The Effect Of Different Extraction Patterns On Maxillary Third Molars In Patients With Skeletal Class ?

Objective: To explore the influence of different premolar extraction patterns on maxillary third molars in patients with skeletal class I through the angle changes and eruption space of maxillary third molars before and after treatment,so as to provide a reasonable reference and guidance for the relationship between the eruption of the maxillary wisdom teeth and orthodontic treatment.Methods: 50 patients who were treated with physiological anchorage in the orthodontics Department of the Fifth Affiliated Hospital of Xinjiang Medical University and have the immaturate third molars were analyzed retrospectively.Fifty patients were divided into three groups,18 in the nonextraction group,16 in the first premolar extraction group and 16 in the second premolar extraction group.9 indexes before and after treatment were measured and analyzed.Before and after orthodontic treatment,the same equipment was used to take lateral radiographs and cephalometric radiographs,and the defining point,tracing point and measurement were accomplished by three doctors.SPSS 22.0 was used for statistical analysis.Results: the changes of ?UM2-UM3,?ANB,UM3-OP before and after treatment in the first premolar extraction group were statistically significant;there were significant differences in ?ANB,UM3,U-ES,UM3-OP,Ganss,Spr-Pt and ?UM3-PP which were in the second premolar extraction group(P < 0.01).Compared with nonextraction group,?UM2-UM3 in the first premolar extraction group was significant difference(P < 0.01)and ?UM3-HP?UM3?U—ES?Ganss?Spr-Pt in the second premolar extraction group were also statistically different(P < 0.01).Compared with the first premolar extraction group,?UM3-HP??UM2-HP?UM3?U—ES in the second premolar extraction group were statistically significant.The difference of the prediction value(D value)of the eruption of the third molar can be concluded that the second premolar extraction group is more likely to erupt to the normal position than the first premolar extraction group.Conclusion: Extraction can improve the eruption of the maxillary third molar,and the further the position of the extraction of the premolar is,the greater the improvement is.