Comparison of the three-dimensional structures of mandibular condyles between adults with and without facial asymmetry: A retrospective study / 대한치과교정학회지

OBJECTIVE: This retrospective study compared the three-dimensional (3D) structure of mandibular condyles between adults with and without facial asymmetry, and whether it influences menton deviation. METHODS: Sixty adult patients were classified into symmetry and asymmetry groups based on the menton deviation on postero-anterior radiographs. The right/left differences of 3D measurements were compared between the two groups, and measurements were compared separately on the right and left sides. The correlations between menton deviation and the right/left differences were analyzed. RESULTS: The mediolateral dimension, neck length, condylar angles to the anteroposterior reference (PO) and midsagittal reference planes, and neck and head volumes showed significantly larger right/left differences in the asymmetry group compared to the symmetry group. Separate comparisons of the right and left sides between the two groups showed that the neck was significantly shorter and neck and head volumes were significantly smaller on the left side, which was deviated side in the asymmetry group. Pearson's correlation analysis showed significant positive correlations of menton deviation with right/left differences in neck length, condylar angle to the PO plane, and neck and head volumes in the asymmetry group. CONCLUSIONS: In individuals with facial asymmetry, menton deviation is associated with the right/left differences caused by a smaller condyle on the deviated side, particularly in neck length and neck and head volumes.

The influence of age on lip-line cant in adults: a cross-sectional study / 대한치과교정학회지

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° 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.

The relationship between condyle position, morphology and chin deviation in skeletal Class III patients with facial asymmetry using cone-beam CT / 대한치과교정학회지

OBJECTIVE: Facial asymmetry is usually evaluated from the difference in length and angulation of the maxilla and mandible. However, asymmetric position or shape of the condyle can also affect the expression of asymmetry. The purpose of this study was to evaluate the correlation between condylar asymmetry and chin point deviation in facial asymmetry. METHODS: Cone-beam CT images of fifty adult skeletal Class III patients were studied. Thirty patients who had more than 4 mm menton deviation were categorized in the asymmetric group. Twenty patients with less than 4 mm menton deviation were assigned to the symmetric group. Anteroposterior and transverse condyle positions were evaluated from the cranial base. The greatest mediolateral diameter (GMD) of the condyle in the axial plane and angulation to the coronal plane were measured. The height and volume of the condyles were evaluated. RESULTS: The symmetric group had no statistical difference between both condyles in position, angulation, GMD, height and volume. In the asymmetric group, the non-deviated side condyle was larger in GMD, height and volume than the deviated side. There was no statistical difference in condyle position and angulation. The GMD, height difference and condylar volume ratio (non-deviated/deviated) were positively correlated with chin deviation. From the linear regression analysis, condylar volume ratio was a significant factor affecting chin deviation. CONCLUSIONS: These findings suggests that the non-deviated side condyle is larger than the deviated side. In addition, condylar asymmetry can affect the expression of facial asymmetry.

Correlation between menton deviation and dental compensation in facial asymmetry using cone-beam CT / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the correlation between menton deviation and dental compensation in facial asymmetry. METHODS: Tooth axis and distance of first molar and canine to the reference plane were investigated by cone-beam computerized tomography. The subjects consisted of 50 patients with asymmetric mandibles (male 21, female 29, mean age 24.3 years). Control groups were also assessed (male 11, female 9, mean age 25.6 years). Nine measurements (5 linear measurements and 4 angular measurements) were measured in order to evaluate the correlation between menton deviation and the linear and angular difference of first molar and canine in the deviated and none-deviated sides using the defined MPR images. The differences between deviated and non-deviated side, according to menton deviation, were statistically analyzed using stepwise multiple regression analysis. RESULTS: From the result, Menton deviation was negatively correlated with mandibular first molar's angular measurement (Delta Angle LM6-Mn plane (dev.-ndev.)) and positively with maxillary fist molar's angular measurement (Delta Angle UM6-FH plane (dev.-ndev.)) (p<0.01). Two angular measurements (Delta Angle LM6-Mn plane (dev.-ndev.), Delta Angle UM6-FH plane (dev.-ndev.)) explained the variability in menton deviation with a significant r2 value of 0.589. CONCLUSIONS: This study suggests that the tooth axis of upper and lower first molars leans towards the deviated side of Menton when there is mandibular asymmetry with Menton deviation.

Posteroanterior cephalometric study of frontal ramal inclination in chin-deviated individuals / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to compare the right and left differences of frontal ramal inclination in chin-deviated individuals. METHODS: Thirty adult patients with clinically apparent chin deviation were selected as the chin-deviated group, and 30 adult patients with symmetric faces were selected as the control group. On the posteroanterior cephalograms, the frontal ramal inclination was measured, and the right and left differences were compared and analyzed. RESULTS: While the control group did not show right and left differences of frontal ramal inclinations, the chin-deviated individuals showed right and left differences of frontal ramal inclination. In chin-deviated individuals, the frontal ramal inclinations of the non-deviated side were statistically greater than those of the deviated side. The right and left differences of frontal ramal inclinations, with menton deviation and the right and left differences of maxillary heights showed statistically significant correlation. CONCLUSION: We conclude that the frontal ramal inclinations should be considered in the diagnosis of facial asymmetry.