• The korean journal of orthodontics
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• v.46 no.2
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• pp.81-86
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• 2016

Objective: The aims of this study were to assess the direction and degree of lip-line cant in Korean adult orthodontic patients and to identify the effects of sex and age on changes in the cant severity. Methods: In this cross-sectional retrospective study, lip-line cant was measured in the frontal photographs of 585 Korean patients (92 men and 493 women) aged 18-48 years. The outcome variables (direction and degree of lip-line cant) were assessed in terms of predictor variables (sex, age, sagittal skeletal relationship, and menton deviation angle). Results: The direction of lip-line cant did not differ according to sex, age, or skeletal classification. Patients had $1.6^{\circ}$ of lip-line cant on average before orthodontic treatment. Middle-aged adults displayed a significant trend toward a lower degree of lip-line cant compared to younger adults (p < 0.01). Multiple linear regression analysis showed that the degree of lip-line cant was weakly negatively correlated with age (p < 0.001). Conclusions: While the direction of lip-line cant did not differ according to the parameters explored here, the degree of cant was correlated with age in adults, independent of menton deviation. Specifically, middle-aged adults tended to display significantly lower degrees of lip-line cant than did younger adults.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.18.1-18.9
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• 2016

Background: The aim of this study was to examine the relationship between improvements in lip asymmetry at rest and while smiling after orthognathic surgery in patients with skeletal class III malocclusion. Methods: This study included 21 patients with skeletal class III malocclusion and facial asymmetry. We used preoperative and postoperative CT data and photographs to measure the vertical distance of the lips when smiling. The photographs were calibrated based on these distances and the CT image. We compared preoperative and postoperative results with the t test and correlations between measurements at rest and when smiling by regression analyses. Results: There were significant correlations between the postoperative changes in canting of the mouth corners at rest, canting of the canines, canting of the first molars, the slope of the line connecting the canines, and the slope of the line connecting first molars. The magnitude of the postoperative lip line improvement while smiling was not significantly correlated with changes in the canting and slopes of the canines, molars, and lip lines at rest. Conclusions: It remains difficult to predict lip line changes while smiling compared with at rest after orthognathic surgery in patients with mandibular prognathism, accompanied by facial asymmetry.

• The korean journal of orthodontics
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• v.53 no.3
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• pp.163-174
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• 2023

Objective: This study evaluated the influence of various gingival displays on the esthetic perception in the presence of upper dental midline discrepancy. Methods: A smiling image of a male subject was altered digitally to produce five image series: normal smile (series A), decreased tooth show (series B), increased gingival show (series C), maxillary cant (series D), and asymmetric upper lip elevation (series E). In each image series, the midline was deviated to the right and left incrementally. A total of 210 raters (four professional groups and laypersons, n = 42 in each group) determined the midline deviation threshold and the attractiveness of midline position in each series. Results: The right and left thresholds were statistically similar for the symmetrical series (A, B, and C), while for series D, the right threshold was significantly lower. In most rater groups, the mean threshold order was: B > A > E > C > D. In all the series, the raters selected the coincident midline as the most attractive series except for series D, for which 1-2-mm deviations to the left were selected as the most attractive by almost all the groups. Conclusions: It is crucial to establish the coincident midline position in a symmetrical smile, especially when a gummy smile exists. In the asymmetrical gingival show, a coincident midline might not be the most esthetic midline position.

• The korean journal of orthodontics
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• v.53 no.6
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• pp.402-419
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• 2023

Objective: This study assessed the differences in soft tissue deviations of the nose, lips, and chin between different mandibular asymmetry types in Class III patients. Methods: Cone-beam computed tomography data from 90 Class III patients with moderate-to-severe facial asymmetry were investigated. The sample was divided into three groups based on the extent of mandibular rolling, yawing, and translation. Soft tissue landmarks on the nose, lips, and chin were investigated vertically, transversely, and anteroposteriorly. A paired t test was performed to compare variables between the deviated (Dv) and nondeviated (NDv) sides, and one-way analysis of variance with Tukey's post-hoc test was performed for intergroup comparisons. Pearson's correlation coefficient was calculated to assess the relationship between the soft and hard tissue deviations. Results: The roll-dominant group showed significantly greater differences in the vertical positions of the soft tissue landmarks between the Dv and NDv than other groups (P < 0.05), whereas the yaw-dominant group exhibited larger differences in the transverse and anteroposterior directions (P < 0.05). Moreover, transverse lip cant was correlated with the menton (Me) deviation and mandibular rolling in the roll-dominant group (P < 0.001); the angulation of the nasal bridge or philtrum was correlated with the Me deviation and mandibular yawing in the yaw-dominant group (P < 0.01). Conclusions: The three-dimensional deviations of facial soft tissue differed based on the mandibular asymmetry types in Class III patients with similar amounts of Me deviation. A precise understanding of soft tissue deviation in each asymmetry type would help achieve satisfactory facial esthetics.