Effects of functional appliance therapy on the dimensions of the upper airway: Herbst versus Twin Block appliances

Abstract

AIMS: To compare, in a randomized controlled clinical trial, the treatment effects of Herbst and Twin-Block (TB) appliances on the dimensions of the upper airway in adolescents. SUBJECTS AND METHOD: Twenty skeletal Class II patients (5 males, 15 females; aged 13.1 ± 1.3 years) were randomized to receive either Herbst or TB treatment. The treatment times of the Herbst and TB appliances were 12.7 ± 1.9 months and 13.0 ± 1.4 months, respectively. Lateral cephalograms were obtained before and after treatment. Upper airway and craniofacial variables of the upper airway were analyzed. RESULTS: Following functional appliance treatment, the angle of the soft palate was significantly deceased in the both Herbst and TB groups (P < 0.01). Retropalatal pharyngeal depth was increased in the Herbst group (P < 0.01) and the thickness of soft palate was increased in the TB group (P < 0.05). When comparing the two groups, the only significant difference was in lower face height. The TB group had a greater increase (5.0 mm) than the Herbst group (3.5 mm; P < 0.05). CONCLUSION: Both Herbst and TB appliances led to some dimensional changes in the craniofacial region and upper airway. The difference between them was only in craniofacial structures but not in upper airway structures.