Long-term effects of Class II Herbst treatment on the pharyngeal airway width.

OBJECTIVE: The aim was to assess the long-term effects of Class II malocclusion treatment with the Herbst appliance on the pharyngeal airway (PA) width in comparison to untreated individuals with Classes I and II malocclusion. METHODS: Lateral cephalometric radiographs of 13 male Class II patients from before (T1) and after (T2) treatment with the Herbst appliance as well as after the end of growth (T3) were retrospectively analyzed and compared to two untreated age- and gender-matched samples with Class I (n = 13) or Class II (n = 13) malocclusion. The PA dimensions were measured using the parameters p (narrowest distance between the soft palate and the posterior pharyngeal wall) and t (narrowest distance between the base of the tongue and the posterior pharyngeal wall). In addition, standard cephalometric measurements were performed. RESULTS: Relevant changes in PA dimensions were only seen for the post-treatment period, during which the distances p and t showed a significant increase in the Herbst group only (∆p: 2.3 mm, ∆t: 3.3 mm) while remaining similar in both untreated groups (∆p: 0.5 mm, ∆t: 0.5 mm, respectively, ∆p: 0.7 mm, ∆t: 1.6 mm). During the same period, posterior face height showed a significantly larger increase in the Herbst group than in both control groups (8.2 versus 5.8 mm, respectively, 5.4 mm), whereas anterior face height (NL-Me) showed a similar development in all groups (4.6 versus 4.4 mm, respectively 3.2 mm). CONCLUSION: In the long term, Herbst treatment resulted in a significant post-treatment increase of PA width, possibly due to an increased lower posterior facial height development compared to untreated individuals.