In the last decade, rotary nickel-titanium (NiTi) instruments have become increasingly popular for preparing root canals. Therefore, the aim of the present article is to review the literature on in vitro evaluation of rotary root canal instruments. The focus is on studies of shaping and cleaning ability, safety and working time. The use of NiTi instruments produced sufficient cleanliness with acceptable preservation of the root canal anatomy. Both centring ability and decreased straightening of root canals is superior with NiTi instruments compared with the manual technique using stainless steel instruments. However, the apical part of the root canal showed similar or fewer remnants of debris after manual instrumentation. These aspects highlight the demand for an efficient irrigation combined with mechanical preparation of the root canal. Additionally, the use of a torque-controlled device and constant speed control is recommended to reduce the risk of instrument fractures. It can be concluded that appropriate handling of engine-driven NiTi systems in combination with sufficient (antimicrobial) irrigation facilitates successful endodontic treatment. Keywords: instrument separation, root canal preparation, rotary nickel-titanium instruments, shaping ability, transportation