title: Morphospatial analysis of soft-tissue profile in patients with Class II Division 1 malocclusion treated using twin block appliances: geometric morphometrics.
abstract: OBJECTIVE
  To study soft-tissue profile changes in patients treated with twin block appliances (TBA) for the correction of Class II division 1 malocclusion. The null hypothesis is that soft-tissue profiles do not show any significant improvements associated with TBA treatment.
  
  
  METHODS
  Longitudinal, retrospective.
  
  
  METHODS
  Scotland, UK, using lateral cephalographs of 46 consecutive, prepubertal children (aged 9-11 years) and 55 adolescents (aged 12-14 years) obtained from an orthodontic practice.
  
  
  METHODS
  The prepubertal children underwent = 13 months of TBA treatment, while the adolescents underwent = 22 months of treatment.
  
  
  METHODS
  Configurations of 13 digitized homologous landmarks of pre- and post-treatment soft-tissue facial profiles were compared using cephalometry, Euclidean distance matrix analysis (EDMA) and thin plate spline (TPS) analysis.
  
  
  RESULTS
  Cephalometry showed that height increases associated with the TBA were in the labiomental areas, and the most significant height decreases were seen in the lip regions. The results of EDMA also indicated significant changes (P < 0.05). The distance between the lips decreased by >5%, with increases in length in the labiomental region. The TPS analysis showed the soft-tissues of the mandibular complex being displaced anteroinferiorly, with anterior displacement of the landmarks of the lip region. These changes showed that the lips were brought into closer proximity with each other, permitting a functional oral seal. Moreover, the labiomental groove became less pronounced, reflecting the underlying dento-alveolar correction.
  
  
  CONCLUSIONS
  Demonstrable improvements in soft-tissue facial profile may be associated with TBA treatment.
authors.affiliation: School of Medicine, University of Puerto Rico, San Juan 00936-5067, USA. gsingh@rcm.upr.edu
authors.forename: G D
authors.initials: GD
authors.lastname: Singh
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D002508:Cephalometry; D002648:Child; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008046:Lip / Q000033:anatomy & histology; D008137:Longitudinal Studies; D008297:Male; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008954:Models, Biological; D015999:Multivariate Analysis; D017289:Orthodontic Appliances, Functional; D009971:Orthodontics, Corrective / Q000295:instrumentation*; D010780:Photogrammetry; D012189:Retrospective Studies; D018709:Statistics, Nonparametric