The statistical characteristics of the electrical activity of the masticatory muscles in their functional impairments and pathology of the supporting tissues of the teeth

Abstract

The aim of the study is to investigate changes in the electrical activity of the masticatory muscles in patients with various forms of parafunctions and combined dental arch deformity, characteristic of periodontal diseases.
Materials and methods.
Three groups of individuals with muscle parafunctions were examined: 1st group (n=21) — patients with teeth clenching, 2nd group (n=19) — individuals with teeth grinding, 3rd group (n=16) — subjects with both teeth clenching and grinding. A control group consisted of 15 physically healthy volunteers. To identify and evaluate neurotic conditions, the K.K. Yahin, D.M. Mendeleevich clinical questionnaire was used. The activity of the masticatory muscles was studied using concentric electrodes on the “Viking Quest” electromyograph. Morphological abnormalities of the temporomandibular joint were identified on series of magnetic resonance imaging.
Results.
Increased abrasion of the hard tooth tissues during jaw clenching is more pronounced in the lateral segments of the dental arch and has a cup-shaped form (100% of patients); grinding of the teeth results in uneven abrasion across the dental arch (more than 85% of patients). Vegetative disorders, obsessive-phobic, and conversion disorders were observed in half of the cases among patients with various forms of masticatory muscle parafunction. All forms of parafunctional activity were accompanied by denervation processes of muscle fibers and an increase in activity amplitude. On the pain side of the temporomandibular joint, a 1.84-fold increase in indicators above the control level was observed in group 1, 1.48-fold in group 2 and 1.61-fold in group 3. On the opposite side, the prevalence of values was 1.58 times in the 1st group; 1.32 times in the 2nd group and 1.46 times in the 3rd group. Jaw clenching was found to shorten the duration of potentials on the painful side — 8.1% and on the opposite side — 3.8%; while grinding teeth, the increase in this indicator was 8.9% and 12.9%, respectively. Displacements of the articular disks in patients with jaw clenching are more often observed in the anterior direction (38% of cases), while during teeth grinding, they occur in the anterolateral vector (42% of cases). Due to the transfer of the vector of increased load from muscles to hard tissue elements of the joint, a compensatory reaction occurs in the form of accumulation of synovial fluid (37% of cases). The clinical picture worsened in the case of developed periodontitis.
Conclusion.
Increased abrasion of the hard tooth tissues has characteristic features depending on the clinical forms of the masticatory muscle’s parafunctions. An ecological momentary assessment of the chewing muscles condition can serve as a tool in the differential diagnosis of clinical forms of muscle parafunctions and to assess the frequency of their manifestations. Disorders of neurotic genesis occur in patients with various forms of parafunction of the masticatory muscles in half of the cases. Muscle parafunction, regardless of its shape, is accompanied by the processes of denervation of muscle fibers in their motor units and an increase in the amplitude of activity. Lateral dislocations of the articular discs are most characteristic in patients with teeth grinding, in the anterior direction — in persons with jaw clenching.