Evaluation of the effectiveness of infrared light-emitting diode photobiomodulation in children with sleep bruxism: Study protocol for randomized clinical trial

BACKGROUND

Sleep bruxism is a masticatory muscle activity characterized as rhythmic (phasic) or nonrhythmic (tonic). In children and adolescents, etiological factors, such as breathing pattern and sleep quality, have recently been addressed in studies investigating sleep bruxism. New therapies for adults, such as botulinum toxin, have been investigated, but such techniques are not applicable for individuals in the growth and development phase.

METHODS

The participants will be 76 children, which will be randomly allocated to a control group, that is group 1, absence of bruxism; group 2, children with bruxism treated with infrared light-emitting diode (LED); and group 3, bruxism treated with occlusal splint. All participants will be submitted to a clinical evaluation to evaluate muscle activity and salivary biomarkers, before and after treatments. Muscle activity will be verified by electromyography of muscles mastication, masseter and temporal, and salivary biomarkers observed will be cortisol and dopamine levels.

DISCUSSION

Photobiomodulation therapy has piqued the interest of researchers, as this noninvasive method has demonstrated positive results in problems related to muscle tissues. This document describes the protocol for a proposed study to evaluate morphological and psychosocial aspects in children and adolescents with awake bruxism and their responses to photobiomodulation therapy with infrared LED. CLINICAL TRIALS:.

Predicting the severity and prognosis of trismus after intensity-modulated radiation therapy for oral cancer patients by magnetic resonance imaging

To develop magnetic resonance imaging (MRI) indicators to predict trismus outcome for post-operative oral cavity cancer patients who received adjuvant intensity-modulated radiation therapy (IMRT), 22 patients with oral cancer treated with IMRT were studied over a two-year period. Signal abnormality scores (SA scores) were computed from Likert-type ratings of the abnormalities of nine masticator structures and compared with the Mann-Whitney U-test and Kruskal-Wallis one-way ANOVA test between groups. Seventeen patients (77.3%) experienced different degrees of trismus during the two-year follow-up period. The SA score correlated with the trismus grade (r = 0.52, p<0.005). Patients having progressive trismus had higher mean doses of radiation to multiple structures, including the masticator and lateral pterygoid muscles, and the parotid gland (p<0.05). In addition, this group also had higher SA-masticator muscle dose product at 6 months and SA scores at 12 months (p<0.05). At the optimum cut-off points of 0.38 for the propensity score, the sensitivity was 100% and the specificity was 93% for predicting the prognosis of the trismus patients. The SA score, as determined using MRI, can reflect the radiation injury and correlate to trismus severity. Together with the radiation dose, it could serve as a useful biomarker to predict the outcome and guide the management of trismus following radiation therapy.

MRI findings of radiation-induced changes of masticatory muscles: a systematic review

BACKGROUND

Radiotherapy to the head and neck regions can result in serious consequences to the temporomandibular joint (TMJ) and chewing muscles. Magnetic resonance imaging (MRI) demonstrates soft-tissue alterations after radiotherapy, such as morphology and signal intensity.

OBJECTIVE

The purpose of this review is to critically and systematically analyse the available evidence regarding the masticatory muscles alterations, as demonstrated on MRI, after radiotherapy for head and neck cancer.

DATA SOURCES

Electronic search of MEDLINE, EMBASE, EBM reviews and Scopus.

INCLUSION CRITERIA

Reports of any study design investigating radiation-induced changes in masticatory muscles after radiotherapy in patients with head and neck cancer were included.

RESULTS AND SYNTHESIS METHODS

An electronic database search resulted in 162 papers. Sixteen papers were initially selected as potentially relevant studies; however, only four papers satisfied all inclusion criteria. The included papers focused on the MRI appearance of masticatory muscles following radiotherapy protocol. Two papers reported outcome based on retrospective clinical and imaging records, whereas the remaining two papers were case reports. Irradiated muscles frequently show diffuse increase in T2 signal and post-gadolinium enhancement post-irradiation. Also, muscle size changes were reported based on subjective comparison with the contralateral side. The quality of all included papers was considered poor with high risk of bias.

CONCLUSION

There is no evidence that MRI interpretations indicate specific radiation-induced changes in masticatory muscles. There is a clear need for a cohort study comparing patients with pre- and post-radiotherapy MRI.

Evaluation of low-level laser therapy effectiveness on the pain and masticatory performance of patients with myofascial pain

This study investigated the effect of low-level laser therapy (LLLT) on the masticatory performance (MP), pressure pain threshold (PPT), and pain intensity in patients with myofascial pain. Twenty-one subjects, with myofascial pain according to Research Diagnostic Criteria/temporomandibular dysfunction, were divided into laser group (n = 12) and placebo group (n = 9) to receive laser therapy (active or placebo) two times per week for 4 weeks. The measured variables were: (1) MP by analysis of the geometric mean diameter (GMD) of the chewed particles using Optocal test material, (2) PPT by a pressure algometer, and (3) pain intensity by the visual analog scale (VAS). Measurements of MP and PPT were obtained at three time points: baseline, at the end of treatment with low-level laser and 30 days after (follow-up). VAS was measured at the same times as above and weekly throughout the laser therapy. The Friedman test was used at a significance level of 5% for data analysis. The study was approved by the Ethics Committee of the Federal University of Sergipe (CAAE: 0025.0.107.000-10). A reduction in the GMD of crushed particles (p < 0.01) and an increase in PPT (p < 0.05) were seen only in the laser group when comparing the baseline and end-of-treatment values. Both groups showed a decrease in pain intensity at the end of treatment. LLLT promoted an improvement in MP and PPT of the masticatory muscles.

A mobilization regimen to prevent mandibular hypomobility in irradiated patients: an analysis and comparison of two techniques

Radiotherapy, when used in head and neck cancer treatment, can produce side effects in the patients, such as decreased salivary production, xerostomia, opportunistic infections, radiation caries, dysphagia, local discomfort and the limitation of mouth opening. The aim of this study was to evaluate the amplitude of mouth opening in patients before and immediately after the completion of radiotherapy, comparing the effectiveness of two physiotherapy exercises. The irradiated sites included the masticatory muscles. The results demonstrated that there were no statistically significant differences between the two instituted exercises; however there was a trend towards better clinical results in group 2. The amplitude of mouth opening showed a trend towards reduction, but this was not statistically significant. When the pterygoid and sternocleidomatoid muscles were included in the irriated field, patients were observed to have more morbidity. This indicates the great importance of these muscles in mouth opening. Based on the results obtained within this study, it is not possible to conclude that physiotherapy exercies are efficacious in preventing trismus. Future longitudinal studies are required to verify the onset of trismus in radiotherapy patients.

Involvement of reticular neurons located dorsal to the facial nucleus in activation of the jaw-closing muscle in rats

The location of excitatory premotor neurons for jaw-closing motoneurons was examined by the use of electrical and chemical stimulation and extracellular single-unit recording techniques in the anesthetized rat. Single-pulse electrical stimulation of the supratrigeminal region (SupV) and the reticular formation dorsal to the facial nucleus (RdVII) elicited masseter EMG response at mean (+/-SD) latencies of 2.22 +/- 0.59 ms and 3.10 +/- 1.14 ms, respectively. Microinjection (0.1-0.3 microl) of glutamate (50 mM) or kainate (0.5-100 microM) into RdVII increased masseter nerve activity in artificially ventilated and immobilized rats by 30.2 +/- 40.5% and 50.7 +/- 46.8% compared to baseline values, respectively. Forty reticular neurons were antidromically activated by stimulation of the ipsilateral trigeminal motor nucleus (MoV). Twenty neurons were found in RdVII, and the remaining 20 neurons were located in SupV, or areas adjacent to SupV or RdVII. Eleven neurons in RdVII responded to at least either passive jaw opening or light pressure applied to the teeth or tongue. Nine neurons responded to passive jaw opening. Five of the nine neurons responded to multiple stimulus categories. A monosynaptic excitatory projection from one neuron in RdVII was detected by spike-triggered averaging of the rectified masseter nerve activity. We suggest that reticular neurons in RdVII are involved in increasing masseter muscle activity and that excitatory premotor neurons for masseter motoneurons are likely located in this area. RdVII could be an important candidate for controlling activity of jaw-closing muscles via peripheral inputs.

The motor cortex is involved in reflexive compensatory adjustment of speech articulation

Although speech articulation relies heavily on the sensorimotor processing, little is known about its brain control mechanisms. Here, we investigate, using transcranial magnetic stimulation, whether the motor cortex contributes to the generation of quick sensorimotor responses involved in speech motor coordination. By applying a jaw-lowering perturbation, we induced a reflexive compensatory upper-lip response, which assists in maintaining the intact labial aperture in the production of bilabial fricative consonants. This reflex response was significantly facilitated by subthreshold transcranial magnetic stimulation over the motor cortex, whereas a simple perioral reflex that is mediated only within the brainstem was not. This suggests that the motor cortex is involved in generating this functional reflexive articulatory compensation.

Quantification of masticatory muscle atrophy after high-dose radiotherapy

PURPOSE

To determine the rate of change in the cross-sectional area of the masticatory muscles after radiotherapy.

METHODS AND MATERIALS

Eligible patients had undergone unilateral radiotherapy between 1993 and 2000 and had a baseline CT scan, a comparable follow-up CT scan a minimum of 1 year later, and no recurrence of cancer. Fourteen patients had their CT series scanned into digital image files. Two anatomically selected CT slices were bisected by the midline sagittal plane and stored under randomly assigned file names. Three observers measured the masseter and medial pterygoid areas on two occasions.

RESULTS

The intraobserver reliability of the muscle area measurements was 96.3% for the masseter and 97.1% for the medial pterygoid. The interobserver reliability of the muscle area measurements was 96.7% for the masseter and 96.3% for the medial pterygoid. On the treated side, the muscles received a median dose of 56 Gy (range 47-63) in 2.0-0.4-Gy fractions. With a median follow-up of 2.9 years (range 1-7.6), mixed-effects regression analysis demonstrated a significant area of reduction of -0.17 cm(2)/y (p = 0.0001) for the masseter and -0.13 cm(2)/y (p = 0.001) for the medial pterygoid. The controlled rate of muscle atrophy was 3.9%/y (95% confidence interval 1.4-6.4) for the masseter and 2.3%/y (95% confidence interval -0.6 to 5.1) for the medial pterygoid.

CONCLUSION

Standard therapeutic radiation doses appear to cause significant masticatory muscle atrophy.

Effects of controllable stress on masticatory behaviour and muscle structure: partial protective effect of clomipramine

The influence of controllable painless stress and clomipramine treatment was evaluated on masticatory behaviour and myosin heavy chain expression in masticatory rat muscles: anterior digastric, anterior temporalis and masseter superficialis. The adult fast isoforms of myosin heavy chains detected were myosin heavy chains 2A, 2X and 2B. The myosin heavy chains composition of anterior temporalis muscle was unchanged by stress or by treatment. In anterior digastric and masseter superficialis muscles, stress induced an increase in 2B and a decrease in 2X and 2A. Under stress, whereas the myosin heavy chains composition of anterior temporalis and anterior digastric muscles was unaffected by clomipramine, this drug modified significantly the myosin heavy chains composition of masseter superficialis muscle which became comparable to that of control muscle. Stress-induced myosin heavy chains transformations led to an increased velocity of anterior digastric and masseter superficialis muscles but not anterior temporalis muscle. Gnawing and mastication were increased by stress and incisor grinding was reduced. Stress shortened the duration of gnawing and increased the fatigability of anterior digastric and masseter superficialis muscles, whereas clomipramine increased the duration of mastication and reduced the fatigability of masseter superficialis muscle. Stress produces selective changes in masticatory muscles and behaviour. This study demonstrates the muscle type-specific protective effect of clomipramine against stress-induced structural transformations of masseter superficialis muscle and the specific concomitant behavioural modifications.

Mobilization regimens for the prevention of jaw hypomobility in the radiated patient: a comparison of three techniques

This study evaluated and compared the Therabite Jaw Motion Rehabilitation System (Therabite Corporation, Bryn Mawr, PA) to tongue blades as a technique for maintaining and/or improving mandibular range of motion in post-irradiated patients. Three groups of patients were evaluated and compared: 1) unassisted exercise, 2) mechanically assisted mandibular mobilization with stacked tongue depressors combined with unassisted exercise, and 3) the Therabite System combined with unassisted exercise. The initial average maximum incisal opening (MIO) for the study population was 21.6 mm, and did not vary significantly among the groups. Measurements were recorded at 2-week intervals for 10 weeks. At week 6 and thereafter, the net increase in MIO of group 3 (13.6 mm [+/- 1.6 mm]) was significantly greater than group 1 (6.0 mm [+/- 1.8 mm]) and group 2 (4.4 mm [+/- 2.1 mm]) (P < .05). The rate of improvement leveled after 4 week in group 1 and group 2. However, the rate of gain in MIO in the Therabite group (group 3) remained constant at 10 weeks. There was no statistical difference between groups 1 and 2.

The physiological effects of radiotherapy on oral tissue

An increasing number of head and neck cancer patients are undergoing radiotherapy along or in conjunction with other treatment modalities. Radiotherapy extending over a period of weeks produces a variety of clinical manifestations. This article discusses the physiological changes that occur due to radiotherapy to elucidate the changes seen clinically.

Restricted opening of the mouth with an extra-articular cause in children

Restricted opening of the mouth with an extra-articular cause (ROMEC) can have very different aetiologies. A series of 6 children, who have been operated on under 4 different diagnoses, are presented. Excluded are common problems such as recent trauma and posttraumatic scarring, craniomandibular dysfunction or elongated coronoid process, and also tumours. Problems of establishing the diagnosis, surgical treatment, postoperative physiotherapy and timing are discussed. It is shown that none of the cases is a perfect result, some outcomes are even very disappointing. It is therefore concluded that absolute trismus should be treated independently of age. The result expected will be mediocre. For final correction it is suggested that the operator should wait preferably until the second growth spurt has passed. The same goes for children presenting primarily with a mouth opening greater than 20 mm.

[Reactive changes in the skeletal muscle tissue to the action of the rays of a carbon dioxide laser]

Cross-striated muscular tissue in white rats was studied histologically and morphometrically after the effect of laser. In the first series of the experiment (25 rats) the tongue, musculus masseter and femoral muscles were cut by means of carbon dioxide laser device "Scalpel-1" changing its power within the limits of 20, 40, 60, 80, 100% from maximum (35V). Immediately after the procedure, the pathological focus along the line of the incision had clear borders and consisted of a line of coagulated necrosis and a zone of necrobiosis. Its size was 48-75 mkm and depended on the power of irradiation and on how the laser ray was directed towards the course of muscular fibres. A definite difference was revealed in the size of zones of coagulated necrosis and necrobiosis of lingual myons situating lengthwise and across the axis of the laser ray. In the second series of the experiments (50 rats) regeneration of the tongue and musculus masseter was studied. On the first day, edema and infiltration were insignificant because of coagulation of the blood vessels. Capillaries with the diameter of 20 mkm were forming from the preserved vessels and growing into the granulation tissue. On the second week, young muscular elements appear in the regenerate. Nonresorbted areas of the coagulated tissue impede myonic regeneration. On the 35-40 th day, fine muscular fibres, connective tissue and capillaires of normal size can be found within the traumatic area. The data obtained are compared with the results on reactivity of skeletal muscles after other types of lesions.