Prognosis of pterygoid muscles tonus in occlusion abnormalities associated with temporomandibular joint disfunction

The article covers the results of prognosis of pterygoid muscles tonus variations in different kinds of sagittal and transversal occlusion abnormalities with temporomandibular joint dysfunction syndrome. We carried out the mechanical analysis of deformations of simplified frame of masticatory muscles, fixed on the three-dimensional model of "standard" skull. At the first stage, the deformities simulated distal, mesial occlusion and lateroposition of the mandible. In cases of distal occlusion, the tonus trend of masticatory muscles is general hypotonic, except posterior fascicles of temporal muscle. In cases of mesial occlusion, the hypertonic tendency is detected in masseter muscle, posterior fascicles of temporal and medial pterygoid muscle, the hypotonic tendency - in lateral pterygoid muscle. Cross bite has a complicated aspects of tonus changes: on the mandible displacement side masseter and medial pterygoid muscles are in hypersthenia and posterior fascicles of temporal muscle are in impaired tonus. At the second stage, the simplified frame of masticatory muscles was distorted in concordance with degree of masseter muscle functional activity. The study reveals that pterygoid muscles is hypotonic on temporomandibular joint dysfunction side and external pterygoid muscle tonus is less then internal pterygoid muscle tonus in 2.0-3.5 times. On the opposite side, pterygoid muscles are hypertonic and external pterygoid muscle tonus is more then internal pterygoid muscle tonus 3.5-6.0 times.