Nociceptive and histomorphometric evaluation of the effects of ozone therapy on the rat masseter muscle in a carrageenan model of myofascial pain.

OBJECTIVE: This study evaluated the effects of intramuscular ozone therapy on nociception, inflammation, and tissue damage caused by the injection of carrageenan in the masseter muscle of rats. DESIGN: Rat masseter muscles were injected with saline or carrageenan. Seventy-seven adult male rats were divided into six groups: Sal, saline; Car, carrageenan; Ibup + Sal, ibuprofen and saline; Ibup + Car, ibuprofen and carrageenan; O3 + Sal, ozone and saline; and O3 + Car, ozone and carrageenan. The mixture of 5% ozone and 95% oxygen (20 µg/mL) was administered three times in the course of a week. Nociceptive responses in the masseter muscles were measured using a head withdrawal threshold, determined by an electronic von Frey anesthesiometer. The animals were euthanized one or eight days after the carrageenan injection, and the masseters were submitted to histological and histomorphometric analyses. RESULTS: Mechanical allodynia and inflammation levels were reduced in the Ibup + Car group compared to the other groups. Myonecrosis was similar among carrageenan-treated groups. Picrosirius red stained sections showed more collagen fibers and more regenerating myofibers in the O3 + Car group compared to the other groups. Eight days after carrageenan injection, the O3 + Car group showed neutrophils close to the regenerating myofibers. CONCLUSIONS: Intramuscular ozone therapy did not alleviate mechanical allodynia, and it did not protect the masseter muscle against the deleterious effects produced by carrageenan, probably due to the mode of administration of this therapeutic agent.

Multifrequency Analysis of Masseter Vestibular Evoked Myogenic Potentials in Young Adults.

PURPOSE: The purpose of this study was to explore the dynamics of multifrequency tone bursts on the masseter vestibular evoked myogenic potential (mVEMP) parameters. Furthermore, it sought to determine the optimal frequency tuning of mVEMP responses. METHOD: Twenty young adults with normal hearing sensitivity participated in the study. Bilateral tone burst evoked mVEMPs were obtained using the zygomatic montage at 250-, 500-, 750-, 1000-, 1500-, and 2000-Hz stimulation frequencies. Self-monitoring biofeedback was given during the procedure to confirm the tension of the masseter muscle between 49.9 and 150.6 rms. Furthermore, the electromyography (EMG) scaling was done to avoid any muscle-related irregularities. RESULTS: Tone burst evoked mVEMPs were found to be 100% present at the stimulation frequencies of 250, 500, 750, and 1000 Hz. There were no ear and gender effects seen for any of the frequencies. Significant shortening of the P1 and N1 latencies with increasing stimulation frequencies was observed. The peak-to-peak amplitude was the highest at 500 Hz and lowest at 2000 Hz tone bursts under both EMG scaled and unscaled conditions. CONCLUSION: The present revealed higher response rates and larger amplitudes study of mVEMP at lower frequencies, and, therefore, the frequency tuning was seen for the stimulation frequency at 500 Hz.

Trigger point dry needling increases masseter muscle oxygenation in patients with temporomandibular disorder.

BACKGROUND: Temporomandibular disorder (TMD) is an umbrella term encompassing various clinical complaints involving the temporomandibular joints, masticatory muscles, and/or associated orofacial structures. Myogenous TMDs are the most frequent cause of chronic orofacial pain. Musculoskeletal pain is commonly associated with myofascial trigger points (MTPs), for which dry needling (DN) is a routine treatment. OBJECTIVE: To investigate muscle oxygenation and pain immediately after DN application on an MTP in the masseter muscle of patients with myogenous TMDs. METHODOLOGY: Masseter muscle oxygen tissue saturation indices (TSI%) were assessed by near-infrared spectroscopy (NIRS) pre- and post-interventions by a randomized, controlled, double-blind, crossover DN/Sham clinical trial (primary outcome). Pain was investigated by the visual analog scale (VAS). In total, 32 individuals aged from 18 to 37 years who were diagnosed with myogenous TMD and myofascial trigger points in their masseter muscles participated in this study. Relative deltas for the studied variables were calculated. Data normality was tested using the Shapiro-Wilk test. According to their distribution, data were analyzed by two-way ANOVA and the Student's t-, and Mann-Whitney tests. Statistical analyses were performed using Prism® 5.0 (GraphPad, USA). RESULTS: We found a significant difference (2,108% vs. 0,142%) between masseter muscle TSI% deltas after the DN and Sham interventions, respectively (n=24). We only evaluated women since men refused to follow NIRS procedures. Pain increased immediately after DN (n=32, 8 men), in comparison to Sham delta VAS. CONCLUSION: These findings show an increase in tissue oxygen saturation in the evaluated sample immediately after the DN intervention on the MTP of patients' masseter muscle. Pain may have increased immediately after DN due to the needling procedure.

The significance of masticatory muscle's relaxation in the treatment of the temporomandibular disorders - Review article.

Temporomandibular disorder (TMD) is a disease of multifactorial etiology and a complex of symptoms, related to disorders of the masticatory muscles, temporomandibular joints and the surrounding orofacial structures. One of the main problems in the course of TMD disorders is the systematic increase in the tension of the masticatory muscles (masseter muscles, temporalis and medial and lateral pterygoid muscles), what is the cause of many damages and the development of pathological conditions in the stomatognathic system. The article discusses the differences in the structure of the masticatory and skeletal muscles, as well as the different nature and isoforms of myosin, which determines the much faster generation of contraction in the masticatory muscles and consequently easier generation of excessive, harmful tensions in the masticatory muscles. The article describes the causes of increased tension in the masticatory muscles and methods of their relaxation used in the basic and supportive treatment of temporomandibular disorders. The use of occlusal splints, physiotherapeutic procedures and TMD treatment with botulinum toxin type A were characterized. A role of psychological support and the methods used for patients with TMD were emphasized.

Effectiveness of Biofeedback in Individuals with Awake Bruxism Compared to Other Types of Treatment: A Systematic Review.

Excessive masticatory muscle activity is generally present in awake bruxism, which is related to increased anxiety and stress. It has been hypothesized that biofeedback could potentially manage awake bruxism, however, its effectiveness has not been empirically analyzed in a systematic manner. Therefore, this systematic review was designed to determine the effectiveness of biofeedback compared to other therapies in adults with awake bruxism. Extensive searches in five databases looking for randomized controlled trials (RCTs) that included biofeedback to manage awake bruxism were targeted. The risk of bias (RoB) assessment was conducted using the Cochrane RoB-2 tool. Overall, four studies were included in this systematic review, all of which used the electromyographic activity of the masticatory muscles during the day and night as the main endpoint. Auditory and visual biofeedback could reduce the excessive level of masticatory muscle activity in a few days of intervention. The majority of the included studies had a high RoB and only one study had a low RoB. The standardization of the biofeedback protocols was also inconsistent, which makes it difficult to establish the ideal protocol for the use of biofeedback in awake bruxism. Thus, it is proposed that future studies seek to reduce methodological risks and obtain more robust samples.

Comparative Efficacy of Platelet-Rich Plasma and Dry Needling for Management of Trigger Points in Masseter Muscle in Myofascial Pain Syndrome Patients: A Randomized Controlled Trial.

AIMS: To compare the efficacy of platelet-rich plasma (PRP) injection vs dry needling (DN) for management of trigger points in the masseter muscle in myofascial pain syndrome (MPS) patients. METHODS: This randomized controlled trial included 30 clinically confirmed cases of myofascial trigger points (MTrPs) in the masseter muscle who were randomly and equally (1:1) assigned to the test (PRP) and control (DN) groups. Both groups were evaluated for pain (visual analog scale [VAS]), range of functional movements, need for pain medication, patient satisfaction (Likert scale), and sleep (VAS) at baseline and 2-week, 1-month, and 3-month follow-ups. VAS pain and Likert score were also obtained at 6-month intervals. RESULTS: The use of PRP solution in MTrPs in MPS patients had a better effect on pain and patient satisfaction compared to DN. CONCLUSION: PRP appears to be a more effective treatment modality compared to DN in the management of MTrPs in MPS patients.

Clinical efficacy of magnesium sulfate injection in the treatment of masseter muscle trigger points: a randomized clinical study.

OBJECTIVE: Myofascial pain syndrome with trigger points is the most common cause of nonodontogenic pain. Although injection of the trigger points is the most effective pain reduction treatment, many patients exhibit recurrence after a short period. Therefore, the aim of the current study was to evaluate the clinical efficacy of magnesium sulfate injections in the treatment of the masseter muscle trigger points when compared to saline injections. MATERIAL AND METHOD: This study randomly (1:1) assigned 180 patients to one of two treatment groups based on whether their trigger points were injected with 2 ml of saline or magnesium sulfate. Pain scores, maximum mouth opening (MMO), and quality of life were measured at the pre-injection and 1, 3, and 6 months post-injection. RESULTS: The pain scores were significantly higher in the saline group during all follow-up assessments, whereas the MMO was significantly higher in the magnesium sulfate group up to 3 months of follow-up (p < 0.001). However, the difference in MMO ceased to be statistically significant after 6 months of follow-up (p = 0.121). Additionally, the patient's quality of life score was significantly higher in the magnesium sulfate group compared to the saline group (p < 0.001). CONCLUSION: Injection of magnesium sulfate is an effective treatment measure for myofascial trigger points. However, further studies with a proper design addressing the limitations of the current study are necessary. CLINICALTRIALS: org (ID: NCT04742140) 5/2/2021.

Accuracy of Palpation Procedures for Locating the C1 Transverse Process and Masseter Muscle as Confirmed by Computed Tomography Images.

OBJECTIVE: The purpose of this study was to examine the accuracy of palpation methods for locating the transverse processes of the first cervical vertebra and masseter muscle using radiographic images as the gold-standard method and the association between personal characteristics with the observed accuracy. METHODS: This was a single-blinded, diagnostic accuracy study. Ninety-five participants (49 women, 58 ± 16 years of age) were enrolled in this study. A single examiner palpated the neck and face region of all participants to identify the transverse processes of the first cervical vertebra and masseter muscles bilaterally. In sequence, participants underwent a multislice computed tomography scan for assessment of the superimposed inner body structure. Two radiologists assessed the computed tomography images using the same criteria and were blinded regarding each other's assessment and the anatomic landmarks under investigation. The palpation accuracy was calculated as the proportion of the correctly identified landmarks in the studied sample. The correlation of the palpation outcome (correct = 1; incorrect = 0) with age, sex (male = 1; female = 0), and body mass index was investigated using the point-biserial correlation coefficient. RESULTS: The right and left transverse processes were correctly located in 76 (80%) and 81 (85%) participants, respectively, and bilaterally in 157 events (83%), as evaluated by the consensus of the 2 radiologists. The masseter muscles were correctly localized bilaterally in 95 of 95 (100%) participants. Body mass showed statistical evidence of a weak, positive correlation with the correct location of the transverse processes of the first cervical vertebra at the right body side (r = .219; 95% confidence interval, 0.018-0.403; P = .033). CONCLUSION: Palpation methods used in this study accurately identified the location of the first cervical vertebra spinous processes and the masseter muscles.

Masseter Muscle Thickness And Elasticity in Bruxism After Exercise Treatment: A Comparison Trial.

OBJECTIVE: The purpose of this study was to evaluate the effects of Rocabado's 6 × 6 exercises on masseter muscle thickness, muscle elasticity, and pain scores in patients with bruxism. METHODS: A total of 58 participants with bruxism were divided into 2 groups as the exercise group (EG) and control group (CG). A self-care program was applied for the participants in the CG. For those in the EG, in addition to the self-care program, an exercise treatment was performed for 6 days per week for a total of 8 weeks. Using ultrasonography, bilateral masseter muscle thickness and elasticity were assessed before and after treatment. Pain was measured using a visual analog scale. Changes over time within the groups and group-time interactions for continuous variables were assessed using mixed 2-way repeated measures analysis of variance. RESULTS: The improvement in muscle elasticity (P = .015; P = .004) and pain values (P = .049; P = .040) were greater in the EG compared with the CG. There was no significant difference between the 2 groups for masseter muscle thickness (P > .05). CONCLUSION: This study suggests that Rocabado's 6 × 6 exercises are effective in the treatment of muscle elasticity and pain values in participants with bruxism.

Assessment of the masseter stiffness in patients during conservative therapy for masticatory muscle disorders with shear wave elastography.

BACKGROUND: The complex structure of the stomatognathic system plays a vital role in chewing, digestion, speaking, breathing, facial expression and swallowing. Its complexity is the primary reason for creating multidisciplinary teams to manage temporomandibular disorders (TMD). We aimed to assess the masseter stiffness in patients undergoing conservative therapy for masticatory muscle disorders and evaluate the efficacy of manual therapy and stabilization occlusal splint in the treatment of masticatory muscle disorders. METHODS: This uncontrolled prospective cohort study included 35 patients with masticatory muscle disorders. The study lasted for eight weeks. The patients were treated with manual therapy and stabilization occlusal splint and evaluated using shear wave elastography of the masseter muscles and patient-reported outcome measures (PROMs) to assess pain, anxiety, quality of sleep, satisfaction with life and perceived stress. RESULTS: After the treatment, the stiffness of both masseter muscles decreased significantly (by 4.21 kPa). The patients reported a significant reduction in pain. At baseline, the median scores ranged from 5 to 8; after treatment, they ranged from 0 to 1 (p < 0.0001). The patients also reported significant improvement in terms of all patient-reported outcome measures. The reduction in stiffness corresponded to the improvement in pain and PROMs, as shown by correlations which were insignificant for all measures. CONCLUSIONS: Conservative therapy of masticatory muscle disorders involving manual therapy and stabilization occlusal splint is effective. It reduces the masseter stiffness as objectively shown in shear wave elastography and improves subjective PROMs scores, including numerical pain assessment and selected questionnaires. Shear wave elastography has the potential for broad application in clinical practice to monitor masticatory muscle disorders treatment effects due to its objectivity and non-invasive character. Further research is recommended on larger patient populations and longer follow-up. TRIAL REGISTRATION: The study was registered at clinicaltrials.gov ( NCT03844854 ). First posted date: 19/02/2019.

Management of temporomandibular disorders with transcutaneous electrical nerve stimulation: A systematic review.

Objective: The objectives of this systematic review were to assess the efficacy of transcutaneous electrical nerve stimulation (TENS) for the management of temporomandibular disorders (TMD) and to determine the indications and most appropriate application modalities.Methods: Papers published in the Medline database, EMBASE, and the Cochrane Library before November 2018 were included.Results: Fourteen articles were retained, corresponding to a total of 532 patients, among which, 285 had a TMD. Immediately after a TENS session, significant relief of pain (19.2% to 77%), significant functional improvement (mouth opening amplitude increased by between 8.7% and 19.46%), and reduced electromyographic activity of the anterior temporalis and masseter muscles were observed. However, studies comparing TENS to other physical medicine modalities (ultrasound and laser) reported equivalent results.Conclusion: Further randomized comparative clinical trials will be necessary to optimize the use of TENS (program, duration of sessions, duration of treatment) for different types of TMD.

Comparison of the efficiency of two alternative therapies for the management of temporomandibular disorders.

Objective: To investigate the effect of ozone and low-level laser (LLL) therapies on pain and function in patients with disc displacement with reduction.Methods: Eighty temporomandibular joints were divided into four groups, namely ozone and laser treatment groups, and two placebo groups. Ozone and LLL therapies were applied over six sessions.Results: Pain on palpation scores demonstrated a statistically significant decrease over time in the treatment groups. Sham laser therapy only reduced the pain on palpation in temporomandibular joints; whereas, sham ozone only affected masseter muscle pain. The ozone treatment group demonstrated significantly better pressure pain threshold scores and mandibular movements than the other groups; however, pressure pain threshold scores of the masseter inferior were significantly higher in the laser group.Discussion: This study supports the use of ozone for pain reduction as an alternative treatment modality and LLL as a supportive therapy for temporomandibular disorders.

Masseter muscle and gingival tissue inflammatory response following treatment with high-fructose corn syrup in rats: Anti-inflammatory and antioxidant effects of kefir.

The aim of the study was to evaluate whether high-fructose corn syrup (HFCS) intake (20% beverages) impacts antioxidative structures and inflammation in the gingival tissue and masseter muscle of rats. Kefir was tested for its potential utility on changes induced by HFCS. Animals were randomly divided into four groups as control, kefir, HFCS, and HFCS plus kefir. HFCS was given as 20% solutions in drinking water while kefir supplementations were given by gastric gavage for 8 weeks. It has been clearly determined that the HFCS diet increased expressions of interleukin (IL)-6, IL-1ß, and tumor necrosis factor-α proinflammatory structures via lymphocyte infiltration by suppressing antioxidant enzymes such as catalase, superoxide dismutase, and glutathione peroxidase in both tissues. Kefir improved these undesirable changes in rats fed with HFCS. The results of this current study, the first investigation to examine the effects of kefir on masseter muscle and gingival tissue, may provide new access to the restorative effects of kefir consumption on oral health disorders caused by high fructose in the diet. PRACTICAL APPLICATIONS: In this study, at an early age, the effects of kefir on improving inflammation via antioxidation in the masseter muscle and gingival tissue were investigated for the first time. We showed that kefir feeding ameliorates lymphocyte infiltration on the high-fructose corn syrup (HFCS)-induced masseter muscle and gingival tissue inflammation in rats. The mRNA expressions of inflammatory parameters measured in the study were supported by protein measurements via ELISA or immunohistochemistry. In the present study, kefir may play an important role in the antioxidation and inflammation process on the masseter muscle and gingival tissue against HFCS.

The Application of Manual Techniques in Masticatory Muscles Relaxation as Adjunctive Therapy in the Treatment of Temporomandibular Joint Disorders.

Temporomandibular disorders (TMD) are primarily characterized by pain as well as disorders concerning the proper functioning of individual elements of the stomatognathic system (SS). The aim of the study was to compare the degree of relaxation of the anterior part of the temporal muscles and the masseter muscles, achieved through the use of post-isometric relaxation and myofascial release methods in patients requiring prosthetic treatment due to temporomandibular joint disorders with a dominant muscular component. Sixty patients who met the inclusion criteria were alternately assigned to one of the two study groups, either group I-patients received post-isometric relaxation treatment (PIR), or group II-patients received myofascial release treatment (MR). The series of ten treatments were performed in both groups. The comparative assessment was based on physiotherapeutic examination, a surface electromyography (sEMG) of the anterior temporal and masseter muscles and the intensity of spontaneous masticatory muscle pain, assessed using the Visual Analogue Scale (VAS). We observed a significant decrease in the electrical activity of examined muscles and a significant drop in the intensity of spontaneous pain in the masticatory muscles both in group I and II. There were no significant differences between groups. Both therapeutic methods may be used as successful forms of adjunctive therapy in the prosthetic treatment of TMD. The trial was registered with an international clinical trials register.

Immediate effects of rhythmic joint mobilization of the temporomandibular joint on pain, mouth opening and electromyographic activity in patients with temporomandibular disorders.

BACKGROUND: Rhythmic joint mobilizations (RJM) of the temporomandibular joint (TMJ) are employed to relieve pain and improve function in patients with temporomandibular disorders (TMD). However, the evidence on the immediate effects of RJM in patients with TMD is scarce. The aim of this study was to assess the immediate clinical and functional effects of RJM in patients with TMD. MATERIALS AND METHODS: This was a one-group quasi-experimental before and after study. Thirty-eight patients with TMD were assessed by means of pain intensity (visual analogue score, VAS), pressure pain threshold (PPT, measured through pressure algometry on the masseter and temporal muscles), mouth opening (MO, measured with a ruler), and surface electromyographic activity of the masseter and temporal muscles (asymmetry index, AI). Measurements were performed before and after a single, 1-min session of RJM of each TMJ. All statistical analyses were performed using the SPSS version 20.0 statistical package. RESULTS: A statistical significant difference was found in pain intensity, PPT and MO after the intervention (p < 0.05). No difference was found in the AI. A large effect size was observed for pain intensity, PPT of the left and right masseter muscles and MO (d = 0.85-1.13), whereas for the left and right temporal muscles the effect size was moderate (d = 0.62) and small, respectively (d = 0.49). CONCLUSION: In this sample of patients with TMD, a single session of RJM of the TMJ seemed to be effective in reducing pain intensity, increasing PPT and improving MO immediately after the intervention, without differences in the AI.

Self-Massage and Low-Level Laser in Treatment of Masseter Myalgia: Short-Term Effect.

INTRODUCTION: The aim of this study was to explore the efficiency of massage in the treatment of masseter myalgia compared with biostimulatory laser. MATERIALS AND METHODS: The instrument Diagnostic Criteria for Temporomandibular Disorders was used to select subjects and monitor treatment outcome. 54 subjects with masseter myalgia of more than 3 months in duration were invited to participated and 42 cases were available at the end and analyzed. Age range was 16-67 years (median 33, interquartile range 25-53), 36% subjects was ≥40 years and there were 62% females in both groups. Both treatment groups (self-massage and laser) had 21 participants and were monitored one months after the start of treatment. Age, gender, distress, somatization, catastrophizing, hypervigilance, health competence and oral parafunctions were also assessed as factors that could influence effectiveness of treatment. RESULTS: Laser and massage are effective in reducing symptoms of chronic myalgia of the masseter in self-reported limitation of jaw function and reducing pain intensities (p<0.001). Increase of mouth opening was present in both groups, but mainly significant in laser group. The differences in the amount of change between groups were not significant. Psychological characteristics and parafunctions, present before the treatment, age and gender did not have major affect the effectiveness of treatment. CONCLUSION: Both treatment modalities are effective in treatment of chronic myalgia in short-term.

Botulinum toxin type A and acupuncture for masticatory myofascial pain: a randomized clinical trial.

BACKGROUND: BoNT-A has been widely used for TMD therapy. However, the potential benefits compared to dry needling techniques are not clear. OBJECTIVE: this study aimed to compare the immediate effects of botulinum toxin type A (BoNT-A) injections and Acupuncture in myofascial temporomandibular disorders (TMD) patients. METHODOLOGY: 54 women were divided into three groups (n=18). AC patients received four sessions of traditional acupuncture, being one session/week during 20-min. BoNT-A patients were bilaterally injected with 30U and 10U in masseter and anterior temporal muscles, respectively. Moreover, a control group received saline solution (SS) in the same muscles. Self-perceived pain was assessed by visual analog scale, while pressure pain threshold (PPT) was verified by a digital algometer. Electromyographic evaluations (EMG) of anterior temporal and masseter muscles were also measured. All variables were assessed before and 1-month after therapies. The mixed-design two-way repeated measures ANOVA and Tukey's post-hoc tests were used for analysis, considering a=0.05. RESULTS: Self-perceived pain decreased in all groups after one month of therapy (P<.001). BoNT-A was not better than AC in pain reduction (P=0.05), but both therapies were more effective in reducing pain than SS (P<0.05). BoNT-A was the only treatment able to improve PPT values (P<0.05); however, a severe decrease of EMG activity was also found in this group, which is considered an adverse effect. CONCLUSION: after one month of follow-up, all therapies reduced the self-perceived pain in myofascial TMD patients, but only BoNT-A enhanced PPT yet decreased EMG.

Comparison of the Efficacy of Botulinum Toxin, Local Anesthesia, and Platelet-Rich Plasma Injections in Patients With Myofascial Trigger Points in the Masseter Muscle.

PURPOSE: Masticatory myofascial trigger points (TrP) are one of the major causes of nondental pain in the orofacial region. Intramuscular injections are considered the first-line treatment for myofascial TrPs. The objectives of this study were to evaluate and compare the effectiveness of local anesthesia (LA), botulinum toxin (BTX), and platelet-rich plasma (PRP) injections for the treatment of myofascial TrPs in the masseter muscle. METHODS: In this retrospective study, the sample was composed of patients with myofascial TrPs in masseter muscle who were treated between 2016 and 2019. Patients were divided into 3 groups according to treatment methods: group I (LA injection), group II (BTX injection), and group III (PRP injection). Primary outcome variable was the average pain level at rest and while chewing, and pressure pain intensity (PPI), Jaw Functional Limitation Scale (JFLS) value, and quality-of-life (measured using Oral Health Impact Profile-14 (OHIP-14)) were secondary outcomes. The outcome variables were assessed at diagnosis, and 1, 3, and 6 months post-treatment. RESULTS: The study consisted of 82 patients (group I, 27; group II, 26; group III, 29). At 1 and 3 months, improvement in all parameters was recorded in all groups. Groups I and II showed superior improvement in all parameters compared with group III at 3 months. Improvements in VAS pain, JFLS, and OHIP-14 values were significantly better in group II than group I at 3 months (P = .009; P = .004; P = .002). At 6 months, significant improvement in VAS pain, JFLS, and OHIP-14 (P = .008; P < .001; P < .01) values was recorded only in group II. CONCLUSIONS: All procedures successfully improved the symptoms of TrPs in the masseter muscle at 1 and 3 months. However, BTX injection seemed superior at the 3-month follow-up and remained effective up to 6 months.

Treatment with the essential amino acid L-tryptophan reduces masticatory impairments in experimental cerebral palsy.

Purpose Children with cerebral palsy (CP) often exhibit difficulties in feeding resulting from deficits in chewing. This study investigates the therapeutic potential of L-tryptophan (TRI) to reduce deficits in chewing in rats subjected to an experimental model of CP.Methods A total of 80 Wistar albino rats were used. Pups were randomly assigned to 4 experimental groups: Control Saline, Control TRI, CP Saline, and CP TRI groups. The experimental model of CP was based on the combination of perinatal anoxia associated with postnatal sensorimotor restriction of the hind limbs. TRI was administered subcutaneously during the lactation period. Anatomical and behavioral parameters were evaluated during maturation, including body weight gain, food intake, chewing movements, relative weight and the distribution of the types of masseter muscle fibers.Results The induction of CP limited body weight gain, decreased food intake and led to impairment in the morphological and functional parameters of chewing. Moreover, for a comparable amount of food ingested, CP TRI animals grew the most. In addition, supplementation with TRI improved the number of chewing movements, and increased the weight and proportion of type IIB fibers of the masseter in rats subjected to CP.Conclusion These results demonstrate that experimental CP impaired the development of mastication and that TRI supplementation increased masticatory maturation in animals subjected to CP.

The use of photobiomodulation for the muscles of head and neck: an integrative review / O uso da fotobiomodulação nos músculos da cabeça e pescoço: revisão integrativa da literatura

ABSTRACT Purpose To carry out an integrative review of the literature on the use of photobiomodulation (PBM) for the head and neck muscles. Research strategy The research took place between June/2019 and March/2021, in the following databases: PubMed, Scopus, Web of Science, LILACS, and SciELO. The MeSH used were Low-Level Light Therapy, Phototherapy, Masseter Muscle, Masticatory Muscles, Tongue, Palate, Mouth, Neck Muscles, and Facial Muscles in English and Portuguese. No limitation was imposed on the year and language of publication. Selection criteria studies that answered the guiding question: what is the use of photobiomodulation to the head and neck muscles?. Results 2857 articles were found, of which 102 were selected for full reading, 52 of those were excluded, giving a total of 50 articles included. The included publications date from 2003 to 2020. Brazil was the country that most published on the topic. With regard to the objectives, 82% of the studies aimed to investigate the analgesic effect of PBM, of these, 50% were related to articular or muscular temporomandibular disorders (TMD). The heterogeneity of the studies makes it impossible to define the dose protocols. Conclusion PBM has been applied to the head and neck muscles mainly for the treatment of pain caused by TMD. There is no treatment protocol to define the doses to be used, due the heterogeneity of the methodologies applied and results found.

RESUMO Objetivos realizar uma revisão integrativa da literatura sobre o uso da fotobiomodulação nos músculos de cabeça e pescoço. Estratégia de pesquisa As buscar foram realizadas nas bases de dados: PubMed, Scopus, Web of Science, LILACS e SciELO. A pesquisa ocorreu entre junho de 2019 e março de 2021. Os descritores utilizados foram Terapia com Luz de Baixa Intensidade, Fototerapia, Músculo Masseter, Músculos Mastigatórios, Língua, Palato, Boca, Pescoço, Músculos do Pescoço, Músculos Faciais e seus respectivos termos em inglês. Não houve limitação de ano de publicação e idioma. Critérios de seleção estudos que respondessem a pergunta norteadora: qual o uso da fotobiomodulação na musculatura de cabeça e pescoço?. Resultados Foram encontrados 2857 artigos, sendo selecionados 102 para leitura completa, dos quais 52 foram excluídos, totalizando 50 artigos incluídos. As publicações incluídas datam de 2003 a 2020. O Brasil foi o país que mais publicou sobre o tema. Quanto aos objetivos, 82% dos estudos pesquisaram o efeito analgésico da fotobiomodulação, e desses, 50% eram relacionados à disfunção temporomandibular (DTM) articular ou muscular. A heterogeneidade dos estudos impossibilita a definição de protocolos dosimétricos. Conclusão A fotobiomodulação tem sido utilizada na musculatura de cabeça e pescoço principalmente para o tratamento da dor proveniente de DTM. Não existe um protocolo de aplicação que defina os parâmetros dosimétricos a serem utilizados, devido a heterogeneidade das metodologias e dos resultados encontrados.