Comparison of two stainless steel files to shape simulated root canals.

The aim of this study was to compare the shaping ability of two stainless steel files using simulated canals. A total of 80 simulated canals of various angles and positions of curvature were prepared by hand using either Mani K-Files or Micro Mega K-Files. Following orifice enlargement each file type was used to prepare 40 canals employing a linear filing motion and an anticurvature stepback technique. Pre- and post-operative longitudinal images of the canals were taken with a video camera 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 post-operative views. Overall, canal preparation with Mani K-Files was significantly quicker (P < 0.005) and was associated with fewer instrument failures. Zips and elbows were observed in 70% of specimens with significantly more (P < 0.05) occurring following preparation with Micro Mega K-Files. Mani K-Files created significantly more (P < 0.01) danger zones. Micro Mega K-Files created significantly wider (P < 0.001) zips with significantly more (P < 0.01) resin removed from the outer aspect of the curves and, thus, significantly more (P < 0.01) transportation. Canal shape had a significant influence on preparation time (P < 0.001), the incidence of zips (P < 0.05) and danger zones (P < 0.005), the width of zips (P < 0.001) and transportation at the zips (P < 0.001). Under the conditions of this study, Mani K-Files were more effective than Micro Mega K-Files and produced canals with better shapes. Original canal shape had a substantial influence on the outcome of shaping procedures.