An endodontist is a dentist who specializes in saving teeth. After completion of dental school, they must complete an additional 2+ years of advanced training in endodontics.
The American Dental Association defines an endodontist as one who performs "routine as well as difficult and very complex endodontic procedures, including root canal treatment, endodontic surgery and special procedures to save teeth after traumatic dental injuries. By focusing their practice on specific procedures such a root canal treatment, surgery and trauma, endodontists are experts at managing a wide array of complex endodontic problems efficiently. Advanced technologies and specialized techniques used by endodontists give them a very accurate view of the inside of the tooth and allow them to treat the tooth quickly and comfortably."