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Updated: Jul 11, 2026

Midface Hypoplasia and Cranial Base Morphology in Syndromic Craniosynostosis: A Comparative Analysis Study Using a Predictive Regression Model
Published on: November 4, 2025
Correlations of frontal lip-line canting with craniofacial morphology and muscular activity
Jin-Hyoung Cho1, Eun-Jung Kim, Byeong-Chae Kim
1Department of Orthodontics, School of Dentistry, Chonnam National University, Gwangju, Korea.
Introduction:
The purpose of this study was to investigate factors affecting lip-line canting by using musculoskeletal analyses.
Methods:
Fifty-six adults with lip-line canting were selected as subjects. They were divided into 3 groups according to the changes of lip line during smiling: increasing (group I), decreasing (group D), and minimal (group M). Lip-line canting at rest was correlated to craniofacial morphology and muscular activity: Regarding craniofacial morphology, various craniofacial measurements in lateral and frontal cephalograms were used, including inclination of the tongue blade placed across both first molars. The zygomaticus major was the focus of the measurement of muscular activity affecting lip-line canting, and its activity during smiling was evaluated by using a needle electrode.
Results:
In group I, lip-line canting at rest showed a significant correlation with the right-left (R/L) difference of muscular activity, but no significant correlation with the measurements of craniofacial morphology. In group D, lip-line canting showed a positive correlation with the measurements of craniofacial morphology, such as the inclination of the tongue blade, and a negative correlation with the R/L difference of muscular activity. In group M, lip-line canting showed no significant correlation with the R/L difference of muscular activity, but a significant correlation with inclination of the tongue blade.
Conclusions:
The results indicate that lip-line canting is caused by craniofacial morphology when the change of lip-line canting during smiling is minimal, whereas lip-line canting is affected by the R/L difference of muscular activity in addition to craniofacial morphology when the cant of lip line markedly changes during smiling. The findings suggest that the cause of lip-line canting can be identified easily by the change of canting during smiling, without complicated musculoskeletal analyses.
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