Performance of self-ligating brackets during alignment of buccally and apically displaced teeth: a comparative study

Aim: To analyze the forces released by four types of passive stainless steel self-ligating brackets (SLBs), and by two nonconventional elastomeric ligature-bracket systems when compared with conventional elastomeric ligatures on stainless steel brackets during the alignment of buccally and apically displaced teeth. Materials and Methods: A model consisting of five brackets (from second premolar through central incisor) was used to assess the forces released by the seven different bracket-ligature systems with 0.012” or 0.014” superelastic wires in the presence of different amounts of buccal and apical displacement canine (from 1.5 mm to 6.0 mm). The comparisons between the different types of bracket/wire/ligature systems were performed with ANOVA on ranks (P < .05). Results: For buccal or apical misalignments of 1.5 and 3.0 mm, both low-friction and conventional systems released forces of adequate magnitude for bracket alignment. In the presence of a large amount of buccal or apical displacement (4.5 mm or 6.0 mm), the low-friction systems produced adequate orthodontic forces, whereas these forces dropped to 0 g for the conventional system. Conclusions: Nonconventional elastomeric ligature-bracket systems produce levels of force available for tooth movement that are very similar to those generated in the presence of passive self-ligating brackets. When apical or buccal tooth displacement is greater than 3.0 mm, conventional bracket/ligature systems are not able to release a clinically adequate amount of orthodontic force.