Efficacy and stability of maxillary arch expansion with clear aligners versus conventional slow maxillary expanders...

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.

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.

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 (P = 0.26). Significantly greater expansion at the canine cusp tip was observed in the CA group. Age was a negative predictor of expansion at the canine region.

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.