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
Objective To study the variation of the dental and basal arch forms before and after orthodontic treatment of patients with skeletal class Ⅱ malocclusion by tooth extraction.Methods The mandibular dental casts of 25 skeletal class Ⅱ patients were laser scanned before and after treatment.The facial axis (FA) points,which were used to represent the dental arch,and the WALA point,which were used to represent the basal bone,were identified for each tooth from the right first molar to the left first molar.We constructed the curve with points of projection of the FA and WALA point on the reference plane,and compared the curve of dental arch and basal bone before and after treatment.Results The width of anterior middle and posterior of the basal arch increased (0.835± 1.259) mm,(1.700±1.280) mm and (2.170±1.227) mm,respectively.While the dental arch had a wider width (1.110±1.566) mm in posterior segment but a narrower one in anterior (3.345±2.907) mm.Conclusions The width of middle and posterior of basal bone represented by WALA ridge becomes wider after orthodontic treatment with tooth extraction in patients with skeletal class Ⅱ malocclusion,while the dental arch turns to a new form,which is more coordinated to the basal bone.