Article

Increased sternocleidomastoid, but not trapezius, muscle activity in response to increased chewing load

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Abstract

Previous findings, during chewing, that boluses of larger size and harder texture result in larger amplitudes of both mandibular and head-neck movements suggest a relationship between increased chewing load and incremental recruitment of jaw and neck muscles. The present report evaluated jaw (masseter and digastric) and neck [sternocleidomastoid (SCM) and trapezius] muscle activity during the chewing of test foods of different sizes and textures by 10 healthy subjects. Muscle activity was recorded by surface electromyography and simultaneous mandibular and head movements were recorded using an optoelectronic technique. Each subject performed continuous jaw-opening/jaw-closing movements whilst chewing small and large boluses of chewing gum and rubber silicone (Optosil). For jaw opening/jaw closing without a bolus, SCM activity was recorded for jaw opening concomitantly with digastric activity. During chewing, SCM activity was recorded for jaw closing concomitantly with masseter activity. Trapezius activity was present in some, but not all, cycles. For the masseter and SCM muscles, higher activity was seen with larger test foods, suggesting increased demand and recruitment of these muscles in response to an increased chewing load. This result reinforces the previous notion of a close functional connection between the jaw and the neck motor systems in jaw actions and has scientific and clinical significance for studying jaw function and dysfunction.

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... Em relação à correlação de dor nos músculos mastigatórios e digástrico com a dor no esternocleidomastoideo, pesquisadores encontraram uma associação entre a atividade dos músculos masseteres e digástricos e a atividade do esternocleidomastoideo 27 . É possível que na presença de dor nos músculos da mastigação, os músculos esternocleidomastoideos sejam requisitados, podendo ser envolvidos em algum processo de fadiga 27 . ...
... Em relação à correlação de dor nos músculos mastigatórios e digástrico com a dor no esternocleidomastoideo, pesquisadores encontraram uma associação entre a atividade dos músculos masseteres e digástricos e a atividade do esternocleidomastoideo 27 . É possível que na presença de dor nos músculos da mastigação, os músculos esternocleidomastoideos sejam requisitados, podendo ser envolvidos em algum processo de fadiga 27 . Entretanto, para esta confirmação, são necessários estudos que avaliem a atividade elétrica dos músculos da mastigação e cervicais. ...
... Entretanto, para esta confirmação, são necessários estudos que avaliem a atividade elétrica dos músculos da mastigação e cervicais. Por sua vez, a associação entre dor nos músculos da mastigação e dor no músculo trapézio também pode estar justificada pela relação existente entre as atividades desses músculos 27 . No presente estudo, ao avaliar a força de correlação, nota-se que o músculo esternocleidomastoideo apresenta, de forma geral, um coeficiente de correlação com os músculos da mastigação maior que o trapézio, exceto com relação ao pterigoideo lateral. ...
Article
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Resumo Introdução As disfunções temporomandibulares apresentam uma variedade de sinais e sintomas que afetam a articulação temporomandibular, músculos da mastigação e estruturas relacionadas e muitos pacientes apresentam queixas cervicais. Objetivo Verificar a correlação de dor à palpação dos músculos da mastigação (masseter, temporal anterior, pterigoideos lateral e medial) e digástrico, com a queixa de dor no pescoço; verificar a correlação de dor à palpação nos músculos da mastigação e digástrico, com dor à palpação no esternocleidomastoideo e trapézio, e se a força de correlação é diferente entre eles. Material e método Foram avaliados 232 prontuários da clínica odontológica das Disfunções Temporomandibulares da Faculdade de Odontologia de Araçatuba, do período de 2011 a 2013. Os dados coletados foram submetidos à análise estatística, com alfa (α) = 0.01 para todos os casos, exceto digástrico quando associado ao trapézio (α) = 0.05. Resultado A maioria dos pacientes era do sexo feminino. Houve correlação positiva entre dor à palpação nos músculos temporal, masseter, pterigoideo lateral, esternocleidomastoideo e trapézio, e queixa de dor no pescoço. Também houve correlação positiva entre a dor em todos os músculos da mastigação (masseter, temporal, pterigoideo lateral e medial) e digástrico e a dor no esternocleidomastoideo. Bem como a correlação de presença de dor nos músculos masseter, temporal, pterigoideo lateral e digástrico com dor no trapézio. A correlação de dor foi mais forte para o músculo esternocleidomastoideo, exceto para o pterigoideo lateral. Conclusão Existe correlação positiva entre a queixa de dor à palpação nos músculos da mastigação, exceto pterigiodeo medial, e os músculos cervicais (esternocleidomastoideo e trapézio). A força de correlação entre a dor do masseter e temporal anterior com o esternocleidomastoideo é mais forte do que com o trapézio.
... Physiologically coordinated jaw and neck muscle activities has been evaluated in regard to jaw clenching Kibana et al., 2002;Politti et al., 2010), jaw opening and closing movements (Eriksson et al., 1998(Eriksson et al., , 2000, and chewing (Guo et al., 2017;Häggman-Henrikson et al., 2013;Häggman-Henrikson & Eriksson, 2004;Igarashi et al., 2000;Shimazaki et al., 2006). For example, bilateral jaw clenching was shown to produce bilateral neck muscle activation and unilateral jaw clenching side produce predominant neck muscle activity (Kibana et al., 2002). ...
... For example, bilateral jaw clenching was shown to produce bilateral neck muscle activation and unilateral jaw clenching side produce predominant neck muscle activity (Kibana et al., 2002). In addition, neck muscle activity was found to occur concomitantly with maximal jaw-opening and jaw-closing cycles in parallel with head extension-flexion movements (Eriksson et al., 1998(Eriksson et al., , 2000, while other results indicated that neck muscles, especially the sternocleidomastoid, may be activated in response to chewing load related to food size and food hardness (Häggman-Henrikson et al., 2013). In consideration of these previous findings, jaw and neck muscles may be activated by chewing load with hard food bolus. ...
... 4.2 | Coherence function analysis for jaw and neck muscle activities during soft and hard gum chewing Intermuscular EMG-EMG coherence function analysis of chewingrelated jaw and neck muscle activities in this study may reveal the consistent functional coordination between jaw and neck muscle activities induced by chewing load using gum hardness (Ishii et al., 2016;Laine & Valero-Cuevas, 2017). It has been reported that simultaneous activation of neck muscle activity during jaw clenching Kibana et al., 2002;Politti et al., 2010) and chewing performance (Guo et al., 2017;Häggman-Henrikson & Eriksson, 2004;Häggman-Henrikson et al., 2013;Igarashi et al., 2000;Shimazaki et al., 2006). In particularly, Igarashi et al. (Igarashi et al., 2000) noted the rhythmical neck muscle activity evoked by biting a wooden stick during cortically induced rhythmical chewing in rabbits, and also Häggman-Henrikson et al. (2013) reported that sternocleidomastoid neck muscle was activated by hard gum chewing in healthy subjects. ...
Article
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Backgrounds Jaw and neck muscles may be activated by chewing load using a hard food. However, it remains unclear how effects the gum hardness to the coordinated features in jaw and neck muscle activities during chewing performance. Objectives This study was conducted to quantitatively elucidate the effects of the hardness of the gum on coordinated features in jaw and neck muscle activities using intermuscular EMG–EMG transfer function and EMG–EMG coherence function analyses in 18 healthy subjects. Methods Jaw and neck muscle activities were aggregated into the first peak frequency of the power spectrum, and power, gain, phase, and coherence parameters between jaw and neck muscle activities were examined in the first peak frequencies during soft and hard gum chewing. Results The first peak frequency was not significantly different between soft and hard gum chewing. In contrast, power values of the jaw and neck muscles were significantly increased by chewing of hard gum as compared with soft gum, whereas gain, phase, and coherence were not significantly changed by gum hardness. Conclusions The chewing rhythm, the quantitative and temporal coordination, and the functional coordination in jaw and neck muscle activities were not changed during soft and hard gum chewing, as well as increased jaw and neck muscles activities. It is therefore concluded that the chewing rhythmicity and jaw and neck muscles coordination accompanied with the increased jaw and neck muscle activities are maintained under the condition of the chewing load using gum hardness in the healthy individuals.
... For voluntary biting tasks, the co-contraction of masticatory and neck muscles has already been studied. Giannakopoulos et al 13,14,16 and Häggman-Henrikson et al 15 have found that there is low-to-moderate co-contraction of the masticatory and neck muscles during (sub) maximum voluntary clenching (MVC) in healthy subjects. This co-contraction is seen in different body positions, 14,16 during different bite forces 13,16 and during the chewing of test foods of different sizes and textures. ...
... This co-contraction is seen in different body positions, 14,16 during different bite forces 13,16 and during the chewing of test foods of different sizes and textures. 15 Muscle co-contraction, a phenomenon in which a muscle is activated co-ordinately with another muscle, is purely observational and therefore does not imply a common generator per se. 17 A more accurate analysis for detecting a common generator would be to perform coherence analysis of the electromyography (EMG) between different muscles. ...
... The sample size is determined based on the number of RMMA episodes used in previous co-activation studies of the masticatory and neck muscles and set at 50 episodes. [13][14][15] The significance threshold for the level of coherence was determined by our coherence-analysing programme with the following formula: ...
Article
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Background: Studies have shown co-contraction of jaw and neck muscles in healthy subjects during (sub)maximum voluntary jaw-clenching, indicating functional interrelation between these muscles during awake bruxism. So far, coherence of jaw and neck muscles has not been evaluated during either awake or sleep bruxism. Objective: The objective of this study is to evaluate the coherence between jaw and neck muscle activity during sleep bruxism. Methods: In a cross-sectional observational design, the electromyographic activity of jaw (masseter, temporalis) and neck (sternocleidomastoid, trapezius) muscles in individuals with 'definite' sleep bruxism was measured using ambulatory polysomnography (PSG). Coherence for masseter-temporalis, masseter-sternocleidomastoid and masseter-trapezius was measured during phasic and mixed rhythmic masticatory muscle activity episodes using coherence-analysing software. Outcome measures were: presence or absence of significant coherence per episode (in percentages), frequency of peak coherence (FPC) per episode, and sleep stage. Results: 632 episodes within 16 PSGs of 8 individuals were analysed. Significant coherence was found between the jaw and neck muscles in 84.9% of the episodes. FPCs of masseter-temporalis were significantly positively correlated with those of masseter-sternocleidomastoid or masseter-trapezius (P<0.001). Sleep stages did not significantly influence coherence of these muscular couples. Conclusion: During sleep bruxism, jaw and neck muscle activation is significantly coherent. Coherence occurs independently of sleep stage. These results support the hypothesis of bruxism being a centrally regulated phenomenon.
... The jaw and neck muscle activities are coordinated while chewing [1][2][3][4]. Kohno et al. [1] first observed that the sternocleidomastoid muscle is more active on the working side than on the non-working side while chewing. Other researchers have replicated co-activation of the chewing side masseter and sternocleidomastoid muscles [3,4]. ...
... Kohno et al. [1] first observed that the sternocleidomastoid muscle is more active on the working side than on the non-working side while chewing. Other researchers have replicated co-activation of the chewing side masseter and sternocleidomastoid muscles [3,4]. Furthermore, the functional relationship between the masseter muscle and the sternocleidomastoid muscle has been elicited from the viewpoints of experimental muscle fatigue by jaw clenching [2] and the increased activity in the sternocleidomastoid muscle in response to the chewing load by hard food [3]. ...
... Other researchers have replicated co-activation of the chewing side masseter and sternocleidomastoid muscles [3,4]. Furthermore, the functional relationship between the masseter muscle and the sternocleidomastoid muscle has been elicited from the viewpoints of experimental muscle fatigue by jaw clenching [2] and the increased activity in the sternocleidomastoid muscle in response to the chewing load by hard food [3]. ...
Article
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This study aims to quantitatively clarify the physiological features in rhythmically coordinated jaw and neck muscle EMG activities while chewing gum using EMG-EMG transfer function and EMG-EMG coherence function analyses in 20 healthy subjects. The chewing side masseter muscle EMG signal was used as the reference signal, while the other jaw (non-chewing side masseter muscle, bilateral anterior temporal muscles, and bilateral anterior digastric muscles) and neck muscle (bilateral sternocleidomastoid muscle) EMG signals were used as the examined signals in EMG-EMG transfer function and EMG-EMG coherence function analyses. Chewing-related jaw and neck muscles activities were aggregated in the first peak of the power spectrum in rhythmic chewing. The gain in the peak frequency represented the power relationships between jaw and neck muscle activities during rhythmic chewing. The phase in the peak frequency represented the temporal relationships between the jaw and neck muscle activities, while the non-chewing side neck muscle presented a broad range of distributions across jaw closing and opening phases. Coherence in the peak frequency represented the synergistic features in bilateral jaw closing muscles and chewing side neck muscle activities. The coherence and phase in non-chewing side neck muscle activities exhibited a significant negative correlation. From above, the bilateral coordination between the jaw and neck muscles activities is estimated while chewing when the non-chewing side neck muscle is synchronously activated with the jaw closing muscles, while the unilateral coordination is estimated when the non-chewing side neck muscle is irregularly activated in the jaw opening phase. Thus, the occurrence of bilateral or unilateral coordinated features in the jaw and neck muscle activities may correspond to the phase characteristics in the non-chewing side neck muscle activities during rhythmical chewing. Considering these novel findings in healthy subjects, EMG-EMG transfer function and EMG-EMG coherence function analyses may also be useful to diagnose the pathologically in-coordinated features in jaw and neck muscle activities in temporomandibular disorders and whiplash-associated disorders during critical chewing performance.
... In addition, the AT muscle is subjected to a fine proprioceptive control of its activity, since it presents a higher number of muscular spindles compared to the masseter muscle [12]. Cervical and jaw muscles show a close functional relationship in the cranio-cervicalmandibular system during jaw-opening/jaw-closing tasks [13] and during chewing tasks [14]. A different recruitment pattern during chewing has recently been reported for the sternocleidomastoid (SCM) and trapezius muscles; while SCM activity was observed in all cycles, trapezius activity was only observed in some cycles [14] . ...
... Cervical and jaw muscles show a close functional relationship in the cranio-cervicalmandibular system during jaw-opening/jaw-closing tasks [13] and during chewing tasks [14]. A different recruitment pattern during chewing has recently been reported for the sternocleidomastoid (SCM) and trapezius muscles; while SCM activity was observed in all cycles, trapezius activity was only observed in some cycles [14] . Therefore, it is important to know if the presence of a natural mediotrusive occlusal contact influences SCM activity. ...
... EMG activity of AT muscles has been recorded during different chewing tests, but most of them were unilateral. As far as we know, SCM activity has mainly been recorded unilaterally during gum chewing141516. Therefore, information on bilateral muscle activity of jaw and cervical muscles during habitual chewing is still lacking. ...
... It has been reported that masticatory movements can physiologically improve the cerebral blood flow [4], and also improve cognition, and mood, and reduce stress by relieving anxiety [5,6]. Further studies have discussed the relationships between masticatory movements and static [7,8] and dynamic [9] balance of body posture, leg muscle activity [10], neck muscle activity [11], head posture [12], and upper body movement [13]. ...
... The existence of three-dimensional rhythmic coordinated movements of the head in response to the masticatory rhythm of mandibular movements during mastication has been reported [11,[22][23][24]. In contrast, it has been reported that the center of gravity of the head is in front of the pinna and near the articular tubercle of the temporal bone [25]. ...
Article
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Purpose: To verify the effect of sitting posture with and without sole-ground contact on chewing stability and masticatory performance. Methods: Thirty healthy subjects were evaluated. The Conformat was used to analyze the center of sitting pressure (COSP), and the three-dimensional motion analysis system was used to analyze changes in head and trunk postures while subjects remained in a sitting position with and without sole-ground contact. The parameters of masticatory performance and movement were calculated as follows. For evaluating masticatory performance, the amount of glucose extraction (AGE) during chewing of a gummy jelly was measured. For evaluating masticatory movements, the movement of the mandibular incisal point was recorded using the Motion Visi-Trainer V1, and parameters of the stabilities of movement path and rhythm were calculated. Results: Head and trunk sway values and the displacement of COSP were significantly smaller with sole-ground contact than those without soleground contact. The masticatory movement path with sole-ground contact showed less variation in the opening distance and more stable movement path compared to those without sole-ground contact. The AGE was significantly greater with sole-ground contact than that without sole-ground contact. Conclusion: Sitting posture with and without sole-ground contact affects chewing stability and masticatory performance.
... It has been reported that mastication can physiologically improve the cerebral blood flow [4], 204 and improve cognition, mood, and relieve stress by relieving anxiety [5,6]. Studies have also been discussed relationships between mastication and leg muscle activity [7], neck muscle activity [8], head posture [9], upper body movement [10]. ...
... It has been reported that the existence of three-dimensional rhythmic coordinated movements of the head in response to the masticatory rhythm of mandibular movements during chewing [15,27], and that chewing induces head extension-flexion movements due to co-contraction of sternocleidomastoid and trapezius muscles along with jaw muscles [8,28]. On the other hand, there are reports that the center of gravity of the head is in front of the pinna and near the articular tubercle of the temporal bone [29], and that the center of rotation of the head movement in healthy individuals is at the top of the cervical spine [30]. ...
... Functional restoration of chewing activities treated by denture wearing has been evaluated from various viewpoints, such as chewing ability [1,2], chewing movements and muscle activities [1][2][3][4], food choice and nutrition [5][6][7], and oral and physical quality of life [6,8,9]. Nevertheless, the effects of denture wearing on the coordinated features of jaw and neck muscles remain unclear in partially edentulous patients, though those muscle activities have been simultaneously examined in healthy dentate subjects during chewing [10][11][12][13], jaw clenching [11,14,15], and opening and closing jaw movements [16,17]. ...
... The electrodes were placed bilaterally on the masseter (Mm: jawclosing muscle), anterior temporal (Ta: jaw-closing muscle), anterior digastric (AD: jaw-opening muscle), and sternocleidomastoid (SCM: neck extensor/protrusion/rotator muscle) muscles. For this study, SCM activity was used as neck muscle activity because that has been reported to coordinate with jaw muscle activities and head movement while chewing [10][11][12][13][14][15][16][17][18]. A piece of chewing gum (1.0 g, Freezone, Lotte, Tokyo, Japan) was used as the test food. ...
Article
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Purpose: This study was performed to examine how denture wearing improves jaw and neck muscle coordination during chewing in partially edentulous elderly patients. Methods: Sixteen patients classified as Eichner’s index B2 or B3 and 16 young dentate subjects were enrolled. Jaw and neck muscle activities during chewing were recorded using electromyography with and without denture wearing, then analyzed using intermuscular Electromyography (EMG)-EMG transfer and EMG-EMG coherence function analyses to clarify quantitative, temporal, and functional coordination of jaw and neck muscle activities while chewing. Occlusal force and masticatory scores were also determined. Results: Denture wearing increased the power values for jaw closing muscle activities, and improved occlusal area and force, and masticatory score. Gain values for jaw closing and opening muscle activities were decreased in those wearing dentures compared to those not wearing dentures. Denture wearing resulted in equivalent gain values for jaw closing and opening muscle activities as compared to the young subjects. Coherence values for chewing and non-chewing side neck muscle activities were increased as compared to not denture wearing. Conclusions: The suitability of denture wearing can be evaluated from the viewpoint of gain as a quantitative parameter showing coordination between jaw closing and opening muscle activities. Such evaluation can be performed from the viewpoint of coherence as a parameter of functional coordination between jaw and neck muscle activities during chewing in partially edentulous elderly patients. The gain parameter in regard to jaw muscle activities may be compensated to a state equivalent to that seen in young subjects by wearing an appropriate denture.
... Thus, a functional integration has been shown between the jaw and neck regions during normal jaw function in healthy individuals [13,14]. Jaw activities such as jaw opening-closing and chewing include movement of both the mandible and the head and activation of jaw and neck muscles in a task-dependent functional relationship [15]. Furthermore, it has been demonstrated in healthy individuals that this integrated function can be altered by mechanical restriction of head movements [16] as well as by experimentally induced masseter pain [17]. ...
... We previously demonstrated an integration between the jaw and neck sensorimotor systems regarding normal function in healthy individuals [13], association between pain and disturbed jaw-neck function after whiplash trauma [18], as well as comorbidity and reciprocal influence between pain in the jaw and neck regions [25,26]. During jaw function, the neck muscles co-activate [15], and it is possible that impaired function of neck/shoulder muscles may lead to effects also on the masticatory system. The present exercise program was based on co-activation of jaw and neck muscles in order to improve co-ordination, strength and overall function. ...
Article
Objectives: To evaluate the effect of a supervised exercise program in patients with localized/regional temporomandibular disorder (TMD) pain and with TMD associated with generalized pain. Material and methods: Consecutively referred patients with localized/regional TMD pain (n = 56; 46 women and 10 men, mean age 44 years) and TMD associated with generalized pain (n = 21; 21 women, mean age 41 years) participated. Patients underwent a 10-session structured supervised exercise program over 10–20 weeks that included relaxation, and coordination and resistance training of the jaw and neck/shoulders. The outcomes were jaw pain intensity on the Numerical Rating Scale, endurance time for jaw opening and protrusion against resistance and chewing, and effect of pain on daily activities. Results: After the exercise program, a reduction in jaw pain was reported by the local (p = .001) and general (p = .011) pain groups. There were no significant differences in jaw pain intensity between the groups, before (p = .062) or after treatment (p = .121). Endurance time increased for both groups for jaw opening/protrusion (both p < .001) and chewing (both p = .002). The effect of jaw pain on daily activities decreased after exercise compared to baseline for both the local (p < .001) and general (p = .008) pain groups. Conclusions: Supervised exercise can reduce TMD pain and increase capacity in patients with TMD. The results suggest that activation of the jaw motor system with exercise has a positive effect in patients with localized/regional TMD pain and TMD associated with generalized pain.
... Thus, a functional integration has been shown between the jaw and neck regions during normal jaw function in healthy individuals [13,14]. Jaw activities such as jaw opening-closing and chewing include movement of both the mandible and the head and activation of jaw and neck muscles in a task-dependent functional relationship [15]. Furthermore, it has been demonstrated in healthy individuals that this integrated function can be altered by mechanical restriction of head movements [16] as well as by experimentally induced masseter pain [17]. ...
... We previously demonstrated an integration between the jaw and neck sensorimotor systems regarding normal function in healthy individuals [13], association between pain and disturbed jaw-neck function after whiplash trauma [18], as well as comorbidity and reciprocal influence between pain in the jaw and neck regions [25,26]. During jaw function, the neck muscles co-activate [15], and it is possible that impaired function of neck/shoulder muscles may lead to effects also on the masticatory system. The present exercise program was based on co-activation of jaw and neck muscles in order to improve co-ordination, strength and overall function. ...
Conference Paper
Objectives: The aim was to evaluate the effect of supervised exercise in patients with localized temporomandibular disorder (TMD) pain and TMD associated with generalized pain. Methods: Consecutive patients with localized TMD pain (n=101; 82 women and 19 men, mean age 42 yrs) and TMD associated with generalized pain (n=52; 48 women and 4 men, mean age 42 yrs) referred to the Department of Clinical Oral Physiology, Umeå, participated in the study. The patients underwent a structured supervised training programme based on ten sessions over a period of about 10 weeks. The programme included relaxation, coordination and resistance training of the jaw and the neck/shoulders. The outcome was evaluated by the endurance time during jaw opening against resistance, ratings of jaw pain intensity on the Numerical Rating Scale (NRS), and by the symptoms’ influence on daily activities as measured on a 7-point rating scale. Results: After the training programme, there was a significant increase in the endurance time for both groups for the jaw opening against resistance task (P<0.001). Compared to the group with localized pain, the generalized pain patients had a lower capacity both at baseline (P<0.001) and after training (P<0.036). Reported jaw pain intensity was lower after the training programme (NRS 3.0) compared to baseline (NRS 3.9; P<0.001) although there were no significant differences between the general and the local pain groups. The influence of pain on daily activities decreased after exercise (2.5) compared to baseline (3.3; P<0.001), with higher scores for the general pain group before (3.6 vs. 3.1; P=0.029) but not after (2.6 vs. 2.4; P=0.380) training. Conclusions: The results indicate that supervised exercise can increase capacity and reduce pain in patients with TMD. The improvement was similar in the general and the local pain groups, although the group with generalized pain had an overall lower capacity. These findings suggest that activation of the jaw motor system with exercise has a similar effect in patients with localized TMD pain and TMD associated with generalized pain.
... Computer analysis of the sEMG data displayed bioelectric activity in area units per second and were divided by 2.000 (sampling rate, per second) by using PASW Statistics 20 (SPSS, Chicago, Il, US) to calculate sEMG mean amplitude (lV). Some reports have recommended the use of normalization (Ferrario et al., 2000;De Felício et al., 2012), while others have used raw data (Santana-Mora et al., 2009;Häggman-Henrikson et al., 2013;Lauriti et al., 2013). This study used raw data for comparisons. ...
... This study did not use normalization procedures, which has been recommended for interindividual comparisons (Ferrario et al., 2000). The approach of this study is commonly used (Santana-Mora et al., 2009;Häggman-Henrikson et al., 2013;Lauriti et al., 2013). Although normalization is a promising method which reduces biological noise and allows useful comparisons, to the authors' knowledge no significant clinical implications regarding sensitivity and specificity have been reported. ...
... The sternocleidomastoid (SM) muscle is a neck muscle with various functions, such as flexing, rotating, and tilting the head and neck. In addition, it plays a role in the chewing process as it helps stabilize the head and neck during jaw movements [8][9][10]. ...
... [1][2][3] This functional integration is proportional, with larger jaw and head movement amplitudes during maximal jawopening and jaw-closing tasks, and larger jaw and head movements together with increased neck muscle activity when chewing boluses of larger size. [2][3][4] Thus, the finding that increased jaw movement amplitudes are linked to increased head movement amplitudes in healthy individuals indicates a functional coupling with coordinated muscle activity in the jaw and neck regions. 3 Pain can modulate motor function, 5,6 reflected in the jaw system by reduced amplitude and speed of movements. ...
Article
Background The jaw and neck motor systems have a close functional integration but the effect of resistance load to the mandible during jaw opening on the jaw-neck integration is not known. Objectives To evaluate the effect of resistance load compared to no load on integrated jaw and neck motor function in individuals free from pain and dysfunction in the jaw and neck regions. Methods Jaw and head movements during continuous jaw opening were recorded with an optoelectronic system (MacReflex®) in 26 pain-free individuals (14 women, 12 men, mean age 22 years). Jaw opening was performed with and without resistance load (1600 g) to the mandible. The relationship between jaw movement amplitude, head movement amplitude, head/jaw ratio (quotient of head and jaw movement amplitude) and resistance load were modelled using linear mixed-model analysis. A p-value <.05 was considered statistically significant. Results The expected head/jaw ratio mean was increased by 0.05 (95% CI: 0.03, 0.08, P<0.001) with resistance load as compared to no load. This corresponds to an increase in expected mean by 55.6%. With resistance load, expected mean head movement amplitude increased by 1.4 mm (95% CI: 0.2, 2.5, P=0.018), and expected mean jaw movement amplitude decreased by 3.7 mm (95% CI: -7.0, -0.5, P=0.025). Conclusion There is a compensation and adaptation of integrated jaw–neck motor function with an altered jaw–neck motor strategy during jaw opening with resistance load compared to no load. The head/jaw ratio demonstrates increased proportional involvement of the neck during increased load on the jaw system.
... 75 Chewing larger sizes and thicker textures of food results in higher jaw and neck muscular recruitment. 76 Clenching the jaw leads to an increase in neck and trunk activity. 77 Furthermore, tooth-grinding tasks in the supine position provoke higher co-contraction than jaw clenching but they still do not differ significantly from those measured during chewing in the seated position. ...
Article
Objectives: To review the dynamic analytical elements used in the functional assessment of the stomatognathic system, summarize the available scientific evidence, and consider interrelations with body posture and cognition. Method and materials: A thorough literature search was conducted using PubMed, the Cochrane Library database, and Google Scholar. Peer-reviewed articles and literature reviews provided up-to-date information addressing three topics: (a) the available knowledge and recent evidence on the relationship between the morphologic aspects of dental/craniofacial anatomy and oral function/dysfunction, (b) mandibular dynamics, considering mobility, functional activity, and existing methodologies of analysis, and (c) a possible correlation between the stomatognathic system, body posture, and cognition. Results: Modern dentistry may be regarded as a human adaptation strategy, helping to conserve healthy teeth for much longer without risking overall health. It is futile to treat patients using a mechanistic, sectorial approach that misrepresents patient behavior and requests, just as it is to affirm the absence of any structure-function relationships. However, it is also evident that there is a lack of general consensus on the precise functional assessment of the stomatognathic system, mostly due to the methodologic heterogeneity employed and the high risk of bias. Despite the abundant evidence produced with the aim of providing solid arguments to define dynamic models of functional assessment of the stomatognathic system, it is yet to become highly empirical, based as it is on operator experience in daily clinical practice. Conclusions: Further efforts from the scientific and clinical community, with the help of progress in technology, remain should this gap be filled and should substantial data on differences between pathologic and physiologic dynamic models of function be provided. Dentistry needs to employ - on a larger scale - objective, dynamic methods of analysis for the functional evaluation of the stomatognathic system, embracing concepts of "personalized medicine" and "interprofessional collaborations."
... At the present state of knowledge, we do not know to what extent and after how long the curves could become structured. To this end, it could be worth underlining that the relationship between the masticatory muscles and the neck muscles is known after a long time [25,26]. It is likely that the muscles of neck and spine may react to the asymmetries of the skull and mandible in the new environment created by the orthodontic device that stiffens the upper arch, giving rise to new pre-contacts starting or worsening the scoliotic curves. ...
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The question of whether orthodontic therapy by means of rapid palatal expansion (RPE) affects the spine during development is important in clinical practice. RPE is an expansive, fixed therapy conducted with heavy forces to separate the midpalatal suture at a rate of 0.2-0.5 mm/day. The aim of the study was to evaluate the influence of RPE on the curves of the spine of juvenile/adolescent idiopathic scoliosis patients. Eighteen patients under orthopedic supervision for juvenile/adolescent idiopathic scoliosis and independently treated with RPE for orthodontic reasons were included in the study: Group A, 10 subjects (10.4 ± 1.3 years), first spinal radiograph before the application of the RPE, second one during the orthodontic therapy with RPE; Group B, 8 patients (11.3 ± 1.6 years), first radiograph during the use of RPE second one after the removal. Group A showed a significant worsening of the Cobb angle (p ≤ 0.005) at the second radiograph after RPE. Group B showed a significant improvement of the Cobb angle (p = 0.01) at the second radiograph after removal of RPE. Based on the results, the use of RPE during adolescence might influence the spinal curves of patients with idiopathic scoliosis.
... In recent years, studies have focused on the neuroanatomic-physiological relationships of the masticatory system and the cervical spine. Studies have shown that neck muscle activity is increased during jaw activities, such as opening the mouth and chewing in the presence of coordinated cervical and trigeminal motor patterns in healthy individuals (6,7) . It has also been shown that in painful cases, cervical movements are restricted due to masseter pain or decreased motor functions of the jaw due to cervical pain (8,9) . ...
Article
Objective: The purpose of this study is to investigate upper cervical segmental dysfunctions in female patients with chronic TMD with and without neck pain and to compare them with healthy subjects. Method: Patients admitted to our hospital with jaw pain were evaluated in this study, and a total of 152 patients and healthy subjects who met the inclusion criteria for the study were divided into 3 groups: TMD with neck pain (n = 94), TMD without neck pain (n = 28) and control (n = 30). Patients with myofascial pain (category I) or disc displacements (category II) were diagnosed based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) guidelines. Upper cervical segmental dysfunctions were identified using functional and pain provocation tests in patients with TMD and healthy subjects. Results: When patients with TMD were classified, there was a significant difference between TMD with neck pain (category I, 62.8%; category II, 37.2%) and TMD without neck pain (category I, 28.6%; category II, 71.4%) groups (p = 0.002). There was a statistically significant dysfunction [difference] in all upper cervical segments in favor of the TMD with neck pain group compared TMD without neck pain group and healthy control group (p < 0.05). 51.1% Occiput-C1, 81.9% C1-C2 and 53.2% C2-C3 segment dysfunction rates were detected in TMD with neck pain group. Conclusion: Upper cervical segmental dysfunction rate was higher in TMD group with neck pain than TMD without neck pain and healthy control group.
... This may explain why dysfunctions and pain experienced in the face may be associated with the neck as well as the other way around (von Piekartz and Hall, 2013). Additionally, masticatory motor activity associated with active mandibular movement such as mouth opening, chewing, and talking, interact with neck muscle activity (Eriksson et al., 1998;H€ aggman-Henrikson et al., 2013). Recently, studies have provided experimental evidence that teeth grinding increases neck muscle co-contraction and indicates an additional neuromuscular interaction between the two muscle groups which may be explained by complex neurophysiological interactions (Giannakopoulos et al., 2013;Giannakopoulos et al., 2018). ...
Article
Purpose: Bruxism is highly prevalent and defined as abnormal habitual mouth activity including clenching of the teeth and increased jaw muscle activity. The association between bruxism and temporomandibular dysfunction (TMD) is debated, in particular the association between cervical spine impairments, bruxism, and TMD. Hence the purpose of this study was to identify the relationship between bruxism, TMD, and cervical spine impairments. Methods: This observational study categorized 55 female volunteers suitable for evaluation to a bruxism (n ¼ 33) or non-bruxism group (n ¼ 22) based on comprehensive screening using questionnaires and visual observation of the mouth by 2 independent dentists. Following this, both groups were evaluated for TMD, severity and location of head/neck pain, neck disability index (NDI), cervical spine impairments, and tissue mechanosensitivity. Regression analysis was used to evaluate the relationship between bruxism, TMD severity, and cervical impairments. Results: Coefficients of pain and bruxism were significantly associated with NDI scores (0.43, p < 0.001; 3.24, p ¼ 0.01) with large and medium sized effects. As a consequence, both severity of TMD and bruxism status are independently associated with cervical impairments. Having TMD is an independent predictor for head/ neck pain and cervical impairments. Pain associated with movement tests and tissue mechanosensitivity was found to be an important factor in bruxism. Conclusion: Clinicians need to be aware that signs of cervical movement impairment are not likely to be associated with bruxism, rather they should focus on improving orofacial function and tissue mechanosensitivity.
... The coordination of movements is characterized by head extension during jaw-opening and head flexion during jaw-closing (Eriksson et al., 1998). These integrated jaw and head movements involve jaw and neck muscles, among others, the masseter, temporal, sternocleidomastoid, and trapezius muscles (Häggman-Henrikson et al., 2013). The simultaneous jaw and head-neck movements during jaw opening-closing tasks Kohno et al., 2001) have been suggested to be based in a functional relationship between the trigeminal and craniocervical sensorimotor systems , also seen during jaw clenching (Clark et al., 1993), and in the trigeminocervical reflex (Sartucci et al., 1986). ...
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A functional integration between the trigeminal and craniocervical sensorimotor systems has been demonstrated, with simultaneous jaw and head–neck movements during jaw opening–closing. We previously showed that pain induction in the masseter muscle increased the relative contribution of the neck component of integrated jaw–neck movements. Induced pain or manipulation of proprioception by vibration did not affect accuracy during a jaw-opening task in men. It is not known how multimodal sensory stimulation, with a combination of pain induction and vibration, affects jaw-opening accuracy and precision. The aim was to investigate how jaw–neck movements, and specifically accuracy and precision of jaw-opening, are affected during concomitant nociceptive and proprioceptive stimulation of the masseter muscle. Twenty-one healthy men performed jaw-opening to a target position, defined as 75% of individual maximum jaw opening, during control (Ctr), vibration of masseter muscles (Vib), pain induction in the masseter (Pain), and concomitant vibration and pain induction in the masseter muscle (VibPain). Simultaneous jaw and head movements were recorded with an optoelectronic system and amplitudes calculated for each jaw opening–closing cycle. Accuracy of jaw movements was defined as the achievement of the target position. Precision of jaw movements was defined as the cycle-to-cycle variability from the mean of cycles 2–10 (coefficient of variation, CV). Differences between the trials were analyzed with Friedman’s test, Dunn’s test, and Benjamini–Hochberg correction. There were no significant differences between the trials for jaw movement amplitudes. For head movements, amplitudes for cycles 2–10 were larger during Pain compared to Ctr and Vib (both p = 0.034), and larger during VibPain compared to Ctr (p = 0.034) and Vib (p = 0.035). There were no differences in accuracy of jaw movements between the trials. For precision of jaw movements, the cycle-to-cycle variability was larger during VibPain compared to Ctr (p = 0.027) and Vib (p = 0.018). For integrated jaw–neck motor strategy, there was a difference between pain and non-pain trials, but no differences between unimodal and multimodal stimulation trials. For achievement of jaw-opening to a target position, the results show no effect on accuracy, but a reduced precision of jaw movements during combined proprioceptive and nociceptive multimodal stimulation.
... 45,46 The degree of activation of the neck muscles is dependent on the type of task, and for chewing depends also on the size and texture of the bolus. 4 During normal chewing, the CPG evokes the basic spatial and temporal pattern for the masticatory rhythm and a dynamic interaction between peripheral such as teeth and bolus and central nervous mechanism adjust the rhythm and force to the bolus size and texture. During the chewing task in the present study, the size or texture of the chewing gum does not change, although the shape and position of the gum in the mouth varies; but for both children and adults, the cycle time during chewing depends mostly on the rhythm generated by the CPG. ...
Article
Background: A functional integration between the jaw and neck regions during purposive jaw movements is well described in adults, but there is a lack of knowledge of such integration during jaw function in children. Objectives: To determine the movement integration between the jaw and neck during jaw motor tasks in 6-year-olds, whether there is a difference between children and adults. Methods: Jaw and neck movements were recorded with an optoelectronic 3D system in 25 healthy 6-year-olds (12 girls, 13 boys) and 24 healthy adults (12 women, 12 men) during paced jaw opening-closing and self-paced gum chewing. Jaw and neck movement amplitudes, intra-individual variation in movement amplitude, ratio between neck-jaw movement amplitudes, and movement cycle time were analysed. Differences between children and adults were evaluated with Mann-Whitney U test for independent samples. Results: Compared to adults, 6-year old children showed larger neck movement amplitudes (P=0.008) during chewing, higher intra-individual variability in amplitudes of jaw (P=0.008) and neck (P=0.001) movements, higher ratio between neck-jaw movement amplitudes for jaw opening-closing (P=0.026) and chewing (P=0.003), and longer jaw movement cycle time (P≤0.0001) during the jaw opening-closing task. Conclusion: Despite integrated jaw-neck movements in 6-year old children, the movement pattern differs from that of adults and may be interpreted as an immature programming of jaw-neck motor behavior. The well-integrated movements observed in adults most likely develop over years, perhaps into adolescence, and needs further research including well controlled longitudinal studies to map this development in order to provide appropriate age-related clinical treatment for functional disorders. This article is protected by copyright. All rights reserved.
... Also experiments in the range of submaximum contractions have observed that anterior and posterior neck muscles co-contract during submaximum bite forces in a variety of bite-force directions, in a range of 2-14% of the MVC 41,42 . Moreover, the activity of jaw (masseter and digastric) and neck (SCM and trapezius) muscles have been tested during chewing different sizes and textures of food, reporting a higher participation of the masseter and SCM muscles with an increased chewing load 43 . Similarly, a coordinated head-neck movement during fast and slow jaw openingclosing tasks was reported by Eriksson 44 , concluding that jaw opening was always accompanied by head-neck extension, while the opposite for jaw closing. ...
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Background In the past few years, growing interest was given to the relationship between the dental occlusion and the body balance. While most research focused on this relationship at static conditions, it is evident that the contribution of the sensory information for balance control is different depending on the environmental constraints. Research question The aim of the present paper was to elucidate whether the stomatognathic system (SS) contributes differently on body balance regulation according to the presence of external disturbances. Methods Literature regarding the different sources involved in the proprioceptive information to the SS was reviewed. The influence of dental occlusion on balance control at different external environments was then explored. Results The main findings are: (i) a plausible evidence between the masticatory and cervical muscles can be described; (ii) a reciprocal connection between the trigeminal and vestibular nuclei supports the influence of the SS on body balance; (iii) traditionally, research involving the relationship between the SS and balance control has focused on strictly controlled situations, thus ignoring the sensory reweighting which occurs depending on the external disturbances; and (iv) the afferences of dental occlusion for balance control seem strengthened when more difficult conditions are present. Conclusion Results of the present review suggest that afferent signals from dental occlusion effectively contribute to balance control when more external perturbations are present, i.e. unstable support surface, fatigue, tasks being performed. However, more studies are needed to elucidate the mechanisms by which dental occlusion may influence balance control focusing on different external environments. This article is protected by copyright. All rights reserved.
... In addition, the results obtained in our previous studies 26,27 during chewing of test food are in agreement with results obtained by Häggman-Henrikson et al for the activity of superficial neck muscles during mincing of foods of different size and hardness, and expand the findings for deep neck muscles. 8 The results are not directly comparable with those from previous investigations, 7,22,23,[36][37][38] because no force-controlled studies at maximum grinding-force and no recordings of the deeper neck muscles are available. However, previous findings of co-contractions for the SCM, SH and IH complexes, reported for maximum jaw muscle activation, 7,22,23,[36][37][38] are confirmed by our results. ...
Article
The objective of this study was to analyse the co-contraction behaviour of jaw and neck muscles during force-controlled experimental grinding in the supine position. Twelve symptom-free subjects were enrolled in the experimental study. Electromyographic (EMG) activity of semispinalis capitis, splenius capitis and levator scapulae muscles was recorded bilaterally with intramuscular fine-wire electrodes, whereas that of sternocleidomastoideus, infrahyoidal, suprahyoidal, masseter and anterior temporalis muscles were registered with surface electrodes. EMG and force measurements were performed during tasks simulating tooth grinding on custom-made intraoral metal splints. The mean EMG activity normalised by maximum voluntary contraction (% MVC) of each of the neck muscles studied during grinding was analysed and compared with previous data from jaw clenching at identical force (100 N) and (supine) position. The occurrence of low-level, long-lasting tonic activation (LLTA) of motor units was also documented. The mean three-dimensional force vector of the grinding forces was 106 ± 74 N. In the frontal plane, the incline to the midsagittal plane ranged between 10° and 15°. In the midsagittal plane, the incline to the frontal plane was negligibly small. Posterior neck muscle activity during grinding ranged between 4.5% and 12% MVC and during clenching with 100 N between 1.8% and 9.9% MVC. Masticatory muscle activity during grinding ranged between 17% and 21% MVC for contralateral masseter and ipsilateral temporalis and between 4% and 6.5% for ipsilateral masseter and contralateral temporalis. LLTA had an average duration of 195 ± 10 seconds. The findings from this study do not support pathophysiological muscle chain theories postulating simple biomechanical coupling of neck and jaw muscles. Co-contractions of neck and masticatory muscles may instead occur as a result of complex neurophysiological interactions.
... The sternocleidomastoid (SCM) is a major muscle of the cervical spine, classically used to define the anterior and posterior triangles of the neck. Clinical interest in the role of the SCM [11] and its contribution to neck disorders [20] relies on a detailed understanding of neck muscle structure and function. This understanding is often based on information found in anatomical texts, with a supporting role from the research literature. ...
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Purpose: The fascicular morphology of the sternocleidomastoid (SCM) is not well described in modern anatomical texts, and the biomechanical forces it exerts on individual cervical motion segments are not known. The purpose of this study is to investigate the fascicular anatomy and peak force capabilities of the SCM combining traditional dissection and modern imaging. Methods: This study is comprised of three parts: Dissection, magnetic resonance imaging (MRI) and biomechanical modelling. Dissection was performed on six embalmed cadavers: three males of age 73-74 years and three females of age 63-93 years. The fascicular arrangement and morphologic data were recorded. MRIs were performed on six young, healthy volunteers: three males of age 24-37 and three females of age 26-28. In vivo volumes of the SCM were calculated using the Cavalieri method. Modelling of the SCM was performed on five sets of computed tomography (CT) scans. This mapped the fascicular arrangement of the SCM with relation to the cervical motion segments, and used volume data from the MRIs to calculate realistic peak force capabilities. Results: Dissection showed the SCM has four parts; sterno-mastoid, sterno-occipital, cleido-mastoid and cleido-occipital portions. Force modelling shows that peak torque capacity of the SCM is higher at lower cervical levels, and minimal at higher levels. Peak shear forces are higher in the lower cervical spine, while compression is consistent throughout. Conclusions: The four-part SCM is capable of producing forces that vary across the cervical motion segments. The implications of these findings are discussed with reference to models of neck muscle function and dysfunction.
... However, the clinical significance for these biological and experimental findings has not been demonstrated [15]. A close integration of the jaw and neck motor systems has been described in animal and human studies demonstrating co-activation and reflex activities of jaw, neck and shoulder muscles [16,17]. Moreover, a recent fMRI analysis in healthy subjects showed that mandibular position and it's alternation by an occlusal splint can affect motor and somatosensory cortical activation and cerebellar networks [18]. ...
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It has been suggested that occlusal splints can improve muscle strength in athletes by affecting the mandibular position. However, research in this area is scarce and conflicting. This pilot study evaluated the upper and lower limb muscle force in three different mandibular positions and assessed the repeatability of these measurements. Twenty one healthy subjects (13 males – 8 females) aged 18-24 years were recruited among physiotherapy students based on strict criteria. Included subjects were free of any temporomandibular, oral or musculoskeletal disorders. For each subjects individually a hard wax bite of 2-4 mm in maximal occlusion was made. Grip strength was measured using the Biometrics® dynamometer. Isometric muscle force of the quadriceps was measured using a BIODEX® dynamometer. Muscle force in shoulder abduction muscles was measured using a MicroFET® dynamometer. Three trials within each session, and in a random order, were done in each of three mandibular positions: 1) closed in maximal occlusion; 2) active mouth opening; 3) closed on wax bite in maximal occlusion. This procedure was repeated after a one week period. To control for confounding of mandibular position, within-session trials and test day, a linear mixed covariance model approach was used. No significant differences were found in muscle force between the three mandibular positions for any of the muscle groups tested (p >0.05). Good repeatability was demonstrated within one session and between two separate days. Findings indicate that in asymptomatic subjects, muscle force in the limbs was not influenced by altered mandibular position.
... There is an intricate relationship between the trigeminal and cervical motor systems, and head-neck movements are an integrated part of normal jaw function (Eriksson et al. 2000). A task-dependent proportional relationship between jaw and neck muscles has been suggested (Häggman-Henrikson, Nordh, et al. 2013), and experimental restriction of head-neck mobility in healthy subjects can impair jaw function (Häggman-Henrikson et al. 2006). Pain can be another cause of a disturbed neuromuscular control in the jaw-neck region, and an altered strategy for jaw-neck motor control after experimental pain has been demonstrated (Wiesinger et al. 2013). ...
Article
The relationship between whiplash trauma and chronic orofacial pain is unclear, especially with regard to the time elapsed from trauma to development of orofacial pain. The aim was to analyze prevalence of jaw pain and disability, as well as the relationship between pain and disability in the jaw and neck regions in the early nonchronic stage after whiplash trauma. In this case-control study, 70 individuals (40 women, 30 men, mean age 35.5 y) who visited an emergency department with neck pain following a car accident were examined within 3 wk of trauma (group 1) and compared with 70 individuals (42 women, 28 men, mean age 33.8 y), who declined to attend a clinical examination but agreed to fill in questionnaires (group 2). The 2 case groups were compared with a matched control group of 70 individuals (42 women, 28 men, mean age 37.6 y) without a history of neck trauma. All participants completed questionnaires regarding jaw pain and dysfunction, rating pain intensity in jaw and neck regions on the Numerical Rating Scale, the Neck Disability Index, and Jaw Disability Checklist. Compared with controls, individuals with a recent whiplash trauma reported more jaw pain and dysfunction. Furthermore, there was a moderate positive correlation between jaw and neck pain ratings for group 1 (r = 0.61, P < 0.0001) and group 2 (r = 0.59, P < 0.0001). In the logistic regression analysis, cases showed higher odds ratios (range, 6.1 to 40.8) for jaw and neck pain and disability compared with controls. Taken together, the results show that individuals with a recent whiplash trauma report more jaw pain and disability compared with controls without a history of neck trauma. Furthermore, the correlation between jaw and neck pain intensity implies that intensity of neck pain in the acute stage after whiplash trauma might be a possible risk factor also for development of chronic orofacial pain.
... Recent studies also support that the neck muscles are activated during jaw-clenching tasks assessed electromyographically [80][81][82]. It seems that the activity of the neck muscles is increased with greater demand for masticatory work [83]. ...
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Abstract BACKGROUND: Recent research has shown a relationship of craniomandibular disability with neck-pain-related disability has been shown. However, there is still insufficient information demonstrating the influence of neck pain and disability in the sensory-motor activity in patients with headache attributed to temporomandibular disorders (TMD). The purpose of this study was to investigate the influence of neck-pain-related disability on masticatory sensory-motor variables. METHODS: An experimental case-control study investigated 83 patients with headache attributed to TMD and 39 healthy controls. Patients were grouped according to their scores on the neck disability index (NDI) (mild and moderate neck disability). Initial assessment included the pain catastrophizing scale and the Headache Impact Test-6. The protocol consisted of baseline measurements of pressure pain thresholds (PPT) and pain-free maximum mouth opening (MMO). Individuals were asked to perform the provocation chewing test, and measurements were taken immediately after and 24 hours later. During the test, patients were assessed for subjective feelings of fatigue (VAFS) and pain intensity. RESULTS: VAFS was higher at 6 minutes (mean 51.7; 95% CI: 50.15-53.26) and 24 hours after (21.08; 95% CI: 18.6-23.5) for the group showing moderate neck disability compared with the mild neck disability group (6 minutes, 44.16; 95% CI 42.65-45.67/ 24 hours after, 14.3; 95% CI: 11.9-16.7) and the control group. The analysis shows a decrease in the pain-free MMO only in the group of moderate disability 24 hours after the test. PPTs of the trigeminal region decreased immediately in all groups, whereas at 24 hours, a decrease was observed in only the groups of patients. PPTs of the cervical region decreased in only the group with moderate neck disability 24 hours after the test. The strongest negative correlation was found between pain-free MMO immediately after the test and NDI in both the mild (r = -0.49) and moderate (r = -0.54) neck disability groups. VAFS was predicted by catastrophizing, explaining 17% of the variance in the moderate neck disability group and 12% in the mild neck disability group. CONCLUSION: Neck-pain-related disability and pain catastrophizing have an influence on the sensory-motor variables evaluated in patients with headache attributed to TMD.
... Recent studies also support that the neck muscles are activated during jaw-clenching tasks assessed electromyographically [80][81][82]. It seems that the activity of the neck muscles is increased with greater demand for masticatory work [83]. ...
Article
Full-text available
Background: Recent research has shown a relationship of craniomandibular disability with neck-pain-related disability has been shown. However, there is still insufficient information demonstrating the influence of neck pain and disability in the sensory-motor activity in patients with headache attributed to temporomandibular disorders (TMD). The purpose of this study was to investigate the influence of neck-pain-related disability on masticatory sensory-motor variables. Methods: An experimental case-control study investigated 83 patients with headache attributed to TMD and 39 healthy controls. Patients were grouped according to their scores on the neck disability index (NDI) (mild and moderate neck disability). Initial assessment included the pain catastrophizing scale and the Headache Impact Test-6. The protocol consisted of baseline measurements of pressure pain thresholds (PPT) and pain-free maximum mouth opening (MMO). Individuals were asked to perform the provocation chewing test, and measurements were taken immediately after and 24 hours later. During the test, patients were assessed for subjective feelings of fatigue (VAFS) and pain intensity. Results: VAFS was higher at 6 minutes (mean 51.7; 95% CI: 50.15-53.26) and 24 hours after (21.08; 95% CI: 18.6-23.5) for the group showing moderate neck disability compared with the mild neck disability group (6 minutes, 44.16; 95% CI 42.65-45.67/ 24 hours after, 14.3; 95% CI: 11.9-16.7) and the control group. The analysis shows a decrease in the pain-free MMO only in the group of moderate disability 24 hours after the test. PPTs of the trigeminal region decreased immediately in all groups, whereas at 24 hours, a decrease was observed in only the groups of patients. PPTs of the cervical region decreased in only the group with moderate neck disability 24 hours after the test. The strongest negative correlation was found between pain-free MMO immediately after the test and NDI in both the mild (r = -0.49) and moderate (r = -0.54) neck disability groups. VAFS was predicted by catastrophizing, explaining 17% of the variance in the moderate neck disability group and 12% in the mild neck disability group. Conclusion: Neck-pain-related disability and pain catastrophizing have an influence on the sensory-motor variables evaluated in patients with headache attributed to TMD.
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Background Current research relates jaw clenching to athletic performance, in terms of force and agility. However, the impact of jaw clenching on sports accuracy is unclear. Objectives To analyse the impact of jaw position and chewing type on free‐throw accuracy and electromyographic (EMG) activity of masticatory muscles during free‐throws. Methods Cross‐sectional study with 25 female basketball players aged 18–44. Each participant executed 18 free‐throws under three different jaw conditions: mandibular rest, maximum intercuspation, and with interdental cotton rolls, in randomised order. Results Chewing type and jaw position were not associated with shooting accuracy ( p = 0.106; p = 0.778). There was a positive correlation between EMG activity of the right masseter and free‐throw accuracy at maximum intercuspation ( r s = 0.402; p = 0.046). In contrast, negative correlations were found with other muscles when the occlusal vertical dimension was altered ( r s = −0.619, p = 0.001; r s = −0.490; p = 0.013; r s = −0.534; p = 0.006). The chewing type affected the EMG of the left masseter in the altered occlusal vertical dimension ( H = 6.969; p = 0.031). Significant differences in EMG recordings were observed across different mandibular positions during free‐throws ( p < 0.001). Conclusions While jaw positioning and chewing type do not impact free‐throw accuracy in amateur female basketball players, the EMG activity of masticatory muscles is linked to shooting performance. This highlights the need for further research on motor behaviour of masticatory muscles in precision sports, especially for athletes using intraoral devices.
Article
Introduction Mastication involves complex tongue movements, coordination of lip, and cheek movements and is associated with head movement to facilitate the intraoral transport of food from ingesting to swallowing; it affects many functions of the whole body. However, studies to evaluate the relationship between masticatory movements and the body posture are still lacking to our knowledge. The purpose of this study was to characterize the effects of masticatory movements on the head, trunk, and body sway during the standing position. Methodology A total of 30 healthy subjects were evaluated. The MatScanTM system was used to analyze changes in body posture (center of foot pressure: COP) and the 3-dimensional motion analysis system was used to analyze changes in the head and trunk postures while subjects remained in the standing position with the rest position, centric occlusion, and masticating chewing gum. Results The total trajectory length of COP and head and trunk sways during masticating chewing gum were significantly shorter and smaller respectively than it was in the rest position and centric occlusion (p<0.016). COP area during masticating chewing gum was significantly smaller than it was in the 2 mandibular positions (p<0.016). Conclusion Masticatory movements positively affect the stability of the head, trunk, and body sways and enhance the postural stability during the standing position.
Article
Purpose: The purpose of this study was to test the hypothesis in healthy subjects that masticatory movements affect head and trunk sways, and sitting and foot pressure distributions during sitting position. Methods: A total of 30 healthy male subjects with an average age of 25.3 years (range, 22-32 years) were evaluated. The CONFORMatTM and MatScanTM system were used to analyze changes in sitting pressure distribution (center of sitting pressure: COSP) and changes in foot pressure distribution (center of foot pressure: COFP) respectively, and the 3-dimensional motion analysis system was used to analyze changes in head and trunk postures while subjects remained sitting position with rest position, centric occlusion, and chewing. The total trajectory length of COSP/COFP, COSP/COFP area, and head and trunk sway values were compared between the three conditions to evaluate whether masticatory movement affected the stability of head and trunk sways, and sitting and foot pressure distributions. Results: Total trajectory length of COSP and COSP area during chewing were significantly shorter and smaller respectively than it was in rest position and centric occlusion (p < 0.016). Head sway value during chewing was significantly larger than it was in rest position and centric occlusion (p < 0.016). Conclusion: Masticatory movements affect sitting pressure distribution and head movements during sitting position.
Article
This study was performed to evaluate the association of jaw and neck muscle coordination with jaw movement activity in order to clarify the relationships of electromyogram(EMG)-EMG findings showing coherence between jaw and neck muscle activities and jaw movement activities while chewing in healthy individuals. Sixteen subjects performed gum chewing, with EMG signals in the jaw and neck muscles and jaw movements were simultaneously recorded. Coherence between jaw and neck muscle activities and jaw movements while chewing, as well as first peak frequency of the power spectrum, was analyzed while left and right side chewing using EMG-EMG coherence function analysis. Those results were used to evaluate the relationship of jaw and neck muscle activities with jaw movements while rhythmical chewing. The results suggest a positive correlation between jaw and neck muscle activity coherence and jaw opening activities while chewing, which was especially evident in non-chewing side neck muscle recordings. Considering findings of previous qualitative evaluation suggested coordinated jaw and head movement activities and enlarged jaw opening activity induced by large-food chewing, present study may suggest the association of quantitative synchrony between jaw closing and non-chewing side neck muscle activities with jaw opening activity while chewing performance in healthy individuals.
Article
Objective: to evaluate mastication in a group of patients with Adolescent Idiopathic Scoliosis (AIS) with a control group, by means of the prevalence of reverse chewing cycles (RCC). Material and methods: this study included a group of patients (N=32; F=24; M=8; mean age ± SD = 14±3 years) with a confirmed diagnosis of Adolescent Idiopathic Scoliosis and a group of control subjects (N=32; F=24; M=8; mean age ± SD = 13±6 years) without spinal disorders. Mastication was recorded with both a hard and a soft bolus, following a standardized protocol, and the prevalence of reverse chewing cycles was compared between the groups. Results: The prevalence of reverse chewing cycles was significantly higher in the Adolescent Idiopathic Scoliosis group, with both a soft and a hard bolus, compared to the control group (p<0,001). Conclusion: the results of this study indicate that the presence of Adolescent Idiopathic Scoliosis influences mastication, i.e. one of the main functions of the stomatognathic system. A multidisciplinary approach to these patients may be relevant in providing the best possible treatment outcomes.
Article
Bruxismus ist keine Krankheit, sondern ein Sammelbegriff für Parafunktionen wie Zähnepressen oder Knirschen. Um Begleitsymptome des Bruxismus zu beeinflussen, ist eine Untersuchung des orofazialen und kraniozervikalen Systems sinnvoll. Die gefundenen auffälligen Zeichen leiten die Therapeuten in der muskuloskelettalen Therapie, die aus Hands-on und -off-Techniken besteht. Publication History Publication Date: 18 May 2021 (online) © 2021. Thieme. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany
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Muscle spindles present in jaw and neck region can be activated by slight changes in neck and body position. Reduction in proprioceptive ability disturb chewing capacity, teeth clenching, biting and also 12 leads to delayed speech. A linkage was found between cervical craniofacial form and masticatory muscle performance that are interrelated in 1 3 s o m a t o g a n t h i c d e v e l o p m e n t. D i ff e r e n t mandibular positions affects cervical stability and 14 shows a strong relation with postural maintenance.
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Objectives The purpose of this study was to assess the effects of oral rehabilitation with complete dentures on bite force and electromyography of the suprahyoid and sternocleidomastoid muscles, and their correlation with occlusal vertical dimension (OVD). The research questions were “What are the effects of rehabilitation with complete dentures on bite force and electromyography of suprahyoid and sternocleidomastoid muscles, and how are they correlated with OVD?” Materials and methods Patients who are wearers of unsatisfactory removable complete dentures were attended in three sessions (T0, T1, and T2). At T0, while the patients still wore the old dentures, they were submitted to bite force and surface electromyographic exams of the suprahyoid and sternocleidomastoid muscles. These exams were repeated, and the OVD was measured while the patients wore their old and new prostheses, 30 days after insertion of the new prosthesis (T1). The exams were repeated 100 days after the insertion of the new prosthesis (T2). The data were submitted to the Shapiro-Wilk normality test, analysis of variance (ANOVA), and Pearson correlation and linear regression, all with 5% significance. Results Fifteen patients participated in the study. No statistically significant difference was observed for bite force or electromyography in T0, T1, or T2. However, the correlation and regression tests showed important interactions between the OVD and maximum voluntary occlusal bite force, as well as the OVD and electromyography during deglutition for the suprahyoid muscles. Conclusion Rehabilitation did not impact bite force nor the activity of the assessed muscles (electromyography). On the other hand, OVD was shown to be an important factor for bite force, and deglutition of water after rehabilitation. Clinical relevance This study shows what are the influences of rehabilitation on oral functions and reinforces the importance of corrected reestablishment of OVD because it has been found to be an important factor for bite force and electromyography during deglutition.
Article
The treatment of a complex temporomandibular disorder (TMD), such as disk displacement with reduction (DDR) associated with arthralgia and myalgia, may depends on understanding the impairments in muscle function. The aim of this study was to investigate the behavior of the anterior temporalis, masseter and sternocleidomastoid muscles in the time and frequency domains during chewing in patients with chronic painful TMD-DDR using electromyographic (EMG) analysis. Thirty-three patients who met the diagnostic criteria for TMD and 32 volunteers without TMD (control group) underwent clinical examination, chewing pattern classification and EMG analysis. For the EMG analyses, the side of habitual unilateral chewing, as determined by the chewing pattern classification, was selected for recording; in cases of bilateral chewing, the recording side was randomly selected. The EMG-EMG coherence function and EMG-EMG transfer function (gain and phase) values were obtained at the first chewing frequency peak, and the working-side masseter signal was used as a reference in the analyses of the other muscles. Compared to the control group, the TMD group showed a longer chewing stroke duration (P = 0.01) as well as changes in the coactivation and coordination strategies of the jaw muscles, evidenced by greater relative energy expenditure (P< 0.01) and impaired differential recruitment (P< 0.05) and coherence (P< 0.01). Delays in peak and temporal asynchrony occurred in the jaw and neck muscles (P< 0.05). Patients with chronic painful TMD-DDR during chewing presented changes in the jaw and neck muscles, with more compromised function of the former, which are specific to chewing.
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Background: Mandibular functions are associated with electromyographic activity of the jaw muscles and also the sternocleidomastoid muscle (SCM). The precise spatiotemporal relation of SCM and masticatory muscles activities during chewing is worthy of investigation. Objective: To analyze the sequential recruitment of SCM and masseter activities during chewing as indicated by the spatiotemporal locations of their activity peaks. Methods: Jaw movements and bilateral surface electromyographic activity of SCM and masseter were recorded during gum chewing in 20 healthy subjects. The timing order was decided by comparing the length of time from the time when the opening started to the time when the surface electromyographic activity reached its peak value. Spatial order was analyzed by locating the peak electromyographic activity onto a standard chewing cycle which was created based on 15 unilateral chewing cycles. Paired t-test, One-way ANOVA and Student-Newman-Keuls post-test were used for comparisons. Results: Although the Time to Peak for the balancing side SCM appeared shorter than for the other three tested muscles, most often it did not reach a level of significance. However, the location of the balancing side SCM's peak activity was further from the terminal chewing position (TCP) than the working side SCM and bilateral masseters (P < 0.05). Conclusions: The balancing side SCM activity reached its peak significantly further away from TCP than the other three tested muscles during chewing. Further studies with spatiotemporal variables included should be helpful to understand the roles of the head, neck, and jaw muscles in orofacial and cervical dysfunctional problems. This article is protected by copyright. All rights reserved.
Article
The aim of this study was to verify the effects of induced masseter-muscle pain on the amplitude of muscle activation, symmetry and coactivation of jaw- and neck-muscles during mastication. Twenty-eight male volunteers, mean age±SD 20.6±2.0 years, participated in this study. Surface electromyography of the masseter and sternocleidomastoid (SCM) muscles was performed bilaterally during mastication of a gummy candy before and after injections of monosodium glutamate solution and isotonic saline solution. As a result, we observed a decrease in the amplitude of activation of the masseter muscle on the working side (p=0.009; d=0.34) and a reduction in the asymmetry between the working and the balancing side during mastication (p=0.007; d=0.38). No changes were observed either on the craniocervical electromyographic variables. In conclusion, experimentally induced pain reduced the masseter muscle activation on the working side, thereby reducing the physiological masseters’ recruitment asymmetry between the two sides during mastication. No effects on SCM activity were detected. These results may partly explain the initial maladaptative changes underlying TMD conditions.
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There is a functional integration between the jaw and neck regions with head extension-flexion movements during jaw-opening/closing tasks. We recently reported that trigeminal nociceptive input by injection of hypertonic saline into the masseter muscle altered this integrated jaw-neck function during jaw-opening/closing tasks. Thus, in jaw-opening to a predefined position, the head-neck component increased during pain. Previous studies have indicated that muscle spindle stimulation by vibration of the masseter muscle may influence jaw movement amplitudes, but the possible effect on the integrated jaw-neck function is unknown. The aim of this study was to investigate the effect of masseter muscle vibration on jaw-head movements during a continuous jaw-opening/closing task to a target position. Sixteen healthy men performed two trials without vibration (Control) and two trials with bilateral masseter muscle vibration (Vibration). Movements of the mandible and the head were registered with a wireless three-dimensional optoelectronic recording system. Differences in jaw-opening and head movement amplitudes between Control and Vibration, as well as achievement of the predefined jaw-opening target position, were analysed with Wilcoxon's matched pairs test. No significant group effects from vibration were found for jaw or head movement amplitudes, or in the achievement of the target jaw-opening position. A covariation between the jaw and head movement amplitudes was observed. The results imply a high stability for the jaw motor system in a target jaw-opening task and that this task was achieved with the head-neck and jaw working as an integrated system.
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Aims: To test the hypothesis that jaw muscles and specific neck muscles, ie, levator scapulae, trapezius, sternocleidomastoideus, and splenius capitis, co-contract at the different submaximum bite forces usually generated during jaw clenching and tooth grinding, and for different bite force directions. Methods: Bite-force transducers that measured all three spatial force components were incorporated in 11 healthy subjects. The test persons developed feedback-controlled submaximum bite forces in a variety of bite-force directions. The electromyographic (EMG) activity of the levator scapulae, splenius capitis, and trapezius muscles was recorded, at the level of the fifth cervical vertebra, by use of intramuscular wire electrodes. The activity of the sternocleidomastoideus and masseter muscles was recorded by surface electrodes. For normalization of the EMG data, maximum-effort tasks of the neck muscles were conducted in eight different loading directions by means of a special force-transducer system. Differences between neck-muscle activity during chewing, maximum biting in intercuspation, and the force-controlled motor tasks were compared with the baseline activity of the various muscles by one-way repeated-measures analysis of variance. Results: The results confirmed the hypothesis. Co-contractions of the neck muscles in the range of 3% to 10% of maximum voluntary contraction were observed. Significant (P < .05) activity differences were recorded as a result of the different force levels and force directions exerted by the jaw muscles. Long-lasting action potential trains of single motor units triggered by jaw clenching tasks were also detected. Conclusion: The findings support the assumption of a relationship between jaw clenching and the neck muscle activity investigated. The low level of co-contraction activity, however, requires further study to elucidate possible pathophysiological interactions at the level of single motor units.
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A functional integration between the jaw and neck regions has been demonstrated during normal jaw function. The effect of masseter muscle pain on this integrated motor behaviour in man is unknown. The aim of this study was to investigate the effect of induced masseter muscle pain on jaw–neck movements during a continuous jaw opening-closing task. Sixteen healthy men performed continuous jaw opening-closing movements to a target position, defined as 75% of the maximum jaw opening. Each subject performed two trials without pain (controls) and two trials with masseter muscle pain, induced with hypertonic saline as a single injection. Simultaneous movements of the mandible and the head were registered with a wireless optoelectronic three-dimensional recording system. Differences in movement amplitudes between trials were analysed with Friedman's test and corrected Wilcoxon matched pairs test. The head movement amplitudes were significantly larger during masseter muscle pain trials compared with control. Jaw movement amplitudes did not differ significantly between any of the trials after corrected Wilcoxon tests. The ratio between head and jaw movement amplitudes was significantly larger during the first pain trial compared with control. Experimental masseter muscle pain in humans affected integrated jaw–neck movements by increasing the neck component during continuous jaw opening-closing tasks. The findings indicate that pain can alter the strategy for jaw–neck motor control, which further underlines the functional integration between the jaw and neck regions. This altered strategy may have consequences for development of musculoskeletal pain in the jaw and neck regions.
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Compelling evidence exists that pain may affect the motor system, but it is unclear if different sources of peripheral limb pain exert selective effects on motor control. This systematic review evaluates the effects of experimental (sub)cutaneous pain, joint pain, muscle pain and tendon pain on the motor system in healthy humans. The results show that pain affects many components of motor processing at various levels of the nervous system, but that the effects of pain are largely irrespective of its source. Pain is associated with inhibition of muscle activity in the (painful) agonist and its non-painful antagonists and synergists, especially at higher intensities of muscle contraction. Despite the influence of pain on muscle activation, only subtle alterations were found in movement kinetics and kinematics. The performance of various motor tasks mostly remained unimpaired, presumably as a result of a redistribution of muscle activity, both within the (painful) agonist and among muscles involved in the task. At the most basic level of motor control, cutaneous pain caused amplification of the nociceptive withdrawal reflex, whereas insufficient evidence was found for systematic modulation of other spinal reflexes. At higher levels of motor control, pain was associated with decreased corticospinal excitability. Collectively, the findings show that short-lasting experimentally induced limb pain may induce immediate changes at all levels of motor control, irrespective of the source of pain. These changes facilitate protective and compensatory motor behaviour, and are discussed with regard to pertinent models on the effects of pain on motor control.
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The aim of this study was to test whether a reciprocal dose-response relation exists between frequency/severity of spinal pain and temporomandibular disorders (TMD). A total of 616 subjects with varying severity of spinal pain or no spinal pain completed a questionnaire focusing on symptoms in the jaw, head and spinal region. A subset of the population (n = 266) were sampled regardless of presence or absence of spinal pain. We used two different designs, one with frequency/severity of spinal pain, and the other, with frequency/severity of TMD symptoms as independent variable. All 616 participants were allocated to four groups, one control group without spinal pain and three spinal pain groups. The subjects in the subset were allocated to one control group without TMD symptoms and three TMD groups. Odds ratios (ORs) were calculated for presence of frequent TMD symptoms in the separate spinal pain groups as well as for frequent spinal pain in the separate TMD groups. The analysis showed increasing ORs for TMD with increasing frequency/severity of spinal pain. We also found increasing ORs for spinal pain with increasing frequency/severity of TMD symptoms. This study shows a reciprocal dose-response-like relationship between spinal pain and TMD. The results indicate that these two conditions may share common risk factors or that they may influence each other. Studies on the temporal sequence between spinal pain and TMD are warranted.
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Eating requires mouth opening, biting, chewing and swallowing and should be performed without dysfunction or pain. Previous studies have shown that jaw opening-closing movements are the result of coordinated activation of both jaw and neck muscles, with simultaneous movements in the temporomandibular, atlanto-occipital and cervical spine joints. Consequently, it can be assumed that pain or dysfunction in any of the three joint systems involved could impair jaw activities. In fact, recent findings support this hypothesis by showing an association between neck injury and reduced amplitudes, speed and coordination of integrated jaw-neck movements. This study investigated the possible association between neck injury and disturbed eating behaviour. Fifty Whiplash-associated disorders (WAD) patients with pain and dysfunction in thejaw-face region and 50 healthy age- and sex-matched controls without any history of neck injury participated in the study. All participants were assessed by a questionnaire, which contained 26 items about eating behaviour, jaw pain and dysfunction. For the WAD group there were significant differences in jaw pain and dysfunction and eating behaviour before and after the accident, but no significant differences between WAD before and healthy. The healthy and the WAD group before the accident reported no or few symptoms. The WAD patients after the accident reported pain and dysfunction during mouth opening, biting, chewing, swallowing and yawning and felt fatigue, stiffness and numbness in the jaw-face region. In addition, a majority also reported avoiding tough food and big pieces of food, and taking breaks during meals. Altogether, these observations suggest an association between neck injury and disturbed jaw function and therefore impaired eating behaviour. A clinical implication is that examination of jaw function should be recommended as part of the assessment and rehabilitation of WAD patients.
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The aim of this study was to investigate masticatory muscle activity during deliberately performed functional and non-functional oral tasks. Electromyographic (EMG) surface activity was recorded unilaterally from the masseter, anterior temporalis and suprahyoid muscles in 11 subjects (5 men, 6 women; age = 34.6 +/- 10.8 years), who were accurately instructed to perform 30 different oral tasks under computer guidance using task markers. Data were analyzed by descriptive statistics, repeated measurements analysis of variance (ANOVA) and hierarchical cluster analysis. The maximum EMG amplitude of the masseter and anterior temporalis muscles was more often found during hard chewing tasks than during maximum clenching tasks. The relative contribution of masseter and anterior temporalis changed across the tasks examined (F 5.2; p < or = 0.001). The masseter muscle was significantly (p < or = 0.05) more active than the anterior temporalis muscle during tasks involving incisal biting, jaw protrusion, laterotrusion and jaw cupping, the difference being statistically significant (p < or = 0.05). The anterior temporalis muscle was significantly (p < or = 0.01) more active than the masseter muscle during tasks performed in intercuspal position, during tooth grinding, and during hard chewing on the working side. Based upon the relative contribution of the masseter, anterior temporalis, and suprahyoid muscles, the investigated oral tasks could be grouped into six separate clusters. The findings provided further insight into muscle- and task-specific EMG patterns during functional and non-functional oral behaviors.
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In an attempt to determine the degree of co-activation present in selected cervical muscles during clenching, we instructed 12 male subjects to produce four brief maximum voluntary contraction (MVC) efforts (clenching) in a position of maximum intercuspation. Surface EMG activity was recorded bilaterally from the masseter and sternocleidomastoid (SCM) muscles. The contraction level for the SCM during clenching was reported as a percentage of the SCM's maximum activity achieved during maximum neck flexion against resistance. All EMG signals for the masseter and SCM were converted to a true RMS voltage signal and digitized at a 100-Hz sampling rate. Mean peak EMG voltage levels were determined for the activity recorded during each brief MVC task. All subjects demonstrated co-activation of the SCM during strong abrupt clenching efforts. The mean levels (+/- S.D.) of SCM activity were 11.8 +/- 9.6% (right) and 14.2 +/- 9.4% (left) of the MVC capacity. Fifty percent of masseter activity was required to achieve 5% activity of the SCM bilaterally, and there was a progressive development of the SCM co-activation which paralleled the masseter activation.
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Recent observations in man of concomitant mandibular and head movements during single maximal jaw-opening/-closing tasks suggest a close functional relationship between the mandibular and the head-neck motor systems. This study was aimed at further testing of the hypothesis of a functional integration between the human jaw and neck regions. Spatiotemporal characteristics of mandibular and associated head movements were evaluated for 3 different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Mandibular and head-neck movements were simultaneously recorded in 12 healthy young adults, by means of a wireless opto-electronic system for 3-D movement recordings, with retro-reflective markers attached to the lower (mandible) and upper (head) incisors. The results showed that rhythmic mandibular movements were paralleled by head movements. An initial change in head position (head extension) was seen at the start of the first jaw-movement cycle, and this adjusted head position was retained during the following cycles. In addition to this prevailing head extension, the maximal jaw-opening/-closing cycles were paralleled by head extension-flexion movements, and in general the start of these head movements preceded the start of the mandibular movements. The results support the idea of a functional relationship between the temporomandibular and the cranio-cervical neuromuscular systems. We therefore suggest a new concept for human jaw function, in which "functional jaw movements" are the result of activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints.
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As shown previously, "functional jaw movements" are the result of coordinated activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints. In this study, the effect of neck trauma on natural jaw function was evaluated in 12 individuals suffering from whiplash-associated disorders (WAD). Spatiotemporal characteristics of mandibular and concomitant head movements were evaluated for three different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Compared with healthy subjects, the WAD group showed smaller magnitude and altered coordination pattern (a change in temporal relations) of mandibular and head movements. In conclusion, these results show that neck trauma can derange integrated jaw and neck behavior, and underline the functional coupling between the jaw and head-neck motor systems.
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The aim of this study was to test the effects of glutamate-evoked jaw or neck muscle pain on electromyographic (EMG) activity of jaw and neck muscles in humans. EMG recordings were made from left (MAL) and right (MAR) masseter muscles, and right sternocleidomastoid (SCM) and splenius (SP) muscles in three different head positions (head rest, head back, head right) or during maximal jaw clenching in 19 men. Glutamate (1 M) or isotonic saline was injected into MAR or SP, and induced pain was recorded on visual analogue scales. EMG activity in MAL and MAR was increased in the head back position compared to head rest and head right positions, whereas EMG activity in SCM and SP was progressively increased as the head was moved from rest position to head back to head right positions. Glutamate-evoked MAR pain was associated with increases in EMG activity in MAR, SCM and SP at rest but not in the head back or head right positions. Glutamate-evoked SP pain was associated with an increase in SP EMG activity at rest and a decrease in SCM EMG activity in the head right position. Decreases in jaw clench-related EMG activity were observed in MAL, MAR and SCM muscles only during glutamate-evoked MAR pain. Isotonic saline injections induced no pain or EMG changes. In conclusion, experimental neck pain is not associated with tonic increases in jaw EMG activity although jaw muscle pain can be linked to increases in neck EMG activity with the head and jaw at rest.
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The purpose of this study was to investigate the functional relationship between masseter muscle (MM) and sternocleidomastoid muscle (SCM) activities and between mandibular and head movements during mastication, under experimental muscle fatigue. The sample consisted of 12 adults with individually normal occlusion. The subjects were asked to chew gum at three different times: before maximum clenching, immediately after maximum clenching, and 3 minutes after maximum clenching. At these times, we examined the activity of the MM and SCM as well as the movement of the mandible and head. The activity and movement were simultaneously measured using both electromyography and the motion capture system. The MM activity time after clenching was significantly shorter than that before clenching, whereas the SCM activity time was significantly longer after clenching. There was no significant difference in the changes of three-dimensional distance of the mandibular movement between the respective times. On the other hand, the changes in the three-dimensional distance of head movement after clenching increased when compared with before clenching. Furthermore, the difference in the time of MM and SCM activity onset and of mandibular and head movement onset after clenching was shorter than that before clenching. A functional relationship exists between the MM and SCM activities and between mandibular and head movements during mastication.
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We have previously introduced a new concept for natural jaw function suggesting that "functional jaw movements" are the result of coordinated jaw and neck muscle activation, leading to simultaneous movements in the temporomandibular, atlanto-occipital and cervical spine joints. Thus, jaw function requires a healthy state of both the jaw and the neck motor systems. The aim of this study was to examine the positioning of the gape in space during maximal jaw opening at fast and slow speed in healthy as well as whiplash-associated disorders (WAD) individuals. A wireless optoelectronic technique for three-dimensional movement recording was used. Subjects were seated in an upright position, with back support up to the mid-scapular level without headrest. The position of the gape in space was defined as the vertical midpoint position of the gape at maximal jaw opening (MP). In healthy, the MP generally coincided with the reference position at the start of jaw opening. In the WAD group, the MP was significantly lower than the reference position. No sex or speed related differences were found. The results suggest that both the width and orientation of the gape in space relies on coordinated jaw and neck muscle activation and mandibular and head-neck movements. This study also suggests an association between neck pain and dysfunction following trauma, and reduced width and impaired positioning of the gape in space. Finally, the MP seems to be a useful marker in evaluation of the functional state of the jaw-neck motor system.
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Mastication is continually modified throughout the chewing sequence in response to the texture of the food. The aim of this work was to compare the effects of an increase in hardness of two model food types, presenting either elastic or plastic rheological properties, on mastication. Each model food type consisted of four products of different hardness. Sensory testing experiments conducted with one group of 14 subjects showed significant perceived differences between products in terms of their increasing hardness. Fifteen other volunteers were asked to chew three replicates of each elastic and plastic product during two sessions. EMGs of masseter and temporalis muscles were recorded simultaneously with jaw movement during chewing. Numerous variables were analyzed from these masticatory recordings. Multiple linear regression analyses were used to assess the respective effects of food hardness and rheological properties on variables characterizing either the whole masticatory sequence or different stages of the sequence. Muscle activities were significantly affected by an increase in hardness regardless of the food type, whereas the shape of the cycles depended on the rheological properties. The masticatory frequency was affected by hardness at the initial stage of the sequence but overall frequency adaptation was better explained by a change in rheological behavior, with plastic products being chewed at a slower frequency. A dual hypothesis was proposed, implicating first a cortical-brain stem preprogrammed mechanism to adapt the shape of the jaw movements to the rheological properties of the food, and second, a brain stem mechanism with mainly sensory feedback from the mouth to adapt muscle force to the food hardness.
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Findings that jaw-opening/-closing relies on both mandibular and head movements suggest that jaw and neck muscles are jointly activated in jaw function. This study tested the hypothesis that rhythmic jaw activities involve an active repositioning of the head, and that head fixation can impair jaw function. Concomitant mandibular and head-neck movements were recorded during rhythmic jaw activities in 12 healthy adults, with and without fixation of the head. In four participants, the movement recording was combined with simultaneous registration of myoelectric activity in jaw and neck muscles. The results showed neck muscle activity during jaw opening with and without head fixation. Notably, head fixation led to reduced mandibular movements and shorter duration of jaw-opening/-closing cycles. The findings suggest recruitment of neck muscles in jaw activities, and that head fixation can impair jaw function. The results underline the jaw and neck neuromuscular relationship in jaw function.
Article
As shown previously, “functional jaw movements” are the result of coordinated activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints. In this study, the effect of neck trauma on natural jaw function was evaluated in 12 individuals suffering from whiplash-associated disorders (WAD). Spatiotemporal characteristics of mandibular and concomitant head movements were evaluated for three different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Compared with healthy subjects, the WAD group showed smaller magnitude and altered coordination pattern (a change in temporal relations) of mandibular and head movements. In conclusion, these results show that neck trauma can derange integrated jaw and neck behavior, and underline the functional coupling between the jaw and head-neck motor systems.
Conference Paper
Objectives: Epidemiological surveys indicate high comorbidity of masticatory-muscle and neck-muscle pain. It is hypothesized that close functional coupling between both muscle groups may be involved in the etiology of myofascial pain conditions. So far, however, interactions between pathophysiological loading of the masticatory system and the adjacent neck muscles, in particular caused by bruxism, lack the confirmation of neuromuscular coupling of both segments at submaximum bite forces. The objective of this study was to test the hypothesis that jaw and neck muscles co-contract during clenching of the masticatory system. Methods: Bite force transducers which measured all three spatial force components were incorporated in 11 healthy subjects. The test persons developed different feedback-controlled submaximum bite forces in a variety of bite-force directions. The corresponding electrical activity (EMG) of the levator scapulae, splenius capitis, and trapezius muscles was recorded by use of intramuscular wire electrodes, and that of the sternocleidomastoideus by use of surface electrodes. The recordings were made at the level of the fifth cervical vertebra. For normalization of the EMG data, maximum effort tasks were conducted. A special force-transducer system, attached to the head, enabled EMG recordings of the neck musculature in eight different loading directions. Results: The results confirmed the initially stated hypothesis. Co-contractions of the neck muscles in the range 2 to 8% of their maximum voluntary contraction were observed. Significant (p < 0.05) activity differences were recorded as a result of the different force levels and force directions exerted by the jaw muscles. Long-lasting action potential trains of single motor units triggered by the jaw clenching tasks were also observed. Conclusions: These findings support the assumption of pathophysiological coupling between jaw clenching and the neck-muscle activity investigated. The small amount of co-contractions, however, requires further studies to elucidate possible pathophysiological interactions at the level of single motor units.
Article
Bruxism may be involved in the aetiology of myofascial neck pain. The objective of this study was to test the hypothesis that anterior and posterior neck muscles co-contract during jaw clenching. Ten test subjects developed different feedback-controlled submaximum bite forces in a variety of bite-force directions by means of bite-force transducers. The electromyographic activity of the sternocleidomastoid and supra/infrahyoidal muscles, and of the semispinalis capitis, semispinalis cervicis, and multifidi muscles was recorded by use of surface electrodes and intramuscular wire electrodes, respectively. For normalization of electromyography data, maximum voluntary contraction tasks of the neck muscles were conducted in eight different loading directions. The results confirmed co-contraction of the neck muscles in the range of 2-14% of the maximum voluntary contraction at a bite force ranging from 50 to 300 N. Significant activity differences were observed as a result of the different force levels and force directions exerted by the jaw muscles. Long-lasting tonic activation of specific neck muscles triggered by the jaw-clenching tasks was also detected. These findings support the assumption of a relationship between jaw clenching and the activity of the neck muscles investigated. The low level of co-contraction activity, however, requires further study to elucidate possible pathophysiological interactions at the level of single motor units.
Article
Experimental muscle pain was elicited by bolus injection of 0.15 ml of 5% hypertonic saline into the human masseter muscle. The sensory experience was described using 10-cm visual analogue scales (VAS) and the McGill Pain Questionnaires (MPQ) on 10 subjects. Effects of pain on deliberately unilateral mastication were quantitatively assessed in 13 other male subjects using kinematic recordings of the mandible and jaw muscle electromyography (EMG). Jaw movement and EMG data were transformed into single masticatory cycles which were averaged within subjects to produce mean masticatory cycles. Injection of 5% saline through normal and anesthetized skin produced similar VAS profiles and MPQ features. Displacement of the mandible during painful mastication was significantly smaller in the vertical axis (10.0 ± 11.5%, P < 0.05) and in the lateral axis (22.6 ± 20.9%, P < 0.05) as compared to pre-pain values. The mean opening and closing velocities of the mandible were significantly reduced (10.5 ± 16.3% and 15.3 ± 21.2%, P < 0.05) and the cumulated distance of the jaw movement was also significantly smaller during pain (10.5 ± 11.8%, P < 0.05). Moreover, agonist EMG activity during pain was significantly lower in the ipsilateral masseter muscle (20.3 ± 25.4%, P < 0.05) as compared to pre-pain root-mean-square (RMS) values. The observed sensory-motor interactions can be explained by a facilitatory effect of activity in nociceptive muscle afferents on inhibitory brain-stem interneurons during agonist action. Thus, generated movements have smaller amplitudes and they are slower which most likely represents a functional adaptation to experimental jaw muscle pain.
Article
The present study aimed to elucidate possible physiological mechanisms behind impaired endurance during chewing as previously reported in WAD. We tested the hypothesis of a stronger autonomic reaction in WAD than in healthy subjects in response to dynamic loading of the jaw-neck motor system. Cardiovascular reactivity, muscle fatigue indicies of EMG, and perceptions of fatigue, exhaustion and pain were assessed during standardised chewing. Twenty-one WAD subjects and a gender/age matched control group participated. Baseline recordings were followed by two sessions of alternating unilateral chewing of a bolus of gum with each session followed by a rest period. More than half of the WAD subjects terminated the test prematurely due to exhaustion and pain. In line with our hypothesis the chewing evoked an increased autonomic response in WAD exhibited as a higher increase in heart rate as compared to controls. Furthermore, we saw consistently higher values of arterial blood pressure for WAD than for controls across all stages of the experiment. Masseter EMG did not indicate muscle fatigue nor were there group differences in amplitude and mean power frequency. Pain in the WAD group increased during the first session and remained increased, whereas no pain was reported for the controls. More intense response to chewing in WAD might indicate pronounced vulnerability to dynamic loading of the jaw-neck motor system with increased autonomic reactivity to the test. Premature termination and autonomic involvement without EMG signs of muscle fatigue may indicate central mechanisms behind insufficient endurance during chewing.
Article
Temporomandibular disorders (TMD), headaches, and spinal pain show co-morbidity and may therefore influence each other. The hypothesis tested is that the presence of any of these conditions will increase the risk of onset of new symptoms within a 2-year period. The study population comprised 280 dental students, who were examined three times at 12-month intervals. The incidence was calculated for a 2-year period, based on subjects without the defined symptom at baseline. Each participant was classified into five different case-control groups, representing incidence cases or no incidence (controls) of: (1) nonpain TMD symptoms; (2) jaw pain; (3) headaches; (4) spinal pain; and (5) TMD pain. Presence of headaches and of spinal pain and signs and symptoms of TMD at baseline were used as independent variables in logistic regression analyses, controlling for age and sex. Incidence cases with TMD pain reported spinal pain at baseline significantly more often than the controls, and were mostly women. Incidence cases with headaches and incidence cases with jaw pain significantly more often had signs of TMD and reported spinal pain at baseline, compared to controls. Incidence cases with nonpain TMD symptoms or spinal pain significantly more often presented with signs of TMD at baseline. Our findings show that pain and dysfunction in trigeminally innervated areas and pain in spinally innervated areas mutually predict the onset of new symptoms in dental students, indicating common pathophysiological mechanisms and individual vulnerability. This may be of importance in risk assessment and treatment planning of individuals with musculoskeletal pain.
Article
1. During chewing, little muscle activity is required to make open-close movements with the mandible, and much additional muscle activity (AMA) of the closing muscles is needed to overcome the resistance of food. The neuromuscular control of the AMA was investigated. 2. Subjects made rhythmic open-close movements at their natural chewing frequency controlled by a metronome. Food resistance was simulated by an external force, acting on the jaw in a downward direction during part of the closing movement. Sequences of cycles with a force were unexpectedly alternated with sequences of cycles without a force. Jaw movement, and surface electromyograph (EMG) of the masseter, temporalis, and digastric muscles on both sides were recorded during cycles before and after the transition from force to no force (Disappear experiment) and vice versa (Appear experiment). 3. The movement trajectory of the second and following cycles after the transition from force to no force or vice versa were similar. Thus adaptation to the changed circumstances occurred in both types of experiments within two open-close cycles. 4. In the first cycle with force in the Appear experiments, the AMA started, on average, 129 ms after the onset of the force. In all other cycles with force, the AMA started, on average, 70 ms before the onset of the force at a low level and steeply increased 23 ms after the onset of the force. 5. In the first cycle without force in the Disappear experiments, the AMA started, on average, 69 ms before the moment at which the force would have started. However, the large contribution to the AMA had disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
The maximum bite force and position of the hyoid bone during natural and extended head posture were studied in 15 adults. All participants had normal occlusions and full dentitions. In addition, there were no signs or symptoms of craniomandibular disorders. The bite force was measured with a bite force sensor placed between the first molars. Six registrations of gradually increasing bite force up to a maximum were made with randomized natural and extended head postures. With one exception, the mean maximum bite force value was found to be higher for every subject with extended head posture compared to natural head posture. The sample mean was 271.6 Newton in natural head posture and 321.5 Newton with 20 degrees extension. With changed head posture, the cephalometric measurements pointed towards a changed position of the hyoid bone in relation to the mandible and pharyngeal airway. The cephalometric changes in the position of the hyoid bone could be due to a changed interplay between the elevator and depressor muscle groups. This was one factor which could have influenced the registered maximum bite force.
Article
Different quantities and sizes of peanuts were offered to six human subjects for mastication at two or three experimental sessions during which jaw movements and chewing cycle duration were measured. The amplitude of vertical movement and cycle duration depended on the position of a chew in a sequence of chews (masticatory sequence). Cycle duration also depended on the position of a given masticatory sequence during the first experimental session, the earlier sequences tending to be longer. Lateral jaw movements fluctuated about a reasonably constant value during a sequence and were unaffected by different food inputs. The amplitude of vertical movements increased markedly with an increase in food weight but was unaffected by change in the initial food particle size. These results were analyzed in the light of previous reports on the comminution of peanuts. It is hypothesized that observed jaw movements were unrelated to food particle size but that the amplitude of each vertical movement depended on the volume of food that was broken by the teeth during the next closing stroke. This food volume was provided and selected by bulk movements of the tongue during the preceding jaw opening.
Article
This paper describes and evaluates the digital MacReflex system for wireless recording of movements in three dimensions. Up to seven high resolution infra-red sensitive CCD video cameras with electronic shutters register the positions of maximally 40 stroboscopically illuminated retro-reflective tape markers. The system is equipped with real-time video processors for computation of position co-ordinates for the markers and for optimised data transmission and storage. Data are output to any type of computer through a standard serial interface, which also provides possibilities for simultaneous A/D-sampling. Dynamic manipulation of the recorded signals in three-dimensional plots is provided by standard software and transformation and evaluation of recorded data are performed in standard software. The described equipment is found to offer a flexible and easily operated solution for recording of movements with high resolution.
Article
This study evaluated the applicability of skin- and teeth-attached reflex markers fixed to the mandible and the head for optoelectronic recording of chewing movements. Markers were attached to the upper and lower incisors and to the skin on the forehead, the bridge of the nose, the tip of the nose and the chin in seven subjects. Chewing movements were recorded in three dimensions using a high-resolution system for wireless optoelectronic recording. Skin markers were systematically displaced due to skin stretch. The largest displacement was observed for the chin marker, whereas minor displacement was found for markers located on the forehead and the bridge of the nose. In repeated recordings, the smallest intra-individual variation in displacement was found for the marker on the bridge of the nose. In spite of relatively large displacement for the chin marker, the temporal estimates of the mandibular movement were not affected. Teeth markers were found to significantly increase the vertical mouth opening, although the duration of the chewing cycle was unaffected. This indicates an increase in chewing velocity. We suggest that markers located on the bridge of the nose are acceptable for recordings of chewing movements. Skin markers on the chin can be reliably used for temporal analysis. They are also acceptable for spatial analysis if an intra-individual variability of 2 mm is allowed. Teeth-attached markers may significantly influence the natural chewing behavior. Thus, both types of marker systems have advantages as well as disadvantages with regard to the accuracy of the chewing movement analysis. Selection of a marker system should be based on the aims of the study.
Article
The rate of breakdown of food in mastication depends on the ratio of two mechanical properties of the food--the toughness and modulus of elasticity (Agrawal et al., 1997)--a result which can be predicted by an analysis of the energetics of fracture. The work input to produce food fragmentation is provided by the masticatory muscles, the activity levels of which depend on sensory feedback from the mouth. Here, we test the hypothesis that the activity of a representative of this musculature is modulated by the above combination of food properties. The surface electrical activity (EMG) of the anterior temporalis muscles of ten human subjects was recorded while subjects chewed standardized volumes of 15 food types. The integrated EMG in these muscles was highly significantly related to the square root of the ratio of the above two food properties. Significant correlations were found between this food property index and integrated EMG, both when data for all chews and all subjects were lumped together (r = -0.86; p < 0.0001) and when correlation coefficients between the index and EMG were plotted for each chew made by each subject. Except for two subjects in the first chew, these coefficients reached and maintained highly significant levels throughout the masticatory sequence. Thus, a clear relationship between the electrical activity of a jaw-closing muscle and the mechanical properties of food has been found for the first time.
Article
To test the hypothesis of a functional relationship between the human mandibular and cranio-cervical motor systems, head-neck movements during voluntary mandibular movements were studied in 10 healthy young adults, using a wireless optoelectronic system for three-dimensional (3D) movement recording. The subjects, unaware of the underlying aim of the study, were instructed to perform maximal jaw opening-closing tasks at fast and slow speed. Movements were quantified as 3D movement amplitudes. A consistent finding in all subjects was parallel and coordinated head-neck movements during both fast and slow jaw opening-closing tasks. Jaw opening was always accompanied by head-neck extension and jaw closing by head-neck flexion. Combined movement and electromyographic recordings showed concomitant neck muscle activity during head-neck movements, indicative of an active repositioning of the head. No differences in 3D movement amplitudes could be seen with respect to speed. The head movement was 50% of the mandibular movement during jaw opening, but significantly smaller (30-40%), during the jaw closing phase. In repeated tests, the 3D movement amplitudes of the concomitant head movements were less variable during slow jaw movement and during the jaw opening phase, than during fast and jaw closing movements, suggesting speed- and phase-related differences in the mechanisms controlling the integrated mandibular and head-neck motor acts. The present results give further support to the concept of a functional trigeminocervical coupling during jaw activities in man.
Article
This study investigated the effects of head posture on mandibular habitual closing movement. Ten healthy subjects were examined. Head posture was evaluated as a sagittally viewed inclination of the head, and was changed from 25 degrees forward bending up to 30 degrees backward bending in 5 degrees increments. The mandibular opening and closing movement was measured at each head posture. As the head bended forward, the closing path approached the maximum intercuspal position from the anterior region, and as the head was bent backward, the closing path approached the maximum intercuspal position from the posterior region. However, the limit of this relationship was found when the head was bent forward to some extent. There was also a correlation between the head posture and the stability of the closing movement. The forward bending of the head decreased the stability of the closing path, and conversely, the backward bending increased the stability of the closing path. It was concluded that the head posture affects the direction and stability of the mandibular closing movement. Possible underlying reasons for these findings are masticatory muscle activity and the tension and resistance of inframandibular soft tissue varying with the change of head posture.
Article
Human mandibular movements in space are the result of combined motions of the mandible and the head-neck. They can be simultaneously monitored by an optoelectronic recording technique via markers at different locations on the mandible and on the head. Markers can be attached to the teeth or to the facial skin. Mandibular movements relative to the head can be calculated by one- or three-dimensional (1D and 3D, respectively) mathematical compensation for head movements. The present study analysed mandibular and associated head movements during maximal jaw opening-closing tasks in 10 healthy subjects using a wireless 3D optoelectronic movement recording system. The study aimed to: (i) estimate the soft tissue related displacement of skin-attached markers at different locations on the face; (ii) compare 1D with 3D mathematical compensation for associated head movements; (iii) evaluate the influence of marker location on the recorded head and mandibular movement amplitudes; and (iv) compare skin-attached markers with teeth-attached markers with regard to temporal estimates of recorded mandibular and head movements. Markers were attached to the upper and lower incisors and to the skin of the forehead, nose-bridge, nose-tip and chin. Soft tissue related displacement of skin-attached markers varied between locations. The displacement for the chin marker was larger than that of other markers. The least displacement was found for the nose-bridge marker. However, relative to mandibular and head movements, respectively, the displacement of the chin marker was of the same order as that of the nose-bridge marker. The temporal estimates were not significantly affected by displacement of the skin-attached markers. Markers at different locations on the head and the mandible registered different amplitudes. The mandibular movement patterns calculated by 1D and 3D compensation were not comparable. It is concluded that markers attached to the chin and the nose-bridge can be reliably used in temporal analyses of mandibular and head movements during maximal jaw opening-closing. With certain limitations, they are acceptable for spatial analyses. Selection of method of marker attachment, marker location, and method of compensation for associated head movements should be based on the aim of the study.
Article
Previous finding of concomitant mandibular and head movements during jaw function suggest a functional relation between the human jaw and neck regions. This study examined the temporal coordination between mandibular and head-neck movements during maximal jaw opening-closing tasks, at fast and slow speed. Twenty-four healthy individuals, median age 25 years, participated in the study. They were seated with firm back support but without head-neck support. Mandibular and head movements were simultaneously monitored by a wireless optoelectronic system for three-dimensional movement recording. The timing of head movement in relation to mandibular movement was estimated at defined time-points (start, peak, end and maximum velocity of movement), and during the entire course of the jaw-opening and jaw-closing phases. The results showed that the head in general started to move simultaneously with or before the mandible, reached the peak position simultaneously with, before or after the mandible, and reached the end position after the mandible. A higher degree of temporal coordination was found for fast speed at the start and the peak positions. The head most often attained maximum velocity after the mandible, and mostly lagged behind the mandible during the entire jaw-opening and -closing phases. These findings support the notion of a functional linkage between the human temporomandibular and craniocervical regions. They suggest that "functional jaw movements" comprise concomitant mandibular and head-neck movements which involve the temporomandibular, the atlanto-occipital and the cervical spine joints, and are caused by jointly activated jaw and neck muscles. It is proposed that these jaw and neck muscle actions, particularly at fast speed, are elicited and synchronized by preprogrammed neural command(s) common to both the jaw and the neck motor systems. From the present results and previous observations of concurrent jaw and head movement during fetal yawning, we suggest that these motor programmes are innate.
Article
Rhythmical head movements and neck muscle activities associated with the masticatory jaw movement were investigated in rabbits. In natural mastication, head movements and neck muscle activities showed a rhythmical feature synchronized with jaw movement. During cortically induced rhythmical jaw movements, some neck muscle showed rhythmical activity induced by biting a wooden stick. Neck muscles may contribute to the rhythmical head movement after loading the tooth with food.
Article
Many studies show a consistent individual chewing pattern; chewing being governed by a pattern generator and regulated by sensory feedback. The aim of this study was to determine the variation in chewing between sessions, replicates and subjects using elastic model foods. Fifteen young male subjects were selected to chew four food products differing in hardness. Four sessions were performed at 1-wk intervals for each subject and, within each session, the four model foods were presented 3 times each. Jaw movement was recorded simultaneously with masseter and anterior temporalis electromyographic activities. Several chewing characteristics increased progressively from one session to the next; the largest increase occurred from the 1st to the 2nd session, with little difference between the last two sessions. No differences were observed between the samples of the same food product within a session. As mastication progressed, the amplitude and speed of the cycles and the muscular work decreased progressively. The first cycle appeared to be very different from the subsequent for all parameters except for occlusal duration. Thus, under our experimental conditions, the origin and amount of variation in chewing patterns were identified and provide information to improve the accuracy and comparability of results in studies of mastication.
Article
It is known that small head movements accompany the movements of the jaw during mastication; however, it is unknown whether these movements occur rhythmically and synchronously. The objective of this study was to determine whether there exists a functional coupling between the head and mandibular movements. Four healthy male adults (mean age 25.5) with normal occlusion and without TMD history were selected as subjects. Using the Trimet system, we measured tridimensionally both the movement of the head and the mandible by tracking upper and lower incisal points, respectively, during tapping movements with different opening range and frequency, then analysed the vertical component of these movements. The upper incisal point moved in opposite direction to the mandible in all tapping strokes in all subjects, during opening the head moved in a cranial direction and during closing in a caudal direction; the incidence rate for this concomitant movement was 98%, implying that the head moves periodically and rhythmically, as the mandible does. The cycle time of these coincident movements showed a correlation coefficient of 0.94. Moreover, the vertical range of head movement was within 10% of the jaw's movement. From these results we concluded that, at least during teeth tapping, the head moves in rhythmical coordination with mandibular movement.
Article
When food is chewed, sensory feedback adapts the motor program to the characteristics of the food. However, the relationship between the physical properties of different foods and the motor response is poorly understood. In this study, we developed edible and well-controlled model foods in order to describe some of the stimulus-response functions of the food-mastication loop. Four gelatine-based visco-elastic model foods identical in shape and size but differing in hardness were prepared. They displayed reproducible sensory and physical characteristics and were distributed on a wide hardness scale. Electromyographic activity of masseter and temporalis muscles and jaw movements in the frontal plane were simultaneously recorded during mastication in 15 young men with intact dentition and good oral status. Almost all EMG and jaw movement parameters were clearly affected by increasing hardness of model foods. However, it is possible to summarise the results by reducing the number of parameters to three: the number of chewing cycles, EMG activity of any one of the two temporal or the two masseter muscles and the amplitude of the opening mandibular movements. Indeed, these were the best transcriptors of the hardness range of the model foods used in this study. As inferred from these parameter recordings, the food hardness modifications were strongest during the first five strokes, began as early as the first stroke and lasted for the whole sequence.
Article
Clinical evidence suggests that head movements may be coupled with oro-facial functions, which are predominantly controlled by somatosensory inputs from the oro-facial area. However, the effects of specific modalities of sensory inputs on the neck muscles' motor activity are still unclear. In the present study, natural pressure stimulation was applied to the rat's upper first molars, while motor unit electromyographic activity was recorded from the dorsal neck splenius muscle. During the hold phase of pressure stimulation, clear tonic discharges were elicited in the splenius muscles on both sides. Mean threshold values were 622.3 mN (+/- 19.6 SEM, n = 39) and 496.8 mN (+/- 26.4 SEM, n = 43) for ipsi- and contralateral sides, respectively (p < 0.001, Mann-Whitney U test). Analysis of our data suggests that periodontal inputs may play an important role in controlling the motor activity of neck muscles, in addition to its well-known coordination of the masticatory function.
Article
Recent findings of simultaneous and well coordinated head-neck movements during single as well as rhythmic jaw opening-closing tasks has led to the conclusion that 'functional jaw movements' are the result of activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital and cervical spine joints. It can therefore be assumed that disease or injury to any of these joint systems would disturb natural jaw function. To test this hypothesis, amplitudes, temporal coordination, and spatiotemporal consistency of concomitant mandibular and head-neck movements during single maximal jaw opening-closing tasks were analysed in 25 individuals suffering from whiplash-associated disorders (WAD) using optoelectronic movement recording technique. In addition, the relative durations for which the head position was equal to, leading ahead of, or lagging behind the mandibular position during the entire jaw opening-closing cycle were determined. Compared with healthy individuals, the WAD group showed smaller amplitudes, and changed temporal coordination between mandibular and head-neck movements. No divergence from healthy individuals was found for the spatiotemporal consistency or for the analysis during the entire jaw opening-closing cycle. These findings in the WAD group of a 'faulty', but yet consistent, jaw-neck behavior may reflect a basic importance of linked control of the jaw and neck sensory-motor systems. In conclusion, the present results suggest that neck injury is associated with deranged control of mandibular and head-neck movements during jaw opening-closing tasks, and therefore might compromise natural jaw function.
Article
Coordinated mandibular and head-neck movements during jaw opening-closing activities suggest a close functional linkage between the jaw and the neck regions. The present study investigated whether size and texture of bolus can influence head-neck behavior during chewing. Using an optoelectronic 3-D recording technique, we analyzed concomitant mandibular and head-neck movements in 12 healthy adults chewing small (3 g) and large (9 g) boluses of chewing gum and Optosil. The main finding was a head extension during chewing, the amount of which was related mainly to bolus size. Furthermore, each chewing cycle was accompanied not only by mandibular movements, but also by head extension-flexion movements. Larger head movement amplitudes were correlated with larger size and, to some extent, also with harder texture of the bolus. The results suggest that head-neck behavior during chewing is modulated in response to changes in jaw sensory-motor input.
Article
We have previously shown an association between neck injury and disturbed jaw function. This study tested the hypothesis of a relationship between neck injury and impaired endurance during chewing. Fifty patients with whiplash-associated disorders (WAD) were compared with 50 temporomandibular disorders (TMD) patients and 50 healthy subjects. Endurance was evaluated during unilateral chewing of gum for 5 min when participants reported fatigue and pain. Whereas all healthy subjects completed the task, 1/4 of the TMD and a majority of the WAD patients discontinued the task. A majority of the WAD patients also reported fatigue and pain. These findings suggest an association between neck injury and reduced functional capacity of the jaw motor system. From the results, we propose that routine examination of WAD patients should include jaw function and that an endurance test as described in this study could also be a useful tool for non-dental professionals.
Article
summary This review emphasizes the following points: 1 The values of the physiological parameters of mastication (number of cycles and total electromyographic activity in the sequence, sequence duration, cycle frequency in the sequence, kinetic characteristics of the cycles) are characteristic of each individual and vary widely from one individual to another. In a given individual their modification reflects an adaptation of mastication to the size of the food bolus, and the hardness and rheological characteristics of the food. 2 The ready-to-swallow food boluses produced by different individuals nevertheless display similar particle size distributions. 3 Ageing entails adaptation of the masticatory function and does not impair swallowing. 4 Observed increase in total electromyographic activity shows that more energy is expended in mastication by full denture wearers. Despite this increased muscle activity, loss of teeth, even if compensated for by complete dentures, hinders the formation of a normal bolus. The food boluses made by denture wearers thus contain many large-size particles. The impaired mastication observed in denture wearers approaches the masticatory disabilities found in persons with neuromotor deficiencies.