A Comparative Study On Different Sagittal Craniofical Patterns Characteristics In Skeletal Class Ⅲ Malocclusion

Objectives: To study the characteristics of different sagittal craniofacial skeletal Class Ⅲmalocclusions during the pre-peak period of growth and development.Method: Selecting patients with skeletal Class Ⅲ mean angle malocclusion in the Department of Orthodontics,the Affiliated Hospital of Xinjiang Medical University from January 2012 to November 2020,and selected eligible study subjects based on inclusion/exclusion criteria70 cases,which including three groups,group one is symbol of the mandibular normal with maxillary hypoplasia,group two is symbol of maxillary normal with mandibular hyperplasia,group three is symbol of the maxillary hypoplasia accompanied by mandibular hyperplasia.The lateral cephalometric X ray film of the subjects were measured and statistical analysis was performed with SPSS17.0.Results: Among the three groups,there were statistically significant differences in the vertical bony indexes of the saddle angle,articular angle,the mandibular plane angle,triangle sum,face-to-height ratio,posterior-to-front height ratio,Y-axis angle and cant of occlusal plane(P<0.05);among them,the values of the saddle angle satisfy group 2 < group 3 < group 1,the values of the mandibular plane angle 、triangle sum and Y-axis angle satisfy group 3 <group 2 < group 1,the values of articular angle satisfy group 1 < group 3 < group2.In the comparison of vertical soft tissue indexes between the three groups,there were statistical differences in UL-E and LL-E(P<0.05);among them,UL-E was lower than the normal value while LL-E was greater than the normal value,but the values of both UL-E and LL-E satisfy group 1 > group 2 > group 3.There were statistical differences in the dental indexes of U1-SN,Mx6-PTV and Md6-PTV(P<0.05);among them,the values of U1-SN greater than the normal value,the values of Mx6-PTV and Md6-PTV less than the normal value.the values of U1-SN,Mx6-PTV and Md6-PTV satisfy group 1 < group 2 < group 3.In the comparison between male and female,there were significant differences in articular angle,cant of occlusal plane and LL-E in group 1(P<0.05).There were significant differences in ANS-Me,face-to-height ratio and L1-MP in group 2(P<0.05).There were statistical differences in mandibular plane angle,triangle sum,N-ANS,ANS-Me,N-Me and the cant of occlusal plane in group 3(P<0.05).There were no statistical differences in other indicators(P>0.05).Conclusion: Different sagittal craniofacial types of normal-angle skeletal Class Ⅲ malocclusion in early peak period have varying degrees.In terms of growth direction: when mandibular normal with maxillary hypoplasia,mandibular tends to rotate clockwise,when maxillary normal with mandibular hyperplasia,mandibular tends to rotate counterclockwise,when maxillary hypoplasia accompanied by mandibular hyperplasia,mandibular overall performance for the trend of counterclockwise and the trend of counterclockwise is larger than other groups;In terms of growth,the mandibular protrusion showed not only sagittal growth but also vertical growth.In terms of compensation: there is compensation in soft tissues and teeth,and the characteristics of compensation are different.In terms of Gender: male than female characteristics performance more obvious,but the compensatory characteristics is not obvious or compensatory time may start late.