en Radiology Radiology Original article Original article <strong>Background and Objectives: </strong>Complete debridement of the root canal system is imperative for successful endodontic treatment. This study compared apical extrusion of debris following the use of different brands of ProTaper system. &nbsp;<br> <strong>Materials and Methods: </strong>This in vitro experimental study was conducted on 80 extracted mandibular molars. After access cavity preparation, working length was determined by a #10 K-file. The teeth were mounted in an experimental setup as explained by Myers and Montgomery and were randomized into 4 groups (n=20) for root canal instrumentation with ProTaper Universal (PTU), Dia-PT file (DPT), PathMax Pro (PMP), and hand files. The root canals were irrigated with double distilled water after using 2 files. After preparation, the debris collecting tubes were separated from the setup. Debris adhering to root surface was also collected by rinsing the canals with 1 mL of double distilled water. The tubes were incubated at 70&deg;C for 5 days. Dried debris was weighed and subtracted from the weight of empty tubes. Data were analyzed by ANOVA.<br> <strong>Results: </strong>The extruded debris in PTU group was significantly higher than that of DPT and PMP groups (P<0.05). The extruded debris in DPT group was significantly lower than that in PTU and hand file groups (P<0.05). The extruded debris in hand file group was significantly higher than DPT and PMP groups (P<0.05). The extruded debris in PMP group was significantly lower than PTU and hand file groups.<br> <strong>Conclusion: </strong>PTU caused maximum and PMP caused minimum extrusion of debris. Root canal Therapy, Smear Layer, Root Canal Preparation 18 22 http://jrdms.dentaliau.ac.ir/browse.php?a_code=A-10-809-1&slc_lang=en&sid=1 H Shahraki ebrahimi saeedbm1234@gmail.com 10031947532846009174 10031947532846009174 No Endodontics Dept, School of Dentistry, Zahedan University of Medical Sciences, Iran A Motameni Tabatabaie saeedbm1234@gmail.com 10031947532846009175 10031947532846009175 No Endodontics Dept, School of Dentistry, Zahedan Universiy of Medical Sciences , Iran S Bakhshi Moqaddam Firouz Abad saeedbm1234@gmail.com 10031947532846009176 10031947532846009176 Yes Endodontics Dept, School of Dentistry, Zahedan Universiy of Medical Sciences , Iran Y Fereydonnia 10031947532846009177 10031947532846009177 No Private Practice, Tehran, Iran