title: A randomized clinical trial of two alternative designs of Twin-block appliance.
abstract: OBJECTIVE
  To test if placing a Southend clasp on the upper and lower incisors during Twin-block appliance treatment will control their angulation and enhance skeletal correction.
  
  
  METHODS
  Prospective, randomized, controlled clinical trial (ISRTCTN 45965219).
  
  
  METHODS
  Orthodontic Department, Royal Preston District General Hospital, Preston, UK.
  
  
  METHODS
  Fifty-two consecutive patients aged 9-30 years undergoing treatment for Class II division 1 malocclusion (ANB>5°, OJ>6 mm).
  
  
  METHODS
  Two alternative designs of Twin-block appliance were allocated randomly. One with a Southend clasp on the upper and lower central incisors and one without. The appliances were identical in all other aspects.
  
  
  RESULTS
  Skeletal and dental changes measured on before and after treatment lateral cephalometric radiographs.
  
  
  RESULTS
  There was a statistically significant change in ANB angle between the Southend group (-3·5°) and the Non-Southend group (-2·6°) (P = 0·004). The change in upper incisor angulation was -6·1° for the Southend group and -12·0° for the Non-Southend group, which was statistically significant (P = 0·005). The change in lower incisor angulation was 3·0° for the Southend group and 6·9° for the Non-Southend group, which was statistically significant (P = 0·005).
  
  
  CONCLUSIONS
  The presence of a Southend clasp on the upper and lower incisors during Twin-block treatment limited their tipping which enhanced the skeletal correction.
authors.affiliation: Royal Preston Hospital Preston, Lancashire, UK. karen.pool@lthtr.nhs.uk
authors.forename: Michael John
authors.initials: MJ
authors.lastname: Trenouth
authors.forename: Stephen
authors.initials: S
authors.lastname: Desmond
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry; D002648:Child; D003799:Dental Stress Analysis; D005260:Female; D006801:Humans; D007180:Incisor; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D016382:Orthodontic Appliance Design; D017289:Orthodontic Appliances, Functional; D011446:Prospective Studies; D013223:Statistics as Topic; D054159:Torsion, Mechanical; D055815:Young Adult