Efficiency of alignment of apically- and buccally-malposed teeth with low-friction versus conventional systems

The objective of this chapter is to present the results of an in vitro study that analyzed the forces released by passive stainless steel self-ligating brackets (SLBs) and by a non-conventional elastomeric ligature on conventional brackets (NCLCB) when compared with conventional elastomeric ligatures on conventional brackets (CLCB) during the alignment of apically- or buccally-malposed teeth in the maxillary arch. An experimental model consisting of five brackets was used to assess the forces released by the three different bracket-ligature systems with 0.012” super-elastic (SE) nickel-titanium (NiTi) wires in the presence of different amounts of apical or buccal canine misalignments (ranging from 1.5 mm to 6 mm). The forces released by each bracket/wire/ligature combination with the three different magnitudes of apical or buccal canine misalignment were tested 20 times. Comparisons between the different types of bracket/wire/ligature systems were carried out by means of analysis of variance on ranks with Dunnett’s post hoc test (P < 0.05). No difference in the amount of force released in presence of a misalignment of 1.5 mm was recorded among the three systems. At 3 mm of apical misalignment, a significantly greater amount of orthodontic force was released by SLB or NCLCB when compared with CLCB, while no significant differences were found among the three systems at 3 mm of buccal canine displacement. When correction of a large amount of misalignment (6 mm) was attempted, a noticeable amount of force for alignment still was generated by the passive SLB and NCLCB systems, while no force was released in presence of CLCB.