title: Early vs late orthodontic treatment of tooth crowding by first premolar extraction: A systematic review.
abstract: OBJECTIVE
  To investigate the body of evidence in the literature about the most favorable time for initiating orthodontic treatment in patients with severe crowding caused by tooth size arch length deficiency (TSALD).
  
  
  METHODS
  Electronic databases (PubMed, Ovid Medline, Scopus, Virtual Health Library, and The Cochrane Library) were searched for articles published between 1900 and April 2014. Studies were included that evaluated treatment of patients with severe crowding caused TSALD, who were treated with first premolar extraction. The association between the stage of development of occlusion at which treatment was started, and the primary and/or secondary outcomes of early and late treatment were investigated.
  
  
  RESULTS
  After application of the eligibility criteria and reading of the full texts, six articles were included in the final review. Of these six articles, all of which were retrospective, four showed that the primary outcome (correction of severe crowding) of the early and late groups was improved, but without statistically significant differences after treatment. Therefore, the findings of secondary outcomes in the literature (postretention crowding relapse, duration of total and active treatment [treatment with appliances], external apical root resorption, and soft tissue profile) were the target of this study. These studies presented low or moderate methodological quality and control of bias.
  
  
  CONCLUSIONS
  Both early and late extraction had a similar effect on correction of crowding. Early treatment had two favorable secondary outcomes (less relapse and reduced active treatment time) vs late treatment. However, the levels of evidence were not sufficient to assert which protocol was superior.
authors.affiliation: a  Postgraduate Student, Department of Pediatrics and Orthodontics, Universidade Federal do Rio de Janeiro Dental School, Rio de Janeiro, Brazil.
authors.forename: Hibernon
authors.initials: H
authors.lastname: Lopes Filho
authors.forename: Lúcio H
authors.initials: LH
authors.lastname: Maia
authors.forename: Thiago C L
authors.initials: TC
authors.lastname: Lau
authors.forename: Margareth M G
authors.initials: MM
authors.lastname: de Souza
authors.forename: Lucianne Cople
authors.initials: LC
authors.lastname: Maia
mesh_terms: D001641:Bicuspid / Q000601:surgery*; D002508:Cephalometry / Q000379:methods; D003724:Dental Arch / Q000473:pathology; D006801:Humans; D008310:Malocclusion / Q000628:therapy*; D009811:Odontometry / Q000379:methods; D009971:Orthodontics, Corrective / Q000379:methods*; D013997:Time Factors; D014081:Tooth Extraction / Q000379:methods; D016896:Treatment Outcome
keywords: Early and late treatment; Early treatment; Serial extraction; Tooth crowding