Shaping ability of .04 and .06 taper ProFile rotary nickel-titanium instruments in simulated root canals.
AIM: The aim of this study was to determine the shaping ability of ProFile .04 and .06 taper rotary nickel-titanium instruments in simulated canals. METHODOLOGY: A total of 40 simulated root canals made up of four different shapes in terms of angle and position of curvature were prepared using the 'crowndown' approach recommended by the manufacturer. Pre-operative pictures of each canal were recorded on optical discs using an image analysis package. The simulated canals were prepared and postoperative pictures superimposed on the original images. RESULTS: No instrument fractures occurred and none deformed; none of the canals became blocked with debris. Change in working distance was, on average, 0.063 mm with 33 canals retaining the correct length. Overall, five zips (12.5%) were created and 24 (60%) canals demonstrated a widened area on the outer aspect of the canal between the end-point and the curve. Two danger zones (5%) were created and two perforations but no ledges were found. Between canal shapes there were highly significant differences (P < 0.0001) for the incidence of zips and elbows but not for the other aberrations. There were highly significant differences (P < 0.0001) for the total width of the canals between the various canal shapes at the apex of the curve, the beginning of the curve and half way to the orifice, and a significant difference (P < 0.05) at the end-point. There were highly significant differences (P < 0.0001) for the amount of resin removed from the outer aspect of the curve at the end-point and at the beginning of the curve, and significant differences (P < 0.05) at the apex of the curve and half way to the orifice. There were highly significant differences (P < 0.0001) for the amount of resin removed from the inner aspect of the curve at the beginning of the curve and half way to the orifice. Overall, transportation was towards the outer aspect of the canal except at the beginning of the curve. CONCLUSIONS: Under the conditions of this study the combined use of .04 and .06 taper ProFile instruments was rapid, effective and produced good canal shapes except in those specimens with short curves that began near the end-point.