Український стоматологічний альманах (Mar 2016)
INDICATORS OF BIOELECTRICAL ACTIVITY OF THE PROPER MASSETER MUSCLES WITH THEIR DIFFERENT MASS IN MALES
Abstract
The biomechanic disorders of entire masticatory complex underlie the formation of extraarticular functional disturbances of the temporomandibular joint. The available data in literature on electromyographic study of the masseter muscular apparatus are sometimes controversial even for healthy individuals. That is why it is reasonable to search solutions of problems on the objectification of the leading characteristics of bioelectric activity of the masseter muscles for people having no dental pathologies in spite of adequate comparison them to various diseases of the muscle and joint complex for their clinical and pathogenetic treatment. The aim of the research is to determine the bioelectric activity of the proper masseter muscles with their different mass for healthy individuals. Objects and methods. The study included 30 male volunteers aged 21-23 of the same body types, who had no pathology of dentition, 10 of them with the small masseter muscles mass, in 10 – moderate, in 10 – high. The mass of masticatory muscles was calculated as follows: m = Vx1.100 g / cm3, where 1.100 g / cm3 is the specific weight of man’s muscle, V – volume of muscle fibers, m – mass of the studied muscle. The amount of chewing muscles was determined using slide calipers with compressed teeth by measuring its width at an angle and body of the mandible, height and thickness. The muscle mass within 13-15 g (14.2 ±0.1 g) was considered as small, 16-19 g (17.6±2.1 g) – as moderate; 20-23 g (21.0 ±1.5 g) – as large. Registration of EMG was conducted on four-channel electromyograph «Neuro-EMG-Micro» (Neurosoft, Russia). For a better objective assessment of muscle condition, the technique of chewing a standard piece of bread (rye bread crumb of yesterday's baking, sized 1х1х1) was used. The data of EMG results were processed by a computer program developed at the Higher State Educational Establishment of Ukraine «Ukrainian Medical Stomatological Academy» (Poltava). Research results. The obtained results confirmed the existence of physiological asymmetry in functional activity of masticatory apparatus both in its small muscle mass, and in large. According to the main performance parameters, the bioelectric activity of left masseter muscle slightly prevails over the right one both in chewing and jaws pressure, reflecting different power of potentials of excitation and frequencies of filling the myogram. While comparing the performance time of activity in masticatory muscles fibers with small and large weight in chewing their relationship was following for the right – 1:1.9, for the left – 1:1.86 at the maximum amplitude of bioenergy for the examined individuals with small mass of right masticatory muscle 678.87+21.16 uV, left – 783.52+18.75 uV; in the large mass – indicators of the right masticatory muscle amounted to 1.061.32+32.43 uV, left – 1,175.12+21.15 uV. The coefficient of bioelectrical activity («K») of the right masseter muscle with its low weight reached 1.40+0.08, left – 1.39+0.10. For individuals with significant weight of masseter muscles, such figure amounted to 1.9+0.13 for the right, and 1.85+0.11 for the left muscle, indicating on the difference in the length of time phases of activity and rest time for muscles with their different masses. Thus, the study convincingly showed the significant difference in terms of basic EMG parameters of proper masseter muscles with their different mass both in the period of mastication and during jaws compression that should be considered in perspective scientific research devoted to evaluating the biopotential not only of masseter but also of temporal and facial muscles, as well as in clinical practice for patients with abnormalities of dental system, defects of dentition, different types of dysfunctional conditions of temporomandibular joint.
