Effect of Herbst appliance on upper airway changes in orthodontic patients

Abstract

With great interest, we read the paper entitled “Three-dimensional changes of the upper airway in patients with Class II malocclusion treated with the Herbst appliance: A cone-beam computed tomography study”.1Oliveira P.M. Cheib-Vilefort P.L. de Pársia Gontijo H. et al.Three-dimensional changes of the upper airway in patients with Class II malocclusion treated with the Herbst appliance: A cone-beam computed tomography study.Am J Orthod Dentofacial Orthop. 2020; 157: 205-211Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar The authors concluded that mandibular advancement with the Herbst appliance increased the volume of the oropharynx significantly, but no significant volumetric modifications were observed in the nasal cavity and nasopharynx. However, we still have a few questions regarding this study. As described by the authors, the patients in both groups were well-matched for “age, gender, sagittal skeletal pattern (ANB angle >4°), and facial appearance of mandibular retrusion.” According to other similar studies,2Zhang J. Chen G. Li W. Xu T. Gao X. Upper airway changes after orthodontic extraction treatment in adults: a preliminary study using cone beam computed tomography.PLoS One. 2015; 10: e0143233PubMed Google Scholar,3Kang J.H. Sung J. Song Y.M. Kim Y.H. Heritability of the airway structure and head posture using twin study.J Oral Rehabil. 2018; 45: 378-385Crossref PubMed Scopus (8) Google Scholar body mass index (BMI) is another important factor that should be taken into consideration, because patients with higher BMI (>25 kg/m2) usually present a restricted pharyngeal airway despite orthodontic treatment. Therefore, was BMI matched between both groups in this study, or in the normal range? In this study, the authors calculated the volumetric changes of the nasal cavity, nasopharynx, and oropharynx, and concluded that no significant volumetric modifications were observed in the nasal cavity and nasopharynx. However, apart from airway size change, morphologic changes, including the changes in height, cross-sectional area, and sagittal dimension, could also reflect the 3-dimensional changes of the upper airway.2Zhang J. Chen G. Li W. Xu T. Gao X. Upper airway changes after orthodontic extraction treatment in adults: a preliminary study using cone beam computed tomography.PLoS One. 2015; 10: e0143233PubMed Google Scholar,4Zimmerman J.N. Lee J. Pliska B.T. Reliability of upper pharyngeal airway assessment using dental CBCT: a systematic review.Eur J Orthod. 2017; 39: 489-496PubMed Google Scholar Particularly, because a Herbst appliance was used for mandibular advancement, the sagittal dimension changes of the upper airway should also be an important parameter for assessment, which could subsequently provide more detailed information for upper airway changes. Therefore, can the author explain more clearly their consideration for not including these parameters? It would possibly reflect the effect of Herbst appliance on upper airway changes better, especially the sagittal dimension. Three-dimensional changes of the upper airway in patients with Class II malocclusion treated with the Herbst appliance: A cone-beam computed tomography studyAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 157Issue 2PreviewThis study aimed to determine the volumetric effects on the upper airways of growing patients with Class II malocclusion treated with the Herbst appliance (HA). Full-Text PDF Authors' responseAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 158Issue 1PreviewWe thank Dr Li and colleagues for their interest in our investigation and for raising questions that are supported by the current literature on this topic. We hope our response can contribute to a better understanding of the study's findings. Full-Text PDF