Main findings
MINOR, SECONDARY, LITTLE
In this trial, we evaluated the stability of the maxillary anterior teeth during two years of retention followed by 1 year without retention. We found minor changes in Little’s irregularity index during these post-treatment periods. After the retention was removed, small but significant mean differences were found between group A (bonded retainer 13–23) and groups B (bonded retainer 12–22), and C (VFR) (1.1 mm versus 0.5 and 0.4 mm, respectively). However, group A had the slightest changes in LII during the 2-year retention period. During the whole 3-year post-treatment time (T3–T1), small and clinically insignificant group differences were found (1.0 to 1.4 mm) (For the secondary outcomes of arch length and overbite, statistically significant changes between the groups were observed (