Conclusions
Within the limitations of this study, the ProTaper Next regular rotary file and the paediatric rotary files have the same impact on canal transportation and centring ability buccolingually. However, the ProTaper Next showed higher transportation liability at the cervical level mesiodistally, which may be attributed to the rectangular cross-section and regular length (25 mm) with the 0.07 mm taper of this file compared to the triangular cross-section of both paediatric files and shorter file lengths (16 and 18 mm) with a lesser 0.06 mm taper.