Hypermobility of the articular heads of the temporomandibular joint: pathology or variant of the norm?

Introduction: Among the large contingent of patients with TMJ dysfunctions, there are persons with hypermobility of the joint heads of the lower jaw. Moreover, at present, the question of the frequency of occurrence of hypermobility of articular heads of the TMJ is not reflected. The aim of the work is to find out the frequency of occurrence of hypermobility of articular head among a healthy population and to evaluate the clinical, radiological, and electromyographic characteristics of the muscular-articular complex in these individuals. Material and methods: Surveys were conducted for 476 students aged 19 to 25 years. For people with revealed articular hypermobility of the articular heads, chewing and temporal muscle electromyography, TMJ aiming zonography in a lateral projection with open and closed mouth were performed with an assessment of the correspondence of the articular fossa of the temporal bone to the size of the articular head, the location of the articular heads relative to the apex of the articular tubercle. Results: Of the examined 476 students, 95 people (20%) revealed hypermobility of the articular heads of TMJ. According to the results of clinical, functional and radiological studies of TMJ, we identified three degrees of hypermobility: light, moderately expressed, significant. With light to moderate degree of hypermobility, electromyography of the temporal and chewing muscles and TMJ zonography did not reveal a difference in performance compared to healthy ones. Most of the examined did not note functional discomfort from the joints. With a significant degree of hypermobility of the articular heads, electromyography of the temporal and chewing muscles revealed a lack of synergism in their work. On TMJ zonograms with an open mouth, the articular heads extended anteriorly beyond the tops of the articular tubercles almost under their outer base. Conclusions: It has been established that hypermobility of the joint heads of the TMJ, which does not cause signs of pathology in the form of masticatory function disorders, discoordination of the masticatory muscles and uncontrolled displacements of the lower jaw, the presence of a pain symptom should be considered as a variant of norm.

[Electromyographic characteristics of temporal and masticatory muscles in patients with compression-dislocation dysfunction of temporomandibular joints of different severity].

OBJECTIVE: Introduction: The main causes of dysfunctional conditions of the temporomandibular joints (TMJ), are occlusal, neurogenic, orthodontic disorders. The muscular component of TMJ is determines the dynamic anatomical and functional state of the mandible Therefore, in the diagnosis of dysfunctions and understanding of their pathogenesis belongs to the electromyographic method of investigation. The aim of the work was a comparative assessment of the bioelectrical activity of the actual chewing and temporal muscles in patients with musculo-articular compressiondislocation dysfunction of the TMJ of various severity. PATIENTS AND METHODS: Materials and methods: Electromyographic studies of temporal and masticatory muscles were performed in 43 patients. Was assess maximal parameters were recorded with the greatest compression of teeth and in the periods of chewing on the side of the pain symptom and on the opposite side (µV), the frequency of filling the myogram (Hz), the time of activity (Ta) and the resting time (Tc), coefficient "K", which determines the ratio of the processes of activity and rest with functional samples (K = Ta / Tc). RESULTS: Results and conclusions: The main feature of the functional properties of the studied muscles in the compression-dislocation dysfunction of the TMJ is the prevalence of the maximum indices of their bioelectrical activity on the side of the joint with the dislocation of the articular head of the mandible in comparison with the joint, which is in a compression state both during periods of compression of the teeth and mastication. This kind of discoordination in the work of the muscular masticatory apparatus is reflected in the severity of the course of dysfunction.