Dental crowns are teeth that are made to resemble your own tooth. Crowns are usually necessary when a root canal is performed, or some trauma happens to the tooth to make it weak. Crowns reinforce and protect the tooth and root. Your dentist will shape the existing tooth and fit you with a temporary crown. After a few weeks, you will return to have the full coverage crown put in permanently. Crowns typically last 20 or more years.