Evaluation of muscle activity, bite force and salivary cortisol in children with bruxism before and after low level laser applied to acupoints: study protocol for a randomised controlled trial.

BACKGROUND: Bruxism is a repetitive activity that causes tooth wear, audible sounds, and discomfort. Preventive measures have been studied for conditions that can exert a negative influence on physiological development in children. Low-level laser therapy administered over acupoints is an effective, painless, low-cost treatment option that has achieved good results. Thus, the aim of the proposed study is to evaluate changes in muscle activity, bite force and salivary cortisol in children with bruxism after the application of low-level laser to accupoints. METHODS: The children will be randomly allocated to four groups of 19 individuals: G1 - low-level laser; G2 - occlusal splint; G3 - placebo laser; and G4 - control (without bruxism). The BTS TMJOINT electromyography will be used to determine muscle activity and a digital gnathodynamometer will be used to measure bite force. Salivary cortisol will be analysed at baseline as well as one and six months after treatment. Two-way ANOVA will be employed and complemented by Tukey's test. DISCUSSION: Bruxism is a repetitive activity of the masticatory muscles that can have negative consequences if not treated, such as tooth wear, noises, discomfort and anxiety. Thus, control and treatment measures should be taken. Although low-level laser therapy over acupoints has been indicated for children, the effects of this treatment modality have not yet been studied. TRIAL REGISTRATION: NCT02757261 on 8 April 2016. This study protocol received a grant from the Brazilian fostering agency São Paulo Research Foundation (FAPESP: #2015/24731-0).

The use of a custom-made mouthguard stabilizes the electromyographic activity of the masticatory muscles among Karate-Do athletes.

AIMS: To analyze and compare the electromyographic activity of the temporal (anterior portion) and masseter muscles among Karate-Do athletes before and after training, with and without the use of a mouthguard. METHODS: Twenty athletes (14 males and 6 females) with a mean age of 23.7 ± 7.5 years participated. They had surface electromyography recordings taken of their bilateral temporal and masseter muscles before and after training under the following conditions: no mouthguard, with a ready-made mouthguard, and with a custom-made mouthguard. Activity was examined at mandibular rest, while clenching, and at maximum voluntary contraction. The data were normalized using the mean maximum voluntary contraction. RESULTS: The right (p = 0.005) and left (p = 0.015) temporal muscles showed significantly lower electromyographic activity with a custom-made mouthguard compared with no mouthguard after training while clenching. The electromyographic activity of the temporal and masseter muscles did not show significant differences when tested at mandibular rest and while clenching before or after training with a custom-made mouthguard (p > 0.05). CONCLUSION: The use of a custom-made mouthguard preserved participants' electromyographic profiles before and after training; thus, they allow for stable muscle activity during the training of Karate-Do athletes.

Effect of surface neuromuscular electrical stimulation on labial and lingual muscles in healthy volunteers.

Neuromuscular electrical stimulation (NMES) may have potential as a treatment for muscle weakness as it may improve strength when applied to the orofacial muscles. However, before incorporating this procedure into clinical practice, research is needed to investigate its effects on lingual and facial muscles of speech and mastication. The aim of this study was to determine what effect(s) submental and labial NMES would have on lingual and labial muscle strength in healthy participants. Fourteen healthy adults (27-49 years old) were assigned to two groups (treatment and control). A pretreatment and post-treatment test using the Iowa Oral Performance Instrument was used to measure the strength of labial and lingual muscles in both groups. Participants in the treatment group received labial and submental NMES while performing a structured labial, buccal, and lingual exercise program. In contrast, participants in the control group completed the same oral motor exercise program without stimulation. RESULTS: On comparing the total change in labial and lingual strength between the two groups, an increase in total labial strength was found in the treatment group compared with the control group. However, the control group showed an increase in total lingual strength compared with the treatment group. Results for all measurements were not statistically significant. This study concluded that NMES may be a promising modality to combine with labial and buccal exercises for improvement of muscle strength.

Optimal duration of ultra low frequency-transcutaneous electrical nerve stimulation (ULF-TENS) therapy for muscular relaxation in neuromuscular occlusion: A preliminary clinical study.

OBJECTIVES: The primary aim of this work was to determine the duration of ultra-low-frequency transcutaneous electrical nerve stimulation (ULF-TENS) application necessary to achieve sufficient relaxation of the masticatory muscles. A secondary aim was to analyze the influence of stimulation on muscle relaxation in pathological subjects and determine whether ULF-TENS has a noteworthy impact on muscle relaxation. METHODS: Sixteen adult subjects with temporomandibular disorders (TMD) and muscle pain and a group of four control subjects were included in this study. ULF-TENS was applied, and muscular activities of the masseter, temporal, and sternocleidomastoid muscles (SCM) were recorded for 60 min. RESULTS: Significant relaxation was achieved in the TMD group from 20, 40, and 60 min for the temporal, masseter, and SCM muscles (p < 0.05), respectively. Maximum relaxation was achieved in 12.5% of the subjects after 20 min, in a further 12.5% after 40 min, and in the remaining 75% after 60 min. Significant relaxation was achieved in the control group from 20 to 40 min for the masseter and temporal muscles, respectively (p < 0.05). DISCUSSION: Taken together, the results suggest that an ideal ULF-TENS application would last 40 min to obtain sufficient muscle relaxation both in patients with masticatory system disorders and healthy subjects, a time constraint that is consistent with everyday clinical practice.

Feeding biomechanics of the cownose ray, Rhinoptera bonasus, over ontogeny.

Growth affects the performance of structure, so the pattern of growth must influence the role of a structure and an organism. Because animal performance is linked to morphological specialization, ontogenetic change in size may influence an organism's biological role. High bite force generation is presumably selected for in durophagous taxa. Therefore, these animals provide an excellent study system for investigating biomechanical consequences of growth on performance. An ontogenetic series of 27 cownose rays (Rhinoptera bonasus) were dissected in order to develop a biomechanical model of the feeding mechanism, which was then compared with bite forces measured from live rays. Mechanical advantage of the feeding apparatus was generally conserved throughout ontogeny, while an increase in the mass and cross-sectional area of the jaw adductors resulted in allometric gains in bite force generation. Of primary importance to forceful biting in this taxon is the use of a fibrocartilaginous tendon associated with the insertion of the primary jaw adductor division. This tendon may serve to redirect muscle forces anteriorly, transmitting them within the plane of biting. Measured bite forces obtained through electrostimulation of the jaw adductors in live rays were higher than predicted, possibly due to differences in specific tension of actual batoid muscle and that used in the model. Mass-specific bite forces in these rays are the highest recorded for elasmobranchs. Cownose rays exemplify a species that, through allometric growth of bite performance and morphological novelties, have expanded their ecological performance over ontogeny.

Management of sleep bruxism in adults: a qualitative systematic literature review.

This paper updates the bruxism management review published by Lobbezoo et al. in 2008 (J Oral Rehabil 2008; 35: 509-23). The review focuses on the most recent literature on management of sleep bruxism (SB) in adults, as diagnosed with polysomnography (PSG) with audio-video (AV) recordings, or with any other approach measuring the sleep-time masticatory muscles' activity, viz., PSG without AV recordings or electromyography (EMG) recorded with portable devices. Fourteen (N = 14) papers were included in the review, of which 12 were randomised controlled trials (RCTs) and 2 were uncontrolled before-after studies. Structured reading of the included articles showed a high variability of topics, designs and findings. On average, the risk of bias for RCTs was low-to-unclear, whilst the before-after studies had several methodological limitations. The studies' results suggest that (i) almost every type of oral appliance (OA) (seven papers) is somehow effective to reduce SB activity, with a potentially higher decrease for devices providing large extent of mandibular advancement; (ii) all tested pharmacological approaches [i.e. botulinum toxin (two papers), clonazepam (one paper) and clonidine (one paper)] may reduce SB with respect to placebo; (iii) the potential benefit of biofeedback (BF) and cognitive-behavioural (CB) approaches to SB management is not fully supported (two papers); and (iv) the only investigation providing an electrical stimulus to the masseter muscle supports its effectiveness to reduce SB. It can be concluded that there is not enough evidence to define a standard of reference approach for SB treatment, except for the use of OA. Future studies on the indications for SB treatment are recommended.

Jendrassik maneuver facilitates cVEMP amplitude: some preliminary observations.

BACKGROUND: The cervical vestibular evoked myogenic potential (cVEMP) is an acoustically driven electrophysiological measure of saccular and inferior nerve function that requires tonic sternocleidomastoid muscle (SCM) activity in order to be elicited. The cVEMP is gaining increased interest in the clinical and research communities based on the anatomical specificity it adds to vestibular test batteries, because it is noninvasive, and since it can be performed with instrumentation commonly found in audiology clinics worldwide. PURPOSE: Because maintaining a constant level of tonic background electromyography (EMG) over the entire course of the recording epoch is a requirement for response elicitation, active participation for some individuals including the elderly and those with cervical problems can be difficult. As a way to facilitate the response for some clinical populations, this study addressed whether cVEMPs could be modulated by remote or local changes in EMG related neural activity by applying various maneuvers during the course of the recording epoch. RESEARCH DESIGN: Keeping acoustic stimulation and recording parameters constant, three separate experimental conditions, Jendrassik maneuver, jaw (teeth) clenching, and forced-eye closure, were used to determine whether cVEMP amplitudes could be enhanced from the control condition. STUDY SAMPLE: Nine adults (2 males; 7 females) ranging in age from 24 to 42 yr with normal pure-tone hearing sensitivity and a negative history of otological disease, neurological disease, and head trauma. DATA COLLECTION AND ANALYSIS: Cervical vestibular evoked myogenic potentials were recorded from the SCM using surface electrodes in response to suprathreshold 500 Hz Blackman windowed tone bursts under a control and three experimental conditions. Three separate one-way repeated measures analyses of variance (ANOVAs) were used to evaluate the effects of these maneuvers on P1/N1 peak-to-peak amplitudes and P1 and N1 peak latencies. RESULTS: A significant main effect of experimental condition was shown to increase P1/N1 peak-to-peak cVEMP amplitude. Post hoc analysis found that Jendrassik maneuver versus control was the only the condition that produced significantly increased response amplitudes in comparison to all other post hoc contrasts. P1 and N1 peak latencies were unchanged across the various experimental conditions. CONCLUSIONS: In adults with normal hearing sensitivity and a negative history of otological disease, neurological disease, and head trauma, Jendrassik maneuver increased cVEMP amplitude by over 39% in comparison to the control condition. Such a simple modulation effect warrants further investigation for application in clinical studies.

Comprehensive treatment of temporomandibular joint disorders.

AIMS: Changing lifestyles, decreasing physical activity, which is increasing the number of degenerative joint diseases of various etiology, and certain dental procedures are increasing the number of patients complaining of pain in their temporomandibular joints. The aim of the study was to assess the benefits of comprehensive physiotherapy sessions in order to decrease the number of temporomandibular joint problems, thereby improving the patient's quality of life. METHODOLOGY: An examination by a dentist determined each patient's treatment plan, which consisted of a medical exam, physical therapy and education. Each form of treatment was applied 10 times at intervals of 7-14 days. The main goal of the therapeutic physical education was to redress the muscle imbalance in the mandibular joint. This was achieved by restoring balance between the masticatory muscles, along with releasing the spastic shrouds found in the masticatory muscles. The aim of education was to teach the patient exercises focused on the temporomandibular joint and masticatory muscles. The intensity of the exercises and their composition were individually adjusted and adapted to their current state. Physical therapy consisted of the application of pulsed magnetic therapy, laser therapy, and non-invasive positive thermotherapy. RESULTS: The above procedure was conducted on a therapeutic group of 24 patients (3 men and 20 women). In the course of therapy, there were no complications, and all patients adhered to the prescribed regime. None reported any side effects. The mean treatment duration was 123 +/- 66 days. The outcome of the therapy was evaluated as described in the methodology, the degree of pain affecting the joint, and the opening ability of the mouth. In both parameters, there was a significant decline in patient pain. CONCLUSIONS: In a study devoted to tactics of rehabilitation treatment for temporomandibular joint disorders, the need for comprehensive long-term therapy, involving education, and learning proper chewing habits was made apparent for recovery and pain reduction. A priority in physical therapy, and combinations of pulsed magnetic therapy and hyperthermia-positive peloids, are also beneficial.

Effect of swallowing exercises in independent elderly.

The aim of this study was to investigate the effects of swallowing exercises on oral function in independent elderly patients visiting the Department of Prosthodontics at Tokyo Dental College Chiba Hospital. Twenty-nine patients aged over 65 years (15 men and 14 women; mean age, 75.0 years) in whom treatment was completed at this college were enrolled in the study. The patients were instructed on how to perform swallowing exercises monthly (including at baseline) for the first 2 months from the start of the study and asked to perform those exercises at least once daily. At the beginning and end of the study (a 3-month study period), the Repetitive Saliva Swallowing Test was conducted and occlusal force, oral diadochokinesis, unstimulated whole saliva flow rate, stimulated whole saliva flow rate, salivary pH at rest, and salivary buffering capacity measured to determine the effects of the exercises on oral function. Analyses demonstrated significant increases in diadochokinesis rate (/ta/ and /ka/) and unstimulated whole saliva flow rate (p<0.05), suggesting that the swallowing exercises promote the maintenance and improvement of oral function in the independent elderly.

Immediate changes in masticatory mechanosensitivity, mouth opening, and head posture after myofascial techniques in pain-free healthy participants: a randomized controlled trial.

OBJECTIVE: This study aimed to assess the immediate effects on masticatory muscle mechanosensitivity, maximal vertical mouth opening (VMO), and head posture in pain-free healthy participants after intervention with myofascial treatment in the temporalis and masseter muscles. METHODS: A randomized, double-blind study was conducted. The sample group included 48 participants (n=48), with a mean age of 21±2.47 years (18-29). Two subgroups were defined: an intervention group (n=24), who underwent a fascial induction protocol in the masseter and temporalis muscles, and a control group (n=24), who underwent a sham (placebo) intervention. The pressure pain threshold in 2 locations in the masseter (M1, M2) and temporalis (T1, T2) muscles, maximal VMO, and head posture, by means of the craniovertebral angle, were all measured. RESULTS: Significant improvements were observed in the intragroup comparison in the intervention group for the craniovertebral angle with the participant in seated (P<.001; F1,23=16.45, R2=0.41) and standing positions (P=.012, F1,23=7.49, R2=0.24) and for the pressure pain threshold in the masticatory muscles, except for M2 (P=.151; M1: P=.003; F1,23=11.34, R2=0.33; T1: P=.013, F1,23=7.25, R2=0.23; T2: P=.019, F1,23=6.41, R2=0.21). There were no intragroup differences for the VMO (P=.542). Nevertheless, no significant differences were observed in the intergroup analysis in any of the studied variables (P>.05). CONCLUSION: Myofascial induction techniques in the masseter and temporalis muscles show no significant differences in maximal VMO, in the mechanical sensitivity of the masticatory muscles, and in head posture in comparison with a placebo intervention in which the therapist's hands are placed in the temporomandibular joint region without exerting any therapeutic pressure.

Orthodontic-surgical treatment: neuromuscular evaluation in skeletal Class II and Class III patients.

OBJECTIVES: The aim of this study was the evaluation of the neuromuscular response to treatment according to diagnostic phases, as a follow-up of patients under surgical orthodontic treatment. The patient sample was subdivided into sub-samples, according to clinical characteristics. MATERIALS AND METHODS: All of the patients who underwent orthognathic surgery in the Department of Orthodontics (University of Milan) were subjected to periodic electromyographic evaluation of the masticatory muscles (masseter and anterior temporal muscles), and to electrokinesiographic evaluation of the mandibular movements. The patient sample comprised 80 patients (37 males; and 43 females) at the end of growth. The electromyographic instruments used in the study included a Freely and a K6-I electromyography. Statistical evaluation was carried out with the Student's t-tests for independent samples. RESULTS: There are many differences between the skeletal Class II and skeletal Class III patients that are shown through the analysis of these data obtained. In the beginning phases of the treatment the muscular activities were higher in the Class II patients than in the Class III patients. Nevertheless this difference was reversed at the end of the treatment. A similar difference could be found in the mandibular kinesiology, in fact the maximum mandibular opening movement was greater in the skeletal Class II patients than in the skeletal Class III patients at the beginning of the treatment. At the end of the treatment this difference was lost. At the beginning of the treatment the Class II patients showed a greater protrusive movement of the mandibular than the Class III patients. At the end the treatment however this gap was reduced without being reversed. CONCLUSIONS: Functional evaluation in patients in surgical orthodontic therapy is an important element in the diagnostic-therapeutic recordings, so as to reduce as much as possible any incorrect neuromuscular activity that can result in relapse.

Reflection of induced and amplified food motivation in impulse activity of the masticatory muscles during electrostimulation of the "hunger center" in the lateral hypothalamus in rabbits.

We studied reflection of artificially induced and amplified food motivation in impulse activity of the masticatory muscles during electrostimulation of "hunger center" of the lateral hypothalamus in the absence and presence of food. The threshold stimulation of the lateral hypothalamus in hungry and satiated animals in the absence of food induced incessant food-procuring behavior paralleled by regular generation of spike bursts in masticatory muscles with biomodal distributions of intervals between pulses. This reaction of masticatory muscles during stimulation of the lateral hypothalamus in the absence of food was an example of the anticipatory reaction reflecting characteristics of the action result acceptor. Higher level of hunger motivation during threshold stimulation of the lateral hypothalamus in hungry and satiated rabbits in the course of effective food-procuring behavior increased the incidence of spike burst generation during the food capture phase, but did not modify this parameter during the chewing phase. Impulse activity of the masticatory muscles reflected convergent interactions of food motivation and support excitation on neurons of the central generator of chewing pattern.

Enhancing the quality of life in elderly women through a programme to improve the condition of salivary hypofunction.

OBJECTIVE: The purposes of this study were to examine the effects of oral exercise intended to improve the function of the oral cavity in the elderly and their quality of life to pave the way for the development of oral-health promotion programmes geared towards the elderly. METHODS: The subjects were 78 female Koreans who resided in Seoul and were aged 65 years and older. During a 3-month period, an oral function promotion programme was conducted twice a week, between 10.00 am and 12.00 pm, applying oral exercise suggested by a Japanese public health centre. A survey was conducted by interviewing the selected women to determine the state of their subjective dry mouth, quality of life related to oral health and jaw functional limitation. Their opening, unstimulated whole saliva and pronunciation speed were measured before and after the oral function exercise programme. RESULTS: The subjects showed a significant improvement in subjective dry mouth symptoms, relevant behaviour, the level of discomfort caused by dry mouth and subjective jaw functional limitation during mastication and swallowing and emotional expression after receiving the oral exercise. After the oral exercise, there was a significant increase in mouth opening, unstimulated whole saliva and speaking speed ('patakala' pronunciation) after oral exercise. There was also significant progress in their quality of life related to oral health. Overall improvement in subjective dry mouth symptoms and relevant behaviour over time after oral exercise had a positive correlation with the level of improvement in discomfort triggered by dry mouth and mastication. The level of improvement in OHIP-14 had a positive correlation with the level of overall improvement in dry mouth symptoms and behaviour, the level of improvement in discomfort by dry mouth and that in mastication and swallowing. CONCLUSION: This study showed the effects of the oral function promotion programme and correlation of oral condition and oral health-related quality of life. It is suggested that this oral function promotion programme has positive effects on both objective and subjective oral conditions. It is strongly recommended that this programme, along with other oral health promotion programmes, be implemented to improve oral function and oral health-related quality of life for the elderly.

The muscle engram: the reflex that limits conventional occlusal treatment.

The engram (the masticatory "muscle memory") is shown to be a conditionable reflex whose muscle conditioning lasts less than two minutes, far shorter than previously thought. This reflex, reinforced and stored in the masticatory muscles at every swallow, adjusts masticatory muscle activity to guide the lower arch unerringly into its ICP. These muscle adjustments compensate for the continually changing intemal and external factors that affect the mandible's entry into the ICP. A simple quick experiment described in this article isolates the engram, enabling the reader to see its action clearly for the first time. It is urged that every reader perform this experiment. This experiment shows how the engram, by hiding the masticatory muscles' reaction (the hit-and-slide), limits the success of the therapist in achieving occlusion-muscle compatibility. This finding has major clinical implications. It means that, as regards the muscle aspect of treating occlusion, the dentist treating occlusion conventionally is working blind, a situation the neuromuscular school of occlusal thought seeks to correct. The controversy over occlusion continues.

The influence of auditory and visual information on the neuromuscular control of chewing crispy food.

The influence of auditory and/or visual information on the neuromuscular control of chewing a crispy food was investigated. Participants chewed biscuits of three different levels of crispness under four experimental conditions: no masking, auditory masking, visual masking, and auditory plus visual masking. The order of the four masking condition blocks was randomized. The sound of chewing was masked by loud sounds on a headphone, and visual masking of the food was achieved by closing the eyes. Mechanical tests were performed on the biscuits to determine their characteristics, yield force, and sound production. Skull vibration, jaw-muscle activity, and jaw movement were measured while the subjects chewed and swallowed the food. Auditory and/or visual masking did not have a significant effect on skull vibration, muscle activity, and number of chewing cycles until swallowing. However, auditory and/or visual masking significantly increased the chewing cycle duration, but only for the participants who started the experiments with auditory and/or visual masking. The other participants were not influenced by masking. The memory of the unmodified stimuli helped these subjects to maintain their habitual chewing rate in later trials.

[Effect of electrostimulation "hunger center" of lateral hypothalamus on the impulse activity of masticatory muscles in unfed and fed rabbits in the absence and the presence of food].

In chronic experiences on rabbits the influence of electrostimulation of "the hunger centres" of the lateral hypothalamus (LH) on impulse activity of chewing muscles of rabbits under the conditions of hunger and satiation was studied. It is established, threshold irritation of the LH of hungry and preliminary fed animals in the absence of food caused the occurrence of incessant search behavior which was followed by the regular generation of bursts of AP by masseter and mylohyoideus muscles with bimodal distributions of interpulse intervals. Such reaction of chewing muscles during irritation of the LH in the absence of food is an example of advancing type reaction. The increase of level of alimentary motivation, arising at threshold irritation of the LH of rabbits under the conditions of hunger and satiety during the resultant food-intake behavior, increased frequency of generation of bursts of AP in a phase of the capture of food, but did not influence on this indicator in a phase of chewing of food. The received results testify about descending stimulating influences of alimentary motivational excitation on neurons of the chewing centre in medulla and on impulse activity of chewing muscles.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the mylohyoid muscle in rabbits under conditions of hunger and satiety.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of mylohyoid muscle were studied in chronic experiments under conditions of hunger and satiety. Threshold stimulation of the lateral hypothalamus in starving and satiated rabbits in the absence of food induced searching behavior associated with burst-like impulse activity with a bimodal distribution of interpulse intervals. Regular spike burst in the mylohyoid muscle during stimulation of the lateral hypothalamus in the absence of food serves as an example of the anticipatory type reaction. Increased food motivation during threshold stimulation of the lateral hypothalamus in starving and satiated rabbits with food offered led to successful food-procuring behavior, during which the frequency of spike bursts in the mylohyoid muscle became comparable with that under conditions of natural foraging behavior stimulated by the need in nutrients. Our results suggest that temporal structure of mylohyoid muscle impulse activity reflects convergent interactions of food-motivation excitation with reinforcement excitation on neurons of the masticatory and deglutitive centers.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the proper masticatory muscle in rabbits under conditions of hunger and satiation.

Threshold stimulation of the lateral hypothalamus in starving and preliminary fed (satiated) rabbits in the absence of feed induces searching behavior associated with burst-like impulse activity of proper masticatory muscle with a bimodal distribution of interpulse intervals, what represents an anticipatory type of reaction. The increase in the level of food motivation during threshold stimulation of the lateral hypothalamus in starving and satiated rabbits with the food offered led to successful food-procuring behavior, during which the frequency and amplitude of spike bursts in the proper masticatory muscle become comparable with those under conditions of natural foraging behavior stimulated by the need in nutrients. Motivational excitation and backward afferentation from food reward are addressed to the same neurons of the masticatory center in the medulla oblongata.