Objectives. The aim of this work is the analysis of neuromuscular and functional effects caused by activator therapy in subjects with skeletal class II and skeletal deep bite malocclusion. Materials and methods. Electromyography (EMG) of masseter and temporal anterior muscles was carried out in 33 subjects at the beginning, after six and twelve months of activator therapy. A Freely electromyographic equipment was used following LAFAS protocol: 1) maximum voluntary clench on cotton rolls; 2) maximum voluntary clench on teeth; 3) Clench-Rest; 4) Tap. Maximum clench on the activator was added to this protocol in order to test neuromuscular changes caused by the appliance. Results. EMG showed an inhibition of muscular contraction during maximum voluntary clench on activator when compared to maximum voluntary clench on teeth. Conclusions. The results of our research confirm activator's mode of action in mandibular growth control, as described in literature. The appliance does not work by increasing active muscular contractions, but inducing elastic passive forces, generated by soft tissues viscoelasticity.
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