The effects of loops on the torsional stiffnesses of rectangular wires: an in vitro study.

Various loop designs have been investigated with respect to the increased torsional flexibility given to the wire by their inclusion. The torsional flexibility of the wire was shown to be enlarged from 26% to 63%, depending on loop design. Both variation in wire cross-section and loop geometry will influence torsional stiffness. Wires with small cross-sectional dimensions will show greater flexibility in torsion. Even small deviations from the stated cross-sectional dimensions can influence the change in torsional stiffness caused by a specific loop design. Inclusion of a reverse-closing loop led to the greatest increase in flexibility, while a Bull loop changed torsional stiffness the least. When vertical flexibility is needed along with reduced torsional stiffness, the T-loop is the loop of choice.