Pharyngeal airway and hyoid bone position changes of skeletal anchored Forsus Fatigue Resistant Device and activator appliances

Abstract

Objectives To evaluate the effects of miniplate anchored Forsus Fatigue Resistant Device (MAF) and activator treatments in the pharyngeal airway dimensions and hyoid bone position.

Materials and methods Thirty-eight patients with mandibular retrusion who were treated with either MAF or activator were selected retrospectively and compared with an untreated control group. The data of 114 lateral cephalograms, comprising those taken before treatment (T1) and at the end of functional treatment (T2), were evaluated with regard to their linear, angular, and area measurements.

Results The mandibular length increased and the hyoid bone moved forward with both treatments (P < 0.05). The horizontal change in the hyoid bone position with MAF treatment was correlated with changes in the point B and ANB angle. Increases of 1.8 mm, 1.4 mm, and 1.8 mm in the pharyngeal airway dimensions were obtained at the levels of the second, third, and fourth cervical vertebra, respectively, with the MAF treatment. On the other hand, an increase of 1.9 mm was found at the level of the fourth cervical vertebra with the activator treatment. The greatest vertical movement in the Menton and the highest increase in the oropharyngeal area were observed in the MAF group (P < 0.05).

Conclusion Both the MAF and activator treatments caused favorable maxillomandibular changes; however, the MAF treatment provided a greater increase in the oropharyngeal area according to both the increase in mandibular length and the change in the vertical position of the mandible.

Clinical relevance Functional appliances were found to be useful in increasing the pharyngeal airway dimensions in the shortterm. The skeletal anchored fixed functional appliance caused a greater increase in the oropharyngeal airway area that may be beneficial for Class II patients who carry a risk of having respiratory problems.