Nickel-titanium (NiTi) rotary instruments are increasingly popular for removal of root canal fillings. In the present paper, previously published studies on cleanliness, working time, fractures, canal aberrations, apical extruded debris and rotational speed during retreatment are reviewed. Recent studies have shown that FlexMaster, K3, ProTaper and RaCe performed well for retreatment of straight root canals. For removal of filling materials from curved root canals, RaCe seemed to be an adequate instrument. However, compared with hand files the abovementioned instruments neither improved root canal cleanliness nor reduced working time. Overall, there are more instrument fractures with NiTi instruments compared with hand files. Further studies should be performed to determine the optimum rotational speed and torque including instrumentation sequence when using NiTi instruments for retreatment.
Keywords: gutta-percha, nickel-titanium, root canal retreatment, rotary instruments