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The predictability of dentoskeletal factors for soft-tissue chin strain during lip closure
Yun-Hee Yu1, Yae-Jin Kim1, Dong-Yul Lee1
1Department of Orthodontics, Graduate School of Clinical Dentistry, Korea University, Seoul, Korea.
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.
