title: Cone-beam computed tomographic evaluation of the long-term effects of orthodontic retainers on marginal bone levels.
abstract: Fixed retainers are widely used after orthodontic treatment, sometimes for extended periods, despite insufficient knowledge of their possible long-term adverse effects on the periodontium. The aim of this study was to evaluate whether bonded orthodontic retainers have an adverse long-term effect on the marginal bone levels of the mandibular front teeth.
  
  
  
  The study included 62 consecutive patients in 3 groups: (1) patients who underwent orthodontic treatment and wore a fixed retainer for 10 years, (2) patients who underwent orthodontic treatment but did not have a fixed retainer, and (3) untreated controls. The marginal bone levels were measured by cone-beam computed tomography 10 years after treatment. Additionally, multivariate data analysis was used to analyze possible correlations between the marginal bone levels at 10 years and the variables obtained from the study casts and profile radiographs.
  
  
  
  The results demonstrated a significantly lower marginal bone level on the buccal side of the mandibular front teeth in the orthodontically treated patients compared with the orthodontically untreated group. There was no difference in the marginal bone levels between the retainer group and the no-retainer group. Multivariate analysis indicated that a low marginal bone level was correlated with a basal open vertical relationship, posterior rotation of the mandible, pretreatment of the incisor protrusion, and extraction therapy.
  
  
  
  Within the limits of this research design, the long-term retention phase in general does not seem to cause any adverse effects on the marginal bone levels after 10 years.
authors.affiliation: Department of Orthodontics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. Electronic address: anna.westerlund@odontologi.gu.se.
authors.forename: Anna
authors.initials: A
authors.lastname: Westerlund
authors.affiliation: Specialist Clinic of Orthodontics, Public Dental Service, Västra Götaland Region, Gothenburg, Sweden.
authors.forename: Charitini
authors.initials: C
authors.lastname: Oikonomou
authors.affiliation: Department of Orthodontics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Ransjö
authors.affiliation: Department of Oral and Maxillofacial Radiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Ekestubbe
authors.affiliation: Specialist Training, Specialist Clinic of Orthodontics, Public Dental Service, Västra Götaland Region, Gothenburg, Sweden.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bresin
authors.affiliation: Department of Oral and Maxillofacial Radiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Lund
mesh_terms: D000328:Adult; D016723:Bone Remodeling; D016022:Case-Control Studies; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging; D018704:Orthodontic Retainers / Q000009:adverse effects*; D009971:Orthodontics, Corrective / Q000009:adverse effects / Q000379:methods; D013997:Time Factors; D014070:Tooth / Q000033:anatomy & histology* / Q000000981:diagnostic imaging