Comparison of Shaping Ability and Apical Debris Extrusion Using 4 Different Nickel-Titanium Single-File Systems

Background: This study compared the shaping ability and apical debris extrusion of four nickel-titanium (Ni-Ti) single-file systems in simulated curved root canals. Methods: Forty simulated curved root canals in resin blocks were randomly assigned to four groups (n = 10): Reciproc Blue (RCB), V-Blue, One Plex, and S-ONE. Images of the simulated root canals were captured before and after instrumentation. The two layers were processed and superimposed using specialized software. Eleven points (Levels 0-10) were selected at 1-mm intervals starting from the apex for evaluation. The amount of resin removed from both the inner (X1) and outer sides (X2) of the root canal, as well as the final canal width (Y), were measured. The centering ratio was calculated using the formula (X1 - X2)/Y to assess the centering ability of the instruments. Apically extruded debris was collected during the root preparation. Results: The preparation times for the root canal were as follows: One Plex > RCB > V-Blue > S-ONE (p < 0.001). All four Ni-Ti files were effective in straightening the root canal, with no significant difference in curvature change (p > 0.05). At the apex, One Plex exhibited significantly greater deviation compared with the other three groups (p < 0.05). At Levels 7-8, the deviation with RCB was significantly greater than with One Plex and S-ONE (p < 0.01). The amount of apical debris extrusion in the One Plex group was significantly higher than that in the others (p < 0.01). Conclusions: S-ONE demonstrated the best centering ability compared with other groups. In contrast, One Plex produced the highest amount of apical debris extrusion and exhibited transportation at the apical foramen. At Levels 6-8, RCB exhibited excessive removal of the inner canal wall relative to S-ONE and One Plex.