Radiation dose to the masseter and medial pterygoid muscle in relation to trismus after chemoradiotherapy for advanced head and neck cancer.

BACKGROUND: We studied the relationship between trismus (maximum interincisor opening [MIO] ≤35 mm) and the dose to the ipsilateral masseter muscle (iMM) and ipsilateral medial pterygoid muscle (iMPM). METHODS: Pretreatment and post-treatment measurement of MIO at 13 weeks revealed 17% of trismus cases in 83 patients treated with chemoradiation and intensity-modulated radiation therapy. Logistic regression models were fitted with dose parameters of the iMM and iMPM and baseline MIO (bMIO). A risk classification tree was generated to obtain optimal cut-off values and risk groups. RESULTS: Dose levels of iMM and iMPM were highly correlated due to proximity. Both iMPM and iMM dose parameters were predictive for trismus, especially mean dose and intermediate dose volume parameters. Adding bMIO, significantly improved Normal Tissue Complication Probability (NTCP) models. Optimal cutoffs were 58 Gy (mean dose iMPM), 22 Gy (mean dose iMM) and 46 mm (bMIO). CONCLUSIONS: Both iMPM and iMM doses, as well as bMIO, are clinically relevant parameters for trismus prediction.

Administration of low-level laser on muscles of mastication following the induction of initial fatigue: protocol for a randomized, controlled, clinical trial.

BACKGROUND: Orofacial pain encompasses painful conditions, such as temporomandibular disorder (TMD). Multidisciplinary health teams seek to control such musculoskeletal disorders to improve the quality and functional capacity of the muscles of mastication. The aim of the proposed study is to evaluate the effect of low-level laser therapy as a form of treatment for the prevention of initial fatigue of the muscles of mastication (masseter and anterior temporal muscles) as well as the recovery of these muscles after induced exhaustion (caused by isometric contraction) in young adults. METHODS: The participants will be 78 healthy male and female volunteers between 18 and 34 years of age. The volunteers will be randomly allocated to a laser group (n = 26), sham group (n = 26), and control group (n = 26). All participants will be submitted to a clinical evaluation to record mandibular movements, bite force, muscle sensitivity to palpation, and initial muscle fatigue. Initial fatigue will be induced by isometric contraction of the jaws. Maximum voluntary contraction will be performed to record the time until initial exhaustion of the masseter muscle (determined by electromyography). The groups will then be submitted to the interventions: active laser therapy (wavelength: 780 nm; fluence: 134 J/cm; power: 50 mW; irradiance: 1.675 W/cm; exposure time: 80 seconds per point) on 3 points of the masseter and 1 point on the anterior temporal muscles on each side; sham laser (placebo effect); or no intervention (control). Maximum voluntary contraction will be performed again after the interventions to record the time until initial exhaustion of the masseter muscle (determined by electromyography). Differences in individual time until exhaustion between the pre- and postintervention evaluations will be measured to determine the effect of low-level laser therapy. DISCUSSION: Although studies have been made with the use of low-level laser therapy in TMDs and on the effect of photobiomodulation on fatigue, this the first study to test this therapy in the prevention of fatigue in this region. The clinical relevance lies in the fact that longer dental procedures could take place if the patients are less prone to fatigue.

Effect of Phototherapy on Masseter and Anterior Temporal Muscles Before Induction of Fatigue: A Randomized, Sham-Controlled, Blind Clinical Trial.

OBJECTIVE: This is a randomized, sham-controlled, blind clinical trial that aimed to evaluate the effect of phototherapy on bite force, mandibular range of motion, sensitivity to palpation, and fatigue in the masseter and anterior temporal muscles of young patients when administered before the induction of fatigue. MATERIALS AND METHODS: Fifty-two healthy volunteers aged 18-23 years were randomly allocated to a laser group and sham group. Both groups were submitted to a clinical evaluation to record mandibular range of motion, bite force, muscle sensitivity to palpation, and muscle fatigue. The laser group was then submitted to phototherapy (780 nm, 25 J/cm2, 50 mW, 20 sec, and 1 J per point) on three points of the masseter and one point of the anterior temporal muscle on each side. The sham group was submitted to the same procedure, but with the device switched off. The volunteers were then instructed to chew two pieces of gum (one on each side) for 6 min, with the pace set by a metronome calibrated to 80 bpm, followed by the reevaluation of all variables. The results were submitted to t-test and Wilcoxon test. A significance level of 5% (p < 0.05) was considered in all analyses. RESULTS: No statistically significant intergroup or intragroup differences were found for the variables analyzed. CONCLUSIONS: With the proposed protocol, phototherapy administered before the induction of fatigue did not lead to any changes in bite force and mandibular range of motion, indicating that further studies are needed with different phototherapy dosimetric parameters.

The analgesic effect of photobiomodulation therapy (830 nm) on the masticatory muscles: a randomized, double-blind study.

This study assesses the efficacy of photobiomodulation therapy (830 nm) for myalgia treatment of masticatory muscles. Sixty patients with muscular myalgia were selected and randomly allocated into 2 groups (n=30): Group A comprised patients given a placebo (control), and Group B consisted of those undergoing photobiomodulation therapy (PBMT). PBMT and placebo were applied bilaterally to specific points on the masseter and temporal muscles. Referred pain elicited by palpation and maximum mouth opening were measured before (EV1) and after (EV2) the treatments. The data were analyzed using statistical tests, considering a significance level of 5%. No significant differences in range were observed for active or passive mouth opening (p ≥ 0.05). Comparing the final outcomes (EV1-EV2) of both treatments, statistical significance was verified for total pain in the right masseter muscle (p = 0.001) and total pain (p = 0.005). In EV2, significant differences in pain reported with palpation were found between Groups A and B for the following: left posterior temporal muscle (p = 0.025), left superior masseter muscle (p = 0.036), inferior masseter muscle (p = 0.021), total pain (left side) (p = 0.009), total masseter muscle (left side) (p = 0.014), total temporal (left side) (p = 0.024), and total pain (p = 0.035). We concluded that PBMT (830 nm) reduces pain in algic points, but does not influence the extent of mouth opening in patients with myalgia.

Efficacy of photobiomodulation therapy on masseter thickness and oral health-related quality of life in children with spastic cerebral palsy.

The study aimed to evaluate the efficacy of photobiomodulation therapy (PBMT) on bilateral masseter muscle thickness and amplitude of mouth opening in children with spastic cerebral palsy (CP), and the impact on their oral health-related quality of life (OHRQOL). Three groups were included: experimental CP group (EG: n = 26 with oral complaints), positive control CP group (PCG: n = 26 without complaints), and negative control group (NCG: n = 26 without CP). In the EG, the masseter muscles on both sides were irradiated with an infrared low-level Ga-Al-As laser (λ = 808 ± 3 nm, 120 mW) using a 3 J/cm2 energy dose per site, with a 20 s exposure time per site (spot area: 4 mm2; irradiance: 3 W/cm2; energy delivery per point: 2.4 J) six times over six consecutive weeks. Masseter thickness, assessed through ultrasonography, and the amplitude of mouth opening were measured in the EG before and after six applications of PBMT and once in the PCG and NCG. The Parental-Caregiver Perception Questionnaire (P-CPQ) was used to evaluate OHRQOL. ANOVA, chi-square, t tests, and multilevel linear regression were used for statistical analysis. In the EG, the study results revealed average increments of 0.77 (0.08) millimeter in masseter thickness (P < 0.05) and 7.39 (0.58) millimeter for mouth opening (P < 0.05) and reduction in all P-CPQ domains (P < 0.001), except for social well-being. The six applications of PBMT increased masseter thickness and mouth opening amplitude and reduced the impact of spastic CP on OHRQOL.

The analgesic effect of photobiomodulation therapy (830 nm) on the masticatory muscles: a randomized, double-blind study

Abstract: This study assesses the efficacy of photobiomodulation therapy (830 nm) for myalgia treatment of masticatory muscles. Sixty patients with muscular myalgia were selected and randomly allocated into 2 groups (n=30): Group A comprised patients given a placebo (control), and Group B consisted of those undergoing photobiomodulation therapy (PBMT). PBMT and placebo were applied bilaterally to specific points on the masseter and temporal muscles. Referred pain elicited by palpation and maximum mouth opening were measured before (EV1) and after (EV2) the treatments. The data were analyzed using statistical tests, considering a significance level of 5%. No significant differences in range were observed for active or passive mouth opening (p ≥ 0.05). Comparing the final outcomes (EV1-EV2) of both treatments, statistical significance was verified for total pain in the right masseter muscle (p = 0.001) and total pain (p = 0.005). In EV2, significant differences in pain reported with palpation were found between Groups A and B for the following: left posterior temporal muscle (p = 0.025), left superior masseter muscle (p = 0.036), inferior masseter muscle (p = 0.021), total pain (left side) (p = 0.009), total masseter muscle (left side) (p = 0.014), total temporal (left side) (p = 0.024), and total pain (p = 0.035). We concluded that PBMT (830 nm) reduces pain in algic points, but does not influence the extent of mouth opening in patients with myalgia.

Dose-volume analysis of radiation-induced trismus in head and neck cancer patients.

INTRODUCTION: Trismus is a treatment-related late side effect in patients treated for cancer in the head and neck region (HNC). The condition can have a considerable negative impact on nutrition, dental hygiene, ability to speak and quality of life. We have previously studied trismus within the frame of a randomized phase 3 study of HNC patients treated with mainly three-dimensional (3D) conformal radiotherapy (CRT) and found a strong association to mean radiation dose to the mastication muscles, especially the ipsilateral masseter muscle (iMAS). In the present study we have investigated trismus prevalence and risk factors in a more recent cohort of patients, treated with todays' more updated radiation techniques. MATERIAL AND METHODS: Maximal interincisal distance (MID) was measured on 139 consecutive patients. Trismus was defined as MID ≤35 mm. Patient-, disease- and treatment-specific data were retrospectively recorded. Differences between groups were analyzed and mean absorbed dose to mastication structures was evaluated. Dosimetric comparisons were made between this study and our previous results. RESULTS: The prevalence of trismus was 24% at a median of 16 months after completion of radiotherapy. In bivariate analysis treatment technique (3DCRT vs. intensity modulated radiotherapy or helical tomotherapy), tumor site (oropharynx vs. other sites) and mean radiation doses to the ipsilateral lateral pterygoid muscle, the paired masseter muscles and the iMAS were significantly associated with MID ≤35 mm. In multivariable analysis only mean radiation dose to the iMAS was significantly associated to MID ≤35 mm. CONCLUSION: Mean radiation dose to the ipsilateral masseter muscle is an important risk factor for trismus development. Dose reduction to this structure during radiotherapy should have a potential to diminish the prevalence of trismus in this patient group.

Effect of low-level laser therapy on adolescents with temporomandibular disorder: a blind randomized controlled pilot study.

PURPOSE: The aim of this pilot study was to evaluate the effect of low-level laser therapy on pain, mandibular movements, and occlusal contacts in adolescents and young adults with temporomandibular disorder. MATERIALS AND METHODS: Individuals aged 14 to 23 years were evaluated. The Research Diagnostic Criteria for Temporomandibular Disorders were used for the diagnosis of temporomandibular disorders. Pain was assessed with a visual analog scale. Occlusal contacts were recorded using the T-Scan III program (Tekscan, Boston, MA). The participants were randomly allocated to 2 groups: active or placebo laser treatment. The laser parameters were as follows: wavelength of 780 nm, energy density of 33.5 J/cm(2), power of 50 mW, power density of 1.67 W/cm(2), and 20-second exposure time. The Kolmogorov-Smirnov test was used to determine the normality of the data distribution. The paired t test was used for the comparisons of the pretreatment and post-treatment results. The SPSS program for Windows (version 15.0; SPSS, Chicago, IL) was used for all analyses, with the level of significance set at 5% (P < .05). RESULTS: No statistically significant differences between groups were found for the right and left anterior temporal muscles (P = .3801 and P = .5595, respectively), superior masseter muscles (P = .087 and P = .1969, respectively), medial masseter muscles (P = .2241 and P = .076, respectively), or inferior masseter muscles (P = .5589 and P = .3268, respectively) after treatment. CONCLUSIONS: No statistically significant differences were found regarding pain, mandibular range of motion, or the distribution of occlusal contacts after treatment with low-level laser therapy. These preliminary results need to be verified in a larger sample of patients to confirm the lack of response to low-level laser therapy.

Quantitative assessment of the masseter muscle's elasticity using Acoustic Radiation Force Impulse.

AIMS: The study proposes Acoustic Radiation Force Impulse (ARFI) assessment of the masseter muscle elasticity in the healthy population and in patients who have undergone head and neck radiation therapy. PATIENTS AND METHODS: Twenty-five healthy controls constituted group A, and 13 patients who had underwent radiotherapy (35Gy minimum) formed group B. ARFI was performed bilaterally in the periphery (P) and the muscle center (C), in relaxation and contraction. Means and standard deviations were obtained for the recorded shear waves velocities (SWV). RESULTS: For group A: in the relaxed right muscle C = 1.87±0.52 m/s and P = 1.96 ±0.55 m/s and in the left muscle C = 1.66 +/- 0.47 m/s, P = 1.67 +/-0.53 m/s. For group B, in relaxation, the right side presented C = 1.67 +/-0.6 m/s, P 1.72 +/-0.56 m/s, the left muscle C = 1.6 +/-0.34 m/s, P = 1.73 +/-0.37 m/s. There were no differences (p> 0.05) between P and C of both groups, regardless of the muscle state. The values for relaxation and contraction in A and B (merged values of the right and left) presented no differences (1.79+/-0.52 m/s vs 1.72 +/-0.73 m/s, p = 0.72 and 1.70 +/-0.48 m/s and vs 1.59 +/-0.77 m/s, p = 0.98). All measurements of group A vs B were not different (1.79 +/-0.52 m/s vs 1.65 +/-0.63 m/s, p = 0.78). CONCLUSIONS: ARFI with SWV measurement enables the quantification of normal and post irradiation elasticity of the masseter. Further studies on a larger population are required to validate the normal and pathologic values.

Evaluation of effect of low-level laser therapy on adolescents with temporomandibular disorder: study protocol for a randomized controlled trial.

BACKGROUND: A number of problems involving the temporomandibular joint (TMJ) and associated structures can lead to temporomandibular disorder (TMD). The aim of the proposed study is to assess the effect of low-level laser therapy on occlusal contacts, mandibular movements, electromyography activity in the muscles of mastication and pain in adolescents with TMD. METHODS/DESIGN: A randomized, controlled, double-blind, clinical trial will be carried out involving 85 male and female adolescents between 15 and 18 years of age. The research diagnostic criteria for TMD will be used to assess all individuals who agree to participate. All participants will be submitted to a clinical examination and electromyographic analysis of the masseter muscles and anterior bundle of the temporal muscles bilaterally, to determine TMD. Based on the clinical findings, the participants will be classified as having or not having TMD. Those with TMD will be divided into four groups, three of which will receive low-level laser therapy and one of which will receive a placebo treatment. The treatments will involve the TMJ region alone, the masseter and temporal muscles alone, or both these regions together. The data will be submitted to descriptive statistical analysis. The chi-square test and Fisher's exact test will be used to determine associations among the categorical variables. The Student's t test and analysis of variance will be used for the comparison of mean electromyographic signals. Pearson's correlation coefficients will be calculated for the analysis of correlations among the continuous variables. TRIAL REGISTRATION: The protocol for this study has been submitted to Clinical Trials - registration number NCT01846000.

[Constraints of the dentist are consistent with the results of an optimal irradiation with modulated intensity in N0 oropharyngeal cancer]. / Les contraintes du chirurgien dentiste sont compatibles avec les résultats d'une irradiation optimale avec modulation d'intensité dans les cancers de l'oropharynx de stade N0.

PURPOSE: We compared intensity-modulated radiotherapy and 3D-conformal irradiation in oropharyngeal cancers according to the requirement of dentists. MATERIAL AND METHODS: From the files of seven patients with cancer of the oropharynx, two dosimetry plannings for 3D-conformal radiotherapy and intensity-modulated radiotherapy with tomotherapy were performed. The dose distributions in the target volumes and organs at risk in relation to the dental sphere were compared. RESULTS: For the planning target volume of the primitive tumour sites, average values of V95%, D2%, D98% and of the conformal index were statistically in favour of tomotherapy. For the planning target volume of node areas, averages values of V95%, D2%, D98% were statistically in favour of tomotherapy. For ipsi- and controlateral parotide glands, average values of V15Gy, V26Gy, V30Gy, V40Gy were significantly lower for tomotherapy. For the submaxillary glands, average values of mean doses and V40Gy were statistically in favour of tomotherapy. For the buccal cavity, the average values of V45Gy were statistically in favour of tomotherapy. For ipsi- and controlateral masseter muscles, the average values of mean doses were statistically in favour of tomotherapy. For the ipsi- and controlateral temporomandibular joints, average values of mean doses and V60Gy were statistically in favour of tomotherapy. For mandibular bone, average values of mean doses and V40Gy, V50Gy, V60Gy and V70Gy were statistically in favour of tomotherapy. For maxillary bone, average values of V40Gy, V50Gy and V60Gy were statistically in favour of tomotherapy. CONCLUSION: The radiation oncologist can constrain the intensity-modulated radiotherapy dosimetry to the needs of dentists to prevent or improve dental care and quality of life.

Does low intensity laser therapy reduce pain and change orofacial myofunctional conditions?

Due to its multifactorial pain aspects, combined therapies are required for the the comprehensive management of temporomandibular joint disorders (TMD). Interdisciplinary forms of therapies, such as laser therapy, and health care or medical professionals, such as speech therapists, have been proposed for this comprehensive management. The aims of this study were the following: 1. verify whether low-intensity laser therapy would promote significant pain remission; 2. evaluate whether this changes orofacial myofunctional conditions in the sample, as tested, using the Orofacial Myofunctional Evaluation with Scores (OMES); and 3. evaluate whether or not the pain improvement would remain stable after a 30-day follow-up for pain conditions. The study included 12 female volunteers diagnosed with myofascial pain and ages ranging from 18 to 60 years old, with or without intra-articular TMD, according to axis I of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Participants were assessed for pain on palpation, using a visual analogue scale (VAS), before treatment (A1), immediately after 30 days of intervention, i.e, after eight sessions of Low Intensity Laser Therapy (LILT) (A2), and 30 days after the end of the treatment with LILT (A3) (follow-up). Comparing the three evaluation times, it was observed that there was a significant decrease in the values of subjective pain to palpation (p < 0.05). The initial pain (A1) differed significantly from the A2, but did not differ significantly from A3.

Laser therapy and needling in myofascial trigger point deactivation.

The aim of this study was to evaluate different approaches to deactivating myofascial trigger points (MTPs). Twenty-one women with bilateral MTPs in the masseter muscle were randomly divided into three groups: laser therapy, needle treatment and control. Treatment effectiveness was evaluated after four sessions with intervals ranging between 48 and 72 h. Quantitative and qualitative methods were used to measure pain perception/sensation. The Wilcoxon test based on results expressed on a visual analog scale (VAS) demonstrated a significant (P < 0.05) decrease in pain only in the laser and needle treatments groups, although a significant increase in the pressure pain threshold was evident only for needling with anesthetic injection (P = 0.0469), and laser therapy at a dose of 4 J/cm² (P = 0.0156). Based on these results, it was concluded that four sessions of needling with 2% lidocaine injection with intervals between 48 and 72 h without a vasoconstrictor, or laser therapy at a dose of 4 J/cm², are effective for deactivation of MTPs.

Zymographic and ultrastructural evaluations after low-level laser irradiation on masseter muscle of HRS/J strain mice.

Low-level laser therapy (LLLT) has been widely used in the treatment of the stomatognathic system dysfunction; however, its biological effect remains poorly understood. This study evaluated the effect of LLLT (GaAlAs, 780 nm, 20 J/cm(2), 40 mW) on masseter muscle of HRS/J mice after different numbers of laser irradiations (three, six, and ten) for 20 s in alternate days. Three experimental groups were defined according to the number of laser irradiations and three control groups (n=5) were used. On the third day after the last irradiation, all animals were killed and the masseter muscle was removed and processed for the following analysis: (a) transmission electron microscopy, (b) zymography, (c) immunohistochemistry for vascular endothelial growth factor (VEGF) and VEGFR-2. The results showed: (a) with six laser applications, a dilation of T tubules, and sarcoplasmic reticulum cistern, increased pinocytosed vesicles in the endothelium; with ten laser applications, few pinocytic vesicles in the endothelium and condensed mitochondria. (b) Under the conditions of this study, the synthesis of other matrix metalloproteinases was not observed, only the MMP-2 and -9. (c) After ten laser irradiations, immunostaining was observed only for VEGFR-2. We conclude that after six laser applications, ultrastructural changes may facilitate the Ca(+2) transfer to cytosol and increase the fluid transport from one surface to another. The ultrastructural changes and no immunostaining for VEGF with ten applications may decrease the metabolic activity as well as damage the angiogenic process, suggesting that an effective number of laser applications may be less than ten, associating to this therapy a better cost-benefit.

Low level laser therapy as an adjunctive technique in the management of temporomandibular disorders.

The purpose of this study was to assess the effect of low level laser therapy on subjects with intra-articular temporomandibular disorders (IA-TMD), and to quantify and compare severity of signs and symptoms before, during, and after the laser applications. The sample consisted of 45 subjects randomly divided into three groups (G) of 15 subjects each: G-I: 15 individuals with IA-TMD submitted to an energy dose of 52.5 J/cm2; G-II: dose of 105.0 J/cm2; and G-III: placebo group (0 J/cm2). In all groups, the applications were performed on condylar points on the masseter and anterior temporalis muscles. Two weekly sessions were held for five weeks, totaling 10 applications. The assessed variables were: mandibular movements and painful symptoms evoked by muscle palpation. These variables were measured before starting the study, then immediately after the first, fifth, and tenth laser application, and finally, 32 days after completing the applications. The results showed that there were statistically significant differences for G-I and G-II at the level of 1% between the doses, as well as between assessments. Therefore, it was concluded that the use of low level laser increased the mean mandibular range of motion and reduced painful symptoms in the groups that received effective treatment, which did not occur in the placebo group.

Influence of laser therapy and muscle relaxant on the masseter muscle under occlusal wear: an ultrastructural study / Influencia de la terapia laser y relajante muscular en el músculo masetero bajo oclusión: un estudio ultraestructural

The aim of this study was to analyze the influence of low-intensity laser therapy and muscle relaxant in the characteristic ultra structural masseter muscle occlusal wear. Animals and Methods: 40 male Wistar rats were randomly divided into four groups: the control group (GI), occlusal wear (G-II), laser occlusal wear (G-III), and the muscle relaxant occlusal wear (G-IV). Under general anesthesia given intraperitoneally, animals in groups II, III and IV had unilateral amputation of upper and lower molar cusps to simulate an occlusal wear situation. The masseter muscle G-III received laser therapy (830nm, 4J/cm2, 40mW, f ~ 2mm) and the procedure was subsequently repeated every other day for 14/30 days. G-IV animals were treated with daily injection of dantrolene ® (2.5 mg / kg in 0.5 ml of H2O). From 24 hours after the elimination peak. The animals were euthanized with an overdose of anesthesia on days 14 and 30 after the removal of the cusps and the ipsilateral masseter muscle was excised and divided in two, one half was routinely processed for light microscopy and other for electron microscopy. There was no statistical difference between each experimental group and the control and between periods in each experimental group. However, the muscle fibers in the G-II showed the most pronounced changes. There is no causal relationship between muscles fibers injuries and occlusion and, despite signs of muscular tissue injury were more evident in the occlusal wear group. Results indicates a moderate action of laser therapy and muscle relaxants in skeletal muscle...

El objetivo del estudio fue analizar la influencia de la terapia láser de baja intensidad y del relajante muscular sobre las características ultraestructurales del músculo masetero en el desgaste oclusal. 40 ratas macho Wistar, se dividieron al azar en cuatro grupos: grupo de control (GI), desgaste oclusal (G-II), laserterapia desgaste oclusal (G-III), y relajante muscular desgaste oclusal (G-IV). Bajo anestesia general por vía intraperitoneal, los animales de los grupos II, III y IV sufrieron amputación unilateral de las cúspides de los molares superiores e inferiores para simular una situación de desgaste oclusal. El músculo masetero del G-III recibió la terapia con laser (830nm, 4J/cm2, 40mW, f ~ 2mm) después del procedimiento el cual se repitió durante 14/30 días. Los animales del G-IV fueron tratados con una inyección diaria de Dantroleno® (2,5 mg/Kg en 0,5 ml de H2O). Los animales fueron sacrificados con una sobredosis de anestesia general en los días 14 y 30. Después de la remoción de las cúspides el músculo masetero ipsilateral se extirpó y se dividió en dos, una mitad fue procesada para microscopía de luz y la otra para microscopía electrónica. No hubo diferencias estadísticamente significativas entre cada grupo experimental y el control, así como, entre los períodos en cada grupo experimental. Sin embargo, las fibras musculares en el G-II mostraron los cambios más pronunciados. En conclusión no existe relación causal entre las lesiones de las fibras musculares y la oclusión, a pesar que los signos de lesión de los tejidos musculares fue más evidente en el grupo con desgaste oclusal. Los resultados indican una acción moderada ejercida por la terapia láser y de los relajantes musculares sobre el músculo esquelético...

Effects of low-level laser irradiation in ultrastructural morphology, and immunoexpression of VEGF and VEGFR-2 of rat masseter muscle.

The present study evaluates by ultrastructural and immunohistochemical methods, the possible changes on muscular tissue affected by LLLI during a treatment, for example, in cases of temporomandibular joint disorders. Sixty male Wistar rats divided into 6 groups (n=10) received ten laser irradiations, with different energy densities (groups I-0; II-0.5; III-1.0; IV-2.5; V-5.0; and VI-20 J/cm(2)). Muscles were removed and processed for transmission electron microscopic and immunohistochemical (VEGF and VEGFR-2) analyses. Captured photomicrographs of immunohistochemistry and transmission electron microscopy were evaluated. It was observed in the irradiated muscles, mitochondria of different shapes and sizes, with increased plasticity evidenced by organelles in fusion, division and the presence of elongated structures with characteristics of mitochondria, proximity with the dilated sarcoplasmatic reticulum, suggesting organelles with large amounts of energy, and the presence of cytoplasmic protrusions in the capillaries with high dosages. All studied groups showed immunostainings for both markers (VEGF and VEGFR-2), but in general those who received higher doses also showed the markings more pronounced, suggesting dose-dependent biomodulation. It was concluded that the LLLI was able to modify the ultrastructural characteristics and immunohistochemical pattern of VEGF and VEGFR-2 in the masseter muscle of rats.

Jaw dysfunction related to pterygoid and masseter muscle dosimetry after radiation therapy in children and young adults with head-and-neck sarcomas.

PURPOSE: To investigate the relationship between jaw function, patient and treatment variables, and radiation dosimetry of the mandibular muscles and joints in children and young adults receiving radiation for soft-tissue and bone sarcomas. METHODS AND MATERIALS: Twenty-four pediatric and young adult patients with head-and-neck sarcomas were treated on an institutional review board-approved prospective study of focal radiation therapy for local tumor control. Serial jaw depression measurements were related to radiation dosimetry delivered to the medial and lateral pterygoid muscles, masseter muscles, and temporomandibular joints to generate mathematical models of jaw function. RESULTS: Baseline jaw depression was only influenced by the degree of surgical resection. In the first 12 weeks from initiation of radiation, surgical procedures greater than a biopsy, administration of cyclophosphamide containing chemotherapy regimes, and large gross tumor volumes adversely affected jaw depression. Increasing dose to the pterygoid and masseter muscles above 40 Gy predicted loss of jaw function over the full course of follow-up. CONCLUSIONS: Clinical and treatment factors are related to initial and subsequent jaw dysfunction. Understanding these complex interactions and the affect of specific radiation doses may help reduce the risk for jaw dysfunction in future children and young adults undergoing radiation therapy for the management of soft-tissue and bone sarcomas.

Histomorphological and angiogenic analyzes of skin epithelium after low laser irradiation in hairless mice.

It is not well-understood how low-laser therapy affects the skin of the applied area. This study analyzes skin of the masseteric region of mice from the HRS/J strain after three different application regimens (three, six or ten applications per regimen) of low intensity laser at 20 J/cm(2) and 40 mW for 20 sec on alternate days. Three experimental groups according to the number of laser applications (three, six or ten) and three control groups (N = 5 animals for each group) were used. On the third day after the last irradiation, all animals were sacrificed and the skin was removed and processed to analyze the relative occupation of the test area by each epithelial layer and the aspects of neovascularization. Data were submitted to statistical analyzes. The irradiated groups compared to their respective controls at each period of time, showed no significant difference in relative occupation of the test area by the layers and epithelium areas for three and six applications, but for ten applications, a significant decrease (P < 0.05) in the basal and granulosum layers, and epithelium areas were found. From the comparisons of the three irradiated groups together, the group with six laser applications showed statistical difference (P < 0.05) in total epithelium and on the layers. Vascular endothelial growth factor (VEGF) and VEGFR-2 immunoreactivities were similar for the control and irradiated groups. Results suggested a biostimulatory effect with low risks associated with superficial tissues, when the treatment aims the deeper layers after six applications.