RESUMO
BACKGROUND: Bruxism is a rhythmic masticatory muscle activity that occurs involuntarily in a non-physiologically functional state. There is a lack of research classifying the functional status of masticatory muscles in patients with different mandibular movement types (centric clenching or eccentric grinding) of bruxism. AIM: To assess the differences of the masticatory muscle activity in patients with different types of bruxism. METHODS: A total of 21 subjects with centric bruxism (CB) and 21 subjects with eccentric bruxism (ECB) were screened from college students according to a questionnaire and their tooth wear features. Sixteen subjects with no bruxism were also recruited. The surface electromyography (EMG) signals of the temporalis anterior (TA) and superficial masseter muscle (MM) were measured in different mandibular positions and during the chewing task. The EMG amplitude and chewing cycle duration parameters were then analyzed. RESULTS: The CB group showed fewer muscle maximal motor units, with the MM being more pronounced, a higher proportion of muscle contractions to be recruited for the same load of chewing activity, and a longer chewing cycle. The ECB group showed more TA maximal motor units and higher MM activity on the non-working side in unilateral chewing. CONCLUSION: CB mainly affects the MM, and patients with CB show reduced masticatory muscle contraction efficiency and chewing cycle efficiency. ECB mainly affects the TA, and patients with ECB show enhanced contraction of non-functional lateral muscle bundles.
RESUMO
BACKGROUND: Condylar osteophytes, a remodeling form of temporomandibular joint osteoarthritis (TMJ OA), mainly manifest as marginal angular outgrowths of the condyle. Previous researchers have advocated surgical removal of condylar osteophytes. Reports on the effect of occlusal splint on TMJ OA patients' joints have mostly focused on treatment with this splint, which can reduce the absorption of the affected condyle and promote repair and regeneration. However, the effect of the splint on the dissolution of condylar osteophytes has not yet been reported. CASE SUMMARY: A 68-year-old female patient suffered from occlusal discomfort with left facial pain for 2 years. Cone beam computed tomography showed a rare osteophyte on top of her left condyle. She was finally diagnosed with TMJ OA. The patient refused surgical treatment and received conservative treatment with a muscle balance occlusal splint. The pain experienced by the patient on the left side of her face was relieved, and her chewing ability recovered after treatment. The osteophyte dissolved, and the condylar cortex remained stable during long-term follow-up observations. CONCLUSION: The muscle balance occlusal splint could be a noninvasive means of treating condylar osteophytes in TMJ OA patients.
