Posterior airway changes during and after Herbst appliance treatment

Objectives Herbst appliance treatment results in posterior airway space (PAS) increase. The published data, however, is based on rather small samples and shows large inter-individual variation. Therefore, the current aim was to investigate PAS changes during and after Herbst plus subsequent multibracket appliance (MBA) treatment in a retrospective cohort study and to search for possible pre-treatment influencing factors. Materials and methods 503 former Class II:1 patients (overjet = 7.8 +/- 2.4 mm, ANB angle = 5.0 +/- 2.1 degrees) who had undergone treatment at 13.8 +/- 3.4 years (Department for Orthodontics, University of Giessen, Germany). Cephalograms from before (T0), after 24.9 +/- 9.2 months of treatment (T1) and 26.1 +/- 8.0 months after treatment (T2) were analysed for PAS changes (area-size and linear distances p, t, pC2, pC3, pC4. In addition, possible influencing pre-treatment characteristics were evaluated: overjet, ANB angle, Wits appraisal, ML/NSL angle, ArGoGn angle, age and skeletal maturity. Results On average, the PAS area increased by 23% during Herbst-MBA treatment (T1-T0) and remained constant (+/- 0%) thereafter (T2-T1). All linear distances also increased (6-19%) during T1-T0 and showed further increase (1-7%) during T2-T1. For all variables a large inter-individual variation existed. With regard to possible influencing factors on PAS changes, significant associations were observed for pre-treatment age and Wits appraisal of the patients. Conclusions PAS increases during Herbst-MBA treatment. For none of the assessed variables, relapse occurred afterwards. Young age and a large Wits appraisal were determined to be beneficial for PAS enlargement. Clinical relevance Herbst-MBA treatment seems to have a positive effect in the majority of Class II patients with reduced PAS.