Floating norms and post-treatment overbite in open bite patients

In this study, the clinical significance of three floating norm systems, the Bergen Box (BB), the Segner-Hasund Harmonybox 1 and 2 (SHH1 and SHH2), as well as the influence of treatment modalities for predicting results of an open bite treatment were investigated. In the BB and SHH1, patients with a steep mandibular plane angle or a skeletal open bite configuration (O1mand, O1mandmax, O1max, or N1mand) were considered 'high risk', while in the SHH2, only the configurations O1mand and O1mandmax were considered high risk. All other configurations were designated 'low risk'. It was postulated that in high risk patients, the overbite was likely to relapse into an open bite after retention. Cephalograms of 83 open bite patients taken before treatment (T1) and at the end of retention (T2) were studied. Patients designated as low risk generally had a normal overbite at T2 after treatment, regardless of which box was used. The risk configurations of the SHH1 and SHH2 at T1 were significant predictors of the overbite at T2, the first being slightly better compared with the SHH2. The main clinical values of the SHH1 and SHH2 are strongly supported by the relatively good success rate in distinguishing a low-risk configuration. Reliable prediction of the treatment results of high-risk patients with risk configurations according to the SHH is improved by evaluating treatment modalities. The posterior bite splint seemed to have a bite opening effect, while a bite closing effect was associated with the use of a removable retention appliance.