title: Five-year postretention outcomes of three retention methods--a randomized controlled trial.
abstract: OBJECTIVE
  Comparison of three different retention strategies 5 years or more postretention.
  
  
  METHODS
  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.
  
  
  METHODS
  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 2.6mm, mean intercanine width 33.6-35.3mm with a significant difference between groups V-S and P, mean intermolar width 46.8-47.4mm and mean arch length 21.8-22.8mm. Mandibular mean LII ranged from 2.0 to 3.4mm with a significant difference between groups V-S and P, mean intercanine width from 25.4 to 26.6mm, mean intermolar width from 40.8 to 40.9mm and mean arch length from 16.9 to 17.3mm. Mean overbite ranged from 1.8 to 2.7mm and mean overjet from 3.7 to 4.1mm.
  
  
  CONCLUSIONS
  A single centre study could be less generalizable.
  
  
  CONCLUSIONS
  The three retention methods disclosed equally favourable clinical results.
  
  
  BACKGROUND
  This trial was not registered.
  
  
  METHODS
  The protocol was not published before trial commencement.
authors.affiliation: Department of Orthodontics, Faculty of Odontology, Malmö University, Sweden gudrunedmantynelius@gmail.com.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Edman Tynelius
authors.affiliation: Department of Orthodontics, Faculty of Odontology, Malmö University, Sweden.
authors.forename: Sofia
authors.initials: S
authors.lastname: Petrén
authors.affiliation: Department of Orthodontics, Faculty of Odontology, Malmö University, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Bondemark
authors.affiliation: Department of Orthodontics, Faculty of Odontology, Malmö University, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Lilja-Karlander
mesh_terms: D000293:Adolescent; D020906:Air Abrasion, Dental / Q000379:methods; D003481:Cuspid / Q000473:pathology; D003724:Dental Arch / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007180:Incisor / Q000473:pathology; D008297:Male; D008310:Malocclusion / Q000473:pathology / Q000628:therapy; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D016382:Orthodontic Appliance Design; D018704:Orthodontic Retainers; D009971:Orthodontics, Corrective / Q000379:methods*; D057887:Overbite / Q000473:pathology / Q000628:therapy; D011446:Prospective Studies; D012008:Recurrence; D016037:Single-Blind Method; D016896:Treatment Outcome