Teeth that have had a root canal treatment typically last a lifetime but on occasion cases can prove more complex and unpredictable. In the event that a retreatment is necessary, the endodontist reopens the tooth and removes the filling material that was placed in the root canals during the prior procedure. The endodontist then carefully examines the tooth, looking for additional canals or new infection. The endodontist then removes any infection, cleans and shapes the canals, and places new filling materials. The opening is then sealed with a temporary filling. Once the tooth heals, a new crown or other restoration is placed on the tooth to protect it.