Abstract: PURPOSE: Using cone-beam CT (CBCT) and Invivo5 software to measure the oropharyngeal airway volume and hyoid position of adults Class Ⅲ skeletal malocclusion and analyze the influence of the maxillary or mandibular position, in order to evaluate oropharynx airway volume and hyoid position ,and provide guidance for reasonable and effective treatment. METHODS: One hundred and eighty cases were randomly selected from CBCT data and divided into three groups. Invivo5 software was used to rebuild 3D image data and establish a 3D coordinate system ,then to measure OPV and hyoid position. LSD t test was performed between each group with SPSS 19.0 software package. RESULTS: OPV for mandibular protrusion of Class Ⅲ was significantly higher than maxillary retrusion of Class Ⅲ and ClassⅠ（P<0.05）, whereas no difference existed between ClassⅠand maxillary retrusion of Class Ⅲ; H-VPS had significant difference as follows: mandibular retrusion of Class Ⅲ, maxillary retrusion of Class Ⅲ,and ClassⅠ（P<0.05）; H-PS in mandibular protrusion of Class Ⅲ was significantly higher than maxillary retrusion of Class Ⅲ and ClassⅠ（P<0.05）, whereas no difference existed between ClassⅠand maxillary retrusion of Class Ⅲ. CONCLUSIONS: The three-dimensional features of airway were different as adults have different types of skeletal malocclusion. The mandibular sagittal position and length had more significant influences on pharyngeal airway volume, shape, direction, and hyoid sagittal position compared with the maxilla. CBCT and Invivo5 are practical tools for evaluation of airway, which can provide clinical evaluation of the three-dimensional features of airway and hyoid position of different skeletal malocclusion, and provide guidance in the formulation of reasonable and effective treatment plan.

Key words: Class Ⅲ, skeletal malocclusion, Pharyngeal airway, Hyoid position, CBCT