Shaping ability of GTTM Rotary Files in simulated resin root canals

The aim of this study was to determine the shaping ability of GT Rotary Files in simulated root canals. Forty canals with four different shapes in terms of angle (40 degrees and 60 degrees) and position of curvature (straight section before curve: 8 and 12 mm) were prepared using a crown-down/stepback technique. Pre-operative and post-operative pictures, recorded using an image analysis system, were super-imposed and aberrations recorded. Measurements were carried out at 5 different points: at the canal orifice (0): half-way to the orifice in the straight section (HO); the beginning of the curve (BC); the apex of the curve (AC): the endpoint (EP). Two instrument fractures occurred and 9 instruments were deformed. Overall, eight zips and one ledge were created. There were significant differences (P < 0.001) for the total width of the canals between the various canal shapes at AC, BC and HO. There were significant differences (P < 0.001) for the amount of resin removed from the outer aspect of the curve at AC, BC and HO; and for the amount of resin removed from the inner aspect of the curve at all five measuring points (0, AC and EP (P < 0.05) and HO and BC (P < 0.001)). Mean transportation was towards the inner aspect of the canal in canals with straight sections of 12 mm regardless the curve angle; towards the outer aspect in canals with straight sections of 8 mm and 40 degrees curves at all the five measuring points, and at AC, BC and HO when the curve was 60 degrees. Under the conditions of this study, GT Rotary Files produced acceptable canal shapes. In narrow and curved canals, the length of the straight section of the canal determines the direction of transportation more than the angle of the curve. In the 60 degrees curves, a high incidence of instrument deformation was found when using the 0.04 tapered instruments.