Motor learning might contribute to a therapeutic anterior shift of the habitual mandibular position-An exploratory study.

Abstract

Passive mandibular advancement with functional appliances is commonly used to treat juvenile patients with mandibular retrognathism. The aim of this study was to investigate whether active repetitive training of the mandible into an anterior position would result in a shift of the habitual mandibular position (HMP). Twenty adult healthy subjects were randomly assigned to one of two groups: a training group receiving six supervised functional training sessions of 10min each and a control group without training. Bonded lateral biteplates disengaged occlusion among both groups throughout the 15-day experiment. Customised registration-training appliances consisted of a maxillary component with an anterior plane and a mandibular component with an attached metal sphere. Training sessions consisted of repeated mouth-opening/closing cycles (frequency: 30/min) to hit an anteriorly positioned hemispherical target notch with this metal sphere. The HMP was registered at defined times during the experiment. The HMP in the training group showed a statistically significant anterior shift of 1.6mm (interquartile range [IQR]: 1.2mm), compared with a significant posterior shift of -0.8mm (IQR: 2.8mm) in the control group (p<.05). Although the anterior shift among the training group showed a partial relapse 4days after the first training block, it then advanced slightly in the 4-day interval after the second training block, which might indicate neuroplasticity of the masticatory motor system. Motor learning by repetitive training of the mandible into an anterior position might help to improve the results of functional appliance therapy among patients with mandibular retrognathism.