| Objective:Analyze morphological characteristics of mandible and chin parts with different vertical bone types and the correlation of morphological characteristics of mandible and chin parts with different vertical bone profiles of adult women with skeletal class I by cone-beam CT,to provide a reference for the clinical diagnosis and correction of orthodontics in patients with different vertical bone types.Methods:86 patients with skeletal class I were selected as subject and grouped according to the SN-GoGn angle(SN plane-mandibular plane angle),including the low-angle group:SN-GoGn≤29°(30 cases),average angle group:29<SN-GoGn≤39°(30 cases),high-angle group:SN-GoGn>39°(26 cases).After importing DICOM data into Invivo 5.2 software,a total of 22 marking points were marked on the cranial jaws,and 42 indexes including line spacing and angle were measured.The spss25.0 statistical software was used to statistical analysis of experimental data.Results:1.After comparison between the two groups,it was found that the mandibular plane angle between the SN plane and FH plane of bone type Ⅰand mandibular plane was statistically significant in the high angle group,the average angle group,and the low angle group(P<0.001),the difference between the angle between the SN plane and the FH plane in different vertical bone type was statistically significant(P<0.05).2.The length of the mandibular branch in the high-angle group was less than that in the low-angle group;the length of the mandibular body,the ratio of the mandibular body to the body,∠Go-Pog-Go’,∠Go-N-Go’,∠Go-S-Go’,∠Co-Go-Me were greater than the low-angle group,the difference was statistically significant(P<0.05).3.The Co-Go of the average-angle group was smaller than that of the low-angle group,and the length of the mandible body,mandibular body-to-body ratio,Go-S-Go’,and ∠Co-Go-Me were larger than the low-angle group,and the difference was statistically significant(P<0.05).∠Co-Go-Me in the average angle group was smaller than that in the high angle group,and the difference was statistically significant(P<0.05).4.The three groups of data show that there was no statistically significant difference in the width of the posterior segment of the mandible(Go-Go’),the width of the condyle(Co-Co’),and the inclination of the mandibular branches on both sides(∠Co-Co’-Go’,∠Co’-Co-Go)between the groups(P<0.05).5.The chin thickness,ratio of chin thickness to chin height,chin angle,mandibular incisor-mandibular plane angle,and inclination of mandibular base bone in the high-angle group were all lower than those in the low-angle group,but the alveolar bone height,chin curvature,and Pog-NB were the largest among the groups,and the difference was statistically significant(P<0.05).6.The chin angle,lower central incisor-mandibular plane angle(IMPA),and mandibular base bone inclination of the average angle group were lower than those of the low-angle group,but were all higher than the high-angle group,the difference was statistically significant(P<0.05).Conclusion:As the plane angle of the mandible increases,the shape of the mandible tends to the following trend.1.The angle between the SN plane and the FH plane of patients with anterior and upper rotation of the mandible tended to decrease.2.There was no significant difference in the width of the posterior segment of the mandible in the skeletal Class Ⅰ adult female with different vertical bone face types.3.The proportion of mandibular body branch of adult females with different skeletal Class Ⅰvertical bone types were correlated with facial aesthetic evaluation.4.As the alveolar protrusion of the chin increased,the protrusion of the chin decreased.5.When the chin part rotated counterclockwise,the lower anterior teeth would compensatory tongue tilt.Adult females with different skeletal Class Ⅰ vertical bone profiles have different jaw and chin shapes.The morphology of mandible and chin was related to the mandibular plane angle. |
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