The radial land is designed to prevent the file from transporting the canal however, the increased contact of the radial land creates a larger area of contact in the canal. 4 Some of these are passive instruments with radial lands (ProFile GT® Rotary System, DENTSPLY Tulsa, The GT Rotary file possesses a more rounded tip, somewhat broader radial lands, and more flutes are present at the apical end. These instruments are usually used in a crown-down technique. The use of RNT has allowed more centered canal preparations and fewer aberrations in the canal. 2 There are a great variety of rotary nickel-titanium (RNT) files and geometric designs available. This is especially important in curved canals because excess straightening can modify the integrity of the canal. 2 These instruments were supposed to keep the original canal shape without deleterious effects because of their super-elastic behavior and shape-memory property. Nickel-titanium (Ni-Ti) rotary-shaping techniques were developed more than a decade ago. 2 However, ledge formation, transportation of the apical foramen, and non-tapered hourglass-shaped preparation are problems that may occur especially during instrumentation of curved canals. 1 Instrumentation provides gross debridement and allows irrigants to mechanically flush the area, dissolve residual tissue, and eradicate any remaining bacteria. According to Schilder, 1 root canal shape should meet these objectives: the root canal preparation should develop a continuously tapering funnel from the root apex to the coronal access cavity the cross-sectional diameter of the preparation should be narrowed at every point apically and wider at each point as the access cavity is approached the root canal preparation should flow with the shape of the original canal the apical foramen should remain in its original position and the apical foramen should be kept as small as possible. Sufficient shaping and cleaning of root canals are a prerequisite for long-term success.
The use of rotary nickel-titanium files has allowed more centered canal preparations and fewer aberrations in the canal. Richard Trushkowsky, DDS and Anabella Oquendo, DDS A Case Using Rotary Endodontics and Resin-Based Fillers
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