Effects of Twin-Blocks on Airway and its Surrounding Structure

Objectives: The aim of the retrospective study was to explore changes after Twin-blocks therapy of airway and hyoid bone position.
Methods: 15 children’s cephalometry records were collected retrospectively, all of whom had Twin-blocks therapy for their retrognathia. Measurements including facial patterns (∠SNA, ∠SNB, Me-SN), hyoid bone (H-PP, H-SN, H-Me) and airway width (MAS, IAS) were recorded. Student-t-test was used to compare parameters pre- and posttreatment; Pearson correlation was applied to identify correlations between parameters.
Results: While the mandible moved anteriorly and inferiorly, the hyoid bone moved to the similar direction. However, the amount of movement varied between mandible and hyoid, no correlation were found between mandible changes and hyoid changes. MAS and IAS were expanded posttreatment and this change was correlated with changes in ∠SNB.
Conclusions: 1. Twin-blocks could expand upper airway while correcting retrognathia in pediatric patients.
2. The differentiated movement of hyoid bone and mandible may indicated complex functional interactions and compensation between hyoid bone and airway.