Cone-beam computed tomographic analysis of apical transportation and centering ratio of ProTaper and XP-endo Shaper NiTi rotary systems in curved canals: an in vitro study

Background Cleaning and shaping of the root canal system is an important step of endodontic treatment. Canal transportation is a common procedural error in preparation of curved canals. This study aimed to compare the canal transportation and centering ratio of two rotary files in curved canals using cone-beam computed tomography (CBCT). Methods Forty-four extracted human mandibular first molars with mature apices and 10 degrees to 30 degrees apical curvature were selected. The samples were randomly divided into two groups (n = 22) with similar curvature. The canals were prepared with ProTaper and XP-endo Shaper file systems according to the manufacturers' instructions. The CBCT images were obtained using Cranex 3D CBCT scanner before and after root canal preparation, and canal transportation and centering ratio of the files at 3, 4 and 5 mm levels from the apex were calculated. Data were compared between the two groups using independent t-test at 0.05 level of significance. Results The ProTaper Universal caused greater canal transportation and had lower centering ratio than XP-endo Shaper in both mesiodistal and buccolingual directions at all levels from the apex. The difference between the two groups regarding canal transportation was significant at all levels from the apex in buccolingual direction (P < 0.05) except for 3 mm from the apex (P > 0.05). The difference between the two groups regarding centering ratio was not significant (P > 0.05) in mesiodistal direction at all levels except for 4 mm from the apex (P < 0.05). Conclusion The ProTaper Universal causes greater canal transportation in both buccolingual and mesiodistal directions than XP-endo Shaper.