Changes In Upper Airway Width,Hyoid And Mandibular During Twin-block Two-stage Treatment In Class Ⅱ Patients

Objectives:1.To explore the effect of Twin-Block(TB)with Rapid Maxillary Expansion(RME)two-stage treatment on upper airway(UA),hyoid and mandibular in classⅡpatients.2.To establish a method of deep learning and image segmentation to identify the three regions of PA and measure the related indices automatically.By this way,we could prove the ability of experiment 1,assess patients’ airway risk during orthodontic treatment,help formulate orthodontic treatment planning,and evaluate airway changes during the orthodontic treatment.Methods:1.A total of 42 class Ⅱ patients in Jilin University Stomatological Hospital were retrospectively included.Patients were divided into tooth extraction and non-tooth extraction group.Tooth extraction group :18(male 6,woman 12,average age11.67±1.14).Non-tooth extraction group:24(male 14,woman10,average age11.38±1.10).The UA,hyoid,mandibular measurements were obtained from lateral cephalometric radiographs taken before treatment(T0),after TB treatment(T1),and at the end of the 2-phase treatment(T2).The measurement index was depicted three times in one month and third month.SPSS 26.0 were used for statistical analysis.The results of the two measurements are averaged.Intragroup comparison was performed for ANOVA test and Tukey HSD test.2.Lateral cephalogram(LC)radiographs from 1165 patients were used to train this Two Step Segmentation model.The lateral cephalogram radiographs of experiment1 patients were included to Another 130 mages were used to validate and test the model.Results:1.UA: nasopharyngeal increased during TB and fixed treatment and palatopharyngeal increased during two-stage treatment in both groups.PNS-Ad2 increased 1.97mm(P=0.038)and 3.21mm(P<0.001)in extraction group,and 2.57mm(P=0.008)and 3.43mm(P<0.001)in non-tooth extraction group SPP-SPPW increased 3.08mm(P=0.015)in extraction group,and 3.96mm(P<0.001)in nontooth extraction group.2.Hyoid: Distance between hyoid and mandible increased and moved downward in extraction group during fixed and two-stage treatment(P<0.05).Distance between hyoid and C3 cervical increased and moved downward in non-extraction group during fixed and two-stage treatment(P <0.05).3.Mandibular: total and effective length of mandibular increased in extraction group during two-stage treatment(P<0.05).NP-FH increased 2.09° in non-extraction group during two-stage treatment(P<0.05).Total and effective length of mandibular increased in this group during each treatment(P<0.05).4.This Two Step Segmentation model used Unet as backbone and got mean dice value of 0.8215,precision of 0.8236 and recall of 0.8361.The widths of line PNS-UPW and line TB-TPPW were compared with the average of three times manual measurements in experiment 1 to make statistical analysis.For these two lines,ICC was found to be 0.603 and 0.834,and Pearson’s coefficient was found to be 0.61 and 0.83.Conclusions:1.TB with RME treatment brought positive effects on nasal、palatopharyngeal airway and remained stable.2.TB with RME treatment brought positive effects on the position of the hyoid.After fixed treatment,the hyoid moved downward without resisting the influence of growth.3.TB with RME treatment brought positive effects on mandible and remained stable.The non-tooth extraction treatment was conducive to the improvement of the chin position.4.This method is reliable to segment three regions(nasopharynx,oropharynx and hypopharynx)of PA automatically and calculate related indices.Manual measurements in experiment 1 are also reliable.