Investigation On Stomatognathic System Function Of Subjects With Anterior Open Bite In Permanent Dentition

The purpose of this study is to investigate the functional characteristics of the subjects with anterior open bite in permanent detition.The subjects consisted of 15 patients with anterior open bite in permanent dentition (mean age 21.5 years). 15 subjects with individual normal occlusion served as control group (mean age 22.7 years). All cases were examined by means of K6-I Evaluation System manufactured by Myotronics US.The first part of this study was to trace and record the mandibular movement of the two groups during (1) at rest, (2) maximum excursions (opening-closing, protrusion, right and left excursions), (3) usual opening-closing , wide and fast opening-closing, (4) swallowing (5) mastication. The dimension of the freeway space was similar between groups. The results showed no differences between groups in the extension of the movements during protrusion or lateral excursions. However, anterior open bite patients exhibited a significant diminishing in the extension of opening. The velocity are not different between groups during opening and closing , but the terminalvelocity of wide and fast closing is sharp down in the open bite patients. The open bite group more frequently showed a pattern of abnormal swallowing. The types of chewing cycles were different between groups and descriptive analysis by K6-I Evaluation was more "poor" in open bite patients.The second part of this study was the electromyography (EMG) investigation of the masticatory muscles (anterior temporalis, masseter muscle) measured with bipolar surface electrodes. EMG of two groups were recorded at rest , during maximal voluntary clenching and slowly closing from the rest position to habitual centric occlusion. The results showed on differences between groups in EMG of posture. A significant decrease in EMG of voluntary clenching was found in the open bite group. The results revealed disharmony in the activity of masticatory muscles in open bite patients.According to all described above, it can be concluded that the stomatognathic function was restricted in anterior open bite patients. And it was considered that anterior open bite may cause TMD.