Rotary nickel-titanium GT and ProTaper files for root canal shaping by novice operators: a radiographic and micro-computed tomography evaluation.

INTRODUCTION: The purpose of this study was to assess canal preparation outcomes in vitro by novice clinicians after standardized teaching sessions. METHODS: All students received a training session. In experiment 1, twenty canals of mandibular molars were prepared with GT and ProTaper rotaries by 10 students. Standardized radiographs were exposed before and after canal preparation, and canal curvature was measured; canals were assessed for patency and preparation time. In experiment 2, mandibular molars (20 canals) were submitted to microcomputed tomography before and after canal preparation with ProTaper and GT rotaries by 2 dental students. Canals were metrically assessed for changes (volume, surface, cross-sectional shape, transportation) during canal preparation by using software. RESULTS: In experiment 1, canal curvature decreased by 7.6 degrees and 7.8 degrees for GT and ProTaper preparations; there were no broken instruments, and 2 canals lost patency. The time for GT preparation was longer than for ProTaper (29.7 +/- 6.8 vs 19.4 +/- 8.1 minutes, P <.05). In experiment 2, canal volumes and surface areas increased (P < .001), and prepared canals were rounder in cross-section and more tapered. Mean canal transportation ranged between 0.14 +/- 0.05 mm and 0.23 +/- 0.09 mm for apical and coronal canal thirds. There were no significant differences between the instruments or the operators regarding center of mass shifts; qualitative and quantitative data for canal transportation were similar to earlier studies with experienced operators. CONCLUSIONS: Both rotary instruments performed adequately with inexperienced operators who received a brief structured training session.

Effects of imaging system and exposure on accurate detection of the second mesio-buccal canal in maxillary molar teeth.

OBJECTIVES: The objectives of this study were to determine observer ability to detect the second mesio-buccal canal (MB2) in maxillary molars using analog film, CMOS, and photostimulable phosphor x-ray detectors across a wide range of radiation exposures and to determine the optimal exposures for these modalities accurately detecting presence of the MB2. RESEARCH DESIGN: Using 6 experimental models with 2 maxillary molars in each, images were generated with the 3 detector modalities at nominal x-ray beam angulations of 0 degrees and 10 degrees across a range of radiation exposures. Observers independently assessed presence of the MB2 in images presented in random order. Horizontal root sections were then evaluated to determine true MB2 presence. RESULTS: For single images at optimal exposures, the correct number of mesiobuccal canals could be identified 55% of the time for CMOS (RVG 6000), 44% of the time for analog x-ray film (InSight), and 39% of the time for photostimulable phosphor (DenOptix). Statistically significant differences were observed between the imaging modalities (chi2 = 23.4, crucial value = 5.99, P < or = .05). RVG 6000 CMOS outperformed both DenOptix photostimulable phosphor (z score = -5.5) and InSight analog direct exposure x-ray film (z score = 4). Exposure affected the rate of accuracy for MB2 detection across the exposure range tested for RVG 6000 and for film, but not to any appreciable degree for DenOptix. CONCLUSIONS: The CMOS detector (RVG-6000) performed best for evaluating presence of the MB2. This was the only modality to exceed 50% reliability with optimal exposure when single images were considered.