ABSTRACT
[Abstract] Objective To investigate the cant of the occlusal planes in Chinese adult class Ⅱ malocclusions with hypodivergent, normodivergent, and hyperdivergent facial vertical patterns using cone-beam CT. Methods The descriptive, cross-sectional study evaluated 123 cephalogram from CBCT(CCB) of patients in Department of Orthodontics, the Affiliated Hospital of Qingdao University. According to cephalometric analysis, 89 Chinese adult class Ⅱ patients were divided into three groups according to the angle between FH-MP and the angle between SN-MP. In comparison, 34 Class I normodivergent malocclusions individuals were selected as the control group. Comparing the cephalometric result between 4 groups. Results As expected,the hyperdivergent group had steeper anterior occlusal planes(14. 73±3. 76) . and posterior occlusal planes(21. 42±5. 77)., there was a significant statistical difference between the hyperdivergent group and other 2 groups in class Ⅱ patients (P<0. 05). The height of maxillary second molar increased from high angle group to low angle group (P<0. 01). Conclusion There are different characters of the occlusal planes in varied vertical facial pattern. The inclinations of anterior and posterior occlusal planes in Chinese class Ⅱ hyperdivergent group were steeper than other 3 groups. The difference of posterior occlusal plane inclination is mainly caused by the height of maxillary second molar.
ABSTRACT
BACKGROUND: A review of previous epidemiological investigations shows that the detection rate of malocclusion is the highest in Angle I, but the classification is limited by the failure to consider the comprehensive mechanism of the formation of malocclusion in the three-dimensional direction of the length, width and height of teeth, jaws and facial structures, and the profound impact of the position of the mandible and facial bones on a person’s appearance. Therefore, the morphological characteristics of the mandible and chin should be fully considered before orthodontic treatment. OBJECTIVE: To compare the similarities and differences of the three-dimensional facial morphology in adult females with different vertical skeletal types of skeletal Class I by measuring the three-dimensional morphology of the chins and mandibles through cone-beam CT multi-planar reconstruction. METHODS: According to SN-MP angle, the cone-beam CT images of 86 females with skeletal Class I aged from 18 to 35 years were imported into MIMCS19.0 to make multi-planar reconstruction, and then the data was divided into three groups: 39° (high angle group, 26 cases). Then, the mandibular linear distance and angle were measured, and the mandibular outline was measured through the three-dimensional reconstruction. RESULTS AND CONCLUSION: With the increase of mandibular plane angle, the morphology of mandible tended to be: (1) the mandible ascending ramus became shorter, and the mandible body grew; (2) the notch of mandibular angle deepened gradually, and the opening of the mandibular angle increased gradually relative to the cranial-jaw; (3) the alveolar process of the chin became longer and the shape of chin became gentle; (4) counterclockwise rotation of the chin and compensatory inclination of lower anterior teeth towards tongue occurred. Comparing different vertical skeletal types of skeletal Class I in adult females, both the morphologies of the mandible and chin are different, and the mandibular plane angle is related to the morphology of the mandible and chin.
ABSTRACT
Objective To study the differences in the inclination of lower incisors among the female patients with beautiful profiles in different vertical skeletal types so as to provide the clinical treatment design for a certain guiding. Methods 137 cephalometric films of female patients with beautiful profiles were selected and divided into three groups based on the vertical facial types(∠SNMP):small degree(n = 31),average degree(n = 89) and larger degree groups(n=17). The angles of∠L1/MP and∠L1/A-Pog were measured and treated with covari-ance analysis for detecting the differences between the groups. Results The index of L1-MP(°)was the smallest in the larger degree group,the largest in the small degree group and average in the average group,with significant differences between the three groups(F = 17.38,P 0.05). Conclusion Lower incisors have compensatory inclined lingually in the group of higher mandible angle,but labially in the group of lower mandible angle.