A Study On The Changes Of Arch And Upper Airway Morphology Before And After Different Extraction Patterns Of Angle ?~1

Objective The influence of different extraction patterns on the changes of dental arch and upper airway morphology before and after the orthodontic treatment of Angle ?~1 permanent teeth and the correlation between them were studied by means of X-ray cephalometric and model measuring methods,so as to provide reference for clinical orthodontic treatment.Methods According to the orthodontic treatment plan,40 patients with complete data of Angle ?~1 malocclusion were selected.There are two orthodontic treatment plans,20 cases in each group.In the first group,four first premolarsis were extracted.In the second group,two first premolars in the upper jaw and two second premolars in the lower jaw were extracted by subtraction.The model and X-ray cephalometric films before and after correction were measured respectively.The changes of the shape of the upper airway and the position of hyoid bone before and after treatment were compared and analyzed.Then the correlation between them and the changes of the shape of dental arch was analyzed.Results1.The difference of upper airway and hyoid position before and after treatment:In the first group,the sagittal diameter of the upper airway was slightly narrowed except for PNS-R,and the other segments were widened in varying degrees,except for the increase of SPP-SPPW and TB-TPPW,there was no statistical difference in the other items(P > 0.05);there was no significant difference in the vertical direction of hyoid position and the horizontal orientation(P>0.05).In the second group,PNS-R also slightly narrowed after extraction(P>0.05).SPP-SPPW,U-MPW and TB-TPPW all increased(P>0.05)and there was no statistical difference in others.The index reflecting the position of hyoid bone had no significant difference except for the increase of H-VL after treatment(P>0.05).2.The difference of arch shape before and after orthodontic treatment:(1)Changes of arch width: in the first group,UW3-3 increased,UW6-6 and LW6-6decreased with statistical difference(P<0.05),LW3-3 increased(P > 0.05).The changes of posterior arch width were greater than those of anterior arch;in the second group,except LW3-3 increased with statistical difference,the other changes were consistent with the maxillary.(2)Changes of arch length: LL3 in the first group increased,but there was no statistical difference(P>0.05),others decreased in varying degrees(P<0.05).UL3 in the second group decreased slightly(P>0.05),others decreased in varying degrees and there was statistical difference(P<0.05).3.There was no significant difference in the difference between the groups before and after treatment with different extraction patterns(P>0.05).4.In the second group,there was a negative correlation between the change of TB-TPPW in the upper airway and the change of the length of the mandibular arch(P<0.05).There was no significant correlation between the change of the position of the other upper airway and hyoid bone and the change of the shape of the arch.Conclusion1.In this study two kinds of tooth extraction model correction are not cause obvious on airway narrowing,hyoid vertical position is almost the same,the sagittal to slightly forward,to Angle ?~1 will cause varying degrees of dental arch form changes.2.There was no significant difference between the two tooth extraction patterns in the influence of upper airway and hyoid bone location.