Gambarini introduced the novel concept of “torque range”—the difference between a rotary file’s operative torque (the torque generated during clinical canal preparation) and its torsional resistance (torque at fracture)—as a more clinically relevant measure of instrument safety. The study compared EdgeFile® X7 and ProTaper Next X1 during root canal preparation and laboratory torsional testing. While both systems demonstrated similar torsional resistance at failure, EdgeFile X7 reached working length significantly faster and required substantially less operative torque than ProTaper Next. As a result, EdgeFile X7 exhibited a torque range nearly twice as large (0.40 N·cm vs. 0.22 N·cm), providing a greater safety margin between the stresses encountered during clinical use and the instrument’s fracture threshold. The authors concluded that EdgeFile X7’s wider torque range reflects greater clinical efficiency and a lower risk of torsional failure, suggesting that this new parameter may better predict real-world performance than torsional resistance testing alone.
The Relevance of Operative Torque and Torsional Resistance of Nickel‑Titanium Rotary Instruments: A Preliminary Clinical Investigation
