Correction of a Class II Malocclusion with the Bionator: Skeletal and Dentoalveolar Eff ects - A Cephalometric Long-Term Study

A correction of Class II malocclusions can be achieved during the growth period by dentoalveolar and skeletal changes, supported by functional orthopaedic appliances. The main functional objective of these devices is to eliminate all factors that may cause the malocclusion such as habits, parafunctions of the surrounding muscles, a forced bite and habitual breathing through the mouth. Retrospective cephalometric short-term studies of patients treated with the functional orthopaedic device Bionator document the kind and magnitude of the changes differentiated by the morphological character of the Class II findings and the growth period. The Class I occlusion is achieved by dentoalveolar compensation during prepuberty and by skeletal growth adaptation during puberty. A comparison of initial and final cephalometric variables of treated and untreated homogeneous control groups demonstrate the effect of the device. Uninfluenced vs. influenced changes during the growth period reveal that the skeletal alterations are the same between the groups and only den-to-alveolar alterations are different. The treatment effect of the bionator is primarily dentoalveolar during prepuberty, later accompanied by individual natural growth during puberty. Long-term studies, 5 and 20 years after termination of the Bionator treatment served for the evaluation of the stability of skeletal and dentoalveolar changes. These cephalometric data illustrate the importance of patients' selection regarding morphological criteria by mandibular growth prediction, following the recommendation of Bjork and Odegaard, and precise planning of incisors positioning for a successful treatment. The comparision of patients successfully treated in the past with an untreated homogeneous test group from ,,Bolton Brush Growth Study" Center show a significant retrusion of the lower incisors and a stronger decrease of the mandubular angle and the interbasal angle MlNL in the bionator group as opposed to a slight lower incisor protrusion.