The effects of masseter muscle pain on biting performance

The Immediate Effect of Changing Mandibular Position on the EMG Activity of the Masseter, Temporalis, Sternocleidomastoid, and Trapezius Muscles

This study investigated the immediate effect of changing mandibular position on the electromyographic (EMG) activity of the masseter (MS), temporalis (TM), sternocleidomastoid (SCM) and trapezius (TR) muscles. Thirty-three (33) asymptomatic subjects (16 males and 17 females), ages 23 to 52 were selected. Surface EMG recordings were obtained for all muscles bilaterally with the mandible in a relaxed open position (relaxed) and during maximal voluntary clenching (fullbite) for the following: a non-repositioning appliance (NONREPOS) and repositioning appliance (REPOS). REPOS significantly reduced EMG activity of all muscles bilaterally during fullbite. During relaxation, reduction in EMG activity was only found for TR bilaterally. NONREPOS decreased the EMG activity bilaterally for TM and TR and unilaterally (left) for MS and SCM during fullbite. During relaxation, NONREPOS decreased muscle activity bilaterally for TR and SCM. A unilateral reduction was found for TM (right). These findings suggest that immediate alterations in mandibular position affect the cranio-cervical system. Both mandibular positions tested lowered the EMG activity of masticatory and cervical muscles in the relaxed and fullbite positions. The trapezius muscle was the most responsive to alterations in mandibular position.

Mastigação e deglutição em mulheres jovens com desordem temporomandibular

OBJETIVO: Avaliar a mastigação e a deglutição em mulheres com e sem desordem temporomandibular (DTM) e investigar a posição da mandíbula e do osso hioide, por serem estruturas importantes para a realização destas funções. MÉTODOS: Setenta mulheres foram avaliadas quanto à presença de DTM segundo o instrumento Critérios de Diagnóstico para Pesquisa de Desordem Temporomandibular, sendo que 34 delas, com DTM, constituíram o grupo de estudo (GE) e 36 participaram do grupo controle (GC). A avaliação da mastigação e deglutição foi baseada no Protocolo de Avaliação Miofuncional Orofacial com Escores (AMIOFE). As variáveis referentes à posição da mandíbula e osso hioide aferidas pela análise cefalométrica. RESULTADOS: Os indivíduos com DTM apresentaram diferença significativa quanto à postura de língua (p=0,03) e lábios (p=0,04) durante a função de deglutição, bem como a adoção mais frequente de um padrão mastigatório unilateral crônico (p=0,03). Além disso, apresentaram posição mais baixa do osso hioide em relação à mandíbula (p=0,00). CONCLUSÃO: A presença de DTM promoveu maior frequência de alterações miofuncionais orofaciais durante as funções de mastigação e deglutição. A maior distância entre o osso hioide e a mandíbula, bem como a presença da sintomatologia álgica, podem justificar, em parte, os comportamentos atípicos da língua e dos lábios observados no grupo com DTM. A repercussão da DTM sobre as funções alimentares em uma faixa etária jovem explica a importância do diagnóstico e da intervenção terapêutica precoce nestes indivíduos.

Persistent orofacial muscle pain

The pathophysiology of persistent orofacial myalgia has been the centre of much controversy. In this article we suggest a novel descriptive term; 'persistent orofacial muscle pain' (POMP) and review current evidence that supports the hypothesis that the induction of POMP involves the interplay between a peripheral nociceptive source in muscle, a faulty central nervous system component and decreased coping ability. In this context it is widely accepted that a complex interaction of variable intrinsic and extrinsic factors act to induce POMP and dysfunction.

Bite force measurement in children with primary dentition

OBJECTIVES

To determine the magnitude of the biting forces in young children aged 3-6 years in the primary dentition and analyse the potential effects of caries and malocclusion on maximum bite force.

METHODS

Children aged 3-6 years of age attending primary schools within a major city in the UK were recruited to participate in this study. The magnitude of the bite force in Newtons (N) was measured bilaterally corresponding with the 1st and 2nd primary molars and central incisors using a new specifically designed single tooth bite force gauge.

RESULTS

Two-hundred and five children were included in the study. The prevalence of dental caries and malocclusion was found to be 30.4% and 17.1% respectively. The levels of bite force recorded showed comparatively wide intra- and inter-individual variation with the maximum of the three bite force measurements ranging from 12.61 (N) to 353.64 (N) (M=196.60, SD=69.77).

CONCLUSION

Bite forces of young children show comparatively wide intra- and inter-individual variation with some similarities with those found in the limited number of previous primary dentition studies undertaken elsewhere. The results will serve to provide key reference values for use both in paediatric dental clinical practice and wider research community.

Masticatory function in temporomandibular dysfunction patients: electromyographic evaluation

Temporomandibular dysfunction (TMD) is a complex disturbance that involves the masticatory muscles and/or temporomandibular joint, causing damage to the masticatory function. This study evaluated the electromyographic activity of the masseter muscle during habitual mastication of bread, apple, banana, cashew nut and paraffin film (Parafilm M) in 25 adult subjects, of both gender, with TMD. The results were compared to those of a control group, composed of 15 adult subjects, of both sexes, free of signs and/or symptoms of TMD. The MYO-TRONICS Inc., K6-I computer software was used for electromyographic processing and analyzed the following parameters: duration of the act, duration of the masticatory cycle and number of cycles. No significant differences were found between subjects in the control group and individuals with TMD as to duration of the masticatory act and of the masticatory cycle, considering all materials used for mastication. The duration of the masticatory act and cycle was longer during mastication of paraffin film in both groups. The number of masticatory cycles was higher for mastication of apple in comparison to mastication of banana, in both groups. It can be concluded that the consistency of foods influences the duration parameters of the act, duration of the cycle and the number of masticatory cycles, and the behavior of the masticatory muscles in individuals with TMD during habitual mastication is similar to that verified in individuals without TMD.

Age and gender influence on maximal bite force and masticatory muscles thickness

The present study aimed investigate the age and gender influence on maximal molar bite force and at outlining the criteria for normal masticatory muscle development in a sample of 177 Brazilian Caucasian dentate individuals aged 7-80 years divided into five age groups: I (7-12 years), II (13-20 years), III (21-40 years), IV (41-60 years), and V (61-80 years). Except for Group V, which comprised nine women and eight men, all groups were equally divided in respect to gender (20 M/20 F). Bite force was recorded with a mouth-adapted 1000N dynamometer and the highest out of three records was regarded as the maximal bite force. The data were submitted to multivariate statistical analysis (SPSS 17.0 p<0.05). Effects of group and gender were found, but no interactions between them. The ANOVA showed significant differences between groups bilaterally. Bonferroni's test showed that group I had significantly lower bite force means at both sides as compared to all groups, except group V. No differences were found between the left and right sides. In all the groups, gender was found to be a significant factor associated with maximal bite force. A global comparison including all the subjects and measures showed that the means of men were approximately 30% higher than those of women. Within-group comparisons yielded similar results in all groups. Muscle thickness was measured with a SonoSite Titan ultrasound tool using a high-resolution real-time 56mm/10MHz linear-array transducer. Three ultrasound images were obtained from the bilateral masseter and temporal muscles at rest and at maximal voluntary contraction. The means of the three measures in each clinical condition were analyzed with multivariate statistical analysis (SPSS 17.0 p<0.05). A gradual increase in thickness of the masseter and temporal muscles was found both at rest and maximal voluntary contraction for groups I to IV, whereas a decrease in muscle thickness was observed in group V. Multivariate analysis showed that in both conditions there was an effect of group and gender. The study of the development of the stomatognathic system in relation to age and gender can provide useful data for the identification of normal and impaired functioning patterns. The results of this study indicate that age and gender are associated with structural and functional alterations in the muscles of the stomatognathic system.

Ocorrência de disfunção temporomandibular (DTM) e sua relação com hábitos orais deletérios em crianças do município de Monte Negro - RO

OBJETIVO: verificar a ocorrência de disfunção temporomandibular em crianças do município de Monte Negro/RO, correlacionando os achados à presença de hábitos orais deletérios. MÉTODOS: investigou-se a presença de quadros de disfunção temporomandibular, classificando-se em disfunção temporomandibular articular, muscular ou mista, bem como a presença de hábitos orais deletérios de sucção (mamadeira, chupeta e digital) e mastigação (onicofagia, morder objetos, morder a mucosa oral ou labial, bruxismo e apertamento dentário), em 79 crianças de seis a 11 anos (41 meninas e 38 meninos). RESULTADOS: dentre as 79 crianças investigadas, 27 (34,18%) apresentaram sinais de disfunção temporomandibular, sendo a disfunção articular a mais encontrada (48,15% n=13), seguida da mista (33,33%, n=9) e, com menor ocorrência, a muscular (18,52%, n=5 crianças). Hábitos orais deletérios foram encontrados em 69,62% (n=55) da amostra, sendo maior o número de crianças com hábitos de mastigação (39,91%, n=26) que de sucção (8,86%, n=7), observando-se casos em que os dois tipos de hábito estavam presentes (27,85%, n=22). Os resultados não demonstraram associação entre a presença de hábitos orais deletérios e disfunção temporomandibular (teste Qui-quadrado), independentemente do tipo de hábito. CONCLUSÃO: das crianças avaliadas, um terço (34%) apresentou sinais de disfunção temporomandibular, não havendo associação entre a disfunção temporomandibular com a presença de hábitos orais deletérios.

Electromyography in evaluation of pain after different types of tonsillectomy: prospective randomized study

BACKGROUND

Combined surface electromyography (sEMG) and visual analogue scale (VAS) pain assessment was performed on randomly assigned adults following tonsillectomy to research the effect of fibrin sealant (Group 1, n = 25), CO(2) laser (Group 2, n = 18) and electrocoagulation (Group 3, n = 40) on postsurgical pain.

METHODS

Timing and amplitude of sEMG activity of masseter, infrahyoid and submandibular muscles were measured during swallowing simultaneously with VAS assessment and compared to normative database.

RESULTS

Postsurgical electric activity of masseter and infrahyoid was significantly higher in comparison with normative database. sEMG and VAS data showed that tonsillectomy ended with fibrin sealant caused less pain than laser or electrocoagulation techniques with no correlation between the VAS score and duration of swallows.

CONCLUSION

Tonsillectomy affects muscle activity significantly by involving additional muscles (infrahyoid) in swallowing. Combined sEMG and VAS data indicated electrocautery as the most painful, laser as less painful, and fibrin sealant as the least painful technique.

Masticatory muscle pain and disordered jaw motor behaviour: Literature review over the past decade

The clinically important relationship between masticatory muscle pain (MMP) and disordered jaw motor behaviour is subject of this concise, evidence-based review of the literature that was published during the past 10 years. Mainly based on studies that used some sort of experimental MMP (e.g., the intramuscular injection of noxious substances like hypertonic saline), it was concluded that MMP has pronounced effects on jaw motor functions like maximal clenching and mastication. The pain-related modulation of oral reflexes further illustrated the effects of MMP on masticatory motor control. Protecting the painful muscle tissues against further damage and allowing for time to heal the damaged tissues by immobilization of the masticatory system seem to be the key outcomes of these effects. Further, MMP was shown to influence the cervical motor system, which may partly explain the mechanism behind the frequently observed co-occurrence of pain in the neck and the jaw. Finally, it was concluded that, even though the evidence is not yet conclusive, also remote pain (non-MMP) can modulate jaw motor behaviour, which indicates the involvement of central mechanisms in this modulation.

Fibrin sealant reduces pain after tonsillectomy: prospective randomized study

OBJECTIVES

Postsurgical pain in adults following tonsillectomy with fibrin sealant or electrocoagulation was assessed by surface electromyography (sEMG), a dysphagia severity rating scale (DSRS), and a visual analog scale (VAS) pain

METHODS

For group 1 (n = 40), hemostasis was achieved by fibrin sealant spraying to the tonsillar fossae. For group 2 (n = 40), hemostasis was achieved by bipolar or needle point electrocautery. The timing of single swallowing and continuous drinking and the mean electrical activity of the masseter, infrahyoid, and submental-submandibular muscles were compared with a normative database during 30 days and with DSRS and VAS scores.

RESULTS

Electrical activity of the masseter and infrahyoid muscles was significantly higher in both groups in comparison with the normative database (p < .05 to p < .005), whereas timing was less affected. The combined sEMG, DSRS, and VAS assessment showed that tonsillectomy ended with sealant causes less pain than electrocoagulation (p < .05). The DSRS score data were in strong positive correlation with the sEMG records, whereas the VAS pain score was less informative.

CONCLUSIONS

The combined sEMG and pain score data indicate that the electrocautery hemostatic technique is more painful and traumatic than the sealant technique. Surface electromyography of swallowing is a simple, reliable evaluation method for postsurgical odynophagia complaints and might be used as an objective tool for pain assessment.

Bite force determination in adolescents with and without temporomandibular dysfunction

The aims of this study were to compare bite force in adolescents with and without temporomandibular dysfunction (TMD), and to investigate the influence of gender, age, height and weight on bite force magnitude. The TMD was evaluated using a self-report questionnaire and the Craniomandibular Index, which has two subscales, the Dysfunction Index and the Palpation Index. Subjects with lower and upper extremity values were used to integrate the control (Group I -n = 20) and TMD (Group II -n = 20) groups, respectively. In addition, the TMD group should have at least one subjective symptom. Bite force was determined with a transducer, which consisted of a pressurized rubber tube connected to a sensor element (MPX 5700 - Motorola SPS, Austin, TX, USA). Analysis of covariance, Pearson's coefficient, Mann-Whitney and t-tests were applied to analyse the data. The results showed that Group II presented smaller values for bite force than Group I and boys had greater values than girls in Group II (P < 0.05). Bite force values were significantly smaller for girls between groups (P < 0.05), whereas for boys there was no statistical difference. Weak positive correlation between bite force and weight, height and age (P > 0.05) and significant negative correlation between bite force and Palpation and Craniomandibular Indexes (P < 0.05) were found. It was concluded that decreased bite force was correlated with TMD in girls, primarily with muscle tenderness.

Effects of evoked pain on the electromyogram and compound muscle action potential of the brachial biceps muscle

Muscle pain is often accompanied by a feeling of muscle fatigue and weakness. We examined the effect of experimental muscle pain on the electromyogram (EMG) during maximal voluntary contraction (MVC), and on the compound muscle action potential (CMAP) of the brachial biceps muscle. Twenty-one healthy subjects were injected intramuscularly with 0.1 ml/30 microg of the vanilloid receptor agonist (capsaicin) or 0.2 ml of 5% hypertonic saline. A Teflon-coated cannulated EMG needle was used to record the EMG interference pattern (IP) at MVC. The CMAP of the brachial biceps muscle was obtained by stimulation of the musculocutaneous nerve at the axilla using surface electrodes. Amplitude, mean frequency of the power spectrum, and turns/s of the interference pattern were reduced after pain induced by capsaicin or hypertonic saline. Latency, amplitude, and area-under-curve of the CMAP did not change after injection of either substance. Acute stimulation of muscle nociceptors thus produced a fatiguelike change in the interference pattern during MVC, possibly due to a decrease in motoneuron firing rate and increased muscle fatigability.