title: Efficiency of mandibular arch alignment with 2 preadjusted edgewise appliances.
abstract: BACKGROUND
  The aim of this study was to compare the efficiency of mandibular arch alignment in 3 dimensions with a self-ligating bracket system (SmartClip, 3M Unitek, Monrovia, Calif) and a conventional preadjusted edgewise twin bracket (Victory, 3M Unitek) in nonextraction patients. This was a prospective, randomized, controlled clinical trial at the Royal London Hospital, School of Dentistry, and Kent and Canterbury Hospital, United Kingdom. Sixty-six consecutive patients satisfying the inclusion criteria were enrolled in the study. They were randomly allocated with a computer-generated system to 1 of the 2 bracket systems.
  
  
  METHODS
  Pretreatment mandibular arch irregularity was measured by using a coordinate measuring machine (Merlin II, International Metrology Systems, Gloucester, United Kingdom). A 0.016-in round martensitic active nickel-titanium aligning archwire (3M Unitek) was placed in all subjects. Mandibular arch irregularity was remeasured 8 weeks later.
  
  
  RESULTS
  Sixty-five subjects completed the study. Bracket type had little influence on alignment efficiency overall (P = 0.08), or in the buccal (P = 0.173) or labial segments (P = 0.528) after adjustment for pretreatment differences by analysis of covariance (ANCOVA). Alignment efficiency was highly correlated to pretreatment irregularity overall (P <0.001), both in the buccal (P = 0.001) and labial (P <0.001) segments. Increasing age appeared to have a negative effect on alleviation of irregularity, although this effect did not reach statistical significance (P = 0.053).
  
  
  CONCLUSIONS
  The null hypothesis that efficiency of alignment in the mandibular arch in nonextraction patients is independent of bracket type was accepted. Alignment efficiency is largely influenced by initial irregularity.
authors.affiliation: Orthodontic Department, Royal London Hospital, London, United Kingdom. padhraigfleming@hotmail.com
authors.forename: Padhraig S
authors.initials: PS
authors.lastname: Fleming
authors.forename: Andrew T
authors.initials: AT
authors.lastname: DiBiase
authors.forename: Grammati
authors.initials: G
authors.lastname: Sarri
authors.forename: Robert T
authors.initials: RT
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D002648:Child; D003724:Dental Arch / Q000503:physiopathology*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000628:therapy*; D008334:Mandible; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009971:Orthodontics, Corrective / Q000295:instrumentation*; D011446:Prospective Studies; D016896:Treatment Outcome; D055815:Young Adult