Segmental torque relevant orthodontic bracket tie-wing deformation in various bracket-archwire-ligature combinations

In fixed appliance therapy, torque moments are transferred through the bracket and are important for the final position of the tooth. Studies have analyzed only the torque-relevant bracket deformation in single bracket-archwire combinations with respect to various archwire rotations, although segmental torque is often used clinically.

In this study, experiments were conducted in an experimental setup with 2-bracket segments with 0.018-in and 0.022-in conventional brackets with commonly used rectangular archwires and ligatures to measure the torque moment and the relevant tie-wings deformation for 6, 7, and 8 mm interbracket distances (IBD).

The torque moment in both 0.018-in and 0.022-in brackets increased as the archwire dimension and rotation increased. The torque moment with stainless steel ligation was significantly larger than that of the elastic ligature for all the archwires tested in both brackets. Each segmental bracket-archwire-ligature-IBD combination tested had shown a significant difference between the distal and mesial tie-wing deformations for varying torque.

We conclude that in both 0.018-in and 0.022-in brackets, the behavior of the 2-bracket segment-archwire-ligature combination with varying IBD was strongly influenced by the individual factors and also in combination.