For unidirectional activations,flat wire is the cross section of choice because more energy can be absorbed into a spring made with a flat wire than with a any other configuration. Another advantage – problem of orientation is solved.
2mm of deactivation-spring activation 4mm-m/f raises to 10:1- bodily movement
Further closure 1-2 mm m/f 12:1-root movement
Clinical situation –should not be reactivated till all three stages are completed