Crown restorations cover and protect teeth that have been weakened by decay, prior restorations, or root canal treatment. Crowns can also be placed to change the bite or for cosmetic purposes. Crowns typically require at least two visits to complete treatment. At the first visit, the dentist will reduce the size of the tooth. This procedure makes room for the crown itself to fit on the remaining portion of tooth, called the preparation. After the reduction is completed, an impression, or mold, of the preparation is made using a rubbery material, or a digital image/scan of the tooth may be made to allow a computer system to make the restoration. A temporary crown is held on the tooth with temporary cement while the crown restoration is being made. It is important to return for the cementation of the new crown as soon as it is ready in order to reduce the risk of new tooth decay or other problems.