Methods
CPD
LITTLE
Ninety adolescent patients treated with fixed orthodontic appliances were enrolled. After gaining informed consent, the patients were randomized in blocks of 30 by an independent person into one of three groups: A) bonded retainer 13–23; B) bonded retainer 12–22; and C) removable vacuum-formed retainer. The primary outcomes were changes in Little’s irregularity index (LII) and single CPD measured on digitalized casts before retention (T1), after 2 years of retention (T2), and 1-year post-retention (T3).