Quality of preparation by two nickel-titanium instruments activated by continuous rotation or adaptive motion: a micro-computed tomography study

Aim. To evaluate the shaping ability of curved root canals using Twisted FileAdaptive (TFA) files (SybronEndo, Orange, CA) and Mtwo (Sweden & Martina, Padova, Italy) activated by continuous rotation or Adaptive motion. Methods. Thirty-two mandibular molars with 2 separate mesial canals and severe angle of curvature were selected. Each canal was randomly assigned to 1 of the 4 experimental groups (n=16): TFA and Mtwo files used in continuous rotation (groups 1 and 3) or in Adaptive motion (groups 2 and 4). Root canals before and after preparation were assessed by micro-computed tomography. Volume, surface area, canal transportation, centering ability and preparation time were recorded and analyzed using 2way analyses of variance. Results. Volume and surface area increased less with TFA files in continuous rotation than in other groups (P<0.001 and P<0.01 respectively for each comparison) that were not different (P>0.05). TFA files had significantly less transportation and centering ability than Mtwo both in continuous and “Adaptive” motion (P<0.0001), only centring ratio for both instruments was improved by adaptive motion compared with continuous rotation (P<0.01). However, no differences were found in canal transportation and centring ability in the apical third for both instruments and motions (P>0.05). Conclusion. Shaping outcomes with TFA files and Adaptive motion were found better than Mtwo and continuous rotation respectively except in the apical third.