title: Vertical changes in Class I malocclusion between 2 different extraction patterns.
abstract: OBJECTIVE
  To compare vertical changes occurring in Class I patients after orthodontic treatment with different extraction patterns in a retrospective study.
  
  
  METHODS
  Records of 47 patients with extraction of maxillary first premolars and mandibular second premolars (4/5, Group A) and 46 patients with extraction of fourth first premolars (4/4, Group B) were obtained in the Orthodontic Department, West China Hospital of Stomatology, Chengdu, Sichuan, China from April 2008 to July 2012. Pretreatment and posttreatment cephalograms were digitized, 8 skeletal and 10 dental cephalometric measurements were selected to evaluate vertical changes. Changes of measurements resulting from orthodontic treatment in each group were compared by paired t-test; changes between 2 groups were compared by Independent t-test.
  
  
  RESULTS
  Before treatment, subjects in Group A showed larger angle formed by the intersection of NA and NB lines, overjet, and overbite than those in Group B. After treatment, both groups showed significant vertical changes after orthodontic treatment without remarkable differences between groups.
  
  
  CONCLUSIONS
  No differences of vertical change were found between the 2 extraction patterns. The hypothesized wedge effects due to mesial movement of posterior teeth might be balanced by the extrusion of posterior teeth as well as the residual growth potentials.
authors.affiliation: Department of Orthodontics, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Yating
authors.initials: Y
authors.lastname: Wang
authors.forename: Haixia
authors.initials: H
authors.lastname: Yu
authors.forename: Chunmiao
authors.initials: C
authors.lastname: Jiang
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.forename: Shu
authors.initials: S
authors.lastname: An
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
authors.forename: Yifan
authors.initials: Y
authors.lastname: Huang
authors.forename: Zhihe
authors.initials: Z
authors.lastname: Zhao
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D002648:Child; D006801:Humans; D008311:Malocclusion, Angle Class I / Q000601:surgery*; D014081:Tooth Extraction / Q000379:methods*