Electromyographic study of postural adaptation during mandibular advancement

Mandibular advancement is currently used in orthodontic treatment or in some treatment of sleeping apnoea syndrome. A previous stabilometric study (Bazert et al. 2008) pointed out that important mandibular propulsion (90% of the maximal propulsion) obtained with a silicone occlusal splint (Sp90), wearing 40min, affects the postural control. The amplitudes of the sagittal (A-P, þ22%, p , 0.02) and transversal (M-L, þ12%, p , 0.05) swings of the foot pressure centre (CP) increased (Figure 1) and the CP position became progressively more posterior (mean: 2 6.19mm, p , 0.05) into the polygone of sustentation. If it is so, a propulsive occlusal splint induces a postural adaptation which is characterised by the modification of the muscular activity. The aim of this study is to detect which muscles participate and contribute to the postural stability, and to evaluate their excitation level using electromyographic data. These data are necessary to estimate the postural impact of the orthodontics appliances.