Evaluation of the upper airway dimensions following Herbst appliance treatment in adolescents: A retrospective study

Abstract

Objectives: This retrospective study investigated dimensional changes in the upper airway following Herbst appliance therapy in adolescents with Class II malocclusion and compared those changes with growth data. Materials and Methods: Lateral cephalograms from 44 Herbst-treated adolescents (23 boys, mean age = 13.3 ± 1.1 years, and 21 girls, mean age = 12.6 ± 1.1 years) were analyzed for the changes in the upper airway and craniofacial variables. Longitudinal cephalometric data of 34 untreated adolescents (15 boys, mean age = 12.6 ± 0.3 years, and 19 girls, mean age = 12.9 ± 0.4 years) were used as growth data for comparison. Results: Following treatment, significant changes were noted in most of the variables. Boys displayed greater downward movement of the hyoid bone than girls did (P = 0.021). Compared with the growth data, a greater increase in retroglossal oropharyngeal depth and hypopharyngeal depth was observed in boys and girls, respectively. Both displayed a decrease in the inclination of the soft palate and a smaller change in nasopharyngeal depth. Conclusion: Herbst appliance therapy enlarges the upper airway dimensions at two dissimilar sites in girls (oropharynx) and boys (hypopharynx). Boys display a greater increase in anterior and posterior facial heights than girls do, potentially accounting for the site dissimilarities. Moreover, a Herbst appliance improves the inclination of the soft palate and restricts the growth of the nasopharynx in both boys and girls.