During retreatment, the endodontist will reopen your tooth and remove the filling materials that were placed in the root canals during the first 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 (or permanent) filling. The next step would be a new crown or other restoration to be placed on the tooth to protect it, as indicated by your dentist.