Influence of Single-file Endodontics on Apical Transportation in Curved Root Canals: An Ex Vivo Micro-Computed Tomographic Study

Introduction: More information regarding the ability of single files to maintain the original canal position is required before adopting a single-file approach to cleaning and shaping. This study compares apical transportation in curved root canals when instrumenting with a single Wave One (WO) file (Dentsply Tulsa Dental Specialties, Tulsa, OK) in a reciprocating motion with that incurred when using a sequence of Twisted Files (TFs; SybronEndo, Orange, CA) in a continuous rotating motion. Methods: Forty mesial canals of mandibular molars were evenly allocated into 2 balanced groups (n=20) with a 17-mm average canal length and 200 average curvature. Canals were accessed in a conventional manner and instrumentation was completed. with a single WO file or a series of TFs. The canals were instrumented according to the manufacturers' protocol: Apical transportation was assessed on a comparison of the pre- and postinstrumentation micro computed tomographic scans at 1-, 2-, 3-, 4-, and 5-mm sections. One-way analysis of variance was performed to assess if a significant difference between systems exists. Results: No significant difference (P>.05) was found between the WO and TF groups. Transportation in the mesial direction was of greater magnitude than distal transportation for both files systems. The mean transportation in the mesial direction was 100.1 +/- 8.8 mu m (WO group) and 101.0 +/- 10.9 mu m (TF group) (P=.5), whereas distal transportation was found to be 80.9 +/- 14.6 mu m (WO group) and 60.3 +/- 11.0 mu m (TF group) (P=.3). Conclusions: The results suggest that no difference exists between the WO file system and the conventional multifile TF system when considering apical transportation in curved canals.