Adolescents Upper-Airway and Hyoid-Bone Changes Following Class II Functional Treatment

Objectives: To determine the effects of functional appliance treatment for class II skeletal malocclusion on upper airway dimensions and hyoid bone position using cone beam computed tomography.
Methods: Four electronic databases were used to search for articles published until March 2016. A search of grey literature and manual search of the references of retrieved articles were also conducted. Two independent reviewers screened the articles for inclusion based on pre-set criteria. The primary outcome measures were short and long-term changes in upper airway dimensions, linear and angular measurements of hyoid bone position. The secondary outcomes were improvement in sleep quality, subjective daytime sleepiness, and sleep-related quality of life. Meta-analyses were conducted using random-effects models.
Results: Six retrospective studies were included. One used removable and the rest used fixed orthopedic appliances. Two of the studies were medium quality and four were low quality. Meta-analyses of two studies revealed an increase in the oropharyngeal volume by 2.89 cm³ (MD=2.89; 95% CI, 1.46, 4.33; p=<0.0001) in the functional appliances group over controls. Transverse and anteroposterior (A-P) dimensions of the oropharynx also increased significantly favoring the functional appliance groups. Two studies found significant anterior positioning of the hyoid bone with functional appliances compared to controls while one did not.
Conclusions: There is limited evidence that suggests short-term improvement in upper airway volume, transverse and A-P dimensions with the use of functional appliances for class II correction in adolescent patients. Evidence on the effects on hyoid bone position is inconclusive. Future high quality studies are warranted.