Introduction: Extraction vs. non-extraction is a crucial decision in orthodontic therapy. Objective: The aim of the present study was to investigate the changes in the dental arch width and buccal corridor after orthodontic treatment using extraction and non-extraction therapy with Damon self-ligating system. Material and Methods: This retrospective study consisted of 35 patients (20 female and 15 male patients with median age of 12.5 years), treated by extracting 4 or 2 premolars, and 37 patients (16 female and 21 male patients with the median age of 12.8 years), treated without premolar extraction. Both groups were treated with Damon self-ligating system. Plaster models before (T0) and after (T1) treatment were measured, and the arch width values were determined at the level of the first molars, second premolars, canines and palatal rugae. Buccal corridor width was measured using the extraoral images at T0 and T1. Paired t-test was used for the analysis of the normally distributed data, and Wilcoxon Mann-Whitney U test was used for the data with non-normal distribution. Values of p<0.05 were set as statistically significant. Results: The upper intercanine width increased significantly in both groups (p<0.01). In the non-extraction group, the arch width increased significantly in the maxillary second premolar and first molar region (p<0.01) as well as in the region of the canines (p=0.04), second premolars (p=0.01) and first molars (p<0.01) of the mandible. The buccal corridor decreased significantly in the non-extraction group (p<0.01). Conclusion: Premolar extraction in combination with Damon self-ligating system did not lead to reduction of the dental arch width in the maxilla, nor did it increase the size of the buccal corridors.

(1) Background: The present study aimed to evaluate the effects of fixed orthodontic treatment using the Damon self-ligating system on incisor inclination and soft tissue facial profile. Additionally, the study compared the outcomes of premolar extraction versus non-extraction approaches on these parameters. (2) Methods: This retrospective study included 72 patients who were treated with the Damon self-ligating bracket system (Damon, Ormco, Orange, CA, USA). Thirty-five patients (mean age 12.5 years; 20 girls and 15 boys) underwent premolar extraction (Group Ex), while 37 patients (mean age 12.8 years; 16 girls and 21 boys) were treated without extractions (Group NonEx). Lateral cephalometric radiographs were taken pre- and posttherapeutically, and measurements were conducted using OnyxCeph3™ (Image Instruments, Chemnitz, Germany). (3) Results: Following orthodontic treatment, the upper incisors in group Ex were significantly more retruded (p < 0.01), while the mandibular incisors in group NonEx were significantly more proinclined (p < 0.01). Both lips in group Ex, and the upper lip in the group NonEx, exhibited a greater distance from the esthetic line post-therapy (p < 0.01). The position of the lips relative to the SR line did not significantly change in group Ex, whereas group NonEx showed a significantly increased lip protrusion (p < 0.01). A weak negative correlation (−0.37) was observed between the increased retroclination of the upper incisors and the retrusion of the upper lip relative to the SR line. (4) Conclusions: Premolar extraction, as part of a treatment strategy for cases with severe crowding, combined with Damon™ self-ligating braces, does not adversely affect the soft tissue profile.