The Study Of Incisor Position In Skeletal Class Ⅲ Patients Of Vertical Facial Types With CBCT

Objective: To verify, via CBCT, whether there are correlations among themorphology of the upper and lower jaws, the position of incisors and vertical facialtype of the skeletal class Ⅲ patients.To compare the difference between centralincisors and lateral incisors in the same facial type.Methods：The FMA angle was used to select14short face type,16normal facetype, and14long face type patients, totally44patients, aged12to18years. TheCBCT images were constructed by3D Dophin Imaging11.5. The followingparameters were measured on the sagittal sections corresponding to the4incisors:thickness of alveolar on three levels; area of the alveolar around incisor roots; heightand area of the upper and lower basal bone; and possible inclination of upper andlower basal bone, and angle between teeth axis and the reference planes, expressedin degrees. Alveolar area on three levels around incisor roots was measured on crosssections. The measurements were processed using one-way ANOVA, LSD-t test andpaired t test.Results：1. Short facial type patients presented greater SN angle of upper incisors andinclination angle of upper and lower basal bone than the long facial type patient,while it showed the opposite results of the axial plane angle of of lower incisors.2.In short facial type, distance between the apex and the palatal of upper incisorsand thickness of labial alveolar creast of upper central incisor are longer than that inthe orther two types. Thickness of palatal alveolar at the center of upper incisor rootsis the narrowest in long facial type patients.3. Contrast to normal and long facial type patients, thickness of lingual alveolarat the center and apex of lower incisor roots and thickness of labial alveolar at thecenter of lower central incisor roots are wider in short facial type patients.4. In long facial type, basal bone height of upper and lower incisors is greater than that in normal and short facial type.5. Short facial type patients had greater values than that in norm and long facialtype patients in these parameters: area of basal bone and area around root at S1, S2,S3levels of upper incisors; area of palatal and the total alveolar in upper lateralincisor.6. Area of basal bone and area of root surrounding at S1, S2levels of lowerincisors in short facial type patients is greater than that in normal and long facial typepatients. At lower central incisor, short facial type patients showed greater area ofpalatal and the total alveolar than long facial type patients.7. In the same facial type, compared with upper lateral incisor, the upper centralincisor showed bigger values of measurment: measured values of area; thickness ofpalatal alveolar at the center of root; distance between apex and palatal; and distancebetween apex and labial.Conclusion:1. Incisor position were significant difference among vertical facial types ofskeletal class Ⅲ patients.2. Incisors inclination in the short facial type group was greater than that in thelong facial type, demonstrated that incisors were labially inclined in the short facialtype group and uprightly in the long facial type.3. Alveolar thickness in the short facial type group was wider than that in thenormar facial type in which alveolar thickness was greater than that in the long facialtype. Basal bone height of upper and lower incisors in the long facial type group wasgreater than that in the other two facial types.4. The short facial type showed the highest maxillary bone area, and the normalfacial type displayed the least mandibular bone area.5. In the same facial type, alveolar of upper central incisor was more than thataround upper lateral incisor.