Introduction: Endodontic preparation in curved and narrow root canals has always been difficult because the prepared canal tends to deviate from its natural axis. Because of their increased shape memory, super elasticity, and cutting efficiency, nickel titanium rotary instruments provide acceptable treatment of curved canals in less time. Recently various single file systems with various metallurgy and designs have been developed to prepare the root canals using either continuous rotation or reciprocation motion. Aim: To compare canal transportation and centering ability in curved root canals after instrumentation with two different single file systems (XP-Endo Shaper, WaveOne Gold) in continuous rotation and reciprocation motion respectively and compared with one well-assessed full-sequence rotary NiTi system (ProTaper NEXT) using cone-beam computed tomography (CBCT).
Materials and Methods: Forty-five human permanent mandibular first molars with mesiobuccal canal curvatures between 20° and 35° were used in this study after removal of distal root. They were divided into three groups (n=15) according to the instrumentation file system. Samples were fixed into acrylic resin block and were scanned before and after preparation using cone-beam computed tomography (CBCT). Scanned images were then superimposed and accessed to determine canal transportation and centering ability at three different levels (apical, middle, and coronal).Data was statistically analyzed one way ANOVA and followed by Duncan multiple range tests (DMRTs) to further assess differences between different treatment groups.
Results: XP-Endo Shaper always has the lowest mean of transportation which was significant with ProTaper Next at 3mm and 9mm and significant with WaveOne Gold and at 9mm from the apex. Also, XP-Endo Shaper showed the highest centering ratio, which was not significant with WaveOne Gold or ProTaper Next at any of the three levels. However, regardless levels of the canal for overall centering ratio, XP Endo Shaper was the highest statistically significant from ProTaper Next and not significant with WaveOne gold.
Conclusion: The findings from the current study suggested that Single file systems are efficient and safe, to prepare severely curved canals. Not only file motion that affects root canal transportation other factors may play a role between different filing systems such, the design of the file and instrument manufacturing alloy.