When your tooth is cracked, broken, or mishappen you can use a crown to cover it. There are also times when a cavity is too large to be fixed with a filling and require a crown. Some dental implants, root canal procedures, and bridges may require a crown to finish the procedure. A crown is an artificial replacement that restores missing tooth structure by surrounding the remaining tooth structure. It can be made of metal, ceramic or polymer materials or a combination of such materials.