Angle Orthod 2011 Nov 20;81(6):953-9. Epub 2011 Jul 20.
Department of Dentistry, University of Alberta, Edmonton, Canada.
Objective: To better understand the mechanics of bracket/archwire interaction through analysis of force and couple distribution along the maxillary arch.
Materials And Methods: An orthodontic simulator was utilized to study high canine malocclusion. Force/couple distributions, referenced to the center of resistance (CR) of each tooth, produced by passive ligation brackets and round wire were measured. Tests were repeated for 12 bracket sets with 12 wires per set.
Results: Propagation of the force/couple systems around the arch was minimal. Binding was observed only on the teeth adjacent to the displaced canine. For most of the teeth, reduced resistance to sliding of the passive ligation bracket yielded minimal tangential and normal forces at the bracket and contributed to lower moments at CR.
Conclusions: Some potential mechanical advantages of passive ligation systems are suggested for the case studied. In particular, limited propagation around the arch reduces the occurrence of unwanted force/couple systems.