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Objective@#To investigate the effect of incisor retraction on three-dimensional morphology of upper airway and fluid dynamics in class Ⅰ adult patients with bimaxillary protrusion.@*Methods@#Thirty class Ⅰ patients with bimaxillary protrusion that received fixed orthodontic treatment in Department of Stomatology, The First Affiliated Hospital of Wenzhou Medical University from January 2011 to September 2014 were selected using random number table. All the patients were treated with extraction of four first premolars and retraction of anterior teeth using implant anchorage. Cone-beam CT (CBCT) scans were performed before and after incisor retraction for all patients. The CBCT data of the upper airway were constructed using Mimics 16.0, and the flow field characteristics inside the upper airway were simulated using Ansys 14.0. The changes of volume (V), mean cross-sectional area (mCSA), maximum lateral diameters/maximum anteroposterior diameters (LP/AP) of cross section, the maximum pressure of airflow (Pmax), the minimum pressure of airflow (Pmin) and pressure drop (△P) of nasopharynx, oropharynx and hypopharynx before and after incisor retraction were measured and compared using paired t test. The correlation between the variation of △P in the most significant pharyngeal part and the morphological variables after incisor retraction was analyzed using Pearson correlation test.@*Results@#No statistical differences were observed in the morphology and flow field in nasopharynx before and after incisor retraction (P>0.05). Before incisor retraction, the oropharyngeal volume and mCSA were (7 580±622) mm3 and (217±40) mm2, respectively, and the hypopharyngeal volume and mCSA were (2 564±162) mm3, and (239±43) mm2, respectively. After incisor retraction, the volumes of oropharynx and hypopharynx were (6 885±601) mm3 and (2 535±156) mm3, respectively, and mCSA of oropharynx and hypopharynx were (197±37) mm2 and (236±42) mm2, respectively. The volume and mCSA of oropharynx and hypopharynx were significantly decreased after incisor retraction (P<0.05). The greatest changes in pharyngeal volume and mCSA occurred in the oropharynx. In addition, the LP/AP of oropharynx after incisor retraction was changed from 1.9±0.6 to 2.1±0.7, which was significantly increased compared with the levels before incisor retraction (P<0.05). After simulation of pharyngeal airflow, the oropharyngeal Pmin, hypopharyngeal Pmax and Pmin were (-13.7±4.3), (-8.3±3.8) and (-42.8±9.5) Pa, respectively, whereas the values turned to (-16.4±6.5), (-11.9±3.6) and (-46.0±11.0) Pa, respectively after incisor retraction, which was significantly reduced (P<0.05). △P of oropharynx was significantly increased from (42.7±10.1) Pa to (45.2±13.0) Pa after incisor retraction (P<0.05) and the variation of oropharyngeal △P was negatively correlated with the variation of V and mCSA in oropharynx before and after incisor retraction (r=-0.681, P=0.001; r=-0.844, P=0.000).@*Conclusions@#The oropharynx was constricted and the pharyngeal resistance was increased after incisor retraction in adult class Ⅰ patients with bimaxillary protrusion. A comprehensive and systematic evaluation of the pharyngeal morphology and ventilatory function were very important for making a scientific and rational clinical treatment plan.
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Objective To compare the mandibular advancement appliance(MAA) with mandibular advancement and left-leaning appliance (MALA) in the treatment of mild or moderate obstructive sleep ap-nea-hypopnea syndrome (OSAHS). Methods Twenty-two cases of mild or moderate OSAHS were treated with MAA, and 19 cases with MALA. After 1-3 months, they were examined again with Epworth score and polysonmography (PSG). Results After 1-3 months of the MAA or MALA treatment, the Epworth score was improved evidently. The apnea -hypopnea index, max apnea time, mean apnea time, oxygen desaturatian index, and the longest time of oxygen desaturation were all lowered after the treatment, and the lowest SaO2 and the mean SaO2 were higher after the treatment. The differences were all distinctive (P<0.05 or<0.01). When patients treated with MAA were compared with those treated with MALA,only the max apnea time [(35.5±6.9),(31.3±6.0) s, respectively] and the longest time of oxygen desaturation [ (41.0±18.9), (29.9±9.3) s, respectively] had significant difference. Conclusion MALA may be helpful for shortening max apnea time and the longest time of oxygen desaturation, thus MAA is an effective alternative to patients of OSAHS. Further research should be done.