A Longitudinal Study Of Mandible Growth Of Angle Class â…¡ Division 2 Malocclusions

Objective:The purpose of this study was to determine the longitudinal growth changes of mandible including the change in mandibular plane angle ,the chin size and the mandibular length from mixed dentition to permanent dentition in Angle Classâ…¡Division 2 malocclusions and normal occlusion using cephalometric analysis. Knowledge of growth and development of the mandible in Angle Classâ…¡Division 2 malocclusions will help the clinician to implement the correct treatment plan in these patients.Methods:3000 students from 3 primary and 3 secondary schools in Chongqing city were randomly selected for this study.The sample consisted of 95 students with Angle Classâ…¡Division 2 malocclusion and 75 students with normal occlusion. Cephalometric radiographs and hand-wrist radiographs were obtained for all the samples. Analysis of the hand-wrist radiographs confirmed that all the selected patients were in the prepubertal or within the pubertal growth spurt period. The author used the Winceph 8.0 software to locate all the cephalometric points.And analysis of all the cephalograms were carried out. The change in mandibular plane angle ,the chin size and the mandibular length from mixed dentition to permanent dentition in Angle Classâ…¡Division 2 malocclusions were evaluated.Results: In the Angle Classâ…¡Division 2 patients, the skeletal mandibular changes are more apparent in the permanent dentition than in the mixed dentition.The study on growth changes of mandible from mixed dentition to permanent dentition on Angle Classâ…¡Division 2 Malocclusions showed that:1) The mandible does not rotate upwards and forwards ,there is no change in the angle SN-MP . The S point seems to move forward relative to the mandible.And there is an increase in Y-axis2) In the mixed dentition, the chin growth occurs at an earlier stage in the Classâ…¡Division 2 malocclusions than in the normal occlusion .But in the permanent dentition ,the growth continues at the same rate in both Classâ…¡Division 2 malocclusions and normal occlusion. The chin is placed more posteriorly in Class II division 2 as compared to normal occlusion.3)Increase in the total mandibular length, mandibular base length, ramus height and length S-Go is much larger in normal occlusion than in Angle Classâ…¡Division 2 malocclusions.Conclusion: This study demonstrated that Class II division 2 patients showed a characteristic mandibular growth from mixed dentition to permanent dentition when compared with normal occlusion patients. The present finding will help the clinicians to come to a diagnosis and reasonable treatment plan in Classâ…¡Division 2 patients.