Tortional Fatigue Resistance of Three Different Rotary Endodontic Instruments with Design Modification

The TF (torsional fatigue) resistance of Dentsply ProTaper Universal (PTU), ProTaper Gold (PTG), and ProTaper Next (PTN) nickel titanium (NiTi) rotary files was evaluated in comparision with simulated files with same design and our study design. For PTU and PTG study design modification is to leave the apical 8 mm of S1 and the apical 3 mm of S2 as un-milled, F1 only the apical 5 mm would have cutting blades leaving the middle and coronal portions un-milled. For PTN is to leave the apical 8 mm of X1and, while for X2 is to leave the coronal 8 mm as un-milled. Ten instruments for each file (S1, S2, F1, X1 and X2); total 240 files (80 pieces for Dentsply, 80pcs for simulated and 80 pieces for study design). A portion of 3 mm from the file tip was clamped with a pin vise. The file was rotated clockwise until fracture. File's cross section is directly related with the torsional fatigue resistance, and the file's plane part was more resistace to torsional fatigue resistance than the fluted part.