RESUMO
Objective To evaluate the root canal deviations in vitro teeth curved root with TF and Protaper instru-ments by cone beam computer tomography( CBCT) . Methods 40 teeth in vitro in the standard collection were ran-domly assigned to two groups, prepared with the crown-down method, the TF group ready to 0. 06/#25; the Pro-taper group ready to F2 . CBCT scans were taken to measure the mesial and distal thicknesses of the tube wall in vitro teeth before and after preparation. The root canal deviation and the rate of shaft center were measured with ref-erence to the formula proposed by Gambill. Results The TF group need less time in preparation and has more effi-ciency(P<0. 05) than the Protaper group; both TF and Protaper devices appeared deformation after 5 root canal preparations in average, no instruments broken. Comparing the offset of the internal and external wall of root canal in 3, 5, 7 mm from the apex, the root canal deviation prepared by the TF group was less than the Protaper group, and its rate of axis center was greater than the Protaper group, closer to 1. Conclusion TF can maintain original root canal morphology in preparing curved root canal, also has higher efficiency;under the noninvasive condition, the root canal forming ability of preparation instruments can be evaluated by CBCT.