Effect of Twin Block Therapy Versus Fixed Functional Appliances on Pharyngeal Airway Space in Skeletal Class II Patients: A Prospective Cephalometric Study

Abstract

Background: Class II malocclusion is one of the most common malocclusion with varied prevalence. Functional therapy with appliances like Twin Block or Fixed functional appliances forms the mainstay of treatment in growing Class II patients. These patients might demonstrate narrow airway due to the retrognathic position of the mandible. This study investigated the effects of twin block and fixed functional appliance therapy (Forsus™ FRD) on the pharyngeal airway space in skeletal Class II patients.

Methods: Forty patients with Class II malocclusion were selected and divided into two equal groups of 20 patients each for both Twin block and Forsus group. Lateral cephalograms were obtained before and after the functional appliance therapy. Evaluation was done for changes in hyoid bone position, pharyngeal airway dimensions and tongue position.

Results: The variables of the study showed better hyoid position in both the groups. In Twin Block group, an increase in hy-apw2 and hy-PoFH suggested anterior positioning of hyoid and a decrease in H-MP and hy-ML indicated superior positioning. In Forsus group an increase in H-H', hy-FH, hy-ML, hy-NL, hy-NSL and hy-OL suggested inferior positioning of hyoid, while an increase in hy-apw2, hy-CVT, hy-PoFH, hy-RL and hy'-tgo indicated anterior positioning of hyoid bone after functional therapy.

Conclusion: Both the twin block and Forsus™ FRD improved the position of the hyoid bone after the functional appliance therapy however the changes were not statistically significant. Twin block and Forsus™ had similar effect on the hyoid bone position, pharyngeal dimensions and the tongue position.

Keywords: Class II malocclusion; Hyoid bone; functional appliances; mandibular retrognathism; pharyngeal airway space; tongue posi-tion.