Efficacy and stability of maxillary arch expansion with clear aligners versus conventional slow maxillary expanders in growing patients: A multicenter prospective cohort study.

Objective: To compare the efficacy and stability of maxillary arch expansion using clear aligners (CAs) and slow maxillary expanders (SMEs) in growing patients with maxillary transverse deficiency. Methods: This prospective multicenter cohort study included 48 growing patients (mean age, 9.3 ± 1.7 years; CA group: n = 24; SME group: n = 24) requiring maxillary expansion. The maxillary arch dimensions at the crown and gingival levels, arch perimeter, and molar buccolingual inclination were assessed at pretreatment (T0), post-expansion (T1), and post-retention (T2). The primary outcome was intermolar transverse expansion. A predefined non-inferiority analysis was performed to determine whether the expansion achieved with CAs was non-inferior to that achieved with SMEs within a clinically acceptable margin. Secondary analyses assessed the magnitude, pattern, and stability of the expansion through intra-and intergroup comparisons across time points. Results: The average duration of the expansion phase (T0-T1) was 8.9 ± 3.4 months in the CA group and 6.3 ± 6.1 months in the SME group, followed by a retention phase (T1-T2) of 8.8 ± 5.0 and 8.3 ± 5.7 months, respectively. Both groups showed significant increases in the arch dimensions at T0-T1 and T0-T2. The SME group showed a greater bodily expansion pattern in the molars at T0-T2, although this difference was not statistically significant ( Conclusions: Based on a predefined non-inferiority margin, the maxillary arch expansion achieved with CAs was not inferior to that obtained with SMEs in growing patients.