Occlusal Relationships and Dental Changes in Mixed Dentition Patients Treated with Clear Aligners: A 2-Year Follow Up

This study assessed the long-term stability of dental arch changes achieved through clear aligner treatment in growing patients during the early mixed dentition stage.

This retrospective study included 20 patients (mean age 8.3 ± 0.4 years) treated with clear aligners according to a standardized sequential expansion protocol. No additional auxiliaries, interproximal reductions, or retentions were used. Dental casts were collected at baseline (T0), end of treatment (T1), and two years post-treatment without retention (T2). Linear and angular measurements (arch width, molar and incisor torque, Henry's angle, overjet, overbite, and Little's index) were assessed on digital models. Friedman ANOVA and Wilcoxon signed-rank tests were applied (α = 0.05).

At T1-T0, significant transversal expansion was achieved in both arches (U6-6 mesial +2.1 mm; L6-6 mesial +2.4 mm; p < 0.05), with favorable torque changes and a reduction in overjet (-1.5 mm). From T1 to T2, only minimal, non-significant relapse was detected, except for a slight reduction in lower left molar torque (-1.1°). The T2-T0 comparison confirmed stable improvements in mesial intermolar widths (upper +2.0 mm; lower +1.6 mm), molar derotations, and overjets (-1.9 mm), with no significant loss of expansion or sagittal correction.

Clear aligners in early mixed dentition achieved significant and stable dental arch modifications over a 2-year follow-up without the use of retention appliances. This therapeutic approach may represent a reliable interceptive option in growing patients.