Mandibular dental arch changes associated with treatment of crowding using self-ligating and conventional brackets

The purpose of this study was to investigate the effect of treatment of mandibular crowding with self-ligating and conventional brackets on dental arch variables. Fifty-six patients were selected from a pool of subjects satisfying the following inclusion criteria: non-extraction treatment in the mandibular or maxillary arches, eruption of all mandibular teeth, no spaces and an irregularity index greater than 2 mm in the mandibular arch, and no adjunct treatment such as etxra- or intraoral appliances. The patients were assigned to two groups: one group received treatment with the self-ligating bracket and the other with a conventional edgewise appliance, both with a 0.022 inch slot. Lateral cephalometric radiographs obtained at the beginning (T1) and end (T2) of treatment were used to assess the alteration in mandibular incisor inclination, and measurements of intercanine and intermolar widths were made on dental casts to investigate changes associated with the correction. The results were analysed with bivariate and multivariate linear regression analysis in order to examine the effect of the bracket systems on arch width or lower incisor inclination, adjusting for the confounding effect of demographic and clinical characteristics. An alignment-induced increase in the proclination of the mandibular incisors was observed for both groups; no difference was identified between self-ligating and conventional brackets with respect to this parameter. Likewise, an increase in intercanine and intermolar widths was noted for both bracket groups; the self-ligating group showed a higher intermolar width increase than the conventional group, whereas the amount of crowding and Angle classification were not significant predictors of post-treatment intermolar width.