title: Arch-width changes in extraction vs nonextraction treatments in matched Class I borderline malocclusions.
abstract: BACKGROUND
  The aims of this study were to identify a sample of borderline Class I extraction and nonextraction patients and to investigate posttreatment changes in arch-width and perimeter measurements.
  
  
  METHODS
  A parent sample of 580 Class I patients was subjected to discriminant analysis, and a borderline subsample of 62 patients, 31 treated with extraction of 4 first premolars and 31 treated without extractions, was obtained. The patients' plaster casts were digitally scanned, and the maxillary and mandibular intercanine and intermolar widths and perimeters were assessed.
  
  
  RESULTS
  The extraction group showed increases in maxillary and mandibular intercanine widths (P <0.001) and decreases in mandibular intermolar width and in maxillary and mandibular perimeters (P <0.001). The nonextraction group showed increases in all 4 arch-width measurements (P ≤0.003), whereas the maxillary and mandibular perimeters were maintained. The posttreatment differences between the 2 groups showed significant differences in the maxillary (P <0.001) and mandibular intermolar widths (P <0.001). Also, the comparison of the arch perimeters between the 2 treatment groups showed adjusted differences of -8.51 mm (P <0.001) and -8.44 mm (P <0.001) for the maxillary and mandibular arches, respectively. The intercanine widths showed no changes between the 2 treatment groups.
  
  
  CONCLUSIONS
  Borderline Class I patients treated with extraction of 4 first premolars had decreased maxillary and mandibular intermolar and perimeter measurements compared with nonextraction patients. The maxillary and mandibular intercanine widths showed no significant difference between the 2 treatment groups.
authors.affiliation: Clinic of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Claudio
authors.initials: C
authors.lastname: Herzog
authors.affiliation: Department of Orthodontics, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Konstantonis
authors.affiliation: Center for Advanced Dental Education, Department of Orthodontics, Saint Louis University, Saint Louis, Mo.
authors.forename: Nikoleta
authors.initials: N
authors.lastname: Konstantoni
authors.affiliation: Clinic of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, Faculty of Medicine, University of Zurich, Zurich, Switzerland. Electronic address: theodore.eliades@zzm.uzh.ch.
authors.forename: Theodore
authors.initials: T
authors.lastname: Eliades
mesh_terms: D000293:Adolescent; D002370:Casts, Surgical; D005260:Female; D006801:Humans; D008297:Male; D008311:Malocclusion, Angle Class I / Q000601:surgery / Q000628:therapy*; D009971:Orthodontics, Corrective / Q000379:methods; D014081:Tooth Extraction / Q000379:methods; D016896:Treatment Outcome