Performance of Self-Ligating Brackets during Alignment of Buccally and Apically Displaced Teeth: A Comparative Study

  • Dr Lorenzo Franchi, Department of Orthodontics, University of Florence, Italy
  • Dr Veronica Giuntini, Department of Orthodontics, University of Florence, Italy
  • Dr Efisio Defraia, Department of Orthodontics, University of Florence, Italy
  • Dr Caterina Masucci, Department of Orthodontics, University of Florence, Italy
  • Dr Tiziano Baccetti, Department of Orthodontics, University of Florence, Italy

Aim: To analyze the forces released by 4 types of passive stainless steel self-ligating brackets (SLBs), and by 2 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 5 brackets (from second premolar through central incisor) was used to assess the forces released by the 7 different bracket-ligature systems with 0.012” or 0.014” superelastic wires in presence of different amounts of buccal and apical displacement canine (from 1.5mm to 6.0mm). 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 3.0mm both low-friction and conventional systems released forces of adequate magnitude for bracket alignment. In presence of a large amount of buccal or apical displacement (4.5mm or 6.0mm) the low-friction systems produced adequate orthodontic forces, while these forces dropped to 0g 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 presence of passive self-ligating brackets. When apical or buccal tooth displacement is greater than 3.0mm conventional bracket/ligature systems are not able to release a clinically adequate amount of orthodontic force.