The aim of this study was to use a randomized controlled trial methodology to evaluate and compare three different retention methods. The capacity of the retention methods to retain orthodontic treatment results was in this first phase analysed on a short-term basis, i.e. after 1 year of retention. The subjects were recruited from adolescents undergoing fixed appliance treatment at an orthodontic clinic in the National Health Service (NHS) in Sweden between 2001 and 2007. Seventy-five patients (45 girls and 30 boys with a mean age of 14.4 years at the start of retention) were randomized into three retention systems; a vacuum-formed retainer in the maxilla and bonded canine-to-canine retainer in the mandible (group V-CTC), a vacuum-formed retainer in the maxilla combined with stripping of the 10 proximal surfaces of the lower mandibular anterior teeth (group V-S), and a prefabricated positioner covering the teeth in the maxilla and mandible (group P). The main outcome measures were: Little's irregularity index (LII), intercanine and intermolar width, arch length, overjet, and overbite. Registrations were made before orthodontic treatment, when the fixed orthodontic appliance was removed, and after 12 months in retention. Differences in means between groups were tested by one-way analysis of variance. After 1 year of retention, no clinically significant difference in retention capacity was found between the three retention methods. Small but significant differences (P < 0.05) were observed between the V-CTC and V-S groups regarding mandibular canine width, mandibular arch length, and overbite. In group P, two patients failed to co-operate.

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.

SUMMARY BACKGROUND: There are few cost evaluation studies of orthodontic retention treatment. The aim of this study was to compare the costs in a randomized controlled trial of three retention methods during 2 years of retention treatment. MATERIALS/METHODS: To determine which alternative has the lower cost, a cost-minimization analysis (CMA) was undertaken, based on that the outcome of the treatment alternatives was equivalent. The study comprised 75 patients in 3 groups consisting of 25 each. The first group had a vacuum-formed retainer (VFR) in the maxilla and a cuspid retainer in the mandible (group V-CTC), the second group had a VFR in the maxilla combined with stripping of the incisors and cuspids in the mandible (group V-S), and the third group had a prefabricated positioner (group P). Direct cost (premises, staff salaries, material and laboratory costs) and indirect costs (loss of time at school) were calculated. Societal costs were defined as the sum of direct and indirect costs. RESULTS: The societal costs/patient for scheduled appointments for 2 years of retention treatment in group V-CTC were €497, group V-S €451 and group P €420. Societal costs for unscheduled appointments in group V-CTC were €807 and in group V-S €303. In group P, there were no unscheduled appointments. CONCLUSIONS/IMPLICATIONS: After 2 years of retention in compliant patients, the cuspid retainer was the least cost-effective retention appliance. The CMA showed that for a clinically similar result, there were differences in societal costs, but treatment decisions should always be performed on an individual basis.

Objective: Comparison of three different retention strategies 5 years or more postretention. Design, Setting, and Participants: Randomized, prospective, single-centre controlled trial. Forty-nine patients (33 girls and 16 boys) were randomly assigned to one of three retention methods during 2 years by picking a ballot shortly before start of retention treatment. Inclusion criteria were no previous orthodontics, permanent dentition, normal skeletal sagittal, vertical, and transversal relationships, Class I dental relationship, space deficiencies, treatment plan with extractions of four premolars followed by fixed straight-wire appliance. Maxillary and mandibular Little's irregularity index (LII), intercanine and intermolar width, arch length, and overbite/overjet were recorded in a blinded manner, altogether 10 measurements on each patient. Significant differences in means within groups assessed by t-test and between groups by one-way analysis of variance. Interventions: Retention methods: removable vacuum-formed retainer (VFR) covering the palate and the maxillary anterior teeth from canine-to-canine and bonded canine-to-canine retainer in the lower arch (group V-CTC); maxillary VFR combined with stripping of the lower anterior teeth (group V-S); and prefabricated positioner (group P). Results: Maxillary mean LII ranged from 1.8 to 2.6 mm, mean intercanine width 33.6-35.3 mm with a significant difference between groups V-S and P, mean intermolar width 46.8-47.4 mm and mean arch length 21.8-22.8 mm. Mandibular mean LII ranged from 2.0 to 3.4 mm with a significant difference between groups V-S and P, mean intercanine width from 25.4 to 26.6 mm, mean intermolar width from 40.8 to 40.9 mm and mean arch length from 16.9 to 17.3 mm. Mean overbite ranged from 1.8 to 2.7 mm and mean overjet from 3.7 to 4.1 mm. Limitations: A single centre study could be less generalizable. Conclusions: The three retention methods disclosed equally favourable clinical results.