title: Dental arch changes in postretention in Class II division 1 extraction cases.
abstract: OBJECTIVE
  The purpose of this study is to evaluate the postretention stability of the dental arches in Class II division 1 patients treated with four bicuspid extractions and the edgewise technique.
  
  
  METHODS
  A digital caliper was used to analyze the dental casts from 29 Class II division 1 malocclusion patients with skeletal type II (14 males, 15 females; ages ranging from 10.2-18.0 years), treated with four bicuspid extractions and the edgewise technique. Intercanine width, intermolar width, arch length, irregularity index, overjet and overbite were evaluated at three times: pretreatment (T1), posttreatment (T2) and postretention (T3) (mean: 4.15 years). Student's t-tests were used to compare the pretreatment-posttreatment, posttreatment-postretention and pretreatment-postretention. Significance was determined at P<0.05.
  
  
  RESULTS
  The results of the study are listed as: (1) The upper and lower intercanine widths significantly increased (P<0.05) between T1-T2 and decreased between T2-T3. However, no significant changes were observed between T1-T3; (2) The upper and lower intermolar widths significantly decreased (P<0.05) between T1-T2, between T2-T3 and between T1-T3, except for the upper intermolar width between T2-T3 which showed no significant change; (3) The upper and lower arch lengths significantly decreased (P<0.05) at posttreatment and postretention due to the closure of extraction spaces. Both the upper and lower arch lengths significantly decreased between T1-T2, T2-T3, and T1-T3, except for the upper arch length between T2-T3, which showed no significant change; (4) The irregularity index was significantly improved after treatment. However, there was a slight increase in incisor irregularity at postretention. At postretention, 75.86% of the patients had mild crowding, 20.68% had moderate crowding, 3.48% had severe crowding; (5) The overjet and overbite significantly decreased (P<0.05) between T1-T2 and increased between T2-T3.
  
  
  CONCLUSIONS
  The changes in the dental arches were small at postretention with a tendency to return towards their original position. The overall stability of Class II division 1 extraction cases is relatively good.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand. Electronic address: niwat.anu@mahidol.ac.th.
authors.forename: Niwat
authors.initials: N
authors.lastname: Anuwongnukroh
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.
authors.forename: Surachai
authors.initials: S
authors.lastname: Dechkunakorn
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.
authors.forename: Kannida
authors.initials: K
authors.lastname: Kunakornporamut
authors.affiliation: Research Office, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.
authors.forename: Peerapong
authors.initials: P
authors.lastname: Tua-Ngam
mesh_terms: D000293:Adolescent; D002648:Child; D003724:Dental Arch / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008312:Malocclusion, Angle Class II / Q000473:pathology* / Q000628:therapy*; D014081:Tooth Extraction
keywords: Class II division 1; Dental arches; Extraction; Postretention