title: Morphological characteristics influencing the orthodontic extraction strategies for Angle's class II division 1 malocclusions.
abstract: BACKGROUND
  Extraction has now been accepted widely in various malocclusions including Angle's class II division 1. However, the levels of scientific evidence in orthodontic treatment planning have been weak, and it is unlikely to systematically provide a rationale and consistent basis in decisions of extraction. This study was retrospectively designed to investigate the initial morphologic characteristics of class II division 1 subjects involving four different extraction strategies, to determine the relevant influential factors when choosing extraction strategies with the most commonly used mechanics and the principle of simplicity in orthodontic treatment based on cases diagnosed and treated by an experienced orthodontist.
  
  
  METHODS
  One hundred and ten samples of Angle's class II division 1 malocclusion with good facial and occlusal outcomes after orthodontic treatment were selected and divided into four groups according to different extraction patterns. For each case, pretreatment models and the lateral radiographs were analyzed. Significant variables of models and craniofacial structures of each group were identified by comparing the measurements using one-way analysis of variance (ANOVA) at a significance level of P < 0.05. Then, binary logistic regression analysis was used and a regression equation was established to quantify the correlations among the significant variables and their contributions to the extraction decisions.
  
  
  RESULTS
  Molar relationship, lower anterior crowding, anterior Bolton index, and anterior overjet measured from models, as well as ANS-Xi-Pm, NBa-PtGn, Li-NsPog', U1-NPog and L1-NPog measured from lateral radiographs were found to be statistically significant. Binary logistic regression analysis revealed that lower anterior crowding, molar relationship, and growth pattern were the three most relevant influential factors with a declining impact contributing to the extraction decisions for Angle's class II division 1 malocclusions.
  
  
  CONCLUSIONS
  Angle's class II division 1 malocclusions exhibit various morphological characteristics. Orthodontists should comprehensively consider the reciprocal impact of multiple factors when choosing different extraction strategies for Angle's class II division 1 malocclusions.
authors.forename: Yongwen
authors.initials: Y
authors.lastname: Guo
authors.forename: Xianglong
authors.initials: X
authors.lastname: Han
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Dongqing
authors.initials: D
authors.lastname: Ai
authors.forename: Huan
authors.initials: H
authors.lastname: Zeng
authors.forename: Ding
authors.initials: D
authors.lastname: Bai
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000601:surgery; D002508:Cephalometry / Q000379:methods; D002648:Child; D003724:Dental Arch / Q000473:pathology; D006801:Humans; D007180:Incisor / Q000473:pathology; D008312:Malocclusion, Angle Class II / Q000473:pathology / Q000628:therapy*; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D003765:Models, Dental; D008963:Molar / Q000473:pathology; D009295:Nasal Bone / Q000473:pathology; D009811:Odontometry / Q000379:methods; D057887:Overbite / Q000473:pathology / Q000628:therapy; D010347:Patient Care Planning; D012189:Retrospective Studies; D014081:Tooth Extraction / Q000145:classification*; D016896:Treatment Outcome