A Comparison And Correlation Study Between Soft And Hard Tissues Changes In Adult And Adolescent Angle ClassⅡ～1 Malocclusion After Treatment With Tooth Extraction

Objective The purpose of this study was to compare the changes of soft and hard tissues and analyze the correlation of them in adult and adolescent Angle Class â…¡1 malocclusion after orthodontics treatment with tooth extraction. Method 42 patients (20 adults and 22 adolescents) with Angle Class â…¡1 malocclusion were selected according to some standards. They all were treated with first premolar extraction technique, and some needed class â…¡1 elastics and facebow headgear. Lateral cephalometric radiographs were used to quantify the skeletal, dental and soft tissue changes before and after treatment. All data were analyzed by SPSS 12.0 software. Results (1)Anteroposteriorly, the length of mandible had been increased and point B and Po had moved forward obviously in adolescent group, but no change was found in adult group. Vertically, there was a downwards displacement of skeletal chin and an obvious increase of the anterior lower facial height in the two groups, but the ratio of posterior to anterior facial height ha d increased in adolescent group while decreased in adult group.(2) Great dental changes were observed in the two groups: upper and lower incisors were all retracted effectively, and the anterior overjet was improved significantly. But compared to adolescent group, the upper incisors of adult group were so excessively backward retracted that they appeared to be some over upright.(3) The soft tissues of two groups were all improved effectively,but there was great difference between the two groups: an effective decrease in soft tissue profile convexity was observed in adolescent group, however no change was found in adult group; The upper and lower labrales were retracted more obviously and nasolabial angle increased more dramatically in adult group than that in adolescent group; The thickness of upper labrale and indentation of lower lip and the length of lower lip had a dramatic increase in the two groups, but the thickness of indentation of upper lip of adolescent group increased while that of adult group decreased. (4) There was a significant correlation between the variables changes of soft facial style and that of the corresponding maxilla in adolescent group, such as between N'-Sn-Po' and N-A-Po, B'-VRL and B-VRL et al.And there were also obviously correlation between variables of soft lip form and the corresponding hard (mainly dental) tissue variables in two groups, but the correlations were very different between the two groups. Conclusions (1) In adolescent group's orthodontics treatment with tooth extraction, by the teeth movement and some skeletal changes, the soft facial style and lip form are improved significantly; But in adult group, by the teeth movement and compensation, the soft lip form is improved effectively without obvious skeletal and soft facial style changes.(2) Orthodontic treatment can improve the soft profile, but it has a limit. To Angle Class II ' malocclusion patient, the upper incisor should not be so excessively retracted that the upper lip appears to be over upright.(3) There are significant correlations between the soft and hard, soft and soft tissue variables changes, but they are very different between the two groups.