| Objective : In this study,the skeletal class Ⅱ malocclusion children with Obstructive Sleep-disordered Breathing were treated with Twin-Block appliance.The changes of upper airway morphology and internal fluid dynamics before and after treatment of TB combined with Adenotonsillectomy and simple TB treatment for skeletal class Ⅱ malocclusion children with Obstructive Sleep-disordered Breathing were simulated and measured by 3D reconstruction measurement software Mimics and Computer Fluid Dynamics,and the clinical efficacy and treatment mechanism of the Twin-Block appliance and Adenotonsillectomy were compared and analyzed.This study uses a new idea and method to study the morphology and function of the upper airway and also provides a valuable theoretical basis for AT combined with TB in orthodontic treatment of children with skeletal Class Ⅱ malocclusion and Obstructive Sleep-disordered Breathing.Methods: 1.Case selection: A total of 16 children with skeletal class Ⅱmalocclusion with OSDB were selected,including 9 males and 7 females,with an age distribution of 8-11 years old and an average age of 9.8 years old.The subjects were divided into 8 cases in group Ⅰ(AT + TB)and 8 cases in group Ⅱ(TB)according to whether Adenotonsillectomy was performed before orthodontic treatment.2.Treatment process: Adenotonsillectomy was recommended in otolaryngology department before orthodontic treatment in both groups.The patients who underwent surgery received orthodontic TB orthodontic treatment one month after recovery,while those who did not underwent surgery directly began orthodontic TB orthodontic treatment.Cone Beam Computered Tomography(CBCT)were collected before treatment(T0)and after treatment(T1).3.Research contents:(1)The 3D model of the upper airway was reconstructed using 3D reconstruction software Mimics and the relevant morphological data(changes in cross-sectional area and volume)of the upper airway were measured;(2)The reconstructed upper airway model was transferred to Geomagic Wrap 2021 for model dressing,and the inlet and outlet were set in Space Claim 2021 R1.The mesh was divided and the internal fluid dynamics of the upper airway was simulated using ANSYS 2021 R1,and the final result was calculated using CFD-POST.The above methods were used to analyze the average velocity and pressure of each section of the upper airway,and the change of pharyngeal cavity resistance,and SPSS 27.0 statistical software was used for intra-group and inter-group comparison.Results: 1.Morphological changes of upper airway:(1)There was statistical significance in the cross-sectional area of the lower palatopharyngeal boundary between the two groups before and after treatment(P<0.01).There were statistical differences in the cross-sectional area of the lower nasopharyngeal boundary between the two groups before and after treatment(P<0.05),but the change in group Ⅰ was greater than that in group Ⅱ,and the difference was statistically significant(P<0.01).There were statistical differences in the cross-sectional area of group Ⅰ before and after treatment of the lower glossopharyngeal boundary(P<0.05),but there was no statistical significance in the change amount of group Ⅱ before and after treatment(P>0.05).(2)Volume changes of upper airway segments: glossopharyngeal segment volume increased significantly in both groups before and after treatment(P<0.01),and laryngopharyngeal segment volume changes were statistically different(P<0.05);Nasopharyngeal segment volume and palatopharyngeal segment volume in both groups were changed before and after treatment(P<0.05),but the changes in group Ⅰ were more significant than those in group Ⅱ(P<0.01).(3)Changes in average gas velocity at each section of the upper airway: There were significant statistical differences in the average flow velocity of the lower palatopharyngeal boundary between the two groups before and after treatment(P<0.01),and the average flow velocity of the lower nasopharyngeal boundary and the lower lingual pharyngeal boundary between the two groups were statistically different(P<0.05),but group Ⅰ was significantly higher than group Ⅱ(P<0.01).(4)Changes in average pressure at each section of the upper airway:Before and after treatment of the lower palatopharyngeal boundary,the average surface pressure of the two groups increased significantly(P<0.01).The average surface pressure of the lower nasopharyngeal boundary and lower lingual pharyngeal boundary was significantly different in group Ⅰ(P<0.01)compared with group Ⅱ(P<0.05),and the changes of the above three sections were statistically significant(P<0.01).(5)Changes of upper airway pharyngeal cavity resistance: The changes of upper airway pharyngeal cavity resistance in group Ⅰ(P < 0.01)and group Ⅱ(P < 0.01)before and after treatment were statistically significant,and the changes of upper airway pharyngeal cavity resistance in group Ⅰ and group Ⅱ were decreased by 59.2% and 26.4%respectively.Conclusion:1.Twin-Block treatment can increase the cross-sectional area of the narrow area in the upper airway and the three-dimensional volume of the entire upper airway segments,increase the gas pressure in the narrow area,and reduce the possibility of airway tremor and collapse.2.Adenotonsillectomy can more significantly increase the volume of the upper airway in nasopharynx,palatopharynx and glossopharynx segments,so as to provide better anatomical conditions for internal gas flow and make internal gas flow more gentle.Adenotonsillectomy is beneficial for children with skeletal class Ⅱ malocclusion who have adenoid and tonsil hypertrophy.3.The three-dimensional model reconstruction of the upper airway combined with CFD simulation is helpful to further understand the interaction between the structure and function of the upper airway,which is a feasible method to study the upper airway. |
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