Herbst appliance effects on pharyngeal airway ventilation evaluated using computational fluid dynamics

Objective: To evaluate the effect of a Herbst appliance on ventilation of the pharyngeal airway (PA) using computational fluid dynamics (CFD).
Materials and Methods: Twenty-one Class II patients (10 boys; mean age, 11.7 years) who required Herbst therapy with edgewise treatment underwent cone-beam computed tomography (CBCT) before and after treatment. Nineteen Class I control patients (8 boys; mean age, 11.9 years) received edgewise treatment alone. The pressure and velocity of the PA were compared between the groups using CFD based on three-dimensional CBCT images of the PA.
Results: The change in oropharyngeal airway velocity in the Herbst group (1.95 m/s) was significantly larger than that in the control group (0.67 m/s). Similarly, the decrease in laryngopharyngeal airway velocity in the Herbst group (1.37 m/s) was significantly larger than that in the control group (0.57 m/s).
Conclusion: The Herbst appliance improves ventilation of the oropharyngeal and laryngopharyngeal airways. These results may provide a useful assessment of obstructive sleep apnea treatment during growth.

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