As you might expect, a crown covers the top of a tooth. There are several reasons a crown may be used in dental treatment.
If a tooth is very weak from decay, a crown can restore structure and stability. Broken or worn teeth may be restored by crowns. In the case of trauma or extensive decay, where very little of the natural tooth is left, a crown can provide the needed structure. They are also used to cover dental implants or teeth with extreme discoloration or irregular shape. In some cases, they are used to support bridges.
Your dentist will decide what material to use for the crown, dependent upon the reason it is being used. Temporary crowns are usually composed of stainless steel. These are used as a short-term solution while the permanent crown is being fabricated. Metals are generally not used for permanent crowns, as they are not as esthetically pleasing as tooth colored materials.
Porcelain may be fused to metal in a color to match surrounding teeth. This provides strength, but there is a possibility of the metal eventually showing through due to wear or gum recession.
Ceramic or porcelain are the most commonly used materials for constructing crowns. They look natural in color and texture and are strong, though not as strong as metal.
Crown applications require more than one office visit to complete. The first visit consists of shaping the tooth so that the crown will fit snugly over it without pushing on the adjacent teeth. An impression of the tooth is made for use in fabricating the permanent crown. Dentist do not create their own crowns. Specialized dental laboratories are used for this purpose. The temporary crown of stainless steel or acrylic construction is placed to protect the tooth until the permanent crown is delivered from the lab.
The next appointment includes removal of the temporary crown. The dentist will then check to make sure that the new crown fits properly before permanently cementing it in place. If it is needed, a local anesthetic may be used.
Out in the world, a bridge connects two roads together. In a dental office, a bridge connects two teeth together. If one or more teeth are missing, a bridge is placed in the gap so that the natural teeth on each side do not move. The bridge has fabricated teeth attached to replace the missing ones. Crowns are placed on the teeth on each side of the gap for support.
Before a bridge can be applied, the teeth on either side must be prepared for crowns, impressions must be taken for the permanent crowns, and a temporary bridge is provided for use during the interim, while you are waiting for the restorations to be made.
A second appointment includes fitting the crowns and permanent bridge. The permanent bridge will only have a temporary fitting, so that you can see if it fits and functions properly. A third appointment is needed to permanently affix the bridge.