Clinical efficiency and reusability of the reciprocating nickel-titanium instruments according to the root canal anatomy.

The application of the single-file technique using the reciprocating motion is gaining concern in root canal preparation. The purpose of this research is to compare the efficiency of the reciprocating motion-employing files (RECIPROC and WaveOne) by measuring the working time for complete canal shaping, and to evaluate their reusability under scanning examinations. One hundred curved root canals of the extracted molars were used. The working length was determined and the glide path was confirmed using a #15 K-file. Canals shaping was completed to the length either with RECIPROC R25 file (n = 50), or with WaveOne Primary file (n = 50). The time taken for the file to reach the working length was also measured. Each file was repeatedly used in a maximum of 10 canals for comparing the change of the efficiency (shaping time) according to the working length, canal curvature, and number of file re-use. The deformations or surface defects of the files after the in vitro use were observed using a scanning electron microscope (SEM). There was no difference under the SEM between the 2 file groups with no initiation of micro-cracks until they were re-used up to 5 canals. WaveOne Primary file showed significantly shorter working time than RECIPROC R25 (p < 0.05). There was a statistically significant correlation between the working time and three variables. As the working length and the curvature of the canal increased, the shaping time was increased in both file systems. Reusability of these reciprocating instruments might be maximum 5 canals with minimal surface deformations.