title: Dentoskeletal effects of 2-phase treatment versus 1-phase treatment with extraction of 4 first premolars in nonhypodivergent class II patients.
abstract: BACKGROUND
  The aim of this study was to compare the effectiveness of 2-phase (a first phase with Twin Block therapy immediately followed by a second phase with fixed appliance therapy with nonextraction) and 1-phase (fixed appliance therapy with extraction of 4 first premolars) treatment of class II division 1 malocclusion.
  
  
  METHODS
  Two groups of successfully treated subjects, aged 10 to 14 years with class II division 1 malocclusion, were evaluated: 2-phase group (n = 70) and 1-phase group (n = 76). Pretreatment and posttreatment lateral cephalograms were traced manually and subjected to Student t test.
  
  
  RESULTS
  In the 2-phase group, the forward positioning of the mandible (Pg-Olp) was less than that of the extraction group. The sagittal mandibular forward growth (Pg-Olp) was, on average, 2.39 ± 0.4 mm in the 2-phase group and 4.56 ± 2.51 mm in the 1-phase group (P = 0.008, P < 0.05). In the vertical plane, the increases in lower facial height and mandibular plane angle were greater in the 2-phase treatment. In the 2-phase group, the lower anterior teeth proclined (Ii-MP) by 7.3 ± 2 degrees, and in the extraction treatment group, it changed -4.1 ± 3.6 degrees. The 1-phase group contributed more sagittal orthopedic effects than did the 2-phase group.
  
  
  CONCLUSIONS
  The proclination of the mandibular incisors in the 2-phase group might restrain the mandibular bone from growing enough and cause the backward and downward rotation of the mandible.
authors.affiliation: Department of Orthodontics, West China Stomatological Hospital, Sichuan, People's Republic of China.
authors.forename: Cui
authors.initials: C
authors.lastname: Ye
authors.forename: Xi
authors.initials: X
authors.lastname: Du
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhao
authors.forename: Zhen
authors.initials: Z
authors.lastname: Tan
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000601:surgery; D002508:Cephalometry; D002648:Child; D005115:Extraoral Traction Appliances; D005260:Female; D006801:Humans; D008297:Male; D008312:Malocclusion, Angle Class II / Q000000981:diagnostic imaging / Q000628:therapy*; D008445:Maxillofacial Development; D017289:Orthodontic Appliances, Functional; D011859:Radiography; D014081:Tooth Extraction; D016896:Treatment Outcome; D014716:Vertical Dimension