DMDDuchenne muscular dystrophy LSCM Left sternocleidomastoid muscle RSCM Right sternocleidomastoid muscle AIM This study aimed to analyse electromyographic activity, masticatory efficiency, muscle thickness, and bite force of individuals with Duchenne muscular dystrophy (DMD).METHOD Forty males aged 4-15 years, 20 with DMD and 20 healthy age-, height-, and weight-matched controls, underwent electromyography and ultrasonography of temporalis, masseter, and sternocleidomastoid muscles during postural control of the jaw, mastication, and maximal molar bite force. RESULTSThe normalized electromyography signals showed higher activity in masseter and temporal muscles at rest, during protrusion, left and right laterality, and fatigue condition in the group with DMD than in the comparison group (p≤0.05). For masticatory efficiency of cycles, in analysis of non-habitual chewing of flavourless gum, and habitual chewing of peanuts and raisins, the group with DMD presented lower averages (p≤0.05). For the muscle thickness, the results showed that there was a lower muscle thickness in the group with DMD for all muscles during the rest and maximal voluntary contraction, except for masseter and sternocleidomastoid in the maximal voluntary contraction. In the maximal molar bite force, the group with DMD presented higher values for both sides than the comparison group (p≤0.05).INTERPRETATION Patients with DMD show muscle changes related to the stomatognathic system, in their activity, bite force, and muscle thickness.Duchenne muscular dystrophy (DMD) is an X-linked lethal neuromuscular disease that affects males. 1,2 Necrosis of skeletal muscle fibres, muscle fibrosis, and the infiltration of adipose tissue are seen from infancy. 3,4 Diagnosis is based on clinical presentation associated with a DNA diagnosis, significant elevations in the serum creatine kinase levels, morphological changes in the affected muscles, and the absence of the protein dystrophin. 5,6 The primary consequence of DMD is the decline of muscle function. Surface electromyography (EMG) has great potential as a measurement instrument in assessing muscle biomechanics.7 Quantitative EMG data can provide information on disease severity in various muscular dysfunctions. 8 The concomitant use of ultrasonography allows for the observation of changes in the muscle architecture, with the substitution of muscle cells by fat and connective tissue. The purpose of this study was to use surface EMG to detect changes in the patterns of EMG signals in patients with DMD to assess the activity of their temporalis, masseter, and sternocleidomastoid muscles bilaterally, and to analyse the masticatory efficiency, maximal molar bite force, and ultrasonography to evaluate muscle thickness of these muscles.These methods of analysis allow for the functional and quantitative study of the muscular system and provide important information about the morphology and activity levels of the muscles.10 Information about alterations in muscles of the stomatognathic system, including bite force...

The postural risk factors for dentists include the ease of vision in the workplace, cold, vibration and mechanical pressure in tissues, incorrect posture, functional fixity, cognitive requirements and work-related organizational and psychosocial factors. The objective was to analyze the posture of endodontists at the workplace. Eighteen right-handed endodontists aged 25 to 60 years (34±3) participated in the study. Electromyography, kinemetry, ergonomic scales (RULA and Couto's checklist) and biophotogrammetry were used to analyze the posture of endodontists during root canal treatment of the maxillary right first and second molars using rotary and manual instrumentation. The variations observed in the electromyographic activities during the performance of rotary and manual techniques suggest that the fibers of the longissimus region, anterior and medium deltoid, medium trapezium, biceps, triceps brachii, brachioradialis and short thumb abductor muscles underwent adaptations to provide more accurate functional movements. Computerized kinemetry and biophotogrammetry showed that, as far as posture is concerned, rotary technique was more demanding than the manual technique. In conclusion, the group of endodontists evaluated in this study exhibited posture disorders regardless of whether the rotary or manual technique was used.

Background Parkinson's disease is a neurological disorder that promotes motor changes in the body. Objective The aim of this study was to investigate the impairment of the stomatognathic function regarding molar bite force, electromyographic activity and thickness of the craniocervical muscles in patients with Parkinson's disease in comparison with those in asymptomatic controls. Methods Twenty‐four subjects were divided into two groups, a Parkinson's disease group (n = 12) and a control group (n = 12). The subjects were evaluated on the basis of molar bite force, electromyographic activity (rest, right and left laterality, protrusion, maximum voluntary contraction) and thickness (rest and maximum voluntary contraction) of the right and left temporal (anterior portion), masseter and sternocleidomastoid muscles. The results were submitted to a multivariate analysis of variance (MANOVA) to compare the means of the two independent groups, considering diagnosis of Parkinson's disease and craniocervical muscles as independent variables. For the post hoc comparisons, Bonferroni correction was used (P < 0.05). Results Parkinson's disease group presented lower mean values both sides for maximal molar bite force, significant increases in the electromyographic activities during mandibular tasks, lower mean thickness values of the masseter and sternocleidomastoid muscles, and higher mean thickness values of the temporalis muscles (anterior portion). Conclusion The results suggest that patients with Parkinson's disease may present functional changes of the stomatognathic system, related to bite force, electromyographic activity and thickness of the craniocervical muscles. The greater temporal muscle thickness in Parkinson's disease patients may compromise their daily life activities, especially with respect to chewing and nutrition.

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