['The objective of this study was to determine the effectiveness of 0.04 ProFile instruments during the removal of root fillings.', 'A total of 30 single-rooted mandibular canines were divided into three groups. The canals were accessed and then prepared with a reciprocating automated device and nickel-titanium files. Three different techniques of obturation were used: Thermafil system (group I), thermomechanical compaction (group II) and lateral condensation (group III). Sealer 26 was used in all three groups. Two weeks after obturation, the fillings were removed using 0.04 ProFile instruments following standardized sequence of size 90, 60, 45, 40, 35 and 30 at a speed of 300 rpm in a crown-down manner. The teeth were subsequently split with a chisel, photographs were taken with a colour video camera and the removal of filling material was assessed visually (by colour) by two examiners. The time required to achieve the working length was also recorded.', 'ProFile instruments reached the working length in all cases. However, complete removal of gutta-percha occurred in only three specimens (two of group I, and one of group II). Thermafil plastic carriers were removed successfully in all specimens of group I.'] Do efficiency of the 0.04 taper ProFile during the re-treatment of gutta-percha-filled root canals?