Morphological Changes Of Dental Arch And Upper Airway After Fixed Orthodontic Treatment Of Angle Class ? Malocclusion

Objective To study and compare the morphological changes of dental arch and upper airway and hyoid bone position after non-extraction and extraction treatment of Angle Class? malocclusion by Model measurement and X-ray cephalometric method.And explore the correlation between the morphological changes of dental arch with upper airway morphology and hyoid bone position,so as to provide clinical guidance of treatment plan for fixed orthodontic treatment of Angle Class ? malocclusion.Methods Forty patients with orthodontic treatment in the Orthodontics Department of our hospital from September 2016 to June 2019 were included in the study.The complete medical records of patients before and after treatment were collected and analyzed.Separated the patients into two groups according to the different treatment plans: the first group was 20 patients with non-extraction(12 males and 8 females,mean age 17.95 ± 2.40 years),and the second group was 20 patients(9 males and 11 females,mean age 18.95 ± 3.17 years)with the extraction method of removing two maxillary second premolars and two mandibular first premolars.The dental arch morphology,upper airway morphology and hyoid bone position were measured before and after treatment by Model measurement and X-ray cephalometric method respectively.To compare the effects of two different treatment methods on dental arch morphology,upper airway morphology and hyoid bone position,and explore whether the morphological changes of dental arch were related to the changes of upper airway morphology and hyoid bone position.Result1.There was no significant difference in dental arch morphology after treatment in the non-extraction group(P> 0.05).In the extraction group,the UMM?UD and LD of dental archmorphology after treatment were significantly decreased(P<0.05),the other indicators were no statistical significance(P> 0.05).Compared the changes of dental arch morphology in the non-extraction and extraction group after treatment,there were significant differences in LCC?UMM?UD?LD(P<0.05);the other comparisons were no statistical significance(P>0.05).2.In the non-extraction group,the PNS-R of the nasopharyngeal segment after treatment was significantly increased(P<0.05),the other indicators were no statistical significance(P>0.05).In the extraction group,the PNS-R and PNS-Ad2 of the nasopharyngeal segment after treatment were significantly increased(P<0.05),the SPP-SPPW of the palatopharyngeal segment was significantly decreased(P<0.05);the other indicators were no statistical significance(P> 0.05).The changes of the non-extraction group in upper airway morphology after treatment were compared with these of the extraction group,there were no significant differences in the indicators of all segments(P> 0.05).3.In the non-extraction group,the H-FH of the hyoid bone vertical position after treatment was significantly increased(P<0.05);the other indicators were no statistical significance(P> 0.05).In the extraction group,the H-FH of the hyoid bone vertical position was significantly increased(P<0.05),the H-VL of the hyoid bone horizontal position was significantly decreased(P<0.05),the other indicators were no statistical significance(P> 0.05).The changes of the hyoid bone position in the non-extraction group and the extraction group after treatment showed no significant differences in the hyoid position(P> 0.05).4.Pearson correlation analysis was performed between the morphological changes of dental arch with upper airway morphology and hyoid bone position before and after treatment in the non-extraction group and the extraction group.There was no statistical significance in the correlation analysis between the changes of indicators(P> 0.05).Conclusion1.In Angle Class ? malocclusion,there was no significant decrease in upper airway after non-extraction treatment,the palatopharyngeal segment of the upper airway has a decreasing tendency after extraction treatment,but the decrease was not obvious compared withnon-extraction treatment.2.After treatment of Angle Class ? malocclusion,the slight changes of dental arch morphology were not directly cause changes of upper airway morphology and hyoid bone position.