A comparative study of Twin-Block and van Beek Headgear-Activator on the three-dimensional morphology of the upper airway in growing children with mandibular retraction in skeletal class II malocclusion

Objectives To compare the variations in the upper airway of children with skeletal Class II mandibular retrognathism treated with van Beek Headgear-Activator (vBHGA) and Twin-Block (TB) appliances. Materials and methods 40 children were involved in this retrospective study and divided into two intervention groups: the vBHGA group and the TB group, each comprising 20 individuals with an average age of 11.13 years. Employing Cone Beam Computed Tomography and Geometric Morphometric analysis, a comprehensive assessment of the upper airway's volume, minimum cross-sectional area (m-CSA), and 3D shape characteristics was conducted pre-and post-treatment. Results The total volume, oropharynx volume, oropharynx m-CSA, and hypopharynx m-CSA significantly increased in both the vBHGA and TB groups (p < 0.05). The sole discrepancy between the two groups was observed in comparing the nasopharynx m-CSA (p < 0.05). A morphological difference was observed in the vBHGA group before and after treatment (p < 0.05), characterized by a wider and shorter airway, positioning of the posterior nasal spine closer to the anterior inferior area, and a more posterior nasopharyngeal wall. However, there were no significant shape differences between the two groups or before and after treatment within the TB group. Conclusion It appears that both vBHGA and TB interventions contribute positively to alleviating upper airway constriction. Nonetheless, the vBHGA group exhibits more alterations in the configuration of the nasopharynx. Clinical relevance Both orthodontic appliances have a positive impact on the upper airway but still have differences, emphasizing the need for individualized consideration when selecting orthodontic interventions. Clinical trial registration This study was also registered with the Chinese Clinical Trial Registry with registration number ChiCTR2400086867.