title: The predictability of dentoskeletal factors for soft-tissue chin strain during lip closure.
abstract: OBJECTIVE
  To investigate the dentoskeletal factors which may predict soft-tissue chin strain during lip closure.
  
  
  METHODS
  The pretreatment frontal and lateral facial photographs and lateral cephalograms of 209 women (aged 18-30 years) with Angle's Class I or II malocclusion were examined. The subjects were categorized by three examiners into the no-strain and strain groups according to the soft-tissue chin tension or deformation during lip closure. Relationships of the cephalometric measurements with the group classification were analyzed by logistic regression analysis, and a classification and regression tree (CART) model was used to define the predictive variables for the group classification.
  
  
  RESULTS
  The lower the value of the overbite depth indicator (ODI) and the higher the values of upper incisor to Nasion-Pogonion (U1-NPog, mm), overjet, and upper incisor to upper lip (U1-upper lip, mm), the more likely was the subject to be classified into the strain group. The CART showed that U1-NPog was the most prominent predictor of soft-tissue chin strain (cut-off value of 14.2 mm), followed by overjet.
  
  
  CONCLUSIONS
  To minimize strain of the soft-tissue chin, orthodontic treatment should be oriented toward increasing the ODI value while decreasing the U1-NPog, overjet, and U1 upper lip values.
authors.affiliation: Department of Orthodontics, Graduate School of Clinical Dentistry, Korea University, Seoul, Korea.
authors.forename: Yun-Hee
authors.initials: YH
authors.lastname: Yu
authors.affiliation: Department of Orthodontics, Graduate School of Clinical Dentistry, Korea University, Seoul, Korea.
authors.forename: Yae-Jin
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Orthodontics, Graduate School of Clinical Dentistry, Korea University, Seoul, Korea.
authors.forename: Dong-Yul
authors.initials: DY
authors.lastname: Lee
authors.affiliation: Department of Orthodontics, Graduate School of Clinical Dentistry, Korea University, Seoul, Korea.
authors.forename: Yong-Kyu
authors.initials: YK
authors.lastname: Lim
keywords: Classification and regression tree; Mentalis; Soft-tissue chin