Three-dimensional analysis of pharyngeal airway form in children with anteroposterior facial patterns.

OBJECTIVE: To test the null hypothesis that the form and size of the pharyngeal airways in preadolescents do not differ among various skeletal patterns. MATERIALS AND METHODS: Sixty healthy children (mean age, 11.79 ± 1.11 years) were divided into three groups by anteroposterior jaw relationships. Using cone-beam computed tomography, the inclination and the volume of the pharyngeal airway were measured and compared with craniocervical angles and cephalometric variables. RESULTS: Children with Class II malocclusion have a larger angle between the FH plane and midplane of the oropharyngeal airway (ang-OA) compared with children with Class I and III malocclusion (P < .01). Ang-OA was significantly correlated with craniocervical angle (ang-cc) and anteroposterior variables, mainly ANB angle, Pog-N perpendicular (P < .01). Airway volume had a positive correlation with facial depth (P < .01). CONCLUSION: Children with Class II malocclusion have more backward orientation and smaller volume of the pharyngeal airway than do children with Class I and III malocclusion. Inclination of the oropharyngeal airway might be a key factor in determining the form of the entire pharyngeal airway and is related to head posture.

Accuracy and landmark error calculation using cone-beam computed tomography-generated cephalograms.

OBJECTIVE: To evaluate systematic differences in landmark position between cone-beam computed tomography (CBCT)-generated cephalograms and conventional digital cephalograms and to estimate how much variability should be taken into account when both modalities are used within the same longitudinal study. MATERIALS AND METHODS: Landmarks on homologous cone-beam computed tomographic-generated cephalograms and conventional digital cephalograms of 46 patients were digitized, registered, and compared via the Hotelling T(2) test. RESULTS: There were no systematic differences between modalities in the position of most landmarks. Three landmarks showed statistically significant differences but did not reach clinical significance. A method for error calculation while combining both modalities in the same individual is presented. CONCLUSION: In a longitudinal follow-up for assessment of treatment outcomes and growth of one individual, the error due to the combination of the two modalities might be larger than previously estimated.

Pharyngeal airway volume and shape from cone-beam computed tomography: relationship to facial morphology.

INTRODUCTION: The aim of this study was to assess the differences in airway shape and volume among subjects with various facial patterns. METHODS: Cone-beam computed tomography records of 62 nongrowing patients were used to evaluate the pharyngeal airway volume (superior and inferior compartments) and shape. This was done by using 3-dimensional virtual surface models to calculate airway volumes instead of estimates based on linear measurements. Subgroups of the sample were determined by anteroposterior jaw relationships and vertical proportions. RESULTS: There was a statistically significant relationship between the volume of the inferior component of the airway and the anteroposterior jaw relationship (P = 0.02), and between airway volume and both size of the face and sex (P = 0.02, P = 0.01). No differences in airway volumes related to vertical facial proportions were found. Skeletal Class II patients often had forward inclination of the airway (P <0.001), whereas skeletal Class III patients had a more vertically oriented airway (P = 0.002). CONCLUSIONS: Airway volume and shape vary among patients with different anteroposterior jaw relationships; airway shape but not volume differs with various vertical jaw relationships. The methods developed in this study make it possible to determine the relationship of 3-dimensional pharyngeal airway surface models to facial morphology, while controlling for variability in facial size.

Working with DICOM craniofacial images.

The increasing use of cone-beam computed tomography (CBCT) requires changes in our diagnosis and treatment planning methods as well as additional training. The standard for digital computed tomography images is called digital imaging and communications in medicine (DICOM). In this article we discuss the following concepts: visualization of CBCT images in orthodontics, measurement in CBCT images, creation of 2-dimensional radiographs from DICOM files, segmentation engines and multimodal images, registration and superimposition of 3-dimensional (3D) images, special applications for quantitative analysis, and 3D surgical prediction. CBCT manufacturers and software companies are continually working to improve their products to help clinicians diagnose and plan treatment using 3D craniofacial images.