What is Airway Volume Analysis?

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Orthodontists have always had an interest in the upper airway, whether it’s the relationship between the airway and facial type, airway shape, or the airway volume. Most airway volume analysis is conducted using 2-dimensional (2D) cephalograms, which create a 2D airway analysis. This method provides limited data, like angular and linear measurements. A more sophisticated 3D airway analysis can be conducted by using 3D technology as the airway is part of a 3D structure. The most recent tool that can reveal the airway in 3D is cone-beam computed tomography (CBCT). The reason for orthodontists needing this information is so they can measure the airway volume for patients with obstructive sleep apnea, in relation to malocclusions, and also in those patients who have had orthodontic treatment.

2D lateral cephalograms

The older lateral cephalograms cost less than CBCT and are easy to use, but they are just limited to two-dimensional imaging, which doesn’t help to view structures in 3D. The use of CBCT has revealed that its reliability and accuracy of craniofacial measurements are far better than to 2D lateral cephalograms.

The use CBCT in the field of dentistry

This 3D diagnostic tool has in recent years become more accessible to the field of dentistry. It is now a reputable and well-acknowledged imaging technique for diagnosing oral and maxillofacial problems. It has in part become the preferred technique because it’s faster so it means the patient is subject to lower radiation doses. CBCT technology is so advanced that it can segment and visualise hollow structures in 3D such as airway volumes and surface areas.

Once the scan or digital image has been taken, the dentist, orthodontist or doctor needs to view the findings in a DICOM viewer, as DICOM is the file format accepted for a medical image. A DICOM viewer allows for a total analysis of any CBCT scan such as measuring airway volume and segmenting. When an image of an airway is segmented and structured this means delineating and removing any surrounding structures so that there is a clearer image which is easier to analyse.

Airway volume analysis and sleep apnea

The orthodontic community has a great interest in airway volume and respiratory function because studies have revealed airway problems are often related to different sorts of malocclusion and it’s been found that nasal obstruction is one of the main aetiological factors for dento-facial anomalies. Also, evaluation of airway volume is one of the diagnostic steps for patients who experience breathing disorders for example obstructive sleep apnoea (OSA) where the victims have marked craniofacial differences, like the position and size of the mandible, enlargement of the posterior airway space, and size of the soft palate and tongue. In these patients, airway volume analysis assessment has been performed, mostly using 2D lateral cephalograms, by identifying specific landmarks and measuring different areas and lengths in the airway region.

Airway volume analysis and malocclusion

Studies have shown that Class 11, division 1 malocclusion occurs because of an obstruction in the upper pharyngeal airway and mouth breathing. However, other research such as de Freitas et al. (2006), drew the conclusion that the width of the lower and upper pharyngeal airway width is not related to either Class I or Class II malocclusions. A further study by Kirjavainen and Kirjavainen in 2007 discovered that with Class II malocclusion, there is a definite association with the upper airway structure being narrower even in the absence of retrognathia.

Many of these studies to do with airway anatomy and its relationship to craniofacial development and growth face limitations because they have been using 2D frontal or lateral cephalograms which are not able to identify the contour of soft tissue in 3D which limits their ability to evaluate both volumes and areas in the upper airway. More and more practitioners take advantage of advances in computed tomography (CT) imaging and the 3D technology which allow them to better visualize the airway and volumetric analysis.

Clinicians are able to undertake the volumetric measurements and calculate the cross-sections of the airway in 3 planes of space, which are axial, coronal and sagittal. The axial plane, which can’t be seen on a lateral cephalogram, is considered to be the most relevant plane from a physiological perspective because it’s perpendicular to the airflow. CBCT systems have been specifically developed for the maxillofacial area.

Easy and accurate evaluation of the anatomy of the airway has been made possible using CBCT. Although there have been many studies published using CBCT to evaluate airways, not many have addressed its accuracy. Recent studies concentrated on evaluating both the reliability and accuracy of the airway volume which was measured on CBCTs digitally and at the most constricted part in the airway. This was compared to the manual measurements carried out on an airway model. They came up with varying results.

What we do at CephX

Our aim at CephX is to assist orthodontic practitioners worldwide to save valuable time by providing accurate analyses of dental imagery. The services we offer are automated, which is the highest quality analyses that helps you to improve the productivity and efficiency of your practice. Currently, we offer a cephalometric analysis service of 2D cephalometric x-rays or of CBCT scans, and 3D teeth segmentation. All the dental practitioner has to do is to upload the patient’s scan, and in no time at all he or she will be in receipt of the full analysis. Another key service we intend to add soon is automatic and instant 2D and 3D airway volume analysis using AI which will be available online.

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