Crowns

What is a crown?
A “cap” is the lay term for a crown. It is a restoration manufactured in a dental laboratory which is placed over a broken tooth to restore it to its normal shape and size. A crown fits over the damaged tooth and protects the remaining part inside. A crown is usually placed when there is insufficient tooth structure to hold an ordinary filling or to improve the appearance of a tooth.

Why are crowns placed?
Crowns are placed for a number of reasons and include the following:

1. To support a large filling when there isn’t enough tooth structure remaining.
2. To attach a bridge.
3. To cover a dental implant.
4. To prevent weak teeth from fracturing.
5. To restore fractured and root treated teeth.
6. To cosmetically change the shape and colour of teeth.
7. To re-establish the occlusion (bite) and to enhance chewing function.

What are crowns made of?
Crowns can be made of different materials depending on a number of clinical factors. Location of the tooth, position of gum tissue, amount of tooth that shows when you smile, colour/shade of tooth and function of the tooth are all considered when deciding on the best material for a crown.Crowns can be made of: Acrylic, Metal, Porcelain, Porcelain fused to metal or Cured re-enforced composite

Acrylic crowns are usually temporary in nature and are not meant for long term use. Metal crowns are used mainly for back teeth where aesthetics is not a major factor. Gold is used in cases where the patient has a heavy bite. Porcelain fused to metal crowns are the most commonly placed crowns and are used in all areas of the mouth. Plain porcelain crowns are becoming more popular especially in cases where aesthetics is important.

How long does it take to make a crown?
It usually takes 2 appointments to complete a crown. The first appointment (usually an hour long) involves the preparation of the tooth and the impression taking. A temporary crown is then fitted. A week later the crown should be ready for placement in the mouth.

How is a crown made?
1. Local anaesthetic is administered for pain free preparation of the tooth.
2. The tooth is drilled removing most of the enamel. All decay is removed as well as most of any remaining filling material.
3. A stump is left which forms the foundation onto which the crown is placed.
4. An impression is taken of the stump as well as of the opposite teeth.
5. A temporary crown, usually made from acrylic, is placed over the stump with temporary cement. This stays in place until the permanent crown is ready.
6. At the following visit the temporary crown is removed and the permanent crown is placed over the stump.
7. If there is too little tooth to work with or in the case of a previously root treated tooth, a post may have to be placed to provide sufficient support for the crown.
8. There are instances where a thin collar of gum is removed in order to “lengthen” the remaining part of the tooth.

How long do crowns last?
10-15 years is considered an acceptable life span for a crown. However, it all depends on how well you look after the tooth.