3D Analysis Of Morphology Characteristic Of Mandibular In High Angle Adult With Different Sagittal Skeletal Pattern And Different Gender By CBCT

Objective:This study was designed to compare the three dimensional differences of the height and width of mandibular cross—sections and the thickness of cortical bone among young adult high angle patients with different sagittal facial pattern and compare the difference between male and female. The study was investigated the correlations between the morphology of mandibular and the maxillofacial structures. Methods:1.This study selected 73 high angle adults(Age:18-30y) whose Me Go(L)-SN angle>37.7° in stomatological hospital affiliated to Nan Chang University from June 2011 to October 2014. The three-dimensional Cone Beam Computed Tomography(CBCT) images of every patient were taken in radiology department under the same condition in our hospital. All of them were divided into three groups of skeletal facial type based on their ANB angles.Of these subjects, 27(12 males and 15 females)were included in the classⅠgroup(0.7o≤ANB≤4.7o),25(10 males and 15 females) in the classⅡgroup(ANB>4.7o), and 21(10 males and 11 females) in the classⅢ group(ANB<0.7o).2.Using the Invivo Dental 5.1 software for reconstructing the CBCT image of each patient, adjusting the middle saggital plane and axial plane in coronal, sagittal and axis view. Cross-sectional slices of the mandible were developed with the cone-beam scans to evaluate the cortical bone between the dentition at 13 locations. Each section was then measured at 8 sites, which included 1 height and 2 width measures of the cross-sectional area and 5 cortical plate thicknesses.3. All the data were analyzed by the means of SPSS 19.0. The One-way analysis of variance was performed among the different sagittal skeletal pattern groups.Independent sample T-test was used to compare the differences of gender. Results:1.All the 3 groups’ height of the cross-sectional area of the mandible decreased from the mandibular symphysis to the posterior segments. But there are no statistically significant differences among the 3 groups.2.All the 3 groups’ upper one third width of the cross-sectional area of the mandible(w1) increased from the mandibular symphysis to the posterior segments, but there are no statistically significant differences among the 3 groups.All the 3 groups’ lower one third width of the cross-sectional area of the mandible(w2) decreased from the mandibular symphysis to the lateral incisor segments,and increased gradually to the first molar segments then decreased in the second molar segments,but there are no statistically significant differences among the 3 groups.3.All the 3 groups’ upper one third thickness of the mandibular lingual cortical bone(a) increased from the mandibular symphysis to the first premolar segment,and decreased to the posterior segments;all the 3 groups’ upper one third thickness of the mandibular buccal cortical bone(b)increased from the mandibular symphysis to the first molar segments,and decreased to the second molar;all the 3 groups’ lower one third thickness of the mandibular lingual cortical bone(c) decreased from the mandibular symphysis to the posterior segments;all the 3 groups’;all the 3 groups’ upper one third thickness of the mandibular buccal cortical bone(d) was thinnest in the lateral incisor,and increased gradually to the posterior segments;all the 3 groups’ thickness of the base of the cortical bone(e) increased from the mandibular symphysis to the cranial segment,and decreased from the cranial segment to the posterior segments.But there are no statistically significant differences among the 3 groups.4.Males vs females1)The height of the mandibular cross-section was greater in the male at almost all the 13 sites of measurement around the mandibular arch statistically significant.2) The upper one third width of the cross-sectional area of the mandible(w1) was greater in male,the differences are statistically significant in left cranial segment(p<0.05).3)The upper one third thickness of the mandibular buccal cortical bone(b) was greater in male,the differences are statistically significant in mandibular symphysis and right second molar segment(p<0.05).4)The lower one third thickness of the mandibular buccal cortical bone(d) was greater in male,the differences are statistically significant in mandibular symphysis,both lateral incisor segments,right cranial segment and both second molar segments.5.In the class III group the upper one third thickness of the mandibular buccal cortical bone(b) was thicker in male, the differences are statistically significant in mandibular symphysis and biolocranial segments. Conclusion:1.There is no significant difference in the height and width of mandibular cross—sections and the thickness of cortical bone among young adult high angle patients with different sagittal facial pattern.2.The height of mandibule among young adult high angle patients was greater in the male.3.The width of mandibular cross—sections and the thickness of cortical bone among young adult high angle patients was greater in the male,but statistically significant differences were evident is some sites.