Comparison of the performance of four files with rounded tips during shaping of simulated root canals

A total of 160 simulated canals of various angles and positions of curvature were prepared by hand using either Mani Flexile Files, Mani SEC-O Files, Maillefer Flexofiles, or Zipperer Flexicut Files. After orifice enlargement, each file type was used to prepare 40 canals employing a balanced force motion and a modified double-flared technique. Pre- and postoperative images of the canals were taken with a videocamera, and stored and manipulated in a computer with image analysis software. The presence of canal aberrations and the amount of material removed as a result of preparation were determined from composite images of superimposed pre- and postoperative views. Significant differences (p < 0.001) in preparation time were observed, with Flexile Files being quickest and SEC-O Files being slowest. Overall, Flexofiles and Flexicut Files deformed significantly more (p < 0.001) than Flexile and SEC-O Files. The incidence of canal blockage was not influenced by instrument type, but the incidence of apical extrusion was significantly greater (p < 0.001) with SEC-O Files. SEC-O Files created significantly fewer (p < 0.001) and significantly narrower (p < 0.001) zips, with significantly less (p < 0.001) removal of material from the outer aspect of the curve and thus significantly less (p < 0.001) transportation. Flexicut Files created the widest canals apically, with the greatest removal of material from the outer aspect of the curve and the most transportation. Flexofiles created significantly more (p < 0.001) perforations. Under the conditions of this study, obvious differences between instruments were highlighted with SEC-O Files preparing canals more safely and with least destruction. The unique rounded tip of the SEC-O Files may have had an influence on the outcome.