Efeitos imediatos da fotobiomodulação com laser de baixa intensidade sobre o músculo orbicular da boca

Abstract

Objectives: To investigate the effects of photobiomodulation therapy on the orbicularis muscle of the mouth comparing the electrical activity and maximal lip pressure before and after irradiation with different doses of low-intensity LASER. Methods: This work was developed in two stages: an integrative review of the literature and an experimental study. To plan the methodology of the clinical study, an integrative review of the literature was done with the objective of analyzing the studies that address the influence of low-intensity LASER on muscle performance, the wavelengths most used, the dose, the number of points for application, the irradiation site and the results obtained. First, the guiding questions were elaborated: 1- Does the application of low-intensity LASER influence muscle performance? 2- What wavelength has been most used? 3- What is the most commonly used dose and forms of application? Afterward, search expressions with descriptors and keywords related to photobiomodulation and muscular performance were created in Portuguese, English, and Spanish. The searches were made on the PubMed, BVS and SciELO platforms. Only original articles that evaluated the effects of low-intensity LASER on muscle endurance, fatigue and/or force were included in the research, the exclusive or associated use of other therapeutic light sources was adopted as exclusion criteria. Data analysis was done by two independent researchers and, after elimination of duplicate references and analysis of abstracts, the articles were obtained in full for reading. From the articles selected for the study, it was registered the author and year of publication, objectives, sample and age range, the wavelength used, dose, number of points, place of application and results. The second stage consists of an experimental, randomized and triple blind work. The non-probabilistic sample consisted of 23 women and 17 men, aged 18 to 33 years (mean of 23.18 and SD = 2.1), who were divided by lot into four groups with 10 individuals each: group control (GC), G1, G4, and G7. Maximum pressure values were obtained with the Iowa Oral Performance Instrument (IOPI). The bulb was placed between two wooden spatulas and the participants were asked to press the bulb with the maximum possible force, with the movement of grasping of the lips, for 2 seconds. Three repetitions were performed, with an interval of thirty seconds between them and the value of the maximum peak was considered the maximum pressure. Electromyographic data were collected in sequence. In order to obtain the signal, the electrodes were placed in the orbicularis muscle of the mouth, one pair in the upper and one in the lower, followed by international standardization and a reference electrode was placed in the region of the participant's wrist. The tasks requested were: protrusion of the lips to obtain the maximum voluntary contraction, rest, isometric protrusion and the repetition of the phrase " Xuxa achou o xale ". The electrical signal was captured in the amplitude domain and normalized by both peak percentage and maximum voluntary contraction (MVC). After the initial evaluation, the LASER was applied with the equipment of the brand DMC, model Therapy EC, 100 mW of power and outlet spot with an area of 0,028 cm2. The dosimetric parameters were selected according to the findings of the integrative review: infrared wavelength (808 nm) and doses of 1 J (G1), 4 J (G4) and 7 J (G7). There was no intervention in the control group. The application was punctual, with contact, in six points of the orbicularis muscle of the mouth. After LASER application, the evaluation procedures were repeated. The data were analyzed by means of pertinent statistical tests and evaluated with a level of significance of 95%. Results: In the integrative review stage, 1,242 articles were initially found, of which 36 were included for complete reading and 27 inserted in the final analysis. The most used wavelength was infrared, the most common doses were 7 J, 30 J and 4 J and only five papers did not find significant responses for at least one of the variables surveyed. Regarding the experimental study, it was observed that in G4 there was a significant increase in the electrical activity of the upper lip during isometric protrusion task when the data were normalized by the MVC. On the lower lip, a decrease in electrical activity was observed during this same task after irradiation with 1 J. The maximum lip pressure increased only in the group submitted to irradiation with 7 J. Conclusion: low-intensity LASER photobiomodulation is capable of promoting changes in the electrical activity and performance of the orbicularis muscle of the mouth.