Effects Of Twin-block Combined With The Maxillary Expansion Appliance On Tongue Position And Upper Airway In Children With Mandibular Retrusion

Objective:By using Twin-block(TB)combined with the maxillary expansion appliance in children with mandibular retrusion and history of mouth breathing for correction,the three-dimensional changes of nasopharynx,oropharynx,glossopharyngeal volume and total upper airway volume of patients before and after correction were measured,and changes in tongue position and maxillary width were observed,in order to provide guidance for similar clinical cases and improve everyone’s awareness of airway problems.Methods:Twenty children with class II malocclusion and mandibular retrusion who were treated in Hefei Stomatological Hospital from September 2020 to May 2022 were selected.The included patients had a history of mouth breathing,and the mandibular plane Angle was average or low Angle,including 12 males and 8 females,with an average age of(10.25±1.58)years,and the treatment time was 6-12 months,with an average(8.25±2.6)months.Twin-block combined with the maxillary expansion appliance was used for treatment,the patient wore more than 22 hours per day,and the spiral expander was applied twice a day with 1/4 turn each time.A cone beam computed tomography(CBCT)was taken before and after treatment.The CBCT before and after treatment was imported into Mimics21.0 software to reconstruct the airway model,the total volume of the upper airway(nasopharyngeal segment + oropharyngeal segment)and the airway volume of the nasopharyngeal segment,glossopharyngeal segment and oropharyngeal segment were measured,the airway cross-sectional area and maximum sagittal diameter at the tip of the uvula of the glossopharyngeal segment were measured,too.The space between the tongue body and the palate was reconstructed,anterior-posterior and height changes of tongue position were observed,and the maxillary width was measured at fixed points on CBCT.SPSS 26.0 software was used to analyze the data,paired-sample t-test was used for data that conformed to normal distribution,and Wilcoxon signed rank test was used for data that did not conform to normal distribution to compare the before and after differences of sample data.Results:After the treatment of Twin-block combined with maxillary expansion appliance,the total upper airway volume(nasopharyngeal segment + oropharyngeal segment)and the nasopharyngeal,oropharyngeal,and glossopharyngeal airway volumes in children with class II malocclusion and mandibular retrusion increased significantly,these differences were statistically significant(P < 0.05).The cross-sectional area and maximum sagittal diameter of the airway at the tip of the uvula in the glossopharyngeal segment increased significantly,these differences were statistically significant(P < 0.05).The width of the maxillary increased significantly,the difference was statistically significant(P < 0.05).The tongue position was elevated and moved forward,numerical differences were statistically significant(P < 0.05).Conclusion:Twin-block combined with maxillary expansion appliance was used to treat mandibular retrusion in children with a history of mouth breathing.After treatment,the total volumes of nasopharynx,oropharynx,glossopharynx and upper airway increased,and the oropharynx expanded significantly in the anteroposterior depth.The width of maxilla increased.The tongue position tends to be normal,which contributes to improved airway patency.