RESUMO
OBJECTIVE: The aim of this study was to evaluate, ex vivo, canal transportation and the centering ability of nickel-titanium rotary instruments manufactured by twisting and by traditional grinding, with the use of microscopic computerized tomography (µCT). STUDY DESIGN: Fifteen mandibular molars were embedded in a rubber-based impression material and submitted to µCT before and after instrumentation. Images were reconstructed, and cross-sections corresponding to distances 1, 2, 3, 4, 5, 6, and 7 mm from the anatomic apex were selected for analysis. Statistical analysis was performed with Mann-Whitney test. RESULTS: Canal transportation and centering ability results were similar for both instruments. Statistically significant differences (P < .05) were observed only at the 3 and 4 mm cross-sections, with lower levels of apical transportation and a better centering ratio associated with twisted instruments than with ground instruments. CONCLUSIONS: Our findings showed that twisted and ground instruments behaved similarly, allowing the preparation of curved canals with little transportation, which occurred in both mesial and distal directions.