Introduction: The aim of this study was to evaluate the smear layer removal ability of stainless steel and NiTi hand files as well as an orthodontic rectangular NiTi wire activated by an ultrasonic device. Methods: 50 palatal root canals of maxillary molars were preflared with a #35 LA Axxess bur at the cervical third and with ProTaper instrument, up to F4 instrument, within working length, at the apical third. The canals were irrigated with 1% sodium hypochlorite and divided into five groups for passive ultrasonic activation (PUI): GI = EDTA + 1 minute (PUI) with a stainless steel#15 K-file; GII = EDTA + 1 minute (PUI) with a NiTi #15 K-file; GIII = EDTA + 1 minute (PUI) with orthodontic NiTi 25 x 11 wire; GIV = EDTA for 3 minutes without PUI; GV = No EDTA and no PUI. Subsequently, each root was sectioned longitudinally and a hemisection was covered with a layer of metal and analyzed by a scanning electron microscope. Images of the three thirds were taken, stipulating scores as follows: 0 = no layer of dentin debris, clean and open dentinal tubules; 1 = moderate dentin debris layer; 2 = thick layer of dentin debris covering the surface of the dentinal tubules. The data for each score were compared statistically. Results: Smear layer was observed in all three thirds. All groups using EDTA differed statistically (p < 0.05) from the group without EDTA. There were no significant differences between the groups activated with ultrasound and the EDTA group without ultrasound. There were no significant differences (p < 0.05) among the three instruments employed. Conclusion: The use of EDTA favored smear layer removal. Activation of EDTA for one minute, regardless of the instrument used, favored cleaner dentin walls.Keywords: Smear layer. Root canal irrigants. Ultrasound. How to cite this article: Filpo-Perez CA, Amoroso-Silva PA, Guimarães BM, Bernardineli N, Bramante CM, Morais CAH, Duarte MAH. Inluence of the type of instrument used in passive ultrasonic irrigation on the smear layer removal capacity.