An electromyographic investigation of masticatory muscles symmetry in normo‐occlusion subjects

Abstract

The influence of occlusal conditions on stomatognathic function can be assessed by electromyography. Electromyographic activity of left and right temporal and masseter muscles was recorded in 30 young healthy adults with a normal occlusion during: (1) a 3-s maximum voluntary clench on cotton rolls positioned on the posterior teeth (standardization recording); (2) a 3-s maximum voluntary clench in intercuspal position; and (3) a 3-s alternate 'maximum' voluntary contraction and relaxation with a 1 Hz frequency. All potentials were standardized as a percentage of the maximum potential of test 1. Waveforms of paired muscles were compared by computing a percentage overlapping coefficient (ratio between each 50-ms overlapped areas and the total areas, up to 100% for symmetric muscles). Waveforms were also analysed for a laterodeviating effect on the mandible given by unbalanced muscular couples, and a torque coefficient (up to 100% for a significant laterodeviating couple on the mandible) was computed. In all subjects, both tests were performed with symmetric muscular patterns (more than 88%) and with negligible laterodeviating couples on the mandible (lower than 10%). The two coefficients allow an assessment of muscular asymmetry during static and dynamic clenching tests, and, together with the standardization of the potentials, could be a useful tool to detect functionally altered occlusal conditions, i.e. conditions where an apparent good morphological situation is not related to a correct neuromuscular status.

Effect of different dental articulating papers on SEMG activity during maximum clenching

“…A decrease from values obtained during MVC has been found for TA and MS muscles respectively, bringing the POC values outside the physiological standards reported by Ferrario et al (Ferrario et al , 2000) most of the times. While the median variations from MVC on natural dentition are quite moderate (-5.7 to -7.8 and from -4.3 to -5.8, for TA and MS muscles respectively), in some cases greater negative changes of POC values up to -25/-30 (see percentiles) were detected; they highlight an effect of articulating paper on the stomatognathic muscular system.…”

“…This technique is regarded as an objective and reliable method for evaluating muscle function and efficiency by detecting electrical potentials; the analysis of the recordings allows the assessment of general muscle activity, the cooperation of different muscles, and the variability of their activity over time (Hugger et al , 2008;van der Bilt, 2011;Wozniak et al , 2013). In our study we followed the EMG protocol proposed by Ferrario et al which is based on a starting normalization record: an MVC is performed on cotton rolls just before the recording of the actual test, with the same electrodes and EMG apparatus (Ferrario et al , 2000;Ferrario et al , 2006). That protocol have been shown to be highly repeatable, allowing the standardization of EMG indices (like POC% and IMP µV/µS%) (Ferrario et al , 2000); moreover, it has been used successfully to discover EMG differences between healthy subjects, patients with temporo-mandibular disorders (TMD) or among patients belonging to different Research Diagnostic Criteria for TMD (Tartaglia et al , 2008).…”

“…After test recordings, a series of SEMG indices were computed as detailed by Ferrario et al (Ferrario et al , 2000) and Tartaglia et al (Tartaglia et al , 2008): POC temporal (POC_TA), POC masseter (POC_MS), anterior-posterior coefficient (APC) and IMPACT (IMP) as detailed below.…”

Influence of craniomandibular and cervical pain on the activity of masticatory muscles in individuals with Temporomandibular Disorder

“…In ATS and MAS, the percentage of overlapping coefficient (OVL%) of the areas of the curves of the linear envelopment of homologous muscles was calculated (16,17) . The APC compares muscle activity between MA and AT muscles.…”

Terapia com placa oclusal com e sem guias anteriores de desoclusão em pacientes com disfunção temporomandibular e zumbido subjetivo

“…2000;27:33-40, 2006;33:341), a fim de determinar valores de referência de índices padronizados eletromiográficos e verificar a relevante reprodutibilidade destes dados encontrou uma boa reprodutibilidade dos índices na mesma sessão e após 6 meses e argumenta que índices EMG poderiam ser propostos para serem usados como norma em comparação com grupos de pacientes. Tartaglia et al (2011) Os fatores que influenciam na EMG relatados na literatura incluem: condições relacionadas à variabilidade fisiológica como idade, sexo, morfologia esquelética (tipo e padrão facial), espessura da pele e peso; tamanho, material, localização orientação e distância inter-eletrodo dos eletrodos; "ruído biológico" (atividade dos músculos que não estão sendo propositalmente registradas influenciando a mensuração daqueles músculos que estão sendo estudados); movimentos do corpo ou da cabeça; condições de dor existentes; expressões faciais; história de bruxismo (hipertrofia muscular resultando em aumento da atividade do músculo); e metodologia estatística (FERRARIO et al, 2000;OKESON, 2006;CASTROFLORIO;BRACCO;FARINA, 2008). Ferrario e Sforza (1996) e Ferrario et al (2000 afirmam que para reduzir o "ruído biológico" e permitir a comparação eficiente entre diferentes sujeitos e diferentes estudos, os potenciais EMG deveriam ser normalizados.…”