Left Masseter Muscles Research Articles

Comparison of the Cone Beam Computed Tomography-Based Analysis of the Masseter Muscle Between Epilepsy Patients and Healthy Subjects.

It is important to investigate the changes in the masseter muscle, one of the chewing muscles, in epilepsy patients and to determine whether epilepsy can be effectively predicted on muscle. The aim of this study is to measure masseter muscle thickness, circumference and cross-sectional area in individuals with epilepsy and healthy individuals. This study was performed with 128 individuals (64 epilepsy patients and 64 healthy subjects) aged between 18 to 59 years. The mean cross-sectional area, thickness and circumference determined by measuring both of the masseter muscles were using cone beam computed tomography. The mean right masseter muscle cross-sectional area varied across age groups in epilepsy individuals (P=0.020). Significant differences were observed in the right masseter muscle circumference among age groups in epilepsy individuals (P=0.003). Significant differences were observed in the mean among age groups in epilepsy individuals (P=0.004). Statistically significant differences were observed in the mean right masseter muscle cross-sectional area between sexes in healthy individuals (P<0.001). Similarly, significant differences were observed in the mean right masseter muscle thickness between sexes in healthy individuals (P<0.001). Significant differences were observed in the mean left masseter muscle cross-sectional area between sexes in healthy individuals (P<0.001). Although jaw joint's muscular dislocations are common, the masseter muscle, which has a very strong function in masticatory movements, is very important in terms of location, neighbourhood and clinical aspects. For this reason, our study examining the masseter muscle morphometric measurements in the epileptic and healthy population using cone beam computed tomography provides important information and normative data.

Acute effects of motor imagery interventions and physical exercise on tongue strength and pain in healthy adults: a randomized, crossover trial

BackgroundMotor imagery (MI) has increasingly been used in physiotherapy. Oral rehabilitation may be a potential application area for MI. The aim of this study is to investigate the acute effects of orofacial and tongue muscle strengthening exercises in the form of physical exercise and motor imagery on pain and tongue strength in healthy adults.Thirty asymptomatic adults were included in this trial. MI skills were evaluated using the Movement Imagery Questionnaire-Revised and the mental chronometer. The pain and strength were assessed using an algometer and a tongue pressure device. Following the baseline evaluations, three interventions: physical exercise, kinesthetic motor imagery, and visual motor imagery, were applied randomly on different days. Pain and tongue strength were re-evaluated immediately after the interventions.ResultsThe physical exercise program did not significantly improve pain and tongue strength (p > 0.05). Following the kinesthetic MI training, a significant increase was detected (p = 0.016, d = 0.51) in the left masseter muscle pain threshold. Visual MI training resulted in improvements in anterior tongue strength (p = 0.002, d = 0.66) and left masseter muscle pain (p = 0.024, d = 0.40).ConclusionsThe present study suggests that different motor imagery strategies may have different effects on tongue muscle strength and pain threshold in healthy adults.

Exploring botulinum toxin’s impact on masseter hypertrophy: a randomized, triple-blinded clinical trial

The present study aimed to assess the effectiveness and functional adverse effects of a single and multiple injections of botulinum toxin A (BoNT-A) for masseter hypertrophy (MH). Twenty-six women complaining about lower third facial enlargement due to MH, received 75 U of BoNT-A (abobotulinum toxin) in each masseter muscles. After 3 months, patients were randomly assigned to receive a second treatment session of Saline Solution: (G1; n = 11) or BoNT-A: (G2; n = 12). Muscle thickness (ultrasound), electrical activity (electromyography; EMG), masticatory performance, and subjective perception of MH were evaluated. Follow-up was performed at 1, 3 and 6 months. Muscle thickness, EMG activity, and masticatory performance were analyzed using ANOVA two-way and Sidak test as post-hoc. Masticatory performance was analyzed by the Friedman’s test and Mann–Whitney test. Regarding inter-groups comparisons, there was a significant decrease in the left masseter muscle thickness in the G2 group at the 6 month follow-up (p < 0.02). For EMG, significant differences were evident at the 6 month assessment, with higher masseter activity for G1 (p < 0.05). For masticatory performance, no significant differences were observed throughout the study (p > 0.05) and a higher improvement in subjective perception of MH was observed in the 1 month follow-up for G2 (p < 0.05). In conclusion, BoNT-A is effective for MH, however multiple injections cause functional adverse effects in masseter muscle.

APPLICATION OF BOTULINUM TOXIN IN CONSERVATIVE TREATMENT OF MASTICATORY MUSCLES DYSFUNCTION

The purpose of this paper is to describe the application of the botulinum toxin in diseases of the temporomandibular system of a muscular type such as masticatory hypertrophy, spasm, bruxism, and tension headaches of idiopathic etiology. The masticatory system is a complex apparatus with great adaptive capacity. Still, when that capacity is exceeded, functional disorders occur followed by a series of symptoms that depend on individual, local, and systemic etiological factors. Occlusal trauma exceeding the physiological limits of the teeth, periodontium, and TMJ leads to a series of functional disorders. Temporomandibular dysfunctions (TMD) are used to describe a large, heterogeneous group of diseases of the temporomandibular joint (TMJ) and its adjacent tissues and organs. Botulinum toxin type A, hemagglutinin complex with 500 IU (DISPORT Ipsen Biopharm, UK) was used for the therapy of muscle disorders like bruxism or night teeth clenching in female patient 26 years old. Depending on the dose that was applied to the targeted muscle, a complete or partial reduction in contraction occurs with reduced function and weakening of the muscle. Two weeks after applying the neuromodulator, the patient reported a reduction in pain and episodes of teeth grinding and clenching. Bilateral hypotrophy of left and right masseter muscles was noticeable after 2 months. We concluded that botulinum toxin could be used as an effective treatment for reducing nocturnal bruxism and myofascial pain in patients with bruxism.

The role of voltage-gated calcium channel α2δ-1 in the occurrence and development in myofascial orofacial pain

Patients who suffer from myofascial orofacial pain could affect their quality of life deeply. The pathogenesis of pain is still unclear. Our objective was to assess Whether Voltage-gated calcium channel α2δ-1(Cavα2δ-1) is related to myofascial orofacial pain. Rats were divided into the masseter tendon ligation group and the sham group. Compared with the sham group, the mechanical pain threshold of the masseter tendon ligation group was reduced on the 4th, 7th, 10th and 14th day after operation(P < 0.05). On the 14th day after operation, Cavα2δ-1 mRNA expression levels in trigeminal ganglion (TG) and the trigeminal spinal subnucleus caudalis and C1-C2 spinal cervical dorsal horn (Vc/C2) of the masseter tendon ligation group were increased (PTG=0.021, PVc/C2=0.012). Rats were divided into three groups. On the 4th day after ligating the superficial tendon of the left masseter muscle of the rats, 10 ul Cavα2δ-1 antisense oligonucleotide, 10 ul Cavα2δ-1 mismatched oligonucleotides and 10 ul normal saline was separately injected into the left masseter muscle of rats in Cavα2δ-1 antisense oligonucleotide group, Cavα2δ-1 mismatched oligonucleotides group and normal saline control group twice a day for 4 days. The mechanical pain threshold of the Cavα2δ-1 antisense oligonucleotides group was higher than Cavα2δ-1 mismatched oligonucleotides group on the 7th and 10th day after operation (P < 0.01). After PC12 cells were treated with lipopolysaccharide, Cavα2δ-1 mRNA expression level increased (P < 0.001). Cavα2δ-1 may be involved in the occurrence and development in myofascial orofacial pain.

Electromyography Analysis of the Masseter Muscle's Activity in the Management of Oral Submucous Fibrosis.

Introduction Oral submucous fibrosis (OSMF) is a persistent, collagen metabolic disorder distinguished by the presence of fibrosis of the connective tissue stroma in the oral mucosa with a higher malignant potential rate for oral cancer. This study aimed to analyze the utility of electromyography (EMG) as the prognostic assessment tool in the management of OSMF with conventional intralesional corticosteroid therapy. Materials and methods This study included 20 OSMF cases of age range 20 to 80 years without systemic comorbidities to assess pre-treatment and post-treatment changes with intralesional corticosteroid therapy as an intervention and to determine if it could be assessed using electromyographic study. Clinical and histopathological grading of OSMF was done. The five clinical parameters were evaluated for measuring treatment prognosis. Among them, mouth opening, tongue protrusion, and burning sensation assessments were quantitative parameters, and palpable fibrotic bands and mucosa colour were qualitative parameters. As OSMF involves changes in muscle plane in moderately advanced and advanced cases, EMG was used as an assessment tool for measuring muscle activity. Among the muscles of mastication, the masseterand temporalis were selected for evaluation. Twenty age and gender-matched healthy controls were required for this study as there are no standardized normal values for amplitude and onset of activity in muscle analysis. The EMG activity of the right and left temporalis and masseter muscles were recorded using surface electrodes and were correlated with five clinical assessment parameters. Results In the right masseter, the rest amplitude of 1.6010 µV of the OSMFwas statistically significant (p-value: 0.050) when compared with 4.1275 µV of the control. The clench amplitude of 133.370 µV of the OSMFwas statistically significant (p-value: 0.062) when compared with 94.310 µV of the control. In the left masseter, the rest amplitude of 1.6695 µV of the OSMFwas statistically significant (p-value 0.066) when compared with 2.5735 µV of the control. In the left masseter, the onset of muscle action of 62.670 ms of the OSMFwas statistically significant (p-value: 0.017) when compared with 131.835 ms of the control. The clench amplitude differences in the right masseter of 133.370 µV pre-treatment, and 102.775 µV post-treatment were statistically significant (p-value: 0.007). The clench amplitude in the left masseter of 102.535 µV pre-treatment, and 92.090 µV post-treatment were statistically significant (p-value: 0.036). The correlation was seen between tongue protrusion and rest amplitude in the right masseter in OSMF (r = 0.376, p-value: 0.023). Conclusion There was a correlation between tongue protrusion and rest amplitude in the right masseter muscle in OSMF patients before treatment. In the right and left masseter, during rest, the amplitude of the OSMF group was lesser than that of the control group. During clench, in the right masseter, the amplitude of the OSMF group was higher than that of the control group. During clench in the left masseter, the onset of muscle action was lesser in the OSMF group than in the control group. After treatment, there was a reduction in clench amplitude in OSMF patients from their pretreatment values signifying muscle relaxation and a better onset of muscle action.

Bichectomy Surgery and EMG Masticatory Muscles Function in Adult Women: A Longitudinal Study

Bichectomy Surgery and EMG Masticatory Muscles Function in Adult Women: A Longitudinal Study

Bioelectrical activity in temporalis and masseter muscles across different gnathic types

Relevance. Discrepancies in the bioelectrical activity of the masseter muscle were observed through surface electromyography analysis. Despite the availability of scientific literature on the morphological and anatomical variances in the mastication muscles and subcutaneous adipose tissue across different gnathic types, these differences are often overlooked in the interpretation of surface electromyography absolute values.Materials and methods. A clinical evaluation, including the measurement of craniofacial parameters and an electromyography study of the right and left temporalis (RTA and LTA) and masseter muscles (RM and LM), was conducted on 73 individuals aged 21 to 24. Subjects were categorized based on upper and lower face gnathic type indices into three groups of 10: Group 1 (brachyfacial type), Group 2 (mesofacial type), and Group 3 (dolichofacial type). The study compared the surface electromyography-derived IMPACT index and average amplitude values of the muscles across groups, alongside analyzing the correlation between electromyographic values and gnathic type indices (GPDu.f./t-t and GPDl.f./ko-ko), with statistically significant differences noted at p ≤ 0.017.Results. Differences in RM and LM parameters, and the IMPACT index during the "Maximal Voluntary Gnathic Clenching of the Jaws" (MVC) test were statistically significant among the groups. An increase in both the IMPACT index and average masseter muscle values was noted in dolichofacial subjects. Significant variations in LM values during the MVC test were observed between dolichofacial and mesofacial subjects. In the MVC test, groups 1 and 3 demonstrated a moderately strong positive correlation between the IMPACT index and GPDu.f./t-t and GPDl.f./ko-ko, while a strong positive correlation was identified between the RM parameter and GPDu.f./t-t and GPDl.f./ko-ko.Conclusion. In the MVC test, the RM and LM parameters, as well as the average IMPACT index, were notably higher in dolichofacial subjects compared to other groups. A direct correlation between the mean right masseter bioelectrical activity and the average IMPACT index with the upper and lower facial gnathic indices was observed in brachyfacial and dolichofacial subjects in the MVC test.

TOPOGRAPHIC AND ANATOMICAL PECULIARITIES OF THE LATERAL REGION OF THE HEAD IN HUMAN FETUSES

HEAD IN HUMAN FETUSESAbstract. In order to clarify the topographical and anatomical peculiarities and variant anatomy of the structures of the lateral region of the head in the fetal period of human ontogenesis, 24 specimens of human fetuses aged from 4 to 10 months of intrauterine development were studied using a complex of morphological research methods (anthropometry, macroscopy, computer tomography, morphometry, reconstruction). We found anatomical variants of the masseter and temporal muscles in human fetuses. Thus, in a 5-month-old fetus, separate muscle bundles were found, which went from the right masseter to the right temporal muscle. In a 6-month-old fetus, the deep part of the left masseter muscle was fused to the left temporal muscle. In human fetuses, the temporal fascia in the direction of the zygomatic arch splits into two layers, between which there are accumulations of adipose tissue. In late fetuses, a formed sub-aponeurotic fi brous space was found. At the end of the fetal period, a deep fi brous space is observed between the periosteum and the inner edge of the temporal muscle. The cellular spaces of the temporal area in front are connected with the buccal fat pad, which creates the prerequisites for the spread of infl ammatory processes. The topographic and anatomical features of the temporal region of human fetuses are: weak development of the temporal muscle and small depth of the temporal fossa – in the middle part from 3.0 to 6.0 mm (depending on the age of the fetus); weakly developed tendinous part of the temporal muscle, which does not reach the temporal line of the parietal bone. The bony base of the temporal area is represented by the squamous part of the temporal bone, the greater wing of the sphenoid bone, part of the parietal and frontal bones, on the inner surface of which arterial grooves and impressions of cerebral gyri are hardly visible, and sometimes not at all clear or absent. Anatomical variants of the structure of the temporal and masticatory muscles, as well as the temporal fascia, can cause complications and errors during the diagnosis and surgical treatment of infl ammatory processes in the postnatal period of human ontogenesis.

ANALYSIS OF THE BIOELECTRICAL ACTIVITY OF THE MASTICATORY MUSCLES, DEFINED ACCORDING TO BERNOULLI'S PRINCIPLE AS "STRONG" OR "FAST", FOR THE PREDICTION OF PATHOLOGICAL TOOTH ABRASION (ACCORDING TO MAGNETIC RESONANCE IMAGING AND ELECTROMYOGRAPHIC STUDIES)

Pathological abrasion is a well-known disease, but it is topical issue of hard dental tissues. The principle of D. Bernoulli and its numerical expression in the form of the coefficient “k” were used. It is calculated by the formula , where k is the calculated coefficient; l is the length of the muscle in this case, the masseter separately on the right and left; s is the cross-sectional area of the muscle. The masseter muscles' length, width, and thickness were determined using SIEMENS MAGNETOM Skyra 3T magnetic resonance imager, 2018.&#x0D; The classical method was used for the electromyographic study of the masseter muscles. We analysed 64 MRI scan results, of which 15 were control subjects with intact dentitions, and 49 were patients with varying degrees of tooth abrasion. After determining the physical parameters as length, width, and thickness of the masseter muscles on the right and left sides, the cross-sectional area of the muscles was determined and the author's coefficient of the numerical expression of the Bernoulli principle for each masseter was proposed.&#x0D; Electromyograms of the masseter muscles in the mode of free chewing were recorded for all subjects with subsequent software analysis. Extrapolation of the obtained coefficients of the numerical expression of the Bernoulli principle of the left and right masseter muscles to the values of quantitative and qualitative indicators of electromyograms of the same muscles revealed a direct dependence of the bioelectrical activity of muscles on the ratio of muscle length to cross-sectional area. Higher values of this coefficient correspond to higher values of bioelectrical bursts of muscle activity, faster contraction and relaxation, shorter chewing time, and longer resting time of the muscle, which is a sign of the biomechanical property "speed". Masseter muscles with such properties are observed in individuals without pathological tooth abrasion. In the groups of patients with pathological tooth abrasion, a decrease in the ratio of the length of the masseter to its crosssectional area is observed in proportion to the increase in the severity of the pathological process. The amplitude of muscle bioelectrical activity bursts decreases, the speed of excitation and relaxation processes decreases, the chewing time is prolonged, and the resting time is reduced, which indicates that the muscle acquires the biomechanical property of "strength". "Fast" masseter muscles do not cause pathological tooth abrasion, while "strong" muscles contribute to the development of pathological tooth abrasion. Employing both Bernoulli's principle and MRI studies on the muscles responsible for mandibular movements will enable a comprehensive investigation into the progression of localized pathological tooth abrasion and provide a more intricate understanding of the muscles' impact on the development of dentoalveolar anomalies.

Longitudinal Study Involving Obesity in Women and Bariatric Surgery: An Electromyographic Approach to the Masseter and Temporal Muscles.

This longitudinal study was aimed to evaluate the electromyographic activity (EMG) of the masticatory muscles during mandibular tasks in women with grade II and III obesity, who were eligible for bariatric surgery. Twenty-one patients were followed up for 3 and 6 months after the Roux-en-Y gastric bypass. The EMG included analyses of the masseter and temporalis muscles during rest, right and left laterality, protrusion, and dental clenching at maximal voluntary contraction with and without parafilm. Data were tabulated and submitted for statistical analysis using the repeated measures test (P&lt;0.05) with the Bonferroni post-test. Significant differences were observed between the right temporal muscle during maximal voluntary contraction (P=0.003) and maximal voluntary contraction with Parafilm M for the right masseter (P=0.01), left masseter (P=0.03), right temporal (P=0.002), and left temporal (P=0.03) muscles. There was gradual decrease in the resting EMG of the masticatory muscles 6 months after surgery. There was an increase in the EMG of the muscles that are the most active in the neuroanatomical movements of laterality and protrusion 6 months after surgery. There was an increase in EMG in maximal voluntary contraction with and without parafilm, 3 and 6 months after surgery. This study suggests that women with severe obesity who underwent bariatric surgery had better functional results of the masticatory muscles 3 and 6 months after the procedure, which is an important parameter in surgical planning, functional recovery, and nutritional status.

Determination of masseter and temporal muscle thickness by ultrasound and muscle hardness by shear wave elastography in healthy adults as reference values.

The purpose of this study is to prospectively investigate the reference values of masseter and temporal muscle thicknesses by ultrasonography and muscle hardness values by shear wave elastography in healthy adults. The sample of the study consisted of a total of 160 healthy individuals aged between 18 and 59, including 80 women and 80 men. By examining the right and left sides of each participant, thickness and hardness values were obtained for 320 masseter muscles and 320 temporal muscles in total. The mean masseter muscle thickness was found to be 1.09 cm at rest and 1.40 cm in contraction. The mean temporal muscle thickness was found to be 0.88 cm at rest and 0.98 cm in contraction. The thickness values of the masseter and temporal muscles were significantly greater in the male participants than in the female participants (P < .001). While there were significant differences between the right and left masseter muscle thickness values at rest and in contraction, the values of the temporal muscles did not show a significant difference between the sides. While the resting hardness (rSWE) of the masseter muscle was transversally 6.91 kPa and longitudinally 8.49 kPa, these values in contraction (cSWE) were found, respectively, 31.40 and 35.65 kPa. The median temporal muscle hardness values were 8.84 kPa at rest and 20.43 kPa in contraction. Masseter and temporal muscle hardness values at rest and in contraction were significantly higher among the male participants compared to the female participants (P < .001). In this study, reference values for the thickness and hardness of the masseter and temporal muscles are reported. Knowing these values will make it easier to assess pain in the masseter and temporal muscles and determine the diagnosis and prognosis of masticatory muscle pathologies by allowing the morphological and functional assessments of these muscles, and it will identify ranges for reference parameters.

Masseter muscle volume measured by MRI correlated with cognitive function in a memory clinic

AbstractBackground“Oral frailty” which indicates a decline in oral function, has been focused on the fact that it can also affect cognitive function in the elderly population. Although Several studies have been attempted for establishing the utility of the cross‐sectional area or volume of masticatory muscles as objective indices reflecting oral frailty, no report has examined the relationship between masticatory muscles volume and cognitive function in detail. In this study, we aimed to clarify the relationship between size of masseter muscle, one of major masticatory muscles, and cognitive function in the elderly.MethodA total of 349 subjects (mean age 77.3 +/‐ 9.2 years, 126 males and 223 females, 58 with subjective cognitive impairment, 88 with mild cognitive impairment, and 203 with dementia), who visited the Memory clinic of Tohoku University Hospital with a chief complaint of forgetfulness by March 2018 were included. Using 3D T1‐weighted images acquired on a 3‐Tesla MRI system, the bilateral masseter muscle cross‐sectional area was automatically calculated for all subjects using a custom deep‐learning image‐processing model trained on a subset of subjects to identify the relevant muscles and consistent section. Then, partial correlations with the MMSE score were conducted, adjusting for age and gender.ResultThe mean left and right masseter muscle cross‐sectional area are 399.3±84.7mm2 in subjective cognitive impairment, 387.9±106.5 mm2 in mild cognitive impairment, and 355.1±88.4 mm2 in dementia, respectively (p &lt; 0.01). Adjusted for age and sex, they showed a significant correlation with MMSE (R = 0.151, p &lt; 0.01). For post‐hoc stratified analysis, there was a significant correlation between mean masseter muscle cross‐sectional area and MMSE with female patients (R = 0.049, p &lt; 0.05), whereas no correlation with male patients after adjusted age (R = 0.025, p &gt; 0.05).ConclusionOur result revealed that the masseter muscle cross‐sectional area obtained from MRI may be related to cognitive function in the patients with complaint of forgetfulness. Therefore the masticatory function may reflect cognitive function in the elderly who are vulnerable in their memory, and the cross‐sectional area of masseter muscle based on MRI could be a potential indicator for predicting dementia risk.

Global Postural Exercise Program Versus Muscle Energy Technique on Management of Temporomandibular Joint Disorders

Objective: To compare between the effects of global postural exercise program against muscle energy technique on maximum pressure pain threshold, maximal mouth opening range of motion as well as quality of life on patients with temporomandibular joint disorders. Methods: 63 patients having temporomandibular disorders were randomized into three groups; Group (A) were given global postural exercise program in addition to conventional therapy (in the form of LASER and hot packs), Group (B) were given muscle energy technique as well as traditional therapy and the Group (C) control were given traditional therapy only. All patients were examined by the pressure algometer, paquimeter and Arabic version of Oral health impact profile 14 questionnaire as well as the duration of treatment were 6 weeks. Results: there were no significant statistical differences revealed pretreatment for all variables, Mmaximal mouth opening range of motion, quality of life scale, as well as pain) as in mouth opening (P=0.130), OHIP-14 (P=0.642), right temporalis muscles (P=0.384), left temporalis muscles (P=0.930), right masseter muscles (P=0.790), left masseter muscles (P=0.064), right trapezius muscle (P=0.403), and left trapezius muscle (P=0.058) among groups where (P&gt;0.05). While after-treatment and follow up , there were significant statistical differences were P value was (P&lt;0.05), in mouth opening (P=0.0001 and P=0.0001, respectively), OHIP-14 (P=0.0001 and P=0.0001, respectively), right temporalis muscles (P=0.035 and P=0.020, respectively), left temporalis muscles (P=0.0001 and P=0.0001, respectively), right masseter muscles (P=0.001 and P=0.0001, respectively), left masseter muscles (P=0.004 and P=0.035, respectively), right trapezius muscle (P=0.0001 and P=0.0001, respectively), and left trapezius muscle (P=0.031 and P=0.001, respectively) between groups. Conclusion: Both Muscle energy technique and global postural exercise program improved mouth opening, pressure pain threshold, as well as quality of life in temporomandibular joint disorders patients, with the superiority of muscle energy technique over global postural exercise program.

Synchronous Muscle Synergy Evaluation of Jaw Muscle Activities during Chewing at Different Speeds, a Preliminary Study.

Human mastication is a complex and rhythmic biomechanical process regulated by the central nervous system (CNS). Muscle synergies are a group of motor primitives that the CNS may combine to simplify motor control in human movement. This study aimed to apply the non-negative matrix factorization approach to examine the coordination of the masticatory muscles on both sides during chewing. Ten healthy individuals were asked to chew gum at different speeds while their muscle activity was measured using surface electromyography of the right and left masseter and temporalis muscles. Regardless of the chewing speed, two main muscle synergies explained most of the muscle activity variation, accounting for over 98% of the changes in muscle patterns (variance accounted for >98%). The first synergy contained the chewing side masseter muscle information, and the second synergy provided information on bilateral temporalis muscles during the jaw closing. Furthermore, there was robust consistency and high degrees of similarity among the sets of muscle synergy information across different rate conditions and participants. These novel findings in healthy participants supported the hypothesis that all participants in various chewing speed conditions apply the same motor control strategies for chewing. Furthermore, these outcomes can be utilized to design rehabilitation approaches such as biofeedback therapy for mastication disorders.

Neuromuscular control of masticatory muscles in people with intellectual disability, middle-aged adults and older adults.

Motor control issues are common for people with intellectual disabilities (PWID), resulting in difficulties with basic activities of daily living, including eating. Mastication, which is crucial for digestion and overall health, is poorly understood in this population. PWID shows frailty similar to older people, highlighting the importance of comparing masticatory motor control with older adults. This study compared the neuromuscular control of the masticatory muscles in middle-aged, PWID and older adults. A cross-sectional analytical design was used. During the mastication task of a carrot piece (2cm in diameter and weighing 0.5g), surface electromyography was used to record muscle activity patterns from the right and left masseter and temporalis muscles. Principal component analysis (PCA) was used to assess neuromuscular control. A z-score normalisation of the first component's variance from PCA to identify those individuals with altered neuromuscular control. A mixed ANOVA was performed to assess the interaction between principal components, groups and body composition. Thirty PWIDs (aged 35-55years), middle-aged adults and 32 older adults were recruited. PWID and older adults showed decreased neuromuscular control of the masticatory muscles compared to middle-aged control adults (P<0.05). PWID had the highest proportion of individuals with altered neuromuscular control of the masticatory muscle (53%) compared to older adults (19%) and middle-aged adults (0%) (P<0.05). Our results indicate that PWID and older adults have reduced neuromuscular control compared to middle-aged adults. Notably, a significant proportion of the PWID showed altered masticatory muscle control compared to older adults. Further research is needed to explore the potential benefits of masticatory muscle training for PWID.

Cervical Impairments in Subjects with Chronic Migraine: An Observational Study.

The aim of this investigation was to compare the thickness of the deep local muscles in the neck region, as well as local and widespread sensitivity and functionality, between individuals with migraine and healthy control subjects. An observational study was carried out in accordance with the STROBE statements. The flexor longus colli and multifidus, two neck-stabilizing muscles, were measured using B-mode ultrasound imaging. The upper trapezius, masseter, temporalis, anterior tibialis, and median nerve all underwent bilateral pressure-pain threshold (PPT) assessments. The statistical program SPSS 29.0 was used to implement the Mann-Whitney U test and Chi-squared test. Spearman Rho was utilized to establish the correlations between the variables. Sixty participants were enrolled in the study. The subjects, who were matched in terms of age, gender, and body mass index (BMI), were equally divided into migraine and control groups. No significant differences between the groups were found in the multifidus CSA regarding both sides at rest (right: p = 0.625; left: p = 0.203). However, in contraction, the multifidus CSA showed a significant decrease on the left side in the patients with migraine compared to the controls (p = 0.032), but no significant differences were found in the right multifidus CSA in contraction between the two groups (p = 0.270). In comparison to the healthy volunteers, the migraine sufferers showed a substantial reduction in CSA in the longus colli muscle on both the left side (p = 0.001) and the right side at rest (p = 0.003), as well as in the CSA of the left longus colli in contraction (p < 0.001). Furthermore, the migraine patients showed significantly lower PPT compared to the healthy subjects in local and widespread areas bilaterally. All the parameters revealed higher sensitization in the migraine group in the following areas: the right and left temporal regions (p < 0.001), the right and left upper trapezius (p < 0.001 and p < 0.01, respectively), the right and left masseter muscles (p < 0.01), the right and left median nerves (p < 0.001 and p < 0.01, respectively), and the right and left anterior tibialis muscles (p < 0.001). In terms of the craniocervical flexion test (CCFT), the migraine patients demonstrated significantly lower values than the healthy subjects (p < 0.001). A moderate positive correlation was noted between the PPT in the right temporalis muscle and that in the left longus colli and the right multifidus in contraction. The PPT in the right temporalis muscle also exhibited a positive correlation with the CCFT, although this correlation was low. Between the PPT values, the upper trapezius on both sides showed a moderate positive correlation with the median nerve bilaterally. This research suggests that individuals with migraine may experience local and widespread pain sensitization. A decrease in functionality due to the low muscle endurance of the deep cervical muscles is also accompanied by low values of muscle thickness in contraction. These findings may help to select more accurate treatment approaches for patients with migraine.

Proposal of a Full Digital Workflow for a Bite Fork to Assess Mandibular Advancement during Drug-Induced Sleep Endoscopy (DISE) for Obstructive Sleep Apnea

(1) Background. Drug-induced sleep endoscopy (DISE) is currently regarded as the gold standard diagnostic procedure to assess the site(s) of upper airway collapse in subjects affected by Obstructive Sleep Apnea Syndrome (OSAS). During DISE, a jaw thrust maneuver is performed to advance the mandible and to predict the effectiveness of outcomes of treatment with mandibular advancement devices (MADs). However, the maneuver is not predictable and could be influenced by specific patients’ anatomical/functional conditions. The aim of this work is to propose a full-digital workflow for customizing an individual mandibular advancement fork, usable by otorhinolaryngologists during DISE. (2) Materials. Two patients with a diagnosis of mild-to-moderate OSAS (AHI ≥ 5 to ≤30/h of sleep) underwent orthodontic examination to verify the usability of the MAD. Intra-oral scans and registration were performed, including bite registration with 65% of mandibular advancement. The latter measurement was used as a reference to design a 3D-printed fork for DISE, as well as for the future MAD. Both patients underwent DISE in the operating room in the presence of an anesthesiologist, otolaryngologist, orthodontic specialist and neurophysiopathology technician. (3) Results. In the intraoperative polysomnography recording, during sleep, the presence of obstructive apnea was confirmed based on respiratory parameters (PNG1, PNG2, PNG3) with associated desaturation and increased muscle activities on PNG4 (mylohyoid muscle), EMG1 (right masseter muscle) and EMG2 (left masseter muscle). With the advancement fork in place, the immediate improvement effect on all respiratory parameters with normal saturation values and the complete suppression of masseter muscles were observed. Accordingly, both patients were considered potential good-responders to the MAD treatment. (4) Conclusions. The preliminary data shown are encouraging and would suggest that the fork represents a stable reference for the otorhinolaryngologist to evaluate the airway patency within the physiological range of movement. The efficiency of the work-flow from data registration to the DISE procedure and laboratory process represent two significant advantages that justify the integration of a digital system in the management of patients affected by OSAS.

Effect of Sustained Jaw Opening on Fatigue, Pressure Pain Sensations, and Stiffness in the Masticatory Muscles

Although the effects of sustained jaw-closing activities on somatosensory sensitivity and fatigue have been investigated, the effects of sustained jaw-opening activities on somatosensory sensitivity in the masticatory muscles remain unclear. Therefore, this study aimed to investigate the effects of sustained jaw opening（e.g. during dental treatment）on fatigue, pressure pain sensations, and stiffness in the masticatory muscles. A total of 35 healthy volunteers performed 30 minutes each of two jaw motor tasks, with a 1-week interval between tasks: unassisted jaw opening and jaw opening assisted by a mouth prop set at the right tooth. The pressure pain threshold（PPT）and muscle stiffness of the left masseter were measured before and after both jaw motor tasks（at 0 and 30 minutes）. Masticatory muscle fatigue was measured every 10 minutes（at 0, 10, 20, and 30 minutes）during each jaw motor task. No significant differences in the PPT were found between before and after the assisted jaw-opening task, but the PPT was significantly lower after compared with before unassisted jaw opening（P < 0.05）. No significant differences in left masseter muscle stiffness were found between any measurement point in either jaw motor task. Masticatory muscle fatigue was significantly higher after 10, 20, and 30 minutes of each jaw motor task compared with that at baseline（0 minutes）. However, no significant differences in masticatory muscle fatigue were found at any measurement point between both jaw motor tasks. The present results suggest that sustained jaw opening during dental treatment may affect pressure pain sensations in the masticatory muscles. In addition, masticatory muscle pain due to sustained jaw opening seems to be affected not only by jaw-opening but also jaw-closing muscle（masseter muscle）.

Electromyographic Analysis of Masticatory and Accessory Muscles in Subjects With Implant-Supported Fixed Prostheses: A Three-Arm Comparative Clinical Study.

Aim This study compares the electromyographic (EMG) activity of the masticatory and accessory muscles in patients with natural teeth and those wearing full-mouth fixed prostheses supported by implants. Method In this study, 30 subjects of 30-69 years performed static and dynamic EMG measurements of masticatory and accessory muscles (masseter, anterior temporalis, SCM, and anterior digastric) and were divided into three groups: Group 1 (G1, Control, Dentate), comprising 10 subjects with 14 or more natural teeth(30-51 years of age); Group 2 (G2, single arch implant-supported fixed prosthesis) composed of 10 patients with unilateral edentulism who were successfully rehabilitated with implant-supported fixed prostheses in the maxilla or mandible, restoring occlusion to 12-14 teeth per arch; (39-61 years of age); and Group 3 (G3, full mouth implant-supported fixed prosthesis) with10 subjects with completely edentulous arches with full mouth implant-supported fixed prosthesis with 12 occluding pairs of teeth (46-69 years of age). The left and right masseter, anterior temporalis, superior sagittal, and anterior digastric muscles were examined at rest, as well as maximum voluntary clenching (MVC), swallowing, and unilateral chewing. On muscle bellies, disposable, pre-gelled silver/silver chloride bipolar surface electrodes were parallel to muscle fibers. BIO-PAKeight® channels recorded electrical muscle activity (Bio-EMG III, BioResearch Associates, Inc. Brown Deer, WI). Results Full mouth embed upheld fixed prostheses patients had higher resting EMG activity than dentate and single curve implants. Full mouth embeds supported fixed prostheses and dentate patients had significantly different temporalis and digastric muscle mean EMG activity. Dentate people used their temporalis and masseter muscles more during the MVC than those with single-curve embedded upheld fixed prostheses limiting natural teeth or full-mouth implants. No event had the crucial item. Neck muscle differences were insignificant. All groups had higher SCM and digastric EMG activity during MVC than at rest. The single curve embed upheld fixed prosthesis group's temporalis and masseter muscles were significantly more active during gulping than the dentate and entire mouth groups. Single curve and entire mouth gulping SCM muscle EMG activity were similar. Digastric muscular EMG activity differed significantly between those with full-arch or partial-arch fixed prostheses and dentures. When instructed to bite one side, the masseter and temporalis front muscle mean EMG activity increased on the unrestricted side. Unilateral biting and temporalis muscle activation were comparable between groups. For the masseter muscle, the mean EMG was also higher on the functioning side, with no truly large differences between the three groups except for right-side biting when comparing the dentate and full mouth embed upheld fixed prosthesis groups and the single curve and full mouth groups. Conclusion The temporalis muscle activity difference was statistically significant in the full mouth implant-supported fixed prosthesis group.The three groups' static (clenching) sEMG analysis showed non-significant temporalis and masseter muscle activity increases. Full mouth swallowing increased digastric muscle activity. All three groups had similar unilateral chewing muscle activity except for the working side masseter muscle.