title: Influence of root parallelism on the stability of extraction-site closures.
abstract: BACKGROUND
  In premolar extraction cases, root parallelism is recommended to preserve the stability of space closures. The influence of the degree of root parallelism on relapse of tooth extraction spaces has been a controversial topic in the literature. The aim of this study was to compare the angle between the long axes of the canine and the second premolar in patients with and without stability of extraction-space closures.
  
  
  METHODS
  A sample of 56 patients, treated with 4 premolar extractions, was divided into 2 groups: group 1, consisting of 25 patients with reopening of extraction spaces; and group 2, consisting of 31 patients without reopening of extraction spaces. Panoramic radiographs of each patient were analyzed at the posttreatment and 1-year posttreatment stages. The data were statistically analyzed by using chi-square tests, t tests, analysis of variance (ANOVA), and Pearson correlation coefficients.
  
  
  RESULTS
  The results showed that the groups did not differ regarding the angle between the canine and the second premolar, and there was no correlation between angular changes and reopening of extraction spaces, showing that dental angular changes are not determining factors for relapse, and other factors should be investigated.
  
  
  CONCLUSIONS
  The final angle and the posttreatment changes observed in the angle between the long axes of the canine and the second premolar showed no influence on the relapse of extraction spaces.
authors.affiliation: Postgraduate student, Department of Orthodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil. kellychiqueto@yahoo.com.br
authors.forename: Kelly
authors.initials: K
authors.lastname: Chiqueto
authors.forename: Guilherme
authors.initials: G
authors.lastname: Janson
authors.forename: Carina Thaís
authors.initials: CT
authors.lastname: de Almeida
authors.forename: Juliana Moura
authors.initials: JM
authors.lastname: Storniolo
authors.forename: Sérgio Estelita
authors.initials: SE
authors.lastname: Barros
authors.forename: José Fernando Castanha
authors.initials: JF
authors.lastname: Henriques
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000000981:diagnostic imaging / Q000601:surgery*; D002648:Child; D003481:Cuspid / Q000000981:diagnostic imaging*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008311:Malocclusion, Angle Class I / Q000628:therapy; D008312:Malocclusion, Angle Class II / Q000628:therapy; D009811:Odontometry / Q000379:methods; D016382:Orthodontic Appliance Design; D018704:Orthodontic Retainers; D019516:Orthodontic Space Closure / Q000295:instrumentation; D009969:Orthodontic Wires; D011862:Radiography, Panoramic; D012008:Recurrence; D012189:Retrospective Studies; D012690:Serial Extraction; D014092:Tooth Root / Q000000981:diagnostic imaging*; D016896:Treatment Outcome; D055815:Young Adult