Effects of Herbst and Pendex appliances treatment on the upper airway: A cone-beam computed tomography analysis

Class II functional appliances are widely used to treat skeletal Class II malocclusion in growing patients, whereas molar distalization is often employed for dental Class II malocclusion. However, the impact of these treatment modalities on upper airway dimensions remains controversial. This study examines the effects of Herbst appliance treatments on the upper airway changes compared with the Pendex appliance in adolescent patients with Class II malocclusion.

Cone-beam computed tomography (CBCT) scans of 50 patients with Class II malocclusion were obtained from a private orthodontic office (Chalfont, Pa). Twenty-five patients were treated with Herbst appliances (12.16 ± 1.89 years; 13 males and 12 females) and 25 patients with Pendex appliances (11.72 ± 1.22 years; 12 males and 13 females). Measurements were taken for volume, length, and cross-sectional areas of the total, retropalatal, and retroglossal upper airway. CBCTs were taken at baseline (T1), after appliance removal (T2), and from final records after fixed edgewise appliance treatment (T3) (T1-T3: 41.11 ± 9.95 months for Herbst appliances and 44.81 ± 9.63 months for Pendex appliances). In addition to 3-dimensional CBCT analysis, 2-dimensional measurements were performed and compared with a Class II untreated control group comprising 25 age- and sex-matched patients from the American Association of Orthodontists Foundation Bolton-Brush Craniofacial Growth Legacy Collection. Differences across time points within groups were assessed using repeated-measures analysis of variance test, whereas between-group differences at individual time points and for changes from T1 to T3 were evaluated using independent-samples t tests adjusted for baseline (T1) outcome values and follow-up duration.

From T1 to T3, both the Herbst and Pendex groups showed a significant increase in total upper airway volume and length. However, the magnitude of these changes did not differ significantly between the 2 groups. In the 2-dimensional analysis, no significant differences were observed among the Herbst, Pendex, and untreated control groups in airway area changes from T1 to T3.

Both the Herbst and Pendex appliances resulted in comparable increases in total upper airway volume and length in adolescent patients with Class II malocclusion, primarily attributable to normal growth.