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.