title: [Casting Nance arch which allowed the upper canine's self-adjustment in the extraction cases].
abstract: OBJECTIVE
  To study the upper canine's self-adjustment after the first premolar extraction and the effect of casting Nance arch in the sustainment of the upper first molar position.
  
  
  METHODS
  Twenty severely crowded adolescents whose upper canines were in labial malposition were chosen. After the treatment plan was made, the upper first premolars were removed, the individually made casting Nance arches were fixed on the upper first molars. The measurement and fixed orthodontic treatment began 6 months later. Graphpad Prism 6.0 software was used for data analysis.
  
  
  RESULTS
  The average movement of the malpositioned canines was （3.6±0.1）mm (P<0.01); while the forward movement of the first molars was （0.2±0.16）mm (P>0.05).
  
  
  CONCLUSIONS
  Extraction of the first premolars is beneficial to the canine's self-adjustment in adolescents and the casting Nance arch could help keeping the first molar's positions.
authors.affiliation: Shanghai Xuhui District Dental Center. Shanghai 200032，China. E-mail:475491422@qq.com.
authors.forename: Fei
authors.initials: F
authors.lastname: Qin
authors.forename: Xiao-qing
authors.initials: XQ
authors.lastname: Ma
authors.forename: Pei-cheng
authors.initials: PC
authors.lastname: Xu
authors.forename: Fei
authors.initials: F
authors.lastname: Xiang
mesh_terms: D000293:Adolescent; D001641:Bicuspid; D003724:Dental Arch; D003748:Dental Equipment; D006801:Humans; D008963:Molar; D014087:Tooth Movement Techniques