RESUMO
The purpose of this study was to compare the shaping ability of three Ni-Ti file systems used by dental students or the experts and consequently to aid in choosing a proper systems for educational courses of dental students and beginners. Fifty students and ten dentists who have clinical experience over two years prepared 180 simulated root canals in resin blocks with three Ni-Ti systems; ProFile(R) (PF), HeroShaper(R) (HS), K3TM (K3). After preparation, the Ni-Ti files were evaluated for distortion and canal preparation time was recorded. The images of pre- and post-instrumented canals were scanned and superimposed. Amounts of increased canal widths, deviation, and centering ratio were calculated at apical 1, 3 and 5 mm levels and statistical analysis was performed. The results were as follows: 1. HS showed the shortest preparation time and instrumented canal width in K3 was significantly larger than other groups (P < 0.05). 2. At 1 and 3 mm levels, all groups had outward deviation. In student group, at the 1 mm level, PF had the least deviation (P < 0.05). 3. In the centering ratio, the PF had the best centering ability compared to the others at 5 mm level. At 1 and 3 mm levels, HS and PF had better abilities than K3. Student group had better ratio than the expert at 3 mm level with PF (P < 0.05). Based on the results, it is surmised that the ProFile(R) is the safest and most ideal instrument for students and beginners.