Comparative analysis of canal transportation and centring ability of three Ni–Ti rotary endodontic systems: Protaper^®, MTwo^® and Revo-S™, assessed by micro-computed tomography

The aim of this study was to use high-resolution micro-CT to evaluate the effects of three Ni–Ti rotary endodontic instruments, Mtwo^® (VDW, München, Germany), ProTaper^® (Dentsply-Maillefer, Ballaigues, Switzerland) and Revo-S™ (MicroMega, Besançon, France), on canal transportation and centring ratio. Fifty-four mesial roots of extracted mandibular molars with an angle of curvature of 25–35° were randomly divided into three groups of eighteen. Each group was instrumented with a previously unused Ni–Ti rotary system. The final instruments used were #30/0.05 taper (Mtwo^®), F3 #30/0.09 apical taper (ProTaper^®) and AS30 #30/0.06 taper (Revo-S™). Teeth were scanned before and after instrumentation using micro-computed tomography with a spatial resolution of 20 μm to measure volume and shaping changes. All images were filtered to improve signal-to-noise ratio. To determine the perimeter of roots and canals exactly, images were segmented in each slice with an edge detection process. Canal transportation and centring ratio were evaluated at 1, 3, 5 and 7 mm from the end of each root. The method developed by Gambill et al. was chosen. ANOVA was conducted with the significance threshold set at p < 0.05. No statistically significant differences were found among the three groups in terms of canal transportation or centring ratio at any level. These systems give similar results with regard to the tested shaping parameters. Under the tested conditions and within the limitations of this study, these systems were able to produce centred preparations of curved canals with minimal transportation.