Dhanyakumar NM, Shivanna V, Sharma S.
Ex Vivo Evaluation of Endodontic Retreatment Using Four Rotary File Systems and Hand Hedstrom Files in the Removal of Gutta-percha and MTA-based Salicylate Resin Sealer. 
CODS J Dent
2018;
10
(2):29-34.