After root canal preparation, CBCT images were obtained using a PreXion 3D Inc. (San Mateo, CA, USA), thickness: 0.100 mm (dimensions 1.170 mm × 1.570 mm × 1.925 mm, FOV: 56.00 mm, voxel 0.100 mm, 33.5 s (1.024 views). Tube voltage was 90 kVp, and the tube current was 4 mA. Exposure time was 33.5 s. Images were examined with the scanner’s proprietary software PreXion 3D Viewer (TeraRecon Inc., Foster City, CA, USA) in a PC workstation running Windows XP professional SP-2 (Microsoft Corp., Redmond, WA, USA), with processor Intel Core 2 Duo-6300 1.86 Ghz (Intel Corp., Santa Clara, CA, USA), NVIDIA GeForce 6200 turbo cache videocard (NVIDIA Corporation, Santa Clara, CA, USA), and Monitor EIZO-Flexscan S2000, resolution 1600 × 1200 pixels (EIZO NANAO Corp., Hakusan, Japan).
A total of 2 examiners (a radiologist and an endodontist) were calibrated using 20% of the specimens, and all images were evaluated to detect the presence or absence of fractured instruments, root perforations (coronal, middle or apical thirds) and deviation from the original trajectory of the root canal (apical transportation). Instruments fractures during preparation were also detected (Figure 1 ). When a consensus was not reached by the two examiners that interpreted the procedural errors using CBCT, a third observer (an endodontist) made the final decision.
A total of 2 examiners (a radiologist and an endodontist) were calibrated using 20% of the specimens, and all images were evaluated to detect the presence or absence of fractured instruments, root perforations (coronal, middle or apical thirds) and deviation from the original trajectory of the root canal (apical transportation). Instruments fractures during preparation were also detected (