title: [Clinical evaluation of lingual fixed retainer combined with Hawley retainer and  vacuum-formed retainer].
abstract: OBJECTIVE
  To evaluate the clinical efficacy of vacuum-formed retainers (VFRs) and lingual fixed retainers combined with Hawley retainers (combined retainers, CRs).
  
  
  METHODS
  Forty five patients immediately after orthodontic treatment were randomly allocated to either VFRs (n=25) or CRs (n=20) groups. Overbite, overjet and calculus index scores (CIS) were recorded at pretreatment (T0), debonding (T1), 6 months (T2) and 12 months (T3) after maintenance. The tooth rotation, intercanine and intermolar width, and Little's index of irregularity were recorded on the study models of lower arches. The difference between the two groups was analyzed with SAS 6.12 software package.
  
  
  RESULTS
  No significant difference was noted during retention time in VFRs(P>0.05). Likewise, there was no significant difference between VFRs and CRs, except that the change of CIS in CRs was significantly larger than those in VFRs(P<0.05). The incidence of breakage of vacuum-formed retainers was 24<, which was comparable with that of lingual fixed retainers (20<).
  
  
  CONCLUSIONS
  Both vacuum-formed retainers and lingual fixed retainers combined with Hawley retainers have good retention during the first 12-month retention period. Considering patients' compliance and retention efficacy, lingual fixed retainer with Hawley retainer at night is a better choice for retention.
authors.affiliation: Department of Orthodontics, Shanghai Tenth People's Hospital, Shanghai Tongji University School of Medicine, Shanghai 200072,China. xu_xcen@126.com
authors.forename: Xiao-cen
authors.initials: XC
authors.lastname: Xu
authors.forename: Ren-mei
authors.initials: RM
authors.lastname: Li
authors.forename: Guo-hua
authors.initials: GH
authors.lastname: Tang
mesh_terms: D006801:Humans; D008310:Malocclusion; D016382:Orthodontic Appliance Design; D018704:Orthodontic Retainers; D014618:Vacuum