| ObjectiveThe aim of this study was to access the changes of upper airway morphology and craniofacial structure of Class Ⅱ hyperdivergent patients treated by extraction. By comparing the values before (TO) and after (T1) treatment, we examined the changes of the upper airway morphology and we could also find the correlation between changes of the upper airway and the craniofacial structure, which would help the clinicians find the key factors during extraction treatment that affect the upper airway morphology.MethodsCone-beam computed tomographic (CBCT) scans and lateral cephalograms were obtained for 20 adult Class Ⅱ hyperdivergent patients who were selected according to the strict diagnostic criteria and treated with premolar extraction before treatment (TO) and after treatment(T1). Using Dolphin software, the upper airway form was reconstructed and the craniofacial structure was calculated. To analyze the variables between T0 and T1, a Paired t-test was applied after the Kolmogorv-Smirnov test at the significance level of 5%. To evaluate the correlation between variables of the upper airway and craniofacial structure, Pearson’s linear correlation coefficient was applied.Results1. Upper airway morphology(1) The volume of the upper airway:the mean volume of the nasopharynx, palatopharygeal increased 141.85 mm3,726.39 mm3 respectively, but these value had no significant changes before and after treatment (P>0.05). The mean volume of the oropharynx, glossopharyngeum significantly increased 2740.99mm3、1978.56 mm3 (P<0.05) and the upper airway minimum cross-sectional area significantly increased 74.45mm2 (P<0.05).(2) The sagittal diameter of the upper airway:the diameter of the upper airway at the palatal plane (PASP) and the occlusal plane (PASO) increased0.48mm,1.13mm respectively, but these value had no significant changes before and after treatment (P>0.05). The diameter of the upper airway at the mandibular plane (PASM) significantly increased 1.73mm (P<0.05).(3) The hyoid position:the position of the hyoid became more upwards at vertical direction, but it had no significant change before and after treatment (P>0.05).(4) The tongue position:the mean distance between the tongue and palate decreased, but it had no significant change before and after treatment (P>0.05).2. Craniofacial structure(1) The upper central incisor position:the upper central incisor retracted significantly, the mean angle of the U1-SN decreased 3.6°, the mean angle of the U1-PP decreased 3.7°, the mean angle of the U1-AP decreased 4.3°, the mean distance between U1-AP decreased 1.02mm, the mean overjet decreased 1.38mm, the mean angle of U1-LI angle increased 4.5°, all the values mentioned above changed significantly (P<0.05).(2) The arch width:the mean width of the upper dentition decreased 1.58mm, the mean width of the lower dentition decreased 1.03mm, all the values mentioned above changed significantly (P<0.05).(3) Occlusal plane:the occlusal plane became flat, the mean angle of the OP-PP decreased 2.01° and it changed significantly (P<0.05).(4) Facial axis angle and mandible:the mean value of the Y axis angle decreased 1.22°, the mean value of the SNB angle increased 0.7°, and both of them changed significantly (P<0.05).(5) The articular angle:the mean value of the articular angle (SArGo) decreased 0.75° and it changed significantly (P<0.05).3. Pearson s correlation analysis(1) Oropharyngeal volume:the change of the oropharyngeal volume and the changes of the Y axis and the articular angle (SArGo) had significantly negative correlation (P<0.05).(2) Upper airway minimum cross-sectional area:the changes of the upper airway minimum cross-sectional area (Min) and the changes of the Y axis angle showed a significantly negative correlation (P<0.05).(3) The sagittal diameter of the upper airway at the mandibular plane (PASM): the change of the PASM had significantly negative correlation with the change of the articular angle (SArGo), the occlusal plane (OP-PP) and the overjet (P<0.05).Conclusions1. Premolar extraction of adult Class Ⅱ hyperdivergent patients will improve the morphology of the upper airway under the comprehensive diagnosis and treatment.2. Among the extraction treatment mechanism of adult Class Ⅱ hyperdivergent patients, the counterclockwise rotation of the occlusion plane and the mandible plane, the close of the facial axis and the unloading of the TMJ can not only maintain the stability of orthodontic treatment but also improve the upper airway morphology. |
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