title: [Bone density changes in the apical area after rapid orthodontic extrusion of subgingivally fractured tooth].
abstract: OBJECTIVE
  To evaluate the bone density changes in the apical area of subgingivally fractured tooth after rapid orthodontic extrusion.
  
  
  METHODS
  Twelve fractured incisors in 11 patients extended 2 - 5 mm below the gingival line were selected. Two weeks after root canal therapy, the subgingival fragment was lifted up and the fracture line was brought 1.5 - 2.0 mm above the level of the gingival line by means of edgewise fixed appliance. After the extrusion completed, the tooth had been stabilized and held for 6 months. The CT Analyser software was used to measure the bone density changes in the apical area on radiographs once a month. Changes of relative value in bone density was quantitatively analyzed.
  
  
  RESULTS
  The average period of extrusion was 11 days. The relative value of bone density in the apical region was -39.6% immediately after extrusion and continuously increased afterwards. In the third month, the value (18.5%) changed most rapidly (P < 0.01).
  
  
  CONCLUSIONS
  Under the continuous and proper tooth axial extrusion force, the tooth moved rapidly and steadily. The bone density in the apical area approached normal value within 3 months after treatment.
authors.affiliation: Department of Prosthodontics, Nanjing Stomatological Hospital, The Affiliated Hospital of Medical School, Nanjing University, Nanjing 210008, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ji
authors.forename: Xiao-ping
authors.initials: XP
authors.lastname: Luo
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Tie-mei
authors.initials: TM
authors.lastname: Wang
authors.forename: Lie
authors.initials: L
authors.lastname: Wu
authors.forename: Cheng-jun
authors.initials: CJ
authors.lastname: Shu
mesh_terms: D000328:Adult; D015519:Bone Density / Q000502:physiology; D005260:Female; D006801:Humans; D007180:Incisor / Q000276:immunology*; D008297:Male; D050793:Orthodontic Extrusion / Q000379:methods*; D009969:Orthodontic Wires; D014082:Tooth Fractures / Q000503:physiopathology / Q000628:therapy*; D014092:Tooth Root / Q000293:injuries*; D020390:Tooth Socket / Q000503:physiopathology*