Comparison of ProTaper, RaCe and Safesider instruments in the induction of dentinal microcracks: a micro-CT study

Aim To evaluate ex vivo the incidence of microcracks in root dentine after canal preparation with ProTaper Universal (PTU), RaCe or Safesider instrumentation systems using microcomputed tomography (micro‐CT). Methodology Thirty freshly extracted mandibular molars with two separate mesial canals and foramina were used. The roots were allocated into three similar groups according to curvature angles and radii of the canals and lengths of the roots. Distal roots were removed and mesial roots were embedded in acrylic resin and instrumented with the PTU, RaCe or Safesider systems up to size 30 (F3 for PTU, size 30, 0.04 taper for RaCe and Safesider) for all instrumentation groups. Dentinal microcracks were evaluated on micro‐CT images of the apical 10 mm of the roots with 1‐mm intervals. Two experienced observers evaluated the images twice in a blinded fashion. The presence of dentinal microcracks (complete/incomplete cracks and craze lines) was noted and analysed statistically using McNemar and chi‐square tests (P = 0.05). Results There were microcracks on uninstrumented root sections. All instrumentation systems significantly increased the number of dentinal microcracks when compared to preoperative specimens (P