The Tooth-alveolar Bone Complex Morphology Of The Maxillary Posterior Region Of Adult Patients With Different Skeletal Patterns By CBCT

Objectives: To evaluate the tooth-alveolar bone complex morphology of the maxillary posterior region of Chinese adult patients with different skeletal patterns by CBCT,and to analyze whether the vertical facial type or Sagittal facial type have connection with the alveolar bone morphology of the maxillary posterior region.Methods: 1.the sample consisted of 84 adult patients with skeletal class II who visited Affiliated Stomatological Hospital of Nanjing Medical University from 2015 to 2018.According to the size of the mandibular plane-anterior skull base plane angle(SN-MP),it is divided into three groups: hypodivergent group: SN-MP <29 °;normodivergent group: SN-MP29 °-40 °;hyperdivergent group: SN-MP > 40 °.The buccolingual inclination of the first and second molars,the thickness and inclination of the alveolar bone,the width of the basal arch,the width of the dental arch,the height of the alveolar bone,the height of molar and the sagittal length of alveolar in the maxillary posterior alveolar region were measured.2.The sample consisted of 81 adult patients with different sagittal skeletal pattern and normal angle of mandibular plane-anterior skull base plane who visited Affiliated Stomatological Hospital of Nanjing Medical University from 2015 to 2018.It is divided into three groups:skeletal class III: ANB<0°;skeletal class I: 0°<ANB<5°;skeletal class II: ANB>5°,the measurement items are the same as the first part.Results: 1.(1)In the matter of arch width among three groups,there was no difference no matter of the level of first or secong molar;the basal arch width of the first and second molars in the hyperdivergent group was narrower in the hypodivergent group;(2)To compared with hyperdivergent and normdivergent groups,the alveolar bone thickness around maxillary first molar in the hypodivergent group are thicker;(3)The inclination of the first molar in the hyperdivergent group is more buccal than that in other groups,besides the inclination of second molar is also more buccal in the hyperdivergent group than that of the hypodivergent group;the palatal alveolar bone of the first molar in the hyperdivergent group is more upright than the hypodivergent group;(4)the distance between dentino-enamel junction and alveolar bone above the maxillary second molar of the hypodivergent group is higher than that of the other groups;(5)In terms of the height from molars to palatal plane,no natter of first or secong molar,there is no different among the groups;the alveolar bone length was longer in the hypodivergent group than that of the other groups.2.(1)class II group have narrower arch width compared with class III group,the basal arch width of the first and second molars have no difference among groups;(2)the bone thickness of the palatal and distal buccal roots of first molar and distal buccal root of second molar is thicker in class I group,and the bone around palatal root of second molar is thicker in class II group;(3)the molars are more buccal in class III group;(4)the distance between dentino-enamel junction and alveolar bone above first molar of the class II group is higher than that of the other groups;(5)In terms of the alveolar bone length there is no different among the groups;the height from molars to palatal plane is smaller in calss II group in second molar level.Conclusions: 1.There was a correlation between vertical facial type and tooth-alveolar bone complex morphology in the maxillary posterior region of adult patients with skeletal class II,Patients with high angles have more narrow basal arches,the inclination of molars are more buccal,and posterior alveolar bone is narrower.Which remind us of orthodontic tooth movement limit of patient with higher mandibular plane angle.2.There was a correlation between sagittal facial type and tooth-alveolar bone complex morphology in the maxillary posterior region of adult patients with normodivergent,class III group have more wider arch and more buccal molar;class II group have narrow arch width and less vertical developmental tooth-alveolar bone complex.Due to more serious absorption of alvaloar bone,the resistance center of molar closer to root.