title: Radiographic evaluation of the effect of orthodontic retraction on the root of the maxillary canine.
abstract: OBJECTIVE
  To evaluate possible apical root resorption following orthodontic retraction of the maxillary canine quantitatively and qualitatively.
  
  
  METHODS
  Twenty maxillary canines in 12 patients were retracted using a prefabricated orthodontic spring. Twenty non-treated mandibular canines from the same patients served as controls. Standardized radiographs were taken of all upper and lower canines before (T0) and after (T2) retraction. Root length and tooth length were measured on the radiographs at T0 and T2, and the root length/tooth length ratio was calculated. Ten orthodontists assessed blind the root apex of the pairs of radiographs taken at T0 and T2 for resorption. Digital subtraction was performed between the pairs of radiographs taken at T0 and T2 and the mean density and the standard deviation of the grey shades of the root apex calculated.
  
  
  RESULTS
  There were no significant differences between root length/tooth length ratio at T0 and T2 for either the maxillary (p = 0.45) or the mandibular canines (p = 0.79). There was considerable variation between observers judgements of root resorption: nine out of ten observers agreed that a resorption had taken place in only one tooth. There were no significant differences between the mean density values in the subtraction images of the upper and lower canines (p = 0.3).
  
  
  CONCLUSIONS
  Quantitative assessment with conventional and subtraction radiography failed to demonstrate root resorption in the maxillary canines. Root resorption could be shown qualitatively in only one tooth. The standardized orthodontic force system used for canine retraction appeared to cause no resorption, or only a small degree of resorption of no clinical relevance.
authors.affiliation: Department of Orthodontics, Royal Dental College, University of Aarhus, Denmark.
authors.forename: G
authors.initials: G
authors.lastname: Perona
authors.forename: A
authors.initials: A
authors.lastname: Wenzel
mesh_terms: D000328:Adult; D003481:Cuspid / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008437:Maxilla; D008875:Middle Aged; D015588:Observer Variation; D009968:Orthodontic Appliances, Removable / Q000009:adverse effects; D011861:Radiography, Dental / Q000379:methods; D012391:Root Resorption / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000503:physiopathology; D018709:Statistics, Nonparametric; D013382:Subtraction Technique; D014087:Tooth Movement Techniques / Q000009:adverse effects*