The endodontic therapy is considered successful when it achieves certain criteria that include the absence of periapical radiolucency, root filling extending to 2 mm within the radiographic apex, root filling with no voids, and a satisfactory coronal restoration1.
However, root canal failure could occur in a percentage of 15 - 22%, and the non-surgical root canal retreatment stays the treatment of choice as a conservative way to control the post-treatment disease2.
In non-surgical root canal retreatment removing all of the old root filling material is essential to improve the chances of success because this material could make a mechanical barrier that potentially retains the bacteria responsible for the case failure and also hinders the contact of irrigating solutions and intracanal dressings to the root canal walls3.
Sealers are used to obturate the root canal irregularities and to fill the voids between the root canal filling and the canal walls4. Many new sealers have been introduced in the market; most commonly used are the resin-based and the bioceramic based sealer, the retreatability of these sealers is still not fully known5.
In more complicated cases of canal irregularities and atypical root canal system, the clinician faces a further challenge in the effective removal of the root canal filling. Internal root resorptions are a pathological condition caused by the inflammatory reaction of the pulp cells leaving a resorptive cavity, the limitations of conventional non-surgical retreatment protocols require a more effective approach to fully remove the root canal fillings6.
Irrigant agitation through Ultrasonic (Passive Ultrasonic Irrigation –PUI) considered efficient when compared to the conventional syringe irrigation because of the acoustic transmission that can break the bacterial biofilm and other materials and debris in the root canal system7 other instruments have been introduced to the market for the same purpose, XP-endo Finisher (FKG Dentaire, Switzerland) stands out because of its special titanium alloy (Martensite-Austenite Elctropolish-Flex) that can react to a different temperature when the instrument reaches the body temperature it transforms from the straight martensite phase to a curved austenite phase the instrument tip could expand up to 6 mm when subjected to pressure, it has been demonstrated that this instrument could improve the removal of Ca(OH)2 from oval canals and reduce the bacterial count in the root canal system8, XP-Endo Shaper (FKG Dentaire) has the same titanium alloy as XP-endo Finisher and according to the manufacturer, this alloy has the ability to adapt to the morphology of the root canal and could expand to reach all canal walls.