Objectives: This study was designed to compare the cleaning efficiency and time needed of tworotary Ni-Ti systems dedicated for root filling removal, ProTaper Universal retreatment (PTUR)and Mtwo retreatment system (Mtwo R) versus conventional instruments (H-files combinedwith Gates-Glidden drills), in the removal of gutta-percha root filling material with or withoutthe use of a solvent (chloroform). Methods: Sixty mandibular molar teeth were used in thisstudy. All teeth had their crowns flattened, the distal roots were sacrificed. Only mesiobuccalcanals which had angle of curvature 20°- 40° were prepared by modified-double flaredtechnique using K-files and Gates-Glidden drills, and then obturated using the lateralcondensaon technique. The samples were then divided into two main groups (n= 30) Group A:without solvent and Group B: with solvent (chloroform). Each group was further subdivided intothree subgroups (n= 10) according to the method used in filling removal: Subgroup i: (PTUR),Subgroup ii: (Mtwo R), Subgroup iii: H-files and Gates-Glidden drills (HG). During filling removal,the time needed for the procedure was recorded using a stopwatch, then roots were splitlongitudinally. Samples were photographed under the stereomicroscope. The images wereanalyzed using image analysis software for quantitative evaluation of remaining filling debris atthe three regions; coronal, middle and apical. Results: it was found that with solvent group leftnon-significantly less remaining filling material than without solvent group after retreatment.Regarding the method of root canal filling removal technique, H-files combined with Gates-Glidden drills showed significantly greater efficiency in root canal filling removal than both PTURand Mtwo R files. There was no significant difference between both the two rotary systems.Regarding the root canal thirds, it was found that apical region recorded the highest statisticallysignificant debris ratio followed by middle region group while coronal region group recordedthe lowest statistically significant debris ratio. The time recorded for filling removal wassignificantly less using PTUR files while there was no significant difference between HG andMtwo R. Conclusions: From the results of the present study, it could be concluded that: 1) Noneof the evaluated retreatment techniques was able to completely remove all the filling material.2) H-files aided by Gates-Glidden drills were more efficient in filling removal than both PTUR andMtwo retreatment files. 3) PTUR system was faster in filling removal than Mtwo R files and HG.4) The use of solvent did not significantly improve the cleaning efficiency of the testedtechniques. 5) The use of solvent shortened significantly the retreatment time