A randomized controlled trial of three orthodontic retention methods in Class I four premolar extraction cases : stability after 2 years in retention

OBJECTIVE: To evaluate three different retention methods in compliant patients after 2 years of retention. DESIGN: Three group randomized controlled trial. MATERIALS AND METHODS: The sample was recruited from patients having their fixed appliance treatment between 2001 and 2007. Seventy-five patients (45 girls and 30 boys with a mean age of 14.4 years at start of retention) were randomized into three retention methods: vacuum-formed retainer in the maxilla and bonded canine-to-canine retainer in the mandible (Group V-CTC), vacuum-formed retainer in the maxilla combined with stripping of the 10 proximal surfaces of the lower mandibular anterior teeth (Group V-S) and prefabricated positioner covering the teeth in the maxilla and the mandible (Group P). The following linear measurements were performed: Little's irregularity index (LII), intercanine width, intermolar width, arch length, overjet, overbite and body height growth. Registrations were made before orthodontic treatment, at start of retention, after 12 and finally 24 months in retention. Differences in means between groups were tested by one-way analysis of variance (SPSS). RESULTS: After 2 years all three retention methods were successful in retaining orthodontic treatment results. The major part of relapse took place during the 1st year of retention. CONCLUSIONS: All 3 types of retention methods were equally effective in controlling relapse to a clinically acceptable level