khalifah ahmed alhaila¹and  A. E. Badr^{2 1Department of Conservative Dentistry and Endodontics, Faculty of Mansoura University, Mansoura, 35516 Egypt 21Department of Endodontics, Faculty of  DentistryMansoura University, Mansoura} Abstract: Objectives:Conventional endodontic treatment is based on shaping, disinfecting, and filling the root canal system[1].  A prepared root canal should have a continuously tapered funnel shape, while maintaining the original outline form of the canal[2].  However, these objectives are often difficult to achieve because of the highly variable root canal anatomy and canal curvature[3].  Several enlargement techniques have been developed to minimize errors, such as ledging, zipping, loss of working length, and apical transportation[4].  Although various  root canal preparation techniques have been developed to overcome the problems, rotary nickel-titanium (NiTi) systems were  developed  to maintain the original canal shape and thus remain better centered^[5-8].