A crown is a tooth-shaped cap placed over a tooth that has been badly damaged or decayed, and is used to protect the tooth from further deterioration.
Crowns may be placed for a number of reasons. Usually the tooth has been broken or damaged a great deal by decay. As a result, a filling alone can’t replace enough of the tooth or make the tooth strong enough. Often times, a crown will be used on top of a root canal treated tooth in order to give it strength. A crown can also be used to hold together parts of a cracked tooth with the goal of stopping the crack from progressing. Another use of crowns is where they are used to hold a bridge in place. Furthermore, crowns can be used to improve appearance as well. They may be placed to cover misshapen or badly discolored teeth.
Crowns can be made of various combinations of metals and ceramics. They can be all ceramic, all metal, or porcelain fused to metal (PFM). The metals used to fabricate crowns include gold alloy, other alloys (palladium) or a base-metal alloy (nickel or chromium). PFM and all-ceramic crowns are fabricated to be the same color as your natural teeth, and they can look just like normal teeth. Today’s ceramics are far superior to those a few years ago, and make an excellent choice for crown restorations.
In certain situations, prefabricated crowns may be appropriate. Prefabricated crowns are made of plastic or stainless steel. Prefabricated crowns are typically used in pediatric situations, where a short term, low cost alternative can be utilized until the child has completed growing. In certain situations, they can also be used on a temporary basis until a permanent crown is made.
Preparing the Tooth
Before placing a crown, Dr. Victor ensures there is a firm foundation for it. This may include x-rays and a special filling called a “crown build-up”. A build-up is needed if large areas of the tooth are decayed, damaged or missing. If you are receiving the crown after root canal treatment, Dr. Victor may also insert a post-and-core as part of this foundation. The post-and-core provides strength to the tooth by spreading the load out over the root as well as the crown.
Once this is done, Dr. Victor will refine the tooth to make room for the new crown. The goal here is to allow the new crown to be the same size as the original tooth. Once the tooth is prepared, Dr. Victor will make a special impression (copy) of the prepared tooth as well as those around it. The impression is then sent to a lab, where the crown is made.
Since it may take several weeks for the lab to make the final crown, you will have a temporary crown placed at the time of the crown prep. This temporary crown is made of plastic, and is not as strong as the final crown, so care must be exercised by the patient to not chew hard substances such as ice or nuts. The temporary crown is also seated with temporary cement, which is designed to be weak. This allows us to easily remove the temporary crown when we go to seat your permanent crown. If by chance the crown comes uncemented, re-seat the crown using toothpaste (this creates a suction to help hold the crown in place) and contact Dr. Victor.
Seating the Permanent Crown
At a second visit, Dr. Victor will remove the temporary crown and test the permanent one. Sometimes crowns need additional polishing or glazing or some other adjustment before they are placed. Once the crown is ready, it’s cemented to your tooth, typically with permanent cement. In certain situations, like when there is a concern that a root canal may be needed in the future, Dr. Victor may seat the crown with temporary cement.