Electromyographic standardized indices in healthy brazilian children and adults

AIM: We aimed to (a) determine values of the electromyographic (sEMG) standardized indices for the assessment of muscular symmetry (left and right side, percentage overlapping coefficient, POC), potential lateral displacing components (unbalanced contractile activities of contralateral masseter and temporalis muscles, TORS), anterior-posterior displacing component (barycenter, BAR), relative activity (most prevalent pair of masticatory muscles, ATTIV), and standardized total activity (IMPACT) in healthy Brazilian children; (b) compare children to health adults. METHODS: We analyzed 19 healthy children (6-12 years, mean age 9.5, SD 2.0), 11 male and 8 female, 19 healthy adults (19-30 years, mean age 25.2, SD 3.5 ), 3 male and 16 female. All subjects had normal natural dentition for age and normal dental occlusion, and no temporomandibular or craniocervical disorders. Additionally, children had Facial Height Ratio (FRH = Jarabak quotient) > 59% and no previous or current orthodontic treatment. sEMGs of masseter and temporal muscles were performed during maximum teeth clenching either on cotton rolls between teeth or in intercuspal position (MVC). EMG indices were calculated with the potentials recorded during the MVC tests standardized by MVC with cotton rolls. Descriptive statistics were computed for all variables that were normally distributed. Mean values were compared by Student’s t tests for independent samples (P< 0.05). RESULTS: Children showed adequate neuromuscular coordination, with mean values similar to those of the adults: POC [%] masseter (85.9±4.0% and 86.2±3.9%), POC [%] temporal (86.4±10.0% and 87.4±2.5%), TORS [%] (89.6±7.1% and 91.8±0.9%), BAR [%] (86.1±8.5% and 87.4±7.1%), and ATTIV [%] (9.4±15.9% and 10.3±8.4%). Because children showed higher activity during MVC than during MVC with cotton rolls, their Impact index [%] (total muscular standardized activity) was higher than in adults (142±51% and 100±31%) p = 0.005. The values obtained for healthy adults were in accordance with literature data. CONCLUSION: The current study was the first to evaluate these EMG indices in Brazilian children. Overall, these findings in healthy subjects with normal occlusion may be interpreted as muscular coordination, independent of dentition stage and craniofacial development. These children data may be used as reference values. ACKNOWLEDGEMENT: This work was supported by Provost’s Office for Research of the University of São Paulo, and the first author received a fellowship from: The State of São Paulo Research Foundation (FAPESP) -Brazil.