Authors’ response

We thank Dr Antosz for his comments related to our article. In general, we agree with his concerns. The airway is surrounded by soft tissues—muscle and fat—as well as hard tissues, such as cartilage and bone. They all play a role in the anatomy and function of the airway. It is normal for the airway to respond to changes in these tissues, and muscle tone is probably the most difficult to account for or measure.

Computerized tomography (CT), along with various software used for segmentation and analyses, can perform relatively accurately when measuring areas with shorter ranges of radiodensity: eg, air and soft tissues. Cone-beam CT (CBCT), on the other hand, has proven to be a superb tool in measuring airway volume. This has been documented in the literature multiple times.

Obviously, it would be great to know the reproducibility of repeated CBCT scans and their subsequent volume analyses with the same patient. However, as one would expect, such calculations would not be possible without a second scan within a relatively short waiting period. This would not only be disallowed by institutional review boards in the United States, but also violate the ALARA (as low as reasonably achievable) principle, our current approach to imaging, along with raising ethical concerns when attempted on living beings. Dr Antosz has valid points, but we hope he can appreciate that CBCT is the best we have at this time. Reproducibility is a concern and will continue to be until radiation is no longer an issue.

To control the variables, methods of scans and data analyses must be consistent and should follow a standard protocol for each patient. Much of the recently published research with 3-dimensional analyses of the airway describes a standard scanning technique with reproducible occlusal, body, and head positions as well as instructions on breathing patterns. This information should later be transferred to capable software by using proper segmentation techniques with clearly defined borders, not the basic automated applications. Furthermore, a power analysis must be implemented to justify a sample size through known amounts of the effect. We believe that our study had demonstrated a series of fine-tuned steps in these areas.

Our results and recommendations do not go beyond suggestions for oral surgeons and orthodontists to be more cognizant of the airway when planning for orthognathic surgery. We were trying to demonstrate the consistency in the observations for our groups under thoroughly defined conditions. We do agree that without repeated tests, there will be questions about validity of a volume measurements using CBCT. What we do not agree with is to halt research moving forward in this direction.

We hope these comments are helpful. We do appreciate the feedback.

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Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Authors’ response
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