Crowns are needed when a tooth has had more damage than a regular filling can repair. This includes badly decayed teeth, broken or cracked teeth, teeth that have had root canals, and teeth that have had previous large fillings. A crown is a cover or "cap" that protects the entire surface of a tooth and restores it to its original shape, size, and function. Crowns can be made from several types of materials including high-strength ceramic and porcelain for beautiful cosmetic results