title: Post-treatment changes in permanent retention.
abstract: OBJECTIVE
  While permanent retention is today the method of choice to stabilize orthodontic treatment outcomes, recent studies have increasingly reported posttreatment changes in tooth position during permanent retention. We conducted this study to analyze changes in the anterior mandible, whether the changes follow an underlying movement pattern, and, aiming for a preventive strategy, whether any risk factors could be identified comparing findings with the pretreatment situations.
  
  
  METHODS
  We included 30 patients who had worn fixed Twistflex retainers (UK 3-3) extending from canine to canine in the mandible. Casts reflecting the intraoral situations before orthodontic treatment (T0), directly after completion of active therapy (T1), and 6 months later (T2) were scanned and superimposed using Imageware Surfacer software. Posttreatment changes (T2-T1) of tooth position within the retainer block were analyzed on 3D virtual models and were compared to pretreatment (T0) and treatment-related (T1-T0) findings to identify potential risk factors.
  
  
  RESULTS
  Almost all analyzed patients revealed three-dimensional changes in tooth position within the retainer block. Comparing these movements, we repeatedly found rotated retainer blocks in labio-oral direction, while the center of rotation was located at the first incisors. This pattern was associated with intercanine expansion and excessive overjet correction during orthodontic treatment. The canines underwent the most pronounced (rotational and translational) movements.
  
  
  CONCLUSIONS
  In general permanent lingual retainers are safe but in special clinical cases retainers can induce undesired tooth movement. Risk factors seem to be intercanine expansion and excessive overjet correction during orthodontic treatment. In specific cases an additional retention device might be needed.
authors.affiliation: Department of Orthodontics, University of Bonn, Welschnonnenstrasse 17, 53111, Bonn, Germany. michael.wolf@uni-bonn.de.|Department of Orthodontics, University of Jena, Jena, Germany. michael.wolf@uni-bonn.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Wolf
authors.affiliation: Department of Orthodontics, University of Bonn, Welschnonnenstrasse 17, 53111, Bonn, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Schulte
authors.affiliation: Orthodontic Practice, Friesenplatz Cologne, Cologne, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Küpper
authors.affiliation: Endowed Chair for Oral Technology, University of Bonn, Bonn, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Bourauel
authors.affiliation: Endowed Chair for Oral Technology, University of Bonn, Bonn, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Keilig
authors.affiliation: Department of Orthodontics, University of Bonn, Welschnonnenstrasse 17, 53111, Bonn, Germany.|Endowed Chair for Oral Technology, University of Bonn, Bonn, Germany.
authors.forename: S N
authors.initials: SN
authors.lastname: Papageorgiou
authors.affiliation: Endowed Chair for Oral Technology, University of Bonn, Bonn, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Dirk
authors.affiliation: Department of Orthodontics, University of Regensburg, Regensburg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Kirschneck
authors.affiliation: Department of Orthodontics, University of Bonn, Welschnonnenstrasse 17, 53111, Bonn, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Daratsianos
authors.affiliation: Department of Orthodontics, University of Bonn, Welschnonnenstrasse 17, 53111, Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Jäger
mesh_terms: D000328:Adult; D002508:Cephalometry; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000209:etiology* / Q000473:pathology / Q000517:prevention & control*; D008334:Mandible / Q000473:pathology; D018704:Orthodontic Retainers / Q000009:adverse effects*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014086:Tooth Mobility / Q000209:etiology / Q000473:pathology* / Q000517:prevention & control*; D016896:Treatment Outcome
keywords: Lingual retainer; Orthodontic retention; Prevention; Tooth movement; Twistflex retainer