Concomitant mandibular and head-neck movements during jaw opening-closing in man

Effect of static and dynamic jaw positions on postural stability among people with blindness

BACKGROUND

In comparison with the people with normal sight, the mean center of gravity (COG) velocity is significantly higher among blind people. A strong relationship has been shown between jaw and neck sensorimotor and postural control. The purpose of this study was to determine the effect of different static and dynamic jaw positions on postural stability among subjects with blindness.

METHODS

Postural stability was measured as COG velocity in 39 blind subjects under the following five conditions: resting jaw (natural jaw position with no instructions, control), open jaw (teeth of both jaws slightly apart), clenched jaw (teeth tightly closed across each other), chewing (a standard bolus of gum at the natural palace), and tongue position (positioned behind the upper incisors) while standing on firm and foam surfaces.

RESULTS

The mean COG velocity while standing on the firm surface during resting, open jaw position, clenched jaw position, chewing, and tongue positions were 0.54, 0.50, 0.44, 0.59, and 0.46 deg/s, respectively. The mean COG velocity while standing on the foam surface during resting, open jaw position, clenched jaw position, chewing, and tongue positions were 1.42, 1.23, 1.10, 1.14, and 1.06 deg/s, respectively. Compared to the firm surface, the COG velocity was significantly higher on the foam surface in all five conditions (p < .001). In the comparison between the conditions, there were no significant differences in either the firm or foam surface in all five conditions (p > .05).

CONCLUSION

People with blindness behave in the same way as sighted subjects on firm and foam surfaces. However, changes in static and dynamic jaw positions do not affect postural stability among them.

[Features of the formation of typical motor patterns of the craniocervical zone in functional disorders in the craniomandibular system]

OBJECTIVE

The aim of the study is to analyze the features of motor patterns formation in the craniocirvical zone with occlusal and functional disorders of the craniomandibular system.

MATERIALS AND METHODS

281 patients (201 women and 80 men) were examined at the age from 21 to 32 years. Two groups of individuals were identified based on the short Gambur test. The first group (I) included persons with intact dentition and without signs of functional disorders (n=30). The second group (II) included persons with intact dentition and dysfunction of the craniomandibular system (CMS) (n=30). All patients were examined by a digital analysis of the occlusal relationship. A digital method of capturing and reconstructing movement was used to assess the motor patterns of the craniocervical zone. Analysis of functional occlusion showed that the first contact in persons with functional impairment is predominantly localized on the molars region (χ²=44.1; df=11, p=0.00001).

RESULTS

In analysis of dynamic occlusion, the time exceed for reaching maximum intercuspation position significantly in group II instead of group I 0.127±0.072 sec and 0.261±0.091 sec (p<0.05). Disconnection time in group II was 0.443±0.096 sec, Which significantly differed from group I (p<0.05). Persons with CCM dysfunction head flexion was 11.00° [9.00°; 13.00°], which is significantly higher than in the comparison group 5.00° [5.00°; 5.50°]. In the transverse plane, an increase in the angle of lateroflexion in persons with functional impairments up to 11.00° [10.00°; 11.00°]. Correlation analysis showed the presence of a direct strong connection between the angle of flexion and the time of separation (r=0.76), as well as the time to reach the maximum intercuspation position (r=0.63).

CONCLUSION

Thus, functional disorders in the form of occlusal aberrations lead to changes in the cervical spine and head position through the formation of new motor patterns.

Jaw-neck motor strategy during jaw-opening with resistance load

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 < .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 = .018), and expected mean jaw movement amplitude decreased by 3.7 mm (95% CI: -7.0, -0.5, p = .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.

Association of cervical spine signs and symptoms with temporomandibular disorders in adults: a systematic review protocol

OBJECTIVE

The objective of this systematic review is to assess the evidence of association of cervical spine signs and symptoms with temporomandibular disorders (TMD). This will help to lend credence to mechanisms supporting the association in order to improve care strategies for this condition.

INTRODUCTION

The association of cervical spine impairments (in relation to neck posture, cervical spine mobility, muscle tenderness, muscle activity, and neck disability) with TMD has been widely discussed in the literature. Clarification of this relationship is important for health professionals to better assess and treat TMD.

INCLUSION CRITERIA

Eligible studies will include participants aged 18 years and over, with a diagnosis of TMD from the Research and Diagnostic Criteria for Temporomandibular Disorders or a revised version. Exclusion criteria will be participants with previous temporomandibular joint surgery, history of trauma or fracture in the temporomandibular joint or the craniomandibular system; serious comorbid conditions such as cancer, rheumatic disease, and neurological problems; primary cervical spine disorders such as disc herniation or spinal degenerative changes; or systemic disease such as ankylosing spondylitis.

METHODS

The search for articles will be conducted in the databases PubMed, PEDro, CINAHL, Web of Science, and Embase, without language or time restrictions. Two independent reviewers will review the title, abstract, and full texts of identified studies; select studies against the inclusion criteria; assess the methodological quality of eligible studies using critical appraisal tools; and perform data extraction. Relevant quantitative data will be pooled with statistical meta-analysis, when possible.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42019123698.

Juvenile/Adolescent Idiopatic Scoliosis and Rapid Palatal Expansion. A Pilot Study

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.

Coordinated features in jaw and neck muscle activities induced by chewing of soft and hard gum in healthy subjects

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.

Can jaw position affect the fine motor activity of the hand during writing?

BACKGROUND

Jaw and neck systems have been shown to be functionally related and changes in either system can modulate gross motor functions, such as posture control. It remains to be seen if any change in jaw position can affect fine motor skills. The objective of this study was to determine the effect of resting, open and clenched jaw positions on various handwriting parameters while standing on firm and unstable surfaces.

METHODS

Handwriting samples were collected from 36 healthy male participants (age, 15-35 years) using a digitizer tablet (WACOM Intuos 4) with noninking pen in the resting, open and clenched jaw positions while standing on firm and unstable surfaces. The measured handwriting parameters included duration, vertical size, horizontal size, absolute size, average absolute velocity, and absolute jerk. Recordings and analyses were performed using NeuroScript MovAlyzeR software.

RESULTS

All handwriting parameters varied among the resting, open, and clenched jaw positions on both the firm and unstable surfaces. However, based on statistical analyses, there were no significant differences in the handwriting parameters among three jaw positions on both surfaces (p > .05).

CONCLUSION

This study revealed that all handwriting parameters varied among the resting, open, and clenched jaw positions on both the firm and unstable surfaces, showing that change in the jaw motor system may potentially affect the fine motor skills. However, on statistical analysis, there was no significant effect of 3 studied jaw positions on fine motor skills as seen on gross motor skills among healthy individuals.

Jaw-neck motor function in the acute stage after whiplash trauma

BACKGROUND

Jaw-neck motor function is affected in the chronic stage following whiplash trauma. It is not known whether motor function is affected also in the early stage after neck trauma.

OBJECTIVES

To determine how jaw and head movement amplitudes and movement cycle times correlate with jaw and neck pain, and neck disability in the acute stage after whiplash trauma.

METHODS

Jaw and head movements during jaw opening-closing were recorded with an optoelectronic system in 23 cases (4 men, 19 women, 18-66 years) within 1 month after whiplash trauma and compared with 27 controls without neck trauma (15 men, 12 women, 20-66 years). Jaw and head movement amplitudes, head/jaw ratio (quotient of head and jaw movement amplitude) and movement cycle times were evaluated in relation to jaw and neck pain (Numeric Rating Scale) and neck disability (Neck Disability Index). Analyses were performed with Mann-Whitney U test and Spearman's correlation.

RESULTS

Compared with controls, cases showed smaller jaw movement amplitudes (P = .006) but no difference in head movement amplitudes, head/jaw ratios or movement cycle times. There were no significant correlations between movement amplitudes or cycle times and jaw and neck pain, and neck disability. Cases with high neck pain intensity had smaller jaw movement amplitudes compared to cases with low neck pain intensity (P = .024).

CONCLUSION

The results suggest that jaw-neck motor function may be affected in the acute stage after whiplash trauma and more so in cases with higher neck pain intensity.

Bruxism, temporomandibular dysfunction and cervical impairments in females - Results from an observational study

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 = 33) or non-bruxism group (n = 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 = 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.

Multimodal Sensory Stimulation of the Masseter Muscle Reduced Precision but Not Accuracy of Jaw-Opening Movements

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.

Temporomandibular disorders: improving outcomes using a multidisciplinary approach

Patients with temporomandibular disorders (TMD) can become very complex. This article aims to highlight the importance of the multimodal and multidisciplinary approach in this type of patients to improve clinical outcomes. At present we have innumerable techniques and tools to approach this type of patients from a biopsychosocial model where active and adaptive type treatments are fundamental. There are various health professions that have competence in the treatment of TMD, however, although in the most complex cases should be treated simultaneously, still too many patients receive unique treatments and only from one point of view. This review exposes the treatments available from a clinical-scientific perspective and also emphasizes the importance of working in specialized units with those professionals who have competencies on the different conditions that may occur.

Jaw-neck movement integration in 6-year-old children differs from that of adults

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 = .008) during chewing, higher intra-individual variability in amplitudes of jaw (P = .008) and neck (P = .001) movements, higher ratio between neck-jaw movement amplitudes for jaw opening-closing (P = .026) and chewing (P = .003), and longer jaw movement cycle time (P ≤ .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 behaviour. 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.

Instant reduction in postural sway during quiet standing by intraoral dental appliance in patients with Whiplash associated Disorders and non-trauma neck pain

OBJECTIVES

This study tested the hypothesis that modulation of jaw sensorimotor control by intraoral dental appliance can reduce postural sway during quiet standing and hence improve standing balance, in patients with whiplash associated disorders (WAD) and non-trauma neck pain.

DESIGN

Postural sway during quiet standing with feet together was examined in 54 WAD patients (40 females) and 10 non-trauma patients (8 females) using wireless 3D movement recording technique. Recordings were performed alternating without and with intraoral dental appliance, and with closed eyes and open eyes, respectively. In this protocol the participants served as their own controls. A reference group of 30 healthy subjects (17 females) was also recorded. Each recording lasted 120 s, followed by 3-5 min of rest. Speed, acceleration and perimeter of postural sway area were documented.

RESULTS

In the patients, but not in the healthy group, the intraoral dental appliance instantly and significantly reduced standing postural sway in recordings with closed and open eyes.

CONCLUSIONS

The prompt reduction in standing postural sway from intervention by intraoral dental appliance i.e. improved standing balance, suggests a potent effect on the postural control system by modulation of the jaw sensorimotor system, probably involving reflex transmission. The result opens for new insight into mechanisms behind postural control and the pathophysiology of balance disorders, and adds to the knowledge on plasticity of the nervous system. It may help developing new procedures for assessment and management of impaired balance in WAD and non-trauma neck pain patients.

Temporomandibular disorder and comorbid neck pain: facts and hypotheses regarding pain-induced and rehabilitation-induced motor activity changes

According to the "pain adaptation model", temporomandibular disorder (TMD)-related pain induces a paradoxical activity of masticatory muscles: an agonistic hypoactivity during jaw closing and an antagonistic activity during jaw opening (agonist/antagonist co-activation). However, this model suffers several weaknesses; notably, it does not explain all types of neck muscle activities in neck pain (NP), which is a very prevalent TMD comorbid condition. In NP, neck muscle antagonistic activity is increased, and agonistic activity is decreased as postulated by the pain adaptation model. However, synergistic and compensatory activity may occur and agonistic activity may be unchanged or even increased as postulated within the "vicious cycle theory". Thus, both theories would apply partly as outlined currently in musculoskeletal disorders (MSD). Besides pain, psychological stress may also induce motor dysfunction in TMD and NP. In NP, rehabilitation may increase agonistic activity and decrease compensatory activity and antagonistic activity, thus inducing a switch from agonist/antagonist co-activation towards reciprocal inhibition. Thus, rehabilitation-induced motor activity changes constitute a new research field that should improve MSD therapeutics. Additionally, immature tongue function (so-called infantile swallow) might be connected to TMD where low agonistic activity of masticatory muscles would be compensated by facial muscle hyperactivity during oropharyngeal phase of deglutition.

Co-contraction behaviour of masticatory and neck muscles during tooth grinding

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.

Effect of voluntary teeth clenching and sitting posture on maximal static force of limb muscles

BACKGROUND

People clench their teeth to activate facial, neck and abdominal muscles when they need to generate heavy muscle force against large resistance like lifting heavy objects, in order to gain possible ergogenic advantage. These are termed as remote voluntary contractions. Aim of this study was to evaluate the effect of voluntary teeth clenching on maximal voluntary contraction of extensors and flexors of the knee, shoulder and elbow joints of the dominant side during slouch and unsupported upright sitting.

METHODS

One hundred healthy young male adults (mean age 23.3 years) participated in this study. Maximal voluntary contraction was measured using a hand-held dynamometer.

RESULTS

Jaw clenching caused different ergogenic effect during slouch versus unsupported sitting postures. The data revealed that during unsupported upright sitting, the effect of jaw clenching consistently results in larger maximal voluntary contraction of both extensor and flexor muscles of all the three studied joints. However, during slouch sitting, only the maximal voluntary contraction of extensors of elbow and flexors of knee were larger with clenched teeth position.

CONCLUSIONS

Jaw clenching can affect the maximal voluntary contraction of limb muscles which is sitting posture dependent. Jaw clenching can consistently facilitate certain muscles of the upper and lower limbs to generate greater force production during upright sitting.

Management of pain in patients with temporomandibular disorder (TMD): challenges and solutions

Thanks to advances in neuroscience, biopsychosocial models for diagnostics and treatment (including physical, psychological, and pharmacological therapies) currently have more clinical support and scientific growth. At present, a conservative treatment approach prevails over surgery, given it is less aggressive and usually results in satisfactory clinical outcomes in mild–moderate temporomandibular disorder (TMD). The aim of this review is to evaluate the recent evidence, identify challenges, and propose solutions from a clinical point of view for patients with craniofacial pain and TMD. The treatment we propose is structured in a multi-modal approach based on a biobehavioral approach that includes medical, physiotherapeutic, psychological, and dental treatments. We also propose a new biobehavioral model regarding pain perception and motor behavior for the diagnosis and treatment of patients with painful TMD.

The Effects of Heel Height on Head Position, Long-Term Average Spectra, and Perceptions of Female Singers

Female singers often wear high heels for auditions and performances. Heel height research in non-singing contexts indicates that wearing heels can affect body alignment and head position. Studies in orthodontics, sleep apnea, and voice science suggest that head and neck positioning can alter the vocal tract. The purpose of this study was to assess the effects, if any, of heel height (barefoot, 10.16-cm stilettos) on three angles of singer head position (calculated from C7-tragus-nasion), long-term average spectra data, and perceptual data (questionnaire) acquired from female (N = 30) soloists during alternating periods of silence and singing. Results indicated that all participants (100%) significantly decreased head position angle measurements (inferior and posterior head and neck movement) when singing in high heels compared with singing barefoot. Participants, on average, significantly increased head position angle measurements (superior and anterior head and neck movement) when singing compared with standing silently, and did so to a greater degree when transitioning from silent heels to singing heels compared with transitioning from silent barefoot to singing barefoot. Long-term average spectra data indicated significant spectral energy differences between barefoot and high heel singing conditions across participants. Most participants (n= 21, 70.00%) indicated they felt comfortable and sang their best while barefoot. Results of this study, the second in a series of experiments addressing the effects of shoe heel height on female singers' vocal production, were discussed in terms of application to vocal pedagogy and directions for future research.

Effects of cervical mobilization and exercise on pain, movement and function in subjects with temporomandibular disorders: a single group pre-post test

Objective

To investigate the effect of a rehabilitation program based on cervical mobilization and exercise on clinical signs and mandibular function in subjects with temporomandibular disorder (TMD). Material and Methods: Single-group pre-post test, with baseline comparison.

Subjects

Twelve women (22.08±2.23 years) with myofascial pain and mixed TMD according to the Research Diagnostic Criteria for Temporomandibular Disorders.

Outcome measures

Subjects were evaluated three times: twice before (baseline phase) and once after intervention. Self-reported pain, jaw function [according to the Mandibular Functional Impairment Questionnaire (MFIQ)], pain-free maximum mouth opening (MMO), and pressure pain thresholds (PPTs) of both masseter and temporalis muscles were obtained. Baseline and post-intervention differences were investigated, and effect size was estimated through Cohen’s d coefficient.

Results

Jaw function improved 7 points on the scale after the intervention (P=0.019), and self-reported pain was significantly reduced (P=0.009). Pain-free MMO varied from 32.3±8.8 mm to 38±8.8 mm and showed significant improvement (P=0.017) with moderate effect size when compared to the baseline phase. PPT also increased with moderate effect size, and subjects had the baseline values changed from 1.23±0.2 kg/cm² to 1.4±0.2 kg/cm² in the left masseter (P=0.03), from 1.31±0.28 kg/cm² to 1.51±0.2 kg/cm² in the right masseter (P>0.05), from 1.32±0.2 kg/cm² to 1.46±0.2 kg/cm² in the left temporalis (P=0.047), and from 1.4±0.2 kg/cm² to 1.67±0.3 kg/cm² in the right temporalis (P=0.06).

Conclusions

The protocol caused significant changes in pain-free MMO, self-reported pain, and functionality of the stomatognathic system in subjects with myofascial TMD, regardless of joint involvement. Even though these differences are statistically significant, their clinical relevance is still questionable.

Head Immobilization can Impair Jaw Function

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.

Head Movements during Chewing: Relation to Size and Texture of Bolus

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.

Does induced masseter muscle pain affect integrated jaw-neck movements similarly in men and women?

Normal jaw opening-closing involves simultaneous jaw and head-neck movements. We previously showed that, in men, integrated jaw-neck movements during jaw function are altered by induced masseter muscle pain. The aim of this study was to investigate possible sex-related differences in integrated jaw-neck movements following experimental masseter muscle pain. We evaluated head-neck and jaw movements in 22 healthy women and 16 healthy men in a jaw opening-closing task. The participants performed one control trial and one trial with masseter muscle pain induced by injection of hypertonic saline. Jaw and head movements were registered using a three-dimensional optoelectronic recording system. There were no significant sex-related differences in jaw and head movement amplitudes. Head movement amplitudes were significantly greater in the pain trials for both men and women. The proportional involvement of the neck motor system during jaw movements increased in pain trials for 13 of 16 men and for 18 of 22 women. Thus, acute pain may alter integrated jaw-neck movements, although, given the similarities between men and women, this interaction between acute pain and motor behaviour does not explain sex differences in musculoskeletal pain in the jaw and neck regions.

Natural mediotrusive contact: does it affect the masticatory and neck EMG activity during tooth grinding?

OBJECTIVES

There is scarce knowledge regarding the influence of a natural mediotrusive contact on mandibular and cervical muscular activity. The purpose of this study was to analyze the EMG activity of the anterior temporalis (AT) and sternocleidomastoid (SCM) muscles during awake grinding in healthy subjects with or without a natural mediotrusive occlusal contact.

METHOD

Fifteen subjects with natural mediotrusive occlusal contact (Group 1) and 15 subjects without natural mediotrusive occlusal contact (Group 2) participated. Bilateral surface EMG activity of AT and SCM muscles was recorded during unilateral eccentric or concentric tooth grinding tasks. EMG activity was normalized against the activity recorded during maximal voluntary clenching in intercuspal position (IP) for AT muscles and during maximal intentional isometric head-neck rotation to each side, for SCM muscles.

RESULTS

EMG activity of AT and SCM muscles showed no statistical difference between groups. EMG activity of AT muscle was higher in the working side (WS) than in the non-WS (NWS) in Group 1 during concentric grinding (0.492 vs 0.331, p = 0.047), whereas no difference was observed in Group 2. EMG activity of SCM was similar between working and NWSs in both groups and tasks. Asymmetry indexes (AIs) were not significantly different between groups.

DISCUSSION

These findings in healthy subjects support the assumption that during awake tooth grinding, central nerve control predominates over peripheral inputs, and reinforce the idea of a functional link between the motor-neuron pools that control jaw and neck muscles.

Automation and apps for clinical dental biomechanics

OBJECTIVES

The aim of this research summary is to introduce the current and ongoing work using smartphone video, tracking markers to measure musculoskeletal disorders of cranial and mandibular origin, and the potential significance of the technology to doctors and therapists.

METHOD

The MPA™ biomechanical measuring apps are in beta trials with various doctors and therapists. The technique requires substantial image processing and statistical analysis, best suited to server-side processing. A smartphone environment has enabled a virtual laboratory, which provides automated generation of graphics and in some cases automated interpretation. The system enables highly accurate real-time biomechanics studies using only a smartphone and tracking markers.

RESULT

Despite the technical challenges in setting up and testing of the virtual environment and with interpretation of clinical relevance, the trials have enabled a demonstration of real-time biomechanics studies. The technology has prompted a lot of discussion about the relevance of rapid assessment tools in clinical practice. It seems that a prior bias against motion tracking and its relevance is very strong with occlusion related use cases, yet there has been a general agreement about the use case for cranial movement tracking in managing complex issues related to the head, neck, and TMJ.

DISCUSSION

Measurement of cranial and mandibular functions using a smartphone video as the input have been investigated. Ongoing research will depend upon doctors and therapists to provide feedback as to which uses are considered clinically relevant.

Diadococinesia oral e função mastigatória em idosos saudáveis

Objetivo Relacionar os achados da diadococinesia (DDC) oral com a função mastigatória em idosos saudáveis.Métodos Análise de prontuários e arquivos de imagens de 35 idosos saudáveis, entre 60 e 74 anos de idade. Considerou-se o tipo mastigatório e outros comportamentos associados à mastigação de uma fatia de pão francês de 1cm de espessura, análise da apreensão do alimento, formação do bolo alimentar e mensuração do tempo de mastigação, utilizando cronômetro. Para avaliação da DDC, foram analisadas as emissões silábicas "pa", "ta", "ka" e a trissílaba "pataka", quanto aos parâmetros fornecidos automaticamente pelo programaMotor Speech Profile Advanced -KayPentax®. Para correlação entre os aspectos qualitativos da função mastigatória e a DDC, foi realizada estatística pertinente.Resultados A análise estatística demonstrou correlação entre o tempo mastigatório e os parâmetros coeficiente de variação do pico da intensidade da sílaba ‘'ta'' e perturbações do período da sílaba ‘'ka'', indicando instabilidade da DDC. Para o tipo mastigatório, apreensão e formação do bolo alimentar não houve correlação com os dados da DDC oral.Conclusão A DDC oral correlacionou-se com o tempo mastigatório em idosos saudáveis, evidenciando que, quanto maior a instabilidade na repetição dos movimentos de ponta e dorso de língua durante a produção articulatória, maior o tempo necessário para a preparação do alimento para a deglutição.

Manual therapy for the management of pain and limited range of motion in subjects with signs and symptoms of temporomandibular disorder: a systematic review of randomised controlled trials

There is a lack of knowledge about the effectiveness of manual therapy (MT) on subjects with temporomandibular disorders (TMD). The aim of this systematic review is to synthetise evidence regarding the isolated effect of MT in improving maximum mouth opening (MMO) and pain in subjects with signs and symptoms of TMD. MEDLINE(®) , Cochrane, Web of Science, SciELO and EMBASE(™) electronic databases were consulted, searching for randomised controlled trials applying MT for TMD compared to other intervention, no intervention or placebo. Two authors independently extracted data, PEDro scale was used to assess risk of bias, and GRADE (Grading of Recommendations Assessment, Development and Evaluation) was applied to synthetise overall quality of the body of evidence. Treatment effect size was calculated for pain, MMO and pressure pain threshold (PPT). Eight trials were included, seven of high methodological quality. Myofascial release and massage techniques applied on the masticatory muscles are more effective than control (low to moderate evidence) but as effective as toxin botulinum injections (moderate evidence). Upper cervical spine thrust manipulation or mobilisation techniques are more effective than control (low to high evidence), while thoracic manipulations are not. There is moderate-to-high evidence that MT techniques protocols are effective. The methodological heterogeneity across trials protocols frequently contributed to decrease quality of evidence. In conclusion, there is widely varying evidence that MT improves pain, MMO and PPT in subjects with TMD signs and symptoms, depending on the technique. Further studies should consider using standardised evaluations and better study designs to strengthen clinical relevance.

Effect of natural mediotrusive contact on electromyographic activity of jaw and cervical muscles during chewing

OBJECTIVE

This study evaluated the effect of a natural mediotrusive contact on the electromyographic (EMG) activity of the anterior temporalis and sternocleidomastoid muscles during chewing in healthy subjects.

MATERIALS AND METHODS

The study sample included two groups of 15 subjects each (Group 1: with natural mediotrusive contact; Group 2: without natural mediotrusive contact). Bilateral surface EMG activity was recorded on anterior temporalis and sternocleidomastoid muscles during unilateral chewing of a half cookie and unilateral chewing of a piece of apple. Anterior temporalis and sternocleidomastoid muscle activity was normalized against activity recorded during maximal voluntary clenching in intercuspal position and maximal intentional isometric head-neck rotation to each side, respectively. The partial and total asymmetry indexes were also calculated. Data were analyzed using Mann-Whitney, Wilcoxon and unpaired t-test.

RESULTS

EMG activity of anterior temporalis and sternocleidomastoid muscles showed no significant difference between the groups. EMG activity of anterior temporalis was similar between working and non-working sides during chewing in both groups. EMG activity of sternocleidomastoid muscle was higher in the working side than in the non-working side in Group 2 subjects. Asymmetry indexes were not significantly different between groups.

CONCLUSIONS

The similar EMG pattern and asymmetry indexes observed suggest the predominance of central nervous control over peripheral inputs on anterior temporalis and sternocleidomastoid motor neuron pools.

Masticatory sensory-motor changes after an experimental chewing test influenced by pain catastrophizing and neck-pain-related disability in patients with headache attributed to temporomandibular disorders

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.

The effects of mouth opening on changes in the thickness of deep cervical flexors in normal adults

[Purpose] The purpose of this study was to identify changes in the thickness of the deep cervical flexors (DCFs) according to the degree of mouth opening (MO) in normal adults. [Subjects] The study’s subjects were 50 normal adults (30 men, 20 women). [Methods] Ultrasound was used to obtain images of muscles, and the NIH ImageJ software was used to measure the thickness of each muscle. [Results] An increase in MO resulted in a corresponding increase in the thickness of the DCFs, and in isometric exercises (IEs), the thickness of the DCFs further increased during MO. [Conclusion] During MO, the thickness of the DCFs increased. This may be due to correlations between mandibular movements and DCFs. Therefore, the results are likely to be utilized as new clinical research data.

Intra-rater and Inter-rater Reliability of Mandibular Range of Motion Measures Considering a Neutral Craniocervical Position

[Purpose] The aim of this study was to determine the inter-rater and intra-rater reliability of the mandibular range of motion (ROM) considering the neutral craniocervical position when performing the measurements. [Subjects and Methods] The sample consisted of 50 asymptomatic subjects. Two raters measured four mandibular ROMs (maximal mouth opening (MMO), laterals, and protrusion) using the craniomandibular scale. Subjects alternated between raters, receiving two complete trials per day, two days apart. Intra- and inter-rater reliability was determined using intra-class correlation coefficients (ICCs). Bland-Altman analysis was used to assess reliability, bias, and variability. Finally, the standard error of measurement (SEM) and minimal detectable change (MDC) were analyzed to measure responsiveness. [Results] Reliability was good for MMO (inter-rater, ICC= 0.95−0.96; intra-rater, ICC= 0.95−0.96) and for protrusion (inter-rater, ICC= 0.92−0.94; intra-rater, ICC= 0.93−0.96). Reliability was moderate for lateral excursions. The MMO and protrusion SEM ranged from 0.74 to 0.82 mm and from 0.29 to 0.49 mm, while the MDCs ranged from 1.73 to 1.91 mm and from 0.69 to 0.14 mm respectively. The analysis showed no random or systematic error, suggesting that effect learning did not affect reliability. [Conclusion] A standardized protocol for assessment of mandibular ROM in a neutral craniocervical position obtained good inter- and intra-rater reliability for MMO and protrusion and moderate inter- and intra-rater reliability for lateral excursions.

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

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

Effect of facial massage on static balance in individuals with temporomandibular disorder - a pilot study

Introduction

The influence of the neuromuscular system on the cervical region and mastication is directly associated with mandibular movements and neck posture. Normal occlusal homeostasis depends on complex sensory feedback mechanisms of the periodontal ligament, temporomandibular joint and other structures of the stomatognathic system. This feedback serves as a regulatory mechanism that helps determine the force and nature of muscle contractions. Alterations in the muscles of mastication, neck muscles, and occlusal characteristics constitute causal factors of imbalances in the postural muscle chains, leading to alterations in the center of pressure (CoP) of the feet. Thus, therapies that seek occlusal reestablishment, such as muscle relaxation techniques, may lead to a restructuring of the global equilibrium of the neuromuscular system and an improvement in body posture.

Purpose

The aim of the present pilot study was to investigate the immediate effect of facial massage on the CoP in the anteroposterior (CoP_AP) and mediolateral (CoP_ML) directions in individuals with temporomandibular disorder (TMD).

Methods

Twenty individuals with a diagnosis of TMD based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were submitted to a facial massage technique. CoP_AP and CoP_ML were evaluated using a force plate. Evaluations were performed under two visual conditions (eyes open and eyes closed) prior to resting in dorsal decubitus (baseline), after 10 minutes of rest (premassage) and after the administration of the massage technique (postmassage).

Results

No significant differences were found regarding CoP_AP velocity with eyes open or the following aspects under either visual condition (eyes open or closed): CoP_ML velocity, RMS of CoP_AP, RMS of CoP_ML, and sway area. The only significant difference was found for mean CoP_AP velocity with eyes closed.

Conclusions

While the results of the present study demonstrate the reliability of the reproduction of the data, facial massage had no immediate influence on postural control in individuals with TMD.

Effect of mandibular mobilization on electromyographic signals in muscles of mastication and static balance in individuals with temporomandibular disorder: study protocol for a randomized controlled trial

BACKGROUND

The stomatognathic system and dysfunction in this system may be related to postural control. The proposal of the present study is to assess the effect of mandibular mobilization in individuals with temporomandibular disorder using surface electromyography of the muscles of mastication and stabilometric variables.

METHODS/DESIGN

A randomized, controlled, blind, clinical trial will be carried out, with the participants divided into three groups: 1) facial massage therapy (control group), 2) nonspecific mandibular mobilization and 3) specific mandibular mobilization. All groups will be assessed before and after treatment using the Research Diagnostic Criteria for Temporomandibular Disorders, surface electromyography of the masseter and temporal muscles and stabilometry. This study is registered with the Brazilian Registry of Clinical Trials (RBR9x8ssz).

DISCUSSION

A large number of studies have employed surface electromyography to investigate the function/dysfunction of the muscles of mastication and associations with signs and symptoms of temporomandibular disorders. However, it has not yet been determined whether stabilometric variables offer adequate reliability in patients with this disorder. The results of the proposed study will help determine whether specific and/or nonspecific mandibular mobilization exerts an effect on the muscles of mastication and postural control. Moreover, if an effect is detected, the methodology defined in the proposed study will allow identifying whether the effect is local (found only in the muscles of mastication), global (found only in postural control) or generalized.

Experimental masseter muscle pain alters jaw-neck motor strategy

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Botulinum toxin type A combined with cervical spine manual therapy for masseteric hypertrophy in a patient with Alzheimer-type dementia: a case report

OBJECTIVE

The purpose of this case study is to present the findings of combining botulinum toxin type A (BoNT-A) and cervical spine manual therapy to address masseter muscle spasticity in a patient with Alzheimer-type dementia.

CASE REPORT

A 78-year-old woman with bilateral spasticity of the masseteric regions for 2 years was referred for physiotherapy. She had trismus and bruxism, and could neither close nor open her mouth normally; thus, she was unable to be fed orally in a normal manner.

INTERVENTION AND OUTCOME

The patient underwent combined treatment with BoNT-A and cervical spine manual therapy. A medical physician (neurologist) performed the BoNT-A injections into 2 points at the center of the lower third of the masseter muscle. A physical therapist performed manual therapy interventions targeted at the cervical spine. Manual therapy started the day after the BoNT-A injection and continued for 5 sessions per week for a total period of 2 weeks. Clinical outcomes were measured including spasticity (Modified Ashworth Scale), functionality (Barthel Index), and jaw opening. Outcomes were conducted at baseline, 2 weeks after treatment, and at 2-month follow-up session after finishing the treatment. The patient improved in all of the outcomes at the end of treatment, and these results were maintained during the follow-up. After treatment, the patient was able to feed with minimal caregiver dependency because oral feeding was possible.

CONCLUSION

The patient in this study responded positively to a combination of BoNT-A and manual therapy, resulting in decreased masseter muscles spasticity and improved trismus and bruxism.