Trial design and outcomes
overbite, overjet
SECONDARY
The study was a single-centre randomized controlled trial (RCT) with three parallel arms and a 1:1:1 allocation ratio.Study casts were produced at four different time points: before treatment (T0); after removal of the fixed orthodontic appliances/start of retention (T1); after 2 years of retention when the retainers were removed (T2); and 1 year after the removal of the retainers (T3).The primary outcomes were the post-treatment and post-retention changes in the irregularity of the six maxillary anterior teeth, according to LII, and a single CPD of 2 mm or more between T1, T2, and T3. Consequently, the changes in LII and CPD between the three retention devices were compared during both the retention period and the post-retention period.The secondary outcomes were changes in arch length, intercanine, and intermolar width, maximum single tooth rotation of maxillary anterior teeth, and changes in overjet and overbite at T1, T2, and T3.