Aim: the aim of this study was to evaluate the amount of filling material left on root canal walls, amount of apically extruded debris, time to reach working length and number of fractured files by using four different nickel-titanium (Ni-Ti) retreatment file systems (Protaper universal, Rogin, Soco-pro, M3 progold).
Methods: Forty extracted human mandibular first molar with two separate mesial canals were prepared by manual k files taper 0.02% up to master apical file #25. Step back technique was performed up to size #40 and then obturated with gutta-percha and Adseal. Samples were equally divided into 4 groups according to the retreatment system used.
Results: Group (I) showed higher efficiency in removal of filling materials with statistically significant difference compared to other groups. Group (I) and Group (IV) extruded the least amount of debris with significant difference to other groups. Group (I) was significantly the fastest in reaching the working length and removal of filling materials. Three D3 in group (I), 3 D2 and 3 D3 in group (II), 2 D1,3 D2 and 5 D3 in group (III) and 1 D1, 3 D2 and 3D3 in group (IV) were broken.
Conclusions: Protaper universal retreatment file system (PTUR) has higher efficiency in removal of root canal filling material from different root sections, M3 pro gold and PTUR systems extruded the least amount of debris, PTUR system took the least time to reach the working length, Soco pro had the highest number of broken files while PTUR had the least number.