The aim of the present long-term follow-up study of orthodontically-treated patients (mean: 15·7 years) was to analyse post-retention changes and to reveal factors which may play a role as predictors for long-term prognosis. Pretreatment, end-of-treatment, and post-retention models of 226 cases with all types of anomaly were used to measure intercanine and intermolar width, arch length, and sum of the mesiodistal dimension of the incisors, Irregularity Index, crowding, molar and canine relationship, overjet, and overbite. In order to assess the influence of sex, initial and end-of-treatment alignment, type of therapy, amount of tooth movement, and presence of third molars on the extent of postretention changes, the total sample was divided into subgroups. Findings indicated that post-retention crowding and incisor irregularity increased more frequently in the mandible than in the maxilla. Pretreatment variables such as increased mesiodistal incisor dimension, severe crowding and incisor irregularity, arch length deficiency, arch constriction, and increased overbite as well as post-treatment spacing, arch expansion, increased arch length, and residual Class II or III molar relationships were found to be associated factors in the process of post-retention increase of crowding and incisor irregularity. ‘Overexpansion’ was found to be a factor in mandibular incisor relapse.

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Pre- and post-treatment lateral radiographs of 120 former patients with skeletal class II, who had been treated with either an Andresen/Häupl type activator or bite jumping plates, were selected for this study. The evaluation results showed that bite jumping plates had a significant inhibition on the forward downward growth and the anterior rotation of the maxilla. The increase of the SNB-angle was significantly higher and there was also more posterior rotation of the maxilla in those patients, who had been treated with an activator. A two-way analysis of variance was carried out and it was possible to show that the independent treatment factors explained only 1/5 to 1/3 of the overall variance of the sample. The differences among the patients seem to depend more on individual growth patterns than just on the type of removable appliance.

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