Effects Of Orthodontics Of Class Ⅱ Division 2 Malocclusion For Non-extraction And Extraction On Morphological Changes Of Upper Airway And It’s Surrounding Structure

Objective To analyze the changes of arch shape,mandible position,upper airway shape and hyoid bone position before and after orthodontic treatment of non-extraction and tooth extraction,and to explore the relationship between arch shape and mandible position and upper airway shape and hyoid position,so as to provide reference for the formulation of orthodontic plan for Class Ⅱ division 2 malocclusion patients.Methods According to the inclusion and exclusion criteria,32 patients with Class Ⅱ division 2 malocclusion were selected from September 2016 to June 2020.The patients were divided into two groups according to the treatment plan of the first diagnosis: the first group was 16 patients(6 men,10 women)without extraction,average age 20.22±2.18 years;The second group consisted of 16 extraction cases(8 men,8 women),that is,extraction of the first maxillary premolars and a mandible incisor,average age 20.35±2.02 years.All X cranial localization lateral radiographs and memory models were measured,the data of arch width,mandible position,sagittal diameter of upper airway and hyoid position were obtained before and after treatment.All measurements were statistically analyzed using statistical software SPSS20.0,α=0.05,P<0.05 that the difference was statistically significant.Analysis of patients before and after treatment using a single factor pair t test,analysis of inter-group differences between the two groups using chi-square inspection and independent sample t test,Pearson correlation analysis method is used to analyze the correlation between two variables.Results1.Changes in arch morphology and mandible position: The width of the upper and lower arch of the two groups increased after treatment.LPP enlargement was most significant in the non-extraction group,the difference of UCC、UPP、LCC and LPP was significant(P<0.05);All the measurement items in extraction group were not significant(P>0.05).The B-N’、Pog-N’、Lm-PP、OB and OJ of both groups decreased,B-S’ and Li-PP increase,the difference of OB、OJ was statistically significant(P<0.05);The difference of Pog-N’ and Li-PP in non-extraction group was also significant(P<0.05).There was no significant difference between the extraction and non-extraction groups except OB(P>0.05).2.The changes of upper airway morphology and hyoid position: there was no significant difference in sagittal diameter and hyoid position in non-extracting group or extraction group before and after treatment(P>0.05),and there was no significant difference between the two groups in each measurement item(P>0.05).3.There was no significant correlation between arch morphology and upper airway morphology or position of hyoid bone(P>0.05).4.The correlation between the position of mandible and upper airway morphology and hyoid position: the SPP-SPPW and OJ、H-VL and Pog-N’ were negatively correlated,the H-MP and Pog-N’、U-MPW and B-S’ was positively correlated of non-extracting group(P<0.05).All the other measurement items had no significant correlation(P>0.05).Conclusion1.There was no significant difference in the sagittal diameter of upper airway and the position of hyoid bone between tooth extraction and non-extraction of Class Ⅱ division 2 malocclusion patients;2.The changes of sagittal diameter of upper airway and hyoid position before and after fixed correction were little related to width of arch of Class Ⅱ division 2 malocclusion patients;3.The changes of sagittal diameter of upper airway and hyoid position before and after fixed correction were closely related to the change of mandibular position of Class Ⅱ division 2 malocclusion patients.