments.
No, you will have a local anaesthetic and the preparation should feel no different from a filling. If the tooth does not have a nerve, and you are having a post crown, you may not need a local anaesthetic.
The crown will be made to match your other teeth as closely as possible. The shade of the neighbouring teeth will be recorded, to make sure that the colour looks natural and matches the surrounding teeth.
Because the shape of the crown will be slightly different from the shape of your tooth before it was crowned, you may be aware of it to begin with. Within a few days it should feel fine, and you will not notice it. The crown may need some adjustment if your bite does not feel comfortable. If so, you should ask your dentist to check and adjust it.
How long your crown lasts depends on how well you look after it. The crown itself cannot decay, but decay can start where the edge of the crown joins the tooth. Therefore, to prevent decay affecting the crown, it is important to keep this area just as clean as you would your natural teeth. Brush for two minutes twice a day with a fluoride toothpaste and clean in between your teeth with ‘interdental’ brushes or floss.