A Retrospective Study For Non-extracted Treatment Patients Using Damon Self-ligating Bracket

Objective: The aim of this study was to find out the reason why the orthodontic treatment outcome were different when we used Damon series self-ligating brackets to treat 25 straight face type patients of moderate and severe dental crowding with non-extraction,and to provide some theoretical basis for determining extraction or non-extraction clinically.Materials and methods: 25 patients were divided into two groups,that were extraction group(n=5)and non-extraction group(n=20),according to whether the anterior teeth appeared excessive labial inclination after leveling and aligning.By measuring the plaster models and cephalometric radiographs to analyze the differences among the soft tissue convexity,the labial inclination of upper and lower incisors,ANB angle,mandibular plane angle,dental crowding,dental and alveolar arch width,the depth of palate,the curve of Spee,and the torque of maxillary teeth and the distance of FA point to WALA ridge.The differences of the dates between the two groups were analyzed by T test with SPSS19.0 software package.Result:1)There was no difference between the two groups in age through the chi-square test.2)There was also no difference in vertical and sagittal skeletal pattern through Mann-Whitney U test.3)The results of T test were: the distance of lower lip to E line and the mento-labial angle in extraction group were significantly less than the non-extraction group;the labial inclination of upper and lower incisors had no difference between the two groups;the crowding of anterior segment and total crowding of maxillary and the total of mandibular dentition in extraction group were significantly higher than non-extraction group;the anterior segment width of maxillary arch and the middle segment width of mandibular in extraction group were significantly higher than non-extraction group;the depth of palatal in extraction group was significantly less than the non-extraction group;the curve of Spee had no difference between the two groups.Conclusion:1)The soft tissue profile with straight or slightly concave and uprighting incisor positions are prerequisite on the moderate and severe dentition crowding with non-extraction treatment.2)Vertical and sagittal skeletal pattern have no direct correlation whether extraction or not.3)The patients of moderate and severe dental crowding with straight face type when choosing whether extraction treatment or not should be combined with the upper and lower dentition crowding,lower lip protrusion,the anterior segment width of maxillary arch and the middle segment width of mandibular and the depth of palate for common assessment.