Revista CEFAC
https://www.revistacefac.org.br/article/doi/10.1590/1982-0216/20262869725
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Original Articles

The immediate effects of low-intensity laser on masseter muscle’s morphological and functional parameters

Efeitos imediatos do laser de baixa intensidade sobre parâmetros morfológicos e funcionais do músculo masseter

Sara Loureiro de Souza Ferreira; Daniele Andrade da Cunha; Sávio Bastos; Marcelo Magno Ramos de Araújo; Gabriely Soares Passos; Erissandra Gomes; Kelli Nogueira Ferraz Pereira Althoff; Aline Natállia Simões de Almeida; Hilton Justino da Silva

http://dx.doi.org/10.1590/1982-0216/20262869725 Revista CEFAC, vol.28, n6, e9725, 2026
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Abstract

Purpose: to analyze the immediate effects of low-intensity laser on morphofunctional parameters of the masseter muscle in healthy adults.

Methods: volunteers aged 18 to 39 years without stomatognathic dysfunction were randomly allocated to two placebo groups, combined for analysis, and two experimental groups. The masseter was irradiated bilaterally at three points in a single session, with 3 Joules per point in one experimental group and 6 Joules per point in the other. Temperature, thickness, tone, stiffness, elasticity, bite force and electrical activity were assessed before and immediately after the session, at rest and during function. Data were analysed with generalized estimating equations and a significance level of 0.05 was assumed.

Results: the thickness of the left masseter, during dental clenching, and the surface temperature of the left masseter changed over time, differently between groups (p=0.030 and p=0.038), with opposite directions between the two doses. The stiffness of the left masseter decreased over time (p=0.006), including in the placebo group, with no group effect or interaction, and the remaining parameters did not change.

Conclusion: a single session of low-intensity laser produced limited and dose dependent immediate changes in two of the seven parameters assessed. The reduction in stiffness occurred in all groups and could not be attributed to the irradiation.

Keywords

Low-Level Light Therapy; Muscle Fatigue; Masseter Muscle; Masticatory Muscles; Physical Functional Performance

Resumo

Objetivo: analisar os efeitos imediatos do laser de baixa intensidade sobre parâmetros morfofuncionais do masseter em adultos saudáveis.

Métodos: voluntários de 18 a 39 anos, sem disfunção estomatognática, foram alocados aleatoriamente em dois grupos placebo, reunidos para a análise, e dois experimentais. O masseter foi irradiado bilateralmente em três pontos, em sessão única, com 3 Joules por ponto em um grupo e 6 Joules no outro. Temperatura, espessura, tônus, rigidez, elasticidade, força de mordida e atividade elétrica foram avaliados antes e imediatamente após a sessão, em repouso e em função, e analisados por equações de estimação generalizadas, com nível de significância de 0,05.

Resultados: a espessura do masseter esquerdo durante apertamento dental e sua temperatura de superfície variaram no tempo de forma distinta entre os grupos (p=0,030 e p=0,038), com direções opostas entre as duas doses. A rigidez do masseter esquerdo diminuiu no tempo (p=0,006), inclusive no placebo, sem efeito de grupo nem interação, e os demais parâmetros não se alteraram.

Conclusão: uma sessão única de laser de baixa intensidade produziu alterações imediatas limitadas e dependentes da dose em dois dos sete parâmetros avaliados. A redução da rigidez ocorreu em todos os grupos e não pôde ser atribuída à irradiação.

Palavras-chave

Terapia com Luz de Baixa Intensidade; Fadiga Muscular; Músculo Masseter; Músculos da Mastigação; Desempenho Físico Funcional

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Submitted date:
04/18/2026

Accepted date:
08/06/2026

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