DYNAMICS OF CHANGES IN THE ELECTROMYOGRAPHIC INDICATORS OF MASTICATING MUSCLES DURING THE PROSTHETIC REHABILITATION OF PATIENTS WITH PATHOLOGICAL ABRASION OF TEETH WHEN USING REMOVABLE PARTIAL FIXED DENTURES

Pathological abrasion of teeth is a fast process, accompanied by changes in the dental tissues and tissues of periodontium, as well as a disorder of the functions of the masticatory muscles and TMJ (temporomandibular joint). According to different authors, the prevalence of pathological abrasion of hard dental tissues ranges from 4% to 57% at a younger age and reaches 91% in the elderly age. The difficulties of prosthetic rehabilitation of this category of patients are caused by combined morpho-functional disorders. Therefore, the ability to assess the condition of the masticatory muscles is quite important for the further development of the doctor's actions and the preparation of a treatment plan. 
The aim of the study was to determine the state of the masticatory muscles using electromyographic studies in individuals with a generalized form of pathological abrasion, namely, with those forms which are combined with defects of dental rows of different localization before treatment and in the distant periods after treatment compared to the norm. 
For clinical assessment of the quality of prosthetic results, we recruited a clinical observation group and a control group. All patients of the clinical group were made constructions of removable partial fixed dentures. To achieve the aim, we used the electromyographic recording of the masticatory muscles’ biopotentials during the masticatory movements in the specified time. 
The results of our research work indicate that after 1 year of use of the above-mentioned dentures, the amplitude indicator during voluntary compression is 602.92±5.98 μV, which is close to the norm (641.58±10.01 μV) and almost three times more than before using this type of dentures (191.16±9.16 μV). A similar pattern is observed during voluntary chewing: the amplitude approaches the norm (643.92±9.11 μV) and is 628.54±5.77 μV compared to the results before using dentures (203.86±9.21 μV). 
The integral indicator of electromyographic research (coefficient “K”) which shows the neuro-reflex activity of the masticatory muscles in patients who used removable partial fixed dentures evidenced a tendency towards positive dynamics of changes in this indicator (1.02±0.01 in the norm versus 1.31 ±0.06 after 1 month, 1.20±0.04 after 6 months and 1.06±0.02 after 1 year).