Comparison of maxillary arch dimensional changes with passive and active self-ligation and conventional brackets in the permanent dentition: a multicenter, randomized controlled trial. 
The purpose of this study was to compare maxillary arch dimensional and inclination changes during alignment with conventional brackets and self-ligation.  Ninety-six patients, ages 16 years and above, were included in this multicenter, 3-group parallel randomized trial.  The main outcome measures were changes in maxillary intercanine, interpremolar, and intermolar dimensions, and molar and incisor inclination changes.  The patients were randomly allocated in permuted blocks of 12 subjects into 3 equal groups with the allocations concealed in opaque sealed envelopes.  Each participant underwent alignment with a standard Damon Q (Ormco, Orange, Calif) wire sequence for a minimum of 34 weeks.  Blinding of clinicians and patients was not possible.  Data were analyzed on a per-protocol basis, since losses to follow-up were minimal.  Complete data were obtained from 87 subjects.  Bracket type had no significant effect on any of the transverse dimensional changes.  No difference in molar inclination was found between passive self-ligation and conventional brackets (0.67°; 95% CI, -2.24, 3.58; P = 0.65) or active self-ligation (0.91°; 95% CI, -1.95, 3.78; P = 0.53).  Similarly, incisor inclination changes with the Damon Q could not be differentiated from those developing with either conventional system (0.44°; 95% CI, -1.93, 2.8; P = 0.71) or In-Ovation C (-0.22°; 95% CI, -2.58, 2.14; P = 0.85).  No harms were encountered.  No difference in the arch dimensional or inclination changes during alignment can be expected between conventional brackets and either active or passive self-ligation.