The purpose of this study was to investigate influence of each file step of ProTaper® system on canal transportation.

Twenty simulated canals were prepared with either engine-driven ProTaper® or manual ProTaper®. Group R-resin blocks were instrumented with rotary ProTaper® and group M-resin blocks were instrumented with manual ProTaper®. Pre-operative resin blocks and post-operative resin blocks after each file step preparation were scanned. Original canal image and the image after using each file step were superimposed for calculation of centering ratio. The image after using each file step and image after using previous file step were superimposed for calculation of the amount of deviation. Measurements were taken horizontally at five different levels (1, 2, 3, 4 and 5 mm) from the level of apical foramen.

In rotary ProTaper® instrumentation group, centering ratio and the amount of deviation of each step at all levels were not significantly different (p > 0.05). In manual ProTaper® instrumentation group, centering ratio and the amount of deviation of each step at all levels except of 1 mm were not significantly different (p > 0.05). At the level of 1 mm, F2 file step had significantly large centering ratio and the amount of deviation (p < 0.05).

Under the condition of this study, F2 file step of manual ProTaper® tended to transport the apical part of the canals than that of rotary ProTaper®.