title: Alignment stability in Class II malocclusion treated with 2- and 4-premolar extraction protocols.
abstract: BACKGROUND
  The purpose of this study was to compare the postretention stability of the correction of mandibular anterior-tooth irregularity in patients with Class II malocclusions whose orthodontic treatments included extraction of 2 or 4 premolars.
  
  
  METHODS
  A total of 66 patients were selected who initially had at least one-half-cusp Class II malocclusions. Nineteen patients (9 male, 10 female) with an initial mean age of 14.04 years were treated with extraction of 2 premolars (group 1); 47 patients (20 male, 27 female) with an initial mean age of 13.03 years were treated with extraction of 4 premolars (group 2). A subgroup of group 2, with a similar amount of initial anterior-tooth irregularity as group 1, was also compared with group 1. Little's irregularity index was used to evaluate anterior tooth irregularity in dental casts obtained from each patient before treatment, after treatment, and 5 years after active treatment. Initial cephalometric variables, initial treatment priority index, pretreatment age, treatment time, and posttreatment time of the groups were compared with t tests. Similarly, Little's irregularity index values at prettreament, posttreatment, and postretention were also compared with the t test. Cephalometric treatment changes within groups were evaluated with dependent t tests.
  
  
  RESULTS
  There were no statistically significant differences in posttretention anterior-tooth irregularity between groups 1 and 2 or the subgroup.
  
  
  CONCLUSIONS
  Treatment of Class II malocclusion with extraction of either 2 maxillary premolars or 4 premolars provides the same mandibular anterior-tooth alignment stability.
authors.affiliation: Department of Orthodontics, Bauru Dental School, University of São Paulo, São Paulo, Brazil. jansong@travelnet.com.br
authors.forename: Guilherme
authors.initials: G
authors.lastname: Janson
authors.forename: Mauro Carlos Agner
authors.initials: MC
authors.lastname: Busato
authors.forename: José Fernando Castanha
authors.initials: JF
authors.lastname: Henriques
authors.forename: Marcos Roberto
authors.initials: MR
authors.lastname: de Freitas
authors.forename: Lívia Maria Andrade
authors.initials: LM
authors.lastname: de Freitas
mesh_terms: D000293:Adolescent; D000328:Adult; D001641:Bicuspid / Q000601:surgery; D002508:Cephalometry / Q000706:statistics & numerical data; D002648:Child; D005260:Female; D006801:Humans; D007180:Incisor / Q000503:physiopathology; D008297:Male; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008334:Mandible; D009971:Orthodontics, Corrective / Q000379:methods*; D012008:Recurrence; D012189:Retrospective Studies; D014081:Tooth Extraction; D016896:Treatment Outcome