| Objective:To observe changes of the pharyngeal airway space and displacement of hyoid and tongue in patients with skeletal Class III malocclusion after the combined orthodontics and orthognathics treatment.Materials and Methods:The subjects for this study were 80 Chineses selected from the files of orthodontic clinc, Stomatological hospital of Nankai University.40 patients were diagnosed as skeletal ClassIII deformities and 40 patients with skeletal I malocclusion as the control group. They were divided into 2 groups:group 1 (20 patients) had mandibular setback surgery via bilateral sagittal split ramus osteotomy (SSRO); group 2 (20 patients) had bimaxillary surgery (SSRO and LeFort I osteotomy). Cone-beam computed tomography (CBCT) were taken before and ap-proximately 6 months after surgery.Raw data obtained from CBCT-scanning were exported as DICOM format and reconstructed into 3D model by Mimics software. To set up a three-dimensional ref-erence frame, which was based by point "S", point "N", point "Ba" and of which point "S" is origin. The upper airway was divided into four sections and velopharyn-geal, tonguepharyngeal and largnopharyngeal airway were needed to measure. Mea-surements of pharyngeal airway included sagittal diameters, transversal diameters, cross sectional areas and volumes in the narrowest level of each part. Three dimen-sional coordinates of point "Pg", point "H", point "T" were also needed to measure. Statistical methods included paired t test, SNK-q test and pearson correlation analysis. Statistical significance was set at P<0.05.Results:1.Group 1:Sagittal diameters, cross sectional areas and volumes of each part were significantly narrower after surgery (P<0.05). The transversal diameter constricted significantly only in largnopharyngeal airway. Cross sectional areas and volumes of each part after surgery were significantly narrower compared with the control group.2.Group 2:A tendency for expansion was found in velopharyngeal airway; The cross sectional areas and volumes in the tonguepharyngeal and largnopharyngeal air-way had decreased significantly in comparison with the preoperative space. Com-pared with the control group, volumes in the tonguepharyngeal and largnopharyngeal airway significantly smaller than normal level (P<0.01)3. The hyoid significantly moved inferoposteriorly and the tongue moved posteri-orly by mean 4.02 mm after surgery (P<0.01)4. There were 19 positive correlations between the amount of mandibular setback and other measurements,9 of which were P<0.01 accounted for 47.37%,5 of which were P<0.05 accounted for 26.31. The most significant relationship was found be-tween the amount of mandibular setback and△total volumes (r=0.834, P<0.01).Conclusions:1. Following combination therapy the pharyngeal airway space decreased and the hyoid moved inferoposteriorly and tongue moved posteriorly;2. In contrast, bimaxillary surgery caused an increase at the velopharyngeal air-way and reduced the amount of mandibular setback to reduce the degree of re-duction of airway space in the tonguepharyngeal and largnopharyngeal level.3. There were great correlations between the amount of mandibular setback and the reduction of upper airway space. These results suggest to control the amount of mandibular setback and monitor the status of sleep apnea to prevent the development of OSAHS.4. A CBCT-based 3D analysis provides an adequate picture of the anatomical characteristics of the upper airways to evaluate morphologic airway changes, and therefore can lead to an improvement of the diagonosis. |
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