<prompt> What is torsional limit?Amount of apical pressure that can be applied to a file to the point of breakageThe beginning of plastic deformation of the instrumentAmount of rotational torque that can be applied to a locked instrument to the point of breakageAmount of force necessary so that a file does not return to its original shape upon unloading of the force  <response>: Torsional limit is the amount of rotational torque that can be applied to a locked instrument to the point of breakage separation. Obviously, an instrument should have sufficient strength to be rotated and worked vigorously without separating in the canal.Smaller instruments less than size 20 can withstand more rotations without breaking than larger greater than size 40 instruments.Ref :Principles and Practice of Endodontics, Richard E Walton, 3rd edition, pg no:156 