Dentoalveolar Transverse Changes in Adolescents Treated with Fixed Appliances or Clear Aligners: A Retrospective Comparative Study

Background: Dentoalveolar transverse constriction is frequently encountered during orthodontic treatment in adolescents. Although both fixed appliances and clear aligners can produce transverse dental arch changes, comparative evidence regarding their expansion patterns in growing patients remains limited. This study aimed to compare dentoalveolar transverse changes associated with two fixed treatment groups and two clear aligner systems in an adolescent population. Methods: This retrospective, non-randomized comparative study included 85 adolescents treated without extractions using conventional MBT fixed appliances (n = 22), Damon Q passive self-ligating appliances (n = 19), Invisalign (n = 21), or ClearCorrect (n = 23). Pretreatment (T0) and post-treatment (T1) digital dental models obtained using a 3Shape TRIOS intraoral scanner were evaluated for maxillary and mandibular transverse arch dimensions, projected palatal area, and maxillary first-molar crown inclination. Intergroup differences in treatment-related changes were compared among the four treatment groups. Results: Significant increases in maxillary transverse dimensions were observed after treatment in all four groups. The greatest mean increases at several maxillary levels were observed in the Damon Q group, including intercanine width (3.66 ± 1.34 mm) and first-molar width (3.69 ± 1.70 mm). In the ClearCorrect group, the mean increases were 3.12 ± 1.90 mm for intercanine width and 2.46 ± 1.42 mm for first-molar width. Projected palatal area increased in all groups, with the greatest mean increase observed with Damon Q (115.16 ± 29.70 mm2). Exploratory assessment of maxillary first-molar clinical crown inclination showed comparatively smaller changes in the ClearCorrect group than in the other treatment groups. Conclusions: All four treatment groups demonstrated increases in dentoalveolar transverse dimensions in this adolescent sample, although the magnitude and pattern of the observed changes differed among groups. Greater transverse increases at several maxillary levels were observed in the Damon Q group, whereas comparatively smaller changes in posterior crown inclination were observed in the ClearCorrect group. Because skeletal maturation was not directly assessed and an untreated control group was unavailable, these findings represent comparative changes observed during treatment and cannot distinguish appliance-related effects from physiological growth or other treatment-related factors.