WHAT ARE CROWNS & BRIDGES?

A crown is a metal and/or porcelain restoration that covers most of the tooth. A bridge is a fixed appliance that replaces one or more teeth and is connected to the adjacent teeth with crowns. The purpose of both crowns and bridges is to strengthen a damaged tooth. The tooth may have been damaged by decay, or have a previous restoration that has fractured. Root canalled teeth are also crowned if sufficient tooth is missing or if the dentist feels that the tooth will last longer by protecting it with the crown. There are several types of crowns. The dentist and patient will make the decision as to which one is best for the patient. The procedure involves several phases. The dentist prepares the tooth and a temporary crown is fabricated and used to temporize the tooth while the crown is being processed in a dental laboratory. The second step is inserting the permanent crown. Failing to return to have the permanent crown placed can cause damage to the underlying tooth due to weakness and microleakage under the temporary resulting in recurrant decay.

Potential For Root Canal Treatment: When crowns or bridges are made, tooth substance is prepared or drilled away so that the metal and/or porcelain can take its place. This procedure may cause inflammation in the pulp (nerve). Most teeth survive this process, but others do not. It may be necessary immediately or at some future date to do a root canal. This may then involve placing a post in the tooth. If a root canal is required after the crown or bridge has been placed, remaking the crown or bridge may be necessary. You would be responsible for the cost of root canal treatment, the post, and the new bridge or crown.

Posts: Posts are "placed" in root canalled teeth to replace missing tooth structure. This is done so that a crown or bridge will have the proper support to stay in place. After a root canal filling is done, the remaining tooth structure in the root can be very thin next to the bone. On rare occasions this thin layer of root is perforated when a post preparation is made. If perforation occurs, the tooth will have to be removed. A post can also fail because there is too much force during function. It may come out or break. If the root breaks the tooth will have to be removed and a bridge or implant restoration will need to be considered.

Gum Retraction: An impression must be made of the prepared tooth to make a crown. The gums are retracted away by thin strings or cords. Some of these cords contain epinephrine (adrenaline) and on occasion can cause rapid heartbeat and lightheadedness. The gum tissue may feel uncomfortable for a few days.

Temporary Crowns Or Bridges: Temporary crowns or bridges are made of plastic to cover the prepared tooth, protect it, provide for chewing, and provide minimal esthetics. The color and shape of the temporary bridge will approximate, but will not be as esthetic as the final crown or bridge.

Esthetics: Crowns and bridges most commonly have a metal framework to provide strength. Porcelain can be used to cover the metal, but in some areas metal may show. If you are uncomfortable with this idea, please discuss these concerns with your doctor, as there are techniques that can help reduce metal showing.

Porcelain: In the back of the mouth, metal crowns and bridges are best. The reason for this is that metal stands up to chewing forces better than porcelain. Porcelain is a close cousin to glass. If you wish to have porcelain on the chewing surfaces of the back teeth, you must understand that it can fracture. All porcelain crowns in the front of the mouth require a certain thickness for esthetics; thus thin or small teeth may need root canal treatment and posts to provide space for the porcelain.

Length Of Service Of Crowns Or Bridges: About five to seven years is the average for a crown with porcelain and about five to ten years for all metal crowns. The length of service for any individual crown or bridge cannot be predicted however. You must keep the crown/bridge clean (free of bacterial plaque) to increase longevity.

Alternatives to Crowns or Bridges:

1. Implants and crowns or bridges if indicated.
2. Removable partial dentures.
3. No treatment.

For more information http://www.ada.org/public/topics/alpha.asp