Centering ability and canal transportation of curved root canals after using different nickel–titanium preparation systems

Purpose To evaluate centering ability and canal transportation in curved root canals after using different nickel–titanium (Ni‑Ti) preparation systems including two rotary systems [Revo‑S and Twisted File (TF)] and hand Ni‑Ti‑Flex K‑files using cone‑beam computed tomography. Materials and methods Seventy‑five extracted human premolars with similar range of canal curvature (25–35°) were used, after crown removal and working length determination, samples were randomly divided into three groups (n = 25) according to the type of instruments used. Group I (Revo‑S), group II (TF) and group III (Ni‑Ti‑Flex). Preinstrumentation and postinstrumentation cone‑beam computed tomography images were recorded at several root canal levels (3, 5, 7, 9, and 11 mm) from the apex under the same circumstances, superimposed and then the centering ability and canal transportation were calculated using specific equations. Results Revo‑S system produced less mean value of canal transportation and more centering ability than TF and Ni‑Ti‑Flex systems. In addition, the middle canal level (7 mm) recorded the least mean value of transportation with the highest centering ability for all used instruments. Conclusion Preparation of curved root canal using rotary systems produced less change in original canal path compared with the hand Ni‑Ti files.