Tassneem Elagib, Hee-Moon Kyung, Bui Quang Hung, Mihee Hong

Assessment of pharyngeal airway in Korean adolescents according to skeletal pattern, sex, and cervical vertebral maturation: A cross-sectional CBCT study.

- Korean J Orthod 2022;52:345-353

I appreciate the author’s wonderful work investigating airway volumes using cone-beam computed tomography (CBCT) by skeletal pattern, sex, and cervical vertebral maturation stages. For better understanding of your work, I would like to ask some questions.

Q1. Could you please explain more in detail how you reoriented the three-dimensional images using naso-frontozygomatic (NFZ) plane and Frankfort horizontal plane? It would be very helpful with some figures.

Q2. In Figure 3B, the projected trending line of nasopharyngeal volume (NPV) is quite different from that of oropharyngeal volume (OPV): NPV clearly showed breakpoint at cervical vertebral maturation (CVM) stage 5 entering a kind of plateau, but OPV did not show any breakpoint. What would be your explanation or assumption regarding such difference?

Q3. Please give us how we can cooperate the result and conclusion of this study to our everyday clinic?

Questioned by

Haeddeuri Kim

Department of Orthodontics, Seoul National University Dental Hospital, Seoul, Korea

Thank you very much for your thoughtful questions which allows us to improve our research.

A1. We followed the protocol in the article published in 2009.1 We used NFZ plane as cranial base reference plane. The NFZ plane was formed by nasion (N) and two frontozygomatic (FZ) points. The Cartesian coordinate value of N point registered as the origin were adjusted based on (0, 0, 0). First, the z-coordinates of both FZ points was set symmetrically in the frontal plane. Second, the y-coordinates of FZ points on the axial plane was adjusted symmetrically. Finally, we manipulated the z-coordinates of left temporal-fossa points and orbitale as close as possible. Figures 1–3 from the article by Dr. Cho was very helpful for this reorientation procedure.¹

A2. It is true that the projected trend-line shows some differences between the NPV and OPV. However, the number of samples was relatively small and no statistical difference was observed. Also, our research is not based on individual assessment of the natural airway growth and development, which is our limitation. In Figure 3B, NPV and OPV actually showed breakpoints at CVM stage 5 only for females. Some previous studies also concluded that female patients showed a significant increase in length from ages 7 to 15 years,² unlike male patients who showed significant increases in dimensions from 7 to 18 years. We suggest that in further studies, the airway volume should be gender-based analysis to provide more appropriate conclusions.

A3. For routine orthodontic practices, many patients are adolescents. Data from CBCT and cephalometric radiographs, particularly SNB, can be used to evaluate and counsel patients about their potential risks of sleep disordered breathing. This allows the patients to be referred for further airway evaluation. In addition, in the case of female patient, airway development is alleviated faster than in male patients, so a more cautious approach is required.

Replied by

Mihee Hong

Department of Orthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea