Aim: To evaluate the apical canal morphological change, centering ability, and apical trans-portation of curved canals after foraminal enlargement 1 mm beyond the apex with different instruments and after apical foramen shaping. Methodology: Thirty-three mesiobuccal molars’ canals with curvatures between 25 and 35 and a radius of less than 10 mm were selected and divided according to the instrument used 1 mm beyond the apical foramen: R-Pilot #12.5/.04(RPG), ProDesign Logic #25/.01(PDG), and ProGlider #16/.02(PGG). After over instrumentation, #25/.05 ProDesign Logic prepared the canals until the apical foramen. Micro-CT scans obtained before instrumentation (time point 1), after instruments use 1 mm beyond foramen (time point 2) and after final prepa-ration (time point 3) were used to evaluate apical canal morphological changes according to the area, the ratio of Feret’s diameters and circularity, transportation and centering. Data were analyzed by parametrical or non-parametrical tests (α=0.05). Results: PDG increased the apical foramen area from time point 1 to 3 (P=0.03). There were no differences in the ratio of Feret’s diameters or circularity (P>.05). In all groups, apical transportation was in mesial direction and increased after final preparation in RPG (P=0.01). Instrument centering ability was better at time point 3 than 2 in PDG (P=0.01), and PDG presented better centering than RPG at time point 3 (P=0.02). Conclusion: Instruments used 1 mm beyond the apical foramen combined with #25/.05 final preparation did not lead to apical canal morphological change. ProDesign Logic #25/.01 followed by #25/.05 improved centering without increasing transportation in root canals
