A variety of instruments and techniques has been developed and described for the preparation of severely curved root canals. This paper reviews the ability of different automated devices and torquelimited handpieces when using rotary nickel-titanium instruments for root canal preparation. In summary, there is currently no scientific evidence that the choice of a special automated device has any clinical influence on the outcome of endodontic treatment. Keywords: automated devices, canal straightening, curved root canals, instrument fracture