title: Bidimensional techniques for stronger anterior torque control in extraction cases: a combined clinical and typodont study.
abstract: OBJECTIVE
  To investigate the capacity of bidimensional techniques for torque control of anterior teeth in extraction cases.
  
  
  METHODS
  Two different bidimensional techniques were distinguished by nomenclature as bidimensional-slot (bDS) and bidimensional-wire (bDW), respectively. (1) In the clinical study, patients were randomly assigned to three groups (ie, bDS [n  =  27], bDW [n  =  24], and control [n  =  25] groups). The major inclusion criterion was mild crowding in the upper arch, with the two upper first premolars (teeth 14 and 24) to be extracted. After space closure through standardized treatment, the torque of the upper central incisors (∠TQ _U1) was calculated using the angle formed by the base of the U1 bracket and the working archwire on cephalograms. (2) In the typodont study, a standardized setup of the upper dentition with teeth 14 and 24 extracted was established. The spaces were closed through water bath followed by elastics, using the bDW or the conventional (control) technique, respectively. In six replicate experiments, after space closure, the ∠TQ _U1 was measured on the standardized lateral photographs.
  
  
  RESULTS
  (1) In the clinical study, after space closure, the ∠TQ_U1 was 9.4° ± 3.4° (bDS), 8.3° ± 3.3° (bDW), and 5.8° ± 2.9° (control), respectively. The ∠TQ_U1 of bDS and bDW were both significantly (P < .05) larger than that of the control, but no statistical difference was found between them. (2) In the typodont study, after space closure, the ∠TQ_U1 of bDW (8.5° ± 0.9°) was significantly (P < .01) larger than that of the control (4.9° ± 1.0°).
  
  
  CONCLUSIONS
  The bDS and the bDW techniques may help enhance anterior torque control in extraction cases.
authors.affiliation: Department of Orthodontics, State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
authors.forename: Na
authors.initials: N
authors.lastname: Tang
authors.forename: Zhenrui
authors.initials: Z
authors.lastname: Xu
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Feng
authors.forename: Liang
authors.initials: L
authors.lastname: Yang
authors.forename: Zhihe
authors.initials: Z
authors.lastname: Zhao
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001641:Bicuspid; D016022:Case-Control Studies; D002648:Child; D003481:Cuspid; D003761:Dental Impression Technique; D005260:Female; D006801:Humans; D008297:Male; D016382:Orthodontic Appliance Design / Q000379:methods*; D019516:Orthodontic Space Closure / Q000379:methods*; D014081:Tooth Extraction; D014087:Tooth Movement Techniques / Q000379:methods*; D019415:Torque; D055815:Young Adult