Simulation in 3D-model of skeletal forms of sagittal malocclusion revealed tendency in tonus' modification of muscles of mastication in formation of distal and mesial occlusion. It's shown that distal occlusion is characterized by hypotonic condition of muscles of mastication, except posterior fibers of temporal muscle. Mesial occlusion is characterized by complex combination of muscle tone with prevalence of hypotonic condition of anterior fibers of temporal muscle, superficial portion of masseter muscle and medial pterygoid muscle. We have detected that using of myofunctional devices in treatment of sagittal malocclusion, temporomandibular joint dysfunction promotes of tone increasing of muscles of mastication.