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Objective: The aim of the study was to determine how the electrical activity of the temporalis, masseter and sternocleidomastoid muscles differs in children with reduced transverse jaw dimension compared to children with normal occlusion., Design: It was a experimental study. Thirty-seven patients were included in the study. 18 in the study group received orthodontic treatment with removable appliances and 19 subjects were classified as normal occlusion subjects in the control group. A panoramic X-ray and digital intraoral scan were taken, followed by an surface electromyography of three muscle pairs (temporalis muscles, masseter muscles, sternocleidomastoid muscles) in resting position, while clenching and clenching on cotton rollers., Results: There was significantly greater activity in the experimental group than in the control group comparing muscles: temporalis muscles and masseter muscles in the resting position. Additionally, significantly greater activity of muscles in the control group was found during clenching. However, the asymmetry index of muscles indicates that there is significantly greater asymmetry of muscles activity in the experimental group. Compared to children with normal occlusion, children with a narrowed transverse dimension of the jaw have statistically significant differences in the bioelectrical activity of the temporalis, masseter and sternocleidomastoid muscles, as well as greater asymmetry in the bioelectrical voltage of the masseter muscles., Conclusions: Patients with reduced transverse dimension of the jaw are characterized by increased resting activity of the masticatory muscles and reduced functional activity of the masticatory muscles. These patients have increased asymmetry in the bioelectrical tension of the masticatory muscles., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Abstract: This study aimed to report clinical data on muscle pain in temporomandibular disorders using thermography, algometry, and surface electromyography (EMG). This was done to support or rule out the hypothesis that painful muscles are always related to muscular hyperactivity. This cross-sectional, analytical study included 50 participants who underwent clinical examination and evaluation of anterior temporal muscles and bilateral masseters using thermography, algometry, and EMG. The muscles with greater pain symptoms had hyporadiation and a lower temperature compared with both contralateral muscles and muscles in the asymptomatic group. There was no muscle hyperactivity at rest on EMG analysis; however, there was a greater capacity for muscle recruitment of these symptomatic muscles after a joint decompression test with cotton rolls, suggesting hypoactivity of the affected muscles in the symptomatic patient group. Muscle pain may be related to hypoactivity of the musculature when there is neurological inhibition of the recruitment of muscle fibers, and treatment must consider these neurophysiological alterations., Level of Evidence: Level IV., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 by Mutaz B. Habal, MD.)

Background: Temporomandibular Disorders (TMD) is the dysfunction of group of muscles and bones in the joint area, the main symptoms of TMD are the pain of the chewing muscles and (or) the temporomandibular joints, mandibular movement disorders and joint noise. This study was designed to explore the therapeutic effects following Individual Musculoskeletally Stable (IMS) position stabilization splint therapy for TMD patients using Fricton index, cone beam computed tomography (CBCT) and surface-Electromyogram (sEMG)., Methods: In this study, we enrolled 31 TMD patients (ranging from 18 to 26 years old, including 7 males and 24 females), first Fricton index was used to evaluate the clinical curative effect of TMD with the treatment of IMS stabilization splint; then CBCT was used to observe the TMJ condylar position changes of TMD before and after the treatment of IMS stabilization splint; finally sEMG was used to observe the changes of electromyography of anterior temporalis (AT) and masseter muscles (MM) of TMD before and after the treatment of IMS stabilization splint., Results: The course of treatment was 6-8 months, with an average of 7.6 months. After the IMS stabilization splint treatment, TMD symptoms relieved, especially in pain, mandibular movement disorder, but still slightly inferior in the treatment of joint noise. And there was a statistically significant difference in the anterior and inner joint space, the condyle had the tendency of moving forward and outward. AT presented reduction significantly of EMG value at rest position after treatment., Conclusions: IMS stabilization splint is a therapeutic reversible treatment for TMD, especially for pain and mandibular movement disorder; it produces effects of forward and outward condylar movement and elimination of the masticatory muscles antagonism., (© 2024. The Author(s).)

Background and Objectives: The aim was to compare the activity of the masseter muscles in children with different types of breathing. Materials and Methods: A cross-sectional study was conducted including patients aged 6-12 years with mixed dentition, who came for oral care at the Master's Degree in Pediatric Dentistry program at the Complutense University of Madrid (UCM), according to inclusion and exclusion criteria. The sample was divided into three groups: nasal breathers without dental alterations (control group), oral breathers with dental malocclusion, and oral breathers with previous orthodontic treatment. An electromyography was performed, and statistic methods were conducted with a 95% confidence to contrast hypothesis. Results: A total of 122 children were analyzed and distributed into three groups. The electrical muscle activity of masseters was significantly different between the study groups ( p < 0.001 for all comparisons). Pairwise comparisons revealed a significantly higher electrical muscle activity in the control group (nasal breathers) during chewing compared to both groups of oral breathers ( p < 0.001 for both comparisons). Orthodontic treatment decreased electrical muscle activity during isometric contraction in oral breathers compared to nasal breathers ( p < 0.001), but did not significantly affect electrical muscle activity during chewing. Higher decompensation values were obtained in oral breathers without previous orthodontic treatment compared the other study groups ( p < 0.001 for both comparisons), although electrical muscle activity values were similar in both groups of oral breathers ( p > 0.05 for both comparisons). Conclusions: Differences in electrical muscle activity between nasal and oral breathers can be confirmed. Oral breathers with and without orthodontic treatment showed lower electrical muscle activity of masseters during chewing than nasal breathers, while at isometric contraction, only oral breathers with previous orthodontic treatment showed lower electrical activity. Higher decompensation values were found in oral breathers without previous orthodontic treatment, in comparison to the control group and oral breathers with previous orthodontic treatment.

Background: Kinesio Taping (KT) is a non-invasive therapy commonly used in physiotherapy (PT). However, the available data on its effectiveness in patients with symptomatic temporomandibular disorders (TMD) remains scarce and contradictory., Objectives: The aim of the study was to evaluate the analgesic and myorelaxant effects of KT in TMD patients with limited mandibular mobility., Material and Methods: A single-blind randomized controlled trial was conducted among female patients aged 20-45 years with Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) group Ib, using a parallel group design and equal randomization (1:1). All patients underwent surface electromyography (sEMG) of the masseter muscle (MAS), pain intensity was assessed using a Numeric Rating Scale (NRS), and temporomandibular joint mobility was measured before and after 6 and 12 days of treatment. The Perceived Stress Scale (PSS-10) questionnaire was administered on the first and last days of treatment. Statistical analysis was performed using analysis of variance (ANOVA). Mauchly's sphericity test determined changes over time and between groups for variables with a normal distribution. Bonferroni's correction was used for post hoc multiple comparisons. Variables with a non-normal distribution were analyzed using the nparLD package and multiple comparison post hoc test, while correlations were assessed using Spearman's coefficient., Results: Each treatment had a significant effect on the bioelectrical sEMG parameters (p = 0.05). Kinesio Taping had a superior analgesic effect compared to the controls (p < 0.001). The combination of KT with therapeutic exercise (TE) proved to be a more effective therapy for improving the maximal mouth opening (MMO) and reducing perceived stress than monotherapy (p < 0.001). Minimally significant clinical differences were observed for sEMG, MMO and PSS-10 parameters after both therapies., Conclusions: Kinesio Taping combined with TE may be considered an effective complementary noninvasive treatment modality for TMD, either as a stand-alone or as part of the therapeutic process in patients experiencing pain and limited mandibular ROM. Additionally, the use of KT and TE was found to have a beneficial effect on perceived stress levels.

Diagnosis of bruxism is challenging because not all contractions of the masticatory muscles can be classified as bruxism. Conventional methods for sleep bruxism detection vary in effectiveness. Some provide objective data through EMG, ECG, or EEG; others, such as dental implants, are less accessible for daily practice. These methods have targeted the masseter as the key muscle for bruxism detection. However, it is important to consider that the temporalis muscle is also active during bruxism among masticatory muscles. Moreover, studies have predominantly examined sleep bruxism in the supine position, but other anatomical positions are also associated with sleep. In this research, we have collected EMG data to detect the maximum voluntary contraction of the temporalis and masseter muscles in three primary anatomical positions associated with sleep, i.e., supine and left and right lateral recumbent positions. A total of 10 time domain features were extracted, and six machine learning classifiers were compared, with random forest outperforming others. The models achieved better accuracies in the detection of sleep bruxism with the temporalis muscle. An accuracy of 93.33% was specifically found for the left lateral recumbent position among the specified anatomical positions. These results indicate a promising direction of machine learning in clinical applications, facilitating enhanced diagnosis and management of sleep bruxism.

It is commonly accepted that exposure to stress may cause overactivity in the orofacial muscles, leading to consistent muscle pain, which is the main symptom of temporomandibular disorders. The central neural mechanism underlying this process, however, remains unclear. The locus coeruleus is considered to play an important role in stress-related behavioral changes. Therefore, the present study was designed to examine the role of locus coeruleus neurons in masseter overactivity induced by stress. C57BL/6 mice were subjected to chronic restraint stress for 14 days to establish an animal model. The behavioral changes and the electromyography of the masseter muscle in mice were measured. The expression of Fos in locus coeruleus was observed by immunofluorescence staining to assess neuronal activation. A chemogenetic test was used to inhibit locus coeruleus neuronal activity, and the behavioral changes and electromyography of the masseter muscle were observed again. The results exhibited that chronic restraint stress could induce anxiety-like behavior, overactivity of the masseter muscle, and significant activation of locus coeruleus neurons in mice. Furthermore, inhibition of noradrenergic neuron activity within the locus coeruleus could alleviate stress-induced anxiety behavior and masseter muscle overactivity. Activation of noradrenergic neurons in locus coeruleus induced by stress may be one of the central regulatory mechanisms for stress-induced anxiety-like behaviors and overactivity of masseter muscles., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose: This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects., Methods: Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant., Results: There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups., Conclusions: The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.

Background: The etiology of sleep bruxism in obstructive sleep apnea (OSA) patients is not yet fully clarified. This prospective clinical study aimed to investigate the connection between probable sleep bruxism, electromyographic muscle tone, and respiratory sleep patterns recorded during polysomnography., Methods: 106 patients with OSA (74 males, 31 females, mean age: 56.1 ± 11.4 years) were divided into two groups (sleep bruxism: SB; no sleep bruxism: NSB). Probable SB were based on the AASM criteria: self-report of clenching/grinding, orofacial symptoms upon awakening, abnormal tooth wear and hypertrophy of the masseter muscle. Both groups underwent clinical examination for painful muscle symptoms aligned with Temporomandibular Disorders Diagnostic Criteria (DC/TMD), such as myalgia, myofascial pain, and headache attributed to temporomandibular disorder. Additionally, non-complaint positive muscle palpation and orofacial-related limitations (Jaw Functional Limited Scale-20: JFLS-20) were assessed. A one-night polysomnography with electromyographic masseter muscle tone (EMG) measurement was performed. Descriptive data, inter-group comparisons and multivariate logistic regression were calculated., Results: OSA patients had a 37.1% prevalence of SB. EMG muscle tone (N1-N3, REM; P = 0.001) and the number of hypopneas (P = 0.042) were significantly higher in the sleep bruxism group. While measures like apnea-hypopnea-index (AHI), respiratory-disturbance-index (RDI), apnea index (AI), hypopnea-index (HI), number of arousals, and heart rate (1/min) were elevated in sleep bruxers, the differences were not statistically significant. There was no difference in sleep efficiency (SE; P = 0.403). Non-complaint masseter muscle palpation (61.5%; P = 0.015) and myalgia (41%; P = 0.010) were significant higher in SB patients. Multivariate logistic regression showed a significant contribution of EMG muscle tone and JFLS-20 to bruxism risk., Conclusion: Increased EMG muscle tone and orofacial limitations can predict sleep bruxism in OSA patients. Besides, SB patients suffer more from sleep disorder breathing. Thus, sleep bruxism seems to be not only an oral health related problem in obstructive apnea. Consequently, interdisciplinary interventions are crucial for effectively treating these patients., Trial Registration: The study was approved by the Ethics Committee of Philipps-University Marburg (reg. no. 13/22-2022) and registered at the "German Clinical Trial Register, DRKS" (DRKS0002959)., (© 2024. The Author(s).)

Rheumatoid arthritis and osteoarthritis both affect the articular cartilage, and are characterized by signs and symptoms that can affect the functions of the human body. This cross-sectional observational study evaluated electromyographic activity in the masseter and temporalis muscles, molar bite force, and mandibular mobility in adult women with rheumatoid arthritis or osteoarthritis. A total of 42 women were distributed into 3 groups: rheumatoid arthritis group (ARG, n=14); osteoarthritis group (OAG, n=14); and a healthy control group (CG, n=14). Electromyography was used to evaluate mandibular tasks at rest, right and left laterality, protrusion, and dental clenching during maximum voluntary contraction, with and without parafilm, and a dynamometer was used to analyse the right and left molar bite forces. A digital caliper was used to measure the range of mandibular movement for maximum mouth opening, right and left laterality, and protrusion. Statistical analyses were performed, including analysis of variance and Tukey's test (P&lt;0.05). Electromyography showed no significant differences between the groups when evaluating the masticatory muscles during the mandibular tasks. Significant difference was observed between the ARG and CG, however, in the maximum right (P=0.007) and left (P=0.02) molar bite forces. Significant difference was observed in the maximum mouth opening of the ARG and OAG groups compared with that of the CG (P=0.009), suggesting that adult women with rheumatoid arthritis or osteoarthritis experience functional alterations in the stomatognathic system, particularly in molar bite force and maximum mouth opening.

Objective: Surface Electromyography of masticatory muscles (sEMG) is used as a tool to support diagnosis and treatment of Temporomandibular disorders (TMDs). The study aimed at examining jaw muscles pattern in individuals with temporomandibular joint disc displacement with reduction (TMJ/DDR). This sort of subjects was supposed to have a different muscular pattern compared to the control group., Materials and Methods: Sixty-four women with unilateral TMJ/DDR and forty TMD-free women underwent a sEMG assessment of masticatory muscles. Descriptive statistics were performed. Student T-Test assessed differences between the two groups. Statistical significance was set at ρ < 0.05., Result: The t-test showed statistically significant results only in BAR and SMI scores (ρ value < 0,0001). The other measurements did not differ between the two groups. BAR index values of all healthy subjects were within the reference range. Almost the entire TMJ/DDR group had BAR index out of reference range and anteriorly placed., Conclusion: Women with TMJ/DDR showed an altered recruitment of the jaw muscles, with significant difference between the activity of the couple of temporalis and the one of masseters, compared to the control group. A lower chewing efficiency was found in the DDR group compared to the control one.

Aim: The aim of this study was to evaluate the electrical activity of the masticatory muscles in children with a bilateral complete cleft lip and palate (BCCLP) and posterior crossbite as well as in noncleft subjects with no malocclusion. Another purpose of the study was to examine the possible factors associated with this muscle activity., Methods: The study included 52 children with mixed dentition and Class I occlusions (20 patients with nonsyndromic BCCLP and 32 subjects with no clefts). All the cleft patients had posterior crossbite. The surface electromyography (sEMG) was used to identify the electrical potentials of the temporalis and masseter muscles. The electromyographical (EMG) recordings were taken with a DAB-Bluetooth Instrument (zebris Medical GmbH, Germany) at rest and during maximum voluntary clenching (MVC). The relationships between muscle EMG activity and independent variables were identified through multivariate logistic regression analysis., Results: The EMG activity of the temporalis muscles at rest was significantly higher in BCCLP patients with malocclusion in comparison with the noncleft subjects with normal occlusion. During MVC, significantly lower electrical potentials of the temporalis and masseter muscles were observed in cleft patients compared to the noncleft group. The presence of BCCLP, unilateral posterior crossbites, increased vertical overlap, and increased overjet are factors strongly associated with higher temporalis muscle EMG activity at rest., Conclusion: The use of surface electromyography in imaging muscle function showed that children with BCCLP and posterior crossbite exhibited altered masticatory muscle potentials at rest and during clenching. The presence of unilateral posterior crossbites, increased vertical overlap, and increased overjet had a significant impact on temporalis muscle activity in cleft patients. This knowledge is important in the aspect of early and proper diagnosis and orthodontic treatment of malocclusions, thereby achieving correct occlusion and improvement in muscle function., Competing Interests: The authors declare that there are no conflicts of interest regarding the publication of this article., (Copyright © 2020 Liliana Szyszka-Sommerfeld et al.)

The aim of the present study was to evaluate intra-day (test) and inter-day (re-test) reliability of surface electromyography (sEMG) signals of the masseter and temporal muscles in patients with Down syndrome (DS). We determined the reliability of sEMG variables in 33 patients with DS. EMG signals were recorded at rest as well as during maximum voluntary clenching and maximum habitual intercuspation (MHI). The signals were analyzed considering the amplitude in the root mean square (RMS), mean frequency (MNF), median frequency (MDF) and approximate entropy (ApEn). The intraclass correlation (ICC 2,1 ) for the three trials recorded during MHI in the two sessions (test and retest) revealed excellent intra-session and inter-session reliability (ICC 2,1  = 0.76 to 0.97) for all sEMG variables and muscles. In the rest position, excellent reliability was found for RMS and ApEn (ICC 2,1  = 0.75 to 1.00) and good to excellent reliability was found for MDF and MNF (ICC 2,1  = 0.64 to 0.93). The intra-session (test) and inter-session (re-test) analyses demonstrated the reliability of nonlinear sEMG variables of the masticatory muscles in adults with Down Syndrome.

Hemifacial microsomia (HFM) is a malformation characterized by asymmetric facial growth with mandibular and muscular involvement. There are no reports focused on the functional status of the masticatory system of patients with HFM. The objective of this work evaluate bite force and electrical activity of masseter muscle in children with HFM, and compare them to healthy controls. A cross-sectional study was performed to compare bite force and electrical activity of masseter muscle between subjects with HFM and healthy children. Mean bite force (MBF) and surface electromyography (EMG) on maximum intercuspation (MIC) and rest position (RP) from both sides of the face were recorded. Comparative statistics between HFM patients and controls were performed using the Mann-Whitney test, Wilcoxon's signed rank test was used to compare the microsomic and healthy hemifaces. Twenty children with HFM and 10 controls were included, average age was 7.2 years (range 3-14). MBF did not show statistical significance between both groups. Surface EMG signal at MIC was significantly diminished when compared to the healthy side ( p  = .003) and to the control group ( p  = .016), this significance was also present at RP when comparing the affected and non-affected sides of the face ( p  < .01) but not against the controls ( p  = .08). This study showed that patients with HFM had diminished EMG values of the masseter muscle on the affected side, compared to healthy individuals, but bite force did not show significant alterations.

Objectives: The objective of this study was to evaluate the electromyographic fatigue of the masseter and temporalis muscles in individuals with and without osteoporosis., Methods: Median frequency of the initial, mid, and final periods of the electromyographic signal in the 33 subjects with osteoporosis (OG) and 33 subjects without osteoporosis [control (CG)] was analyzed., Results: OG showed a decrease in median frequency along the electromyographic signal, with a significant difference for the right masseter: initial vs. mid periods, initial vs. final periods; left masseter: initial vs. final periods; temporal (right and left): initial vs. mid periods, initial vs. final periods, and mid vs. final periods. Percentage comparison of median frequency between the initial and mid periods and between initial and final periods in the OG showed a significant difference in the masticatory muscles., Discussion: The findings suggest that osteoporosis is associated with changes in the function of masticatory muscles, especially when measured by electromyographic fatigue.

Objective: To assess the electromyographic activity of the masseter and temporal muscles in cleft patients who underwent 1-stage palate repair versus 2-stage palate repair., Methods: Thirty-two patients with nonsyndromic complete unilateral cleft lip and palate operated by 2 different protocols for palate repair, 1-stage (group 1, n = 16) versus 2-stage with delayed hard palate closure (group 2, n = 16) were available in the retrospective longitudinal study. Standardized electromyographic records of the masseter and anterior portion of temporal muscles were obtained with 2 repetitions during mastication and rest., Results: No statistically significant (all P > 0.05) differences were observed in the electromyographic data between the groups 1 and 2., Conclusion: There were similar electromyographic activity of masseter and temporal muscles during mastication and at rest after 1- and 2-stage palate closure.

Background: To evaluate the EMG activity and thickness of right masseter (RM), left masseter (LM), right temporal (RT) and left temporal (LT) muscles and bite force in children with temporomandibular disorders (TMD)., Material and Methods: Forty five children (mean age 8.8 years; 22 boys and 23 girls) were examined on the basis of the RDC/TMD and the Faces Pain Scale-Revised (FPS-R) was used to determine the level of severity of the signs and symptoms of TMD, resulting in four groups: GI - without TMD (n=10); GII - with mild TMD (n=18), GIII: with moderate TMD (n=12) and GIV: with severe TMD (n=5). The data of electromyographic activity, maximum bite force and muscle thickness were tabulated and submitted to statistical analysis (ANOVA, P≤0.05)., Results: Children with TMD signs and symptoms had lower EMG activity than children of the control group. There was significant difference among the groups for the LT at rest (P=0.01), right (P=0.03) and left (P=0.05) laterality, and for the LM (P=0.01) and LT (P=0.03) muscles in maximum voluntary contraction. There were no statistically significant differences among the groups regarding muscle thickness. The bite force was lower in the TMD groups than children of the control group, with significant statistical difference for the right region (P=0.03)., Conclusions: The severity of TMD signs and symptoms affected the EMG activity and the molar bite force in children. However, structural changes in the thickness of masticatory muscles are not perceptible in children with TMD signs and symptoms.

Temporomandibular disorder (TMD) incidences are believed to be related to parafunctional behaviours like teeth clenching. This pilot study aimed to (i) develop an automated clench-detection algorithm, and (ii) apply the algorithm to test for differences in nocturnal clenching in women with and without TMD. Subjects gave informed consent to participate. Adult women were categorised using Diagnostic Criteria for TMD according to presence/absence (+/-) of both TM joint disc placement (DD) and chronic pain (P) into two groups (+DD+P, -DD-P) with 12 subjects each. Surface temporalis electromyography was recorded during oral tasks performed by subjects at two laboratory sessions. The data were used to characterise muscle activity per N of bite force (μV/N) for each subject, develop the clench-detection algorithm and test its accuracy. Ambulatory surface temporalis electromyography was self-recorded by each subject over three nights and analysed using the algorithm and bite force (N) versus muscle activity μV/N calibrations. Bonferroni-adjusted homoscedastic t-tests assessed for significant between-group differences in clenching (P < 0·05). Sensitivity, specificity and accuracy of algorithm-detected laboratory clenches were all ≥96%. During self-recordings 95% of clenches had durations of <4 s and peak forces of <10 N in both groups. Mean clench durations were significantly longer (P = 0·042) in +DD+P (1·9 ± 0·8 s) than -DD-P subjects (1·4 ± 0·4 s). Mean temporalis duty factors (%clench time/total recording time) were significantly larger (P = 0·041) in +DD+P (0·47 ± 0·34%) than -DD-P (0·26 ±0·22%) subjects. Nocturnal temporalis muscle activities detected by a validated algorithm were longer per clench and recording time in +DD+P compared to -DD-P women., (© 2017 John Wiley & Sons Ltd.)

Objective: This study investigated differences in surface electromyography (sEMG) activity of the masseter and anterior temporalis muscles in children with and without temporomandibular disorders (TMD)., Participants: Thirty-four children aged 8-12 years were recruited, comprising 17 children with TMD and 17 without TMD (control group [CG]). The children were quasi-matched for sex, age, weight, and height. sEMG data were obtained using Myosystem ® Br-1 equipment with 12 channels to evaluate the bilateral masseter, anterior temporalis, and suprahyoid muscles. For sEMG analysis, raw and normalized root mean square (RMS) values were obtained at rest and during maximum clenching. The sEMG ratios of the raw RMS data of the bilateral masseter in relation to the anterior temporalis muscles (sEMG-M/AT ratio) were also assessed. Mann-Whitney tests (p ≤ 0.05) were used to compare sEMG ratio between TMD group and CG., Results: Significant prevalences of pain during chewing (53% vs. 0%, X 2  = 5.87, p = 0.01), TMJ pain (58% vs. 0%, X 2  = 6.67, p = 0.01), neck pain (58% vs. 18%, X 2  = 3.77, p = 0.05) and pain in the temples (47% vs. 6%, X 2  = 5.44, p = 0.02) were identified in the TMD group compared to CG. Our results revealed lower sEMG-M/AT ratios during maximum clenching (p = 0.01) in children with TMD compared to those in the asymptomatic CG., Conclusion: The results showed that children with TMD preferentially used their temporalis muscles during maximum voluntary clenching, probably as a consequence of nociceptive inputs in order to obtain pain relief., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objectives: The aim of this study was to investigate whether the presence of a natural mediotrusive contact influences electromyographic (EMG) pattern activity in patients with temporomandibular disorders (TMDs)., Method: Bilateral surface EMG activity of the anterior temporalis (AT), masseter (MM), and sternocleidomastoid (SCM) muscles was recorded in 43 subjects during unilateral chewing and tooth grinding. Thirteen patients had TMD and a natural mediotrusive contact (Group 1), 15 had TMD without a natural mediotrusive contact (Group 2), and 15 were healthy subjects without mediotrusive contacts (Group 3). All subjects were examined according to the Research Diagnostic Criteria for TMD (RDC/TMD). All EMG values were standardized as the percentage of EMG activity recorded during maximum isometric contraction on cotton rolls., Results: EMG activity from all muscles measured showed no significant differences between groups during chewing and grinding. Overall, in all groups, the EMG activity during chewing was higher in the working side than the non-working side in AT and MM muscles. During grinding, these differences were only found in masseter muscles (mainly in eccentric grinding). SCM EMG activity did not show significant differences during chewing and grinding tasks. Symmetry, muscular balance, and absence of lateral jaw displacement were common findings in all groups., Discussion: EMG results suggest that the contribution of a natural mediotrusive occlusal contact to EMG patterns in TMD patients is minor. Therefore, the elimination of this occlusal feature for therapeutic purposes could be not indicated.

The aim of the study was to reveal correlation of dental morphology and bioelectric activity of masticatory muscles. The study included 76 young adults (47.4% females and 52.6% males) divided in 3 groups according to dental morphology features: intact teeth (26 patients), dental decay in fissures with intact cusps (25 patients), pronounced dental decay with varying degree of crown destruction (25 patients). Electromyography (EMG) was used to document the bioelectric activity (BEA) of temporal and masticatory muscles. The study showed high level of correlation of destructive teeth changes with BEA of masticatory muscles. Intragroup correlation proved direct link of BEA to the number of decayed teeth. EMG activity differed significantly between groups 2 and 3. There was no statistically significant difference between groups 3 and 1 mostly because of high variability of BEA in group 3. Relative activity of temporal and masticatory muscles increased in groups 2 and 3 by 2 and 4% and 38 and 19%, correspondingly. There was no significant impact of gender or emotional status on masticatory muscles BEA.

The aim of the present study was to determine whether any specific frequency bands of surface electromyographic (sEMG) signals are more susceptible to alterations in patients with temporomandibular disorders (TMD), when compared with healthy subjects. Twenty-seven healthy adults (19 women and eight men; mean age: 23±6.68years) and 27 TMD patients (20 women and seven men; mean age: 24±5.89years) voluntarily participated in the experiment. sEMG data were recorded from the right and left masseter muscles (RM and LM) and the right and left anterior temporalis muscles (RT and LT) as the participants performed tests of chewing (CHW) and maximal clenching effort (MCE). Frequency domain analysis of the sEMG signal was used to analyze differences between TMD patients and healthy subjects in relation to the Power Spectral Density Function (PSDF). The analysis focused on the median frequency (MDF) of the sEMG signal and PSDF frequency bands after the EMG spectrum was divided into twenty-five frequency band of 20Hz each. The Mann-Whitney test was used to compare MDF between TMD patients and healthy subjects and the frequency bands were analyzed using three-way ANOVA with three factors: frequency band, muscle and group. The results of the analysis confirmed that the median frequency values in TMD patients were significantly higher (p<0.05) than those recorded for healthy subjects in the two experimental conditions (MCE and CHW), for all of the muscles assessed (RM, LM, RT and LT). In addition, frequency content between 20 and 100Hz of the normalized PSDF range was significantly lower (p<0.05) in TMD patients than in healthy. This study contributes to quantitatively identify TMD dysfunctions, by non-invasive sEMGs; this assessment is clinically important and still lacking nowadays., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

To test the hypotheses that experimental noxious stimulation of the anterior temporalis muscle results in significant decreases in jaw movement amplitude and velocity, and there are significant correlations between scores of mood or pain-related cognitions and amplitude and velocity. The jaw movements of 14 asymptomatic participants were recorded during standardised open/close jaw movements and free and standardised chewing tasks. Tonic infusion of hypertonic saline into the right anterior temporalis muscle maintained pain intensity between 40 and 60 mm on a 100-mm visual analogue scale. Tasks were performed in a single session in the following sequence: baseline condition, test 1 condition (during hypertonic or isotonic saline infusion), test 2 condition (during saline infusion) (10-min rest between conditions). Participants completed the Depression, Anxiety and Stress Scale (DASS-21) and the Pain Catastrophizing Scale (PCS). Amplitude and velocity of opening and closing were compared between conditions with a repeated-measures analysis of variance (anova), and Spearman's rank correlation coefficient explored correlations; statistical significance: P < 0·05. For any of the three tasks, there were no significant differences in kinematic variables between any condition and no significant correlations between DASS-21 or PCS scores and kinematic variables during hypertonic saline infusion. The absence of a significant reduction in velocity or amplitude of open/close or chewing jaw movements during experimental temporalis muscle pain is not consistent with the Pain Adaptation Model proposing decreases in kinematic measures in pain. The lack of significant correlations between psychological variables and measures of jaw movement may reflect the low scores reported by our study sample., (© 2016 John Wiley & Sons Ltd.)

This study evaluated the bite force, electromyographic activity, and mandibular mobility in patients undergoing surgery for facial fracture treatment that required a coronal approach. Ten men were divided into two groups: group I, coronal approach with pre-auricular extension (n=4, average age 34.5 years); group II, coronal approach (n=6, average age 24.8 years). The maximum bite force was measured using a dynamometer and mandibular mobility using a calliper. The electromyographic activity of the right masseter (RM), left masseter (LM), right temporal (RT), and left temporal (LT) muscles was evaluated using a Myosystem-Br1 apparatus. Patients were evaluated at 1, 2, 3, and 6 months after surgery. Data were analysed using the repeated measures test (SPSS 21.0; P≤0.05). Statistically significant differences were found for electromyographic activity at rest (group II: LM P=0.00), left laterality (group I: RT P=0.02; group II: RT P=0.04), and maximum voluntary contraction (group I: RM P=0.04 and RT P=0.04; group II: RM P=0.05, LM P=0.00, and LT P=0.01 and for maximum molar bite force in the right (group I, P=0.00; group II, P=0.01) and left (group II, P=0.01) molar regions. The subjects regained electromyographic activity, maximum bite force, and mandibular mobility throughout the period evaluated., (Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

Objective: The aim of this study was to assess the activity of the masseter and temporalis muscles using surface electromyography (EMG) in patients with zygomaticomaxillary complex (ZMC) fractures., Patients and Methods: This prospective study was carried out on 25 patients who had ZMC fractures. Fifteen patients were managed by open reduction and rigid fixation (ORIF) using titanium miniplates. This study, using surface electromyography, analyzed the activity of the masseter and temporalis muscles of 25 patients with ZMC fractures; 15 of them were surgically treated under general anesthesia (GA). Evaluations were made before surgery and 6 weeks after surgery by recording the mean of muscle contraction of 20 motor unit action potential (MUAP) against resistance, and statistical analyses were performed., Results: A significant EMG difference between the normal and ZMC fracture sides was found (P < 0.0001) for both masseter and temporalis muscles and was significantly improved after ORIF. However, postoperative EMV values of the repaired side was significantly less than measured postoperatively in the normal side (P < 0.0001) for both muscles., Conclusion: ZMC fractures significantly diminish muscular activity of the masseter and temporalis and even though significant recovery of muscle activity was revealed after 6 weeks, it is still less than normal activity, highlighting the importance of postoperative rehabilitation.

Introduction: The use of surface electromyography (SEMG) is controversial in the diagnosis and subsequent treatment of temporomandibular disorders (TMD), although there is some evidence that the pattern of the masticatory muscles in TMD patients differs from controls. The aim of this study was to compare relative time of mandibular elevator muscle activation at different levels of activity and median frequency (MF) during sustained clenching., Methods: Twenty-two women, aged between 18 and 48years, volunteered to participate in the study. The TMD group had 14 participants diagnosed as group Ia muscle disorders (RDC/TMD). The control group had eight healthy individuals. SEMG records were obtained from masseter and temporal muscles during 10s of sustained clenching. Normalized SEMG amplitudes were classified as minimal, moderate and maximal and time of activation in each level of activity was calculated and compared using two-way ANOVA (groups versus time). A slope of the linear regression line that fits MF values over time was calculated as a fatigue index for elevator muscles., Results: Only the temporal muscles of the TMD group showed longer activation time at moderate and minimal activity levels compared to controls. Fatigue indexes were greater for the TMD group compared to controls., Conclusion: Results showed motor control strategies during sustained clenching that differentiate controls from TMD patients., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Due to the multifactor etiology of temporomandibular disorder (TMD), the precise diagnosis remains a matter of debate and validated diagnostic tools are needed. The aim was to determine the accuracy of surface electromyography (sEMG) activity, assessed in the amplitude domain by the root mean square (RMS), in the diagnosis of TMD. One hundred twenty-three volunteers were evaluated using the Research Diagnostic Criteria for Temporomandibular Disorders and distributed into two groups: women with myogenous TMD (n=80) and women without TMD (n=43). The volunteers were then submitted to sEMG evaluation of the anterior temporalis, masseter and suprahyoid muscles at rest and during maximum voluntary teeth clenching (MVC) on parafilm. The accuracy, sensitivity and specificity of the muscle activity were analyzed. Differences between groups were found in all muscles analyzed at rest as well as in the masseter and suprahyoid muscles during MVC on parafilm. Moderate accuracy (AUC: 0.74-0.84) of the RMS sEMG was found in all muscles regarding the diagnosis of TMD at rest and in the suprahyoid muscles during MVC on parafilm. Moreover, sensitivity ranging from 71.3% to 80% and specificity from 60.5% to 76.6%. In contrast, RMS sEMG did not exhibit acceptable degrees of accuracy in the other masticatory muscles during MVC on parafilm. It was concluded that the RMS sEMG is a complementary tool for clinical diagnosis of the myogenous TMD., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Purpose: To understand the effects of HIV type 1 on the function of the masticatory muscles., Methods: Sixty individuals were selected from both genders, aged between 22 and 57years (mean 36.77±9.33years), and divided into two groups: Group HIVG, 30 individuals with HIV subtype 1, and Group CG, 30 healthy individuals (control group). The individuals were submitted to assessments of their masticatory muscle activity, biting strength and thickness of the masticatory muscles by means of electromyography, maximal molar bite force and ultrasound imaging, respectively. The resultant data were statistically analyzed by t-tests (p<0.05)., Results: The HIVG normalized EMG data from a mandibular rest position, protrusion, right and left laterality movement of the jaw showed that HIVG presented a relative increase in EMG activity compared to the CG. The HIVG had a lower masticatory cycle ability while chewing Parafilm M®, Raisins and Peanuts when compared to CG. During rest conditions, the ultrasound images showed a greater average muscular thickness in the right and left temporal region compared to CG. Upon maximal voluntary contraction, an increased average thickness was seen in the temporalis muscles and left sternocleidomastoid muscle when compared to the CG., Conclusion: Based on the results of this research, it can be concluded that individuals with acquired immunodeficiency syndrome showed muscular changes related to the stomatognathic system, especially concerning EMG activity and muscle thickness., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objective: To determine differences in masticatory muscle usage between temporomandibular joint disorders diagnostic groups., Setting and Sample Population: Seventy-one informed and consented subjects (27 men; 44 women) participated at the University at Buffalo., Material and Methods: Research diagnostic criteria and imaging data were used to categorize subjects according to the presence/absence +/- of TMJ disc placement (DD) and chronic pain (P) (+DD+P, n=18; +DD-P, n=14; -DD-P, n=39). Electromyographic (EMG)/bite-force calibrations determined subject-specific masseter and temporalis muscle activities per 20 N bite-force (T20N , μV). Over 3 days and nights, subjects collected EMG recordings. Duty factors (DFs, % of recording time) were determined based on threshold intervals (5-9, 10-24, 25-49, 50-79, ≥80% T20N ). anova and Tukey-Kramer post hoc tests identified 1) diagnostic group differences in T20N and 2) the effects of diagnostic group, gender, time and interval on muscle DFs., Results: Mean (±SE) temporalis T20N in +DD+P subjects was significantly higher (71.4±8.8 μV) than masseter T20N in these subjects (19.6±8.8 μV; p=0.001) and in -DD-P subjects (25.3±6.0 μV, p=0.0007). Masseter DFs at 5-9% T20N were significantly higher in +DD-P women (3.48%) than +DD-P men (0.85%) and women and men in both other diagnostic groups (all p<0.03), and in +DD+P women (2.00%) compared to -DD-P men (0.83%; p=0.029). Night-time DFs at 5-9% T20N in +DD-P women (1.97%) were significantly higher than in -DD-P men (0.47%) and women (0.24%; all p<0.01)., Conclusions: Between-group differences were found in masticatory muscle activities in both laboratory and natural environmental settings., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Purpose: The aims of this study were to evaluate the results of electromyographies (EMGs) of the masseter muscle after mandibular third molar surgery and to determine the relationships between clinical variables and EMG results., Patients and Methods: Seventy patients were included in the study. The parameters of the patients' masseter muscles were measured using EMG prior to operation and 7 and 21 days post-operation. Clinical variables were also recorded before and after the third molar surgeries., Results: When the masseter muscle EMG results from the tooth-extracted side were compared with those from the non-extracted (control) side, significant differences in the areas of voltage, power spectral densities and median frequencies (p = 0.011, 0.017 and 0.041, respectively) were found 7 days postoperatively. Additionally, there were significant associations between some clinical variables (i.e. postoperative swelling, bone reduction and pericoronitis) and the EMG results 7 days postoperatively, (p < 0.05). However, there were no significant differences 21 days postoperatively., Conclusion: This study revealed that the postoperative changes in EMG activities were transient. Although there have been controversies about the reliability of EMG, this study showed that some EMG variables could be used to evaluate postoperative changes in masseter muscle activity.

The study was conducted to evaluate the effect of early physical rehabilitation by comparing the differences of surface electromyographic (sEMG) activity in the masseter and anterior temporalis muscles after surgical correction of skeletal class III malocclusion. The prospective study included 63 patients; the experimental groups contained 31 patients who received early systematic physical rehabilitation; the control group (32 patients) did not receive physiotherapy. The amplitude of sEMG in the masticatory muscles reached 72.6-121.3% and 37.5-64.6% of pre-surgical values in the experimental and control groups respectively at 6 weeks after orthognathic surgery (OGS). At 6 months after OGS, the sEMG reached 135.1-233.4% and 89.6-122.5% of pre-surgical values in the experimental and control groups respectively. Most variables in the sEMG examination indicated that recovery of the masticatory muscles in the experimental group was better than the control group as estimated in the early phase (T1 to T2) and the total phase (T1 to T3); there were no significant differences between the mean recovery percentages in the later phase (T2 to T3). Early physical rehabilitative therapy is helpful for early recovery of muscle activity in masticatory muscles after OGS. After termination of physical therapy, no significant difference in recovery was indicated in patients with or without early physiotherapy., (Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Introduction: The aim of this study was to evaluate the reliability of surface electromyography of the masticatory muscles in patients with cerebral palsy., Methods: Surface electromyography was performed over the masseter and temporal muscles in 15 patients with cerebral palsy with the mandible at rest and during maximum clenching effort in two sessions. The data were analyzed using the root mean square amplitude, mean frequency, median frequency, zero crossings and approximate entropy., Results: In the within-day evaluations, intraclass correlation coefficients were higher (0.80-0.98) for the all electromyography variables and muscles during maximum clenching effort. In the resting position, the coefficients revealed good to excellent reliability (0.61-0.95) for root mean square, mean frequency, median frequency and zero crossings and fair to good reliability (0.53-0.74) for approximate entropy. In the between-day evaluations, the coefficients revealed good to excellent reliability (0.60-0.86) for mean frequency, median frequency, zero crossings and approximate entropy. In the resting position, the coefficients revealed poor to fair reliability (0.23-0.57) for all electromyography variables studied. The root mean square had the highest standard errors during maximum clenching effort (2.37-5.91) and at rest (1.47-6.86)., Conclusion: Mean frequency, median frequency and approximate entropy are the most reliable variables of surface electromyography signals of the masseter and temporal muscles during maximum clenching effort in individuals with cerebral palsy. These measures can be used to evaluate the function and behaviour of the masticatory muscles in this population following oral rehabilitation and surgical oral procedures as well as for the study the physiology of these muscles., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Because temporomandibular disorders (TMDs) rehabilitation continues to be a challenge, a more comprehensive picture of the orofacial functions in patients with chronic pain is required. This study assessed the orofacial functions, including surface electromyography (EMG) of dynamic rhythmic activities, in patients with moderate-severe signs and symptoms of chronic TMD. It was hypothesized that orofacial motor control differs between patients with moderate-severe chronic TMD and healthy subjects. Seventy-six subjects (46 with TMD and 30 control) answered questionnaires of severity of TMD and chewing difficulties. Orofacial functions and EMG during chewing were assessed. Standardized EMG indices were obtained by quantitative analysis of the differential EMG signals of the paired masseter and temporal muscles, and used to describe muscular action during chewing. TMD patients showed significant greater difficulty in chewing; worse orofacial scores; longer time for free mastication; a less accurate recruitment of the muscles on the working and balancing sides, reduced symmetrical mastication index (SMI) and increased standardized activity during EMG test than healthy subjects. SMI, TMD severity and orofacial myofunctional scores were correlated (P<0.01). Impaired orofacial functions and increased activity of the muscles of balancing sides during unilateral chewing characterized the altered orofacial motor control in patients with moderate-severe chronic TMD. Implications for rehabilitation are discussed., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Unlabelled: In adults, sleep bruxism (SB) may be related to reports of pain or fatigue in the muscles of mastication, resulting from multiple muscle contractions that occur during the night. In children, little is known about the consequences of this parafunction., Purpose: The objective was to compare the electromyographic activity (EMG) of the masseter and anterior portion of the temporalis muscles in children with and without SB; acquisitions were made at rest (RE) and in maximal intercuspal (MI) positions of the mandible., Methods: Twenty children with signs and symptoms of SB (mean age 7.20 years ± 0.52) and 20 controls without signs or symptoms of SB (mean age 7.40 years ± 0.50) were selected. The controls were matched to the type of occlusal morphology evaluated according to Björk et al. (Acta Odontol Scand 22:27-40, 1964). Muscle activity was measured with the mandible at RE, MI and maximal clenching with cotton roll (MC), on the left and right sides. Data from the RE and MI (mV) were normalized by calculating them as % MC. The results were analyzed by descriptive statistics, Shapiro-Wilk test, Wilcoxon and Mann-Whitney tests., Results: The subjects' age did not differ significantly between groups. EMG of temporalis muscle at RE differed between the right and left sides in both groups. There was no significant difference in EMG of masseter and temporalis muscles between groups., Conclusion: Children with SB showed no significant difference in EMG of masticatory muscles at RE and in MI positions of the mandible when compared with the control group.

The use of surface electromyography (sEMG) to identify subjects with chronic temporomandibular disorders (TMD) is controversial. The main objective of this study is to determine the diagnostic accuracy of EMG to differentiate between healthy subjects and those with TMD. This study evaluated 53 individuals with TMD who were referred to the university service and who fulfilled the eligibility criteria during the period of the study. Thirty-eight dental students were also recruited satisfying same eligibility criteria but without TMD. The inclusion criteria were to be fully dentate, have normal occlusion, and be righthanded. The exclusion criteria were periodontal pathology, caries or damaged dental tissues, orthodontic therapy, maxillofacial disease, botulinum A toxin therapy, and psychological disorders. The means of the masseter muscles, right (RM) and left (LM), and temporalis muscles, right (RT) and left (LT), and intraindividual indexes during resting and during clenching were calculated. Raw sEMG activity was used to determine the cutoff points and calculate the diagnostic accuracy of sEMG. The diagnostic accuracy of these variables for a diagnosis of TMD was evaluated by using the Receiver Operating Characteristic (ROC) curve and the area under it (AUC). A new transformed diagnostic variable was obtained by using the Generalized Additive Models (GAM). Optimal cutoff points were obtained where the sensitivity and specificity were similar and by the Youden index. The highest estimated AUC was 0.660 (95% CI 0.605-0.871) corresponding to the rLT variable during rest. When rLT and rACTIVITY (differences divided by sums of temporalis versus masseter muscles) were considered as a linear combination, the AUC increased to 0.742 (95% CI; 0.783-0.934). In conclusion, the raw sEMG evaluation of rest provided moderate sensitivity and specificity to discriminate between healthy individuals and those with TMD. The use of the indexes (mainly assessing the dominance of temporalis over masseter muscles during rest) is strongly recommended to increase the discriminatory capacity of raw sEMG evaluation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objective: A study was designed to determine changes in the amplitude of the EMG muscular activity of the Masseter and Temporalis muscles at clench in children with a Class II, division 1 malocclusion treated with the pre-orthodontic Trainer functional appliance, for 12 months., Study Design: 36 Class II, division 1 malocclusion patients (mean age 7.6 ± 1.3 years) composed the treated group and wore the functional appliance; 22 children with a similar age and malocclusion composed the untreated controls; and, 20 children with no dental malocclusion participated as normal controls. Electromyographic (EMG) muscular activity of the Temporalis and Masseter muscles were recorded before and after treatment., Results: Subjects in the treated group reported a bilateral significant increase in the muscular electrical activity in the both tested muscles (p < 0.001). After treatment, they recorded values similar to those measured in normal controls, whereas the untreated controls remained on lower values., Conclusion: These results confirm that treatment with the pre-orthodontic Trainer functional appliance significantly increases the EMG muscular activity in the Temporalis and Masseter muscles at clench in patients with Class II, division 1 malocclusion.

Background: The aim of the present study was to analyse the influence of temporomandibular disorder (TMD) on electromyographic activity in the masseter and temporal muscles of adolescents and investigate a possible association with the number of occlusal contacts., Methods: The Helkimo Index was administered for the diagnosis of TMD and classification of the adolescents into three groups: without TMD; with mild TMD; and with moderate/severe TMD. Carbon paper was used for the determination of occlusal contact points. A standardised electromyographic evaluation was performed on the masticatory muscles at rest, during habitual chewing and during maximum voluntary clenching. The readings were normalised to maximum voluntary clenching. Statistical analysis involved the chi-squared test and Fisher's exact test. The Kruskal-Wallis test and one-way analysis of variance with Dunn's post hoc test were used to compare differences between groups. Pearson's correlation coefficients (r) were calculated for the determination of correlations between the number of occlusal contacts and RMS values., Results: Electromyography revealed significant differences in the right and left masseter and temporal muscles at rest and during chewing among the three groups. These differences were not observed during maximum voluntary clenching. No statistically significant differences were found between the groups with and without TMD regarding the number of occlusal contacts., Conclusion: Electromyographic activity in the masseter and temporal muscles was greater among adolescents with moderate to severe TMD.

Objectives: Oral submucous fibrosis (OSMF) is an insidious chronic disease that is associated with significant functional morbidity and an increased risk for malignancy. It initially affects the lamina propria of the oral mucosa, and, as the disease progresses, it involves the submucosa and deeper tissue, including muscles of the oral cavity, resulting in loss of fibroelasticity. OSMF is a pre-malignant condition mainly caused by areca nut chewing. The aim of this study was to find out the involvement of muscles of mastication and facial expression in patients with OSMF by assessing the cross-sectional thickness and activity of the masseter, anterior temporalis and orbicularis oris muscles by ultrasonography and electromyography and comparing with healthy controls and also to find out any correlation between the ultrasonographic cross-sectional thicknesses of the masseter, anterior temporalis and orbicularis oris muscles with electromyographic activity., Methods: 40 patients with OSMF were included in the study group, and the patients were divided into four groups on the basis of interincisal mouth opening, i.e. Group I (mouth opening >35 mm), Group II (mouth opening between 30 and 35 mm), Group III (mouth opening between 20 and 30 mm) and Group IV (mouth opening <20 mm). Ultrasonographic cross-sectional thickness and electromyographic activity (amplitude and duration) of the masseter, anterior temporalis and orbicualris oris muscles were recorded in patients with OSMF and 20 controls. Intergroup comparison of ultrasonographic cross-sectional thickness and activity (amplitude and duration) was done, and Pearson's correlation coefficient was applied to find out any relation between ultrasonographic and electromyographic findings., Results: Thickness and activity of the masseter muscle was significantly reduced in Group IV (mouth opening <20 mm) when compared with the control group. The anterior temporalis and orbicularis oris muscles remained unaffected. A positive correlation was observed between the thicknesses of the masseter muscle and the amplitude in Groups I, II and III; the anterior temporalis muscle in Group II and the control group; and the orbicularis oris muscle in Groups II, III and IV., Conclusions: It was concluded that, among the muscles studied, there was an early involvement of the masseter muscle in patients with OSMF compared with that of other muscles.

Objectives: The purpose of our study was to show neuromuscular transmission abnormality in the masseter muscle of generalised myasthenia gravis (MG) patients and to compare motor end-plate failure of the masseter with the extensor digitorum communis (EDC) and periocular muscles., Methods: Motor end-plate function was evaluated during voluntary contraction of the masseter muscle of 20 generalised MG patients aged between 16 and 63 years, as well as 20 age-matched healthy volunteers. The mean jitter value was calculated for each group and compared. The upper limit of normal jitter was also calculated and the number of jitters exceeding this cut-off value was counted for each group for comparison. In MG patients, jitter analysis was also performed in periocular and EDC muscles along with the masseter and the number of single fibre-like potentials with abnormal jitter was counted for each muscle. All tests were performed during the same session with a concentric needle electrode (CNE)., Results: For the masseter muscle, the mean jitter of all potential pairs was significantly higher in the patient group (24.7 ± 9.6 μs in healthy volunteers, 71.9 ± 41 μs in patients). The calculated mean jitter for the 18th highest value in healthy volunteers was 33.8 ± 5.9 μs (upper 95% confidence limit was 45.6 μs). The number of abnormal jitters (≥ 46 μs) was significantly higher in the patient group (276 out of 402 jitters) compared to healthy volunteers (10 out of 400 jitters). In the patient group, the number of single fibre-like potentials with abnormal jitter was found to be similar for the masseter, periocular and EDC muscles., Conclusion: The masseter muscle has diagnostic importance in generalised MG. The ratio of high jitters to all of the calculated jitters in a particular muscle was similar for masseter, periocular and EDC muscles., Significance: Jitter analysis of the masseter muscle during voluntary contraction is easy to perform and it was found as informative as other muscles in patients with generalised MG., (Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

Background: The aim of this study was to compare electromyographic data of two groups of patients (open and deep skeletal bite) before and after surgical orthodontic treatment., Methods: All patients who underwent orthognathic surgery at the Department of Orthodontics (University of Milan) were subjected to periodic electromyographic evaluation of the masticatory muscles (masseter and anterior temporal muscles) and to electrokinesiographic evaluation of mandibular movements. The sample comprised 72 patients (35 open skeletal bite patients and 37 deep skeletal bite patients) at the end of craniofacial growth. The electromyographic instruments used in the study included a Freely and a K6-I electromyograph. Statistical evaluation was carried out with Student's t tests for independent samples., Results: Lots of differences between open and deep skeletal bite patients have been underlined by the analysis of the electromyographic data obtained. These results have been obtained with both electromyographic systems. Muscular activity in microvolts is higher in deep skeletal bite patients at the beginning of the treatment than in open bite ones, but during the following phases of the treatment, the two values became similar., Conclusions: Morphologic differences between open and deep bite patients can also be demonstrated by instrumental examinations, and their correction after surgical treatment is observable on electromyographic and electrognatographic exams.

Purpose: The purposes of this study were to 1) investigate longitudinal changes in electromyographic masticatory activity subsequent to orthognathic surgery (OGS) in patients with skeletal Class III malocclusion, and 2) compare masticatory muscle activity and skeletal factors in patients with stable versus relapsed mandibular positions after OGS., Materials and Methods: A consecutive series of patients with skeletal Class III malocclusion who underwent 2-jaw OGS (35 patients, 17 men and 18 women; age, 24.5 ± 5.0 yr) were included. Lateral cephalometric films were obtained preoperatively (T1), 1 month after OGS (T2), and at completion of orthodontic treatment (T3). Serial cephalometric tracings and analyses were obtained. Surface electromyograms of the anterior temporalis and masseter muscles were recorded at T1, T2, and T3 (6 mo after OGS). Resting tonus, maximum voluntary clench with habitual intercuspation and on cotton pads, and maximum muscle firing were evaluated. Percentage of overlapping coefficient and torque coefficient were calculated. Patients were categorized further into stable and relapse groups according to the sagittal relapse rate of mandibular setback. These surface electromyographic variables were compared between the 2 groups., Results: On average, the mandible showed a significant setback of 10.19 mm and a relapse of 1.12 mm (10.99%). Surgical relapse did not correlate with gender or genioplasty. Serial surface electromyographic data indicated a significant decrease from T1 to T2 that then recovered from T2 to T3. No significant difference between T1 and T3 was noted. Percentage of overlapping coefficient was significantly decreased after OGS. The torque coefficient did not differ significantly from T1 to T3. The relapse group (relapse, >11%; n = 15) had a greater resting tonus of the anterior temporalis muscle at T3, a larger percentage of overlapping coefficient at T1, and a greater maximum voluntary clench of the masseter muscles at all times than in the stable group (n = 20). The relapse group exhibited a greater decrease in facial height (2.18 mm) from T2 to T3 than did the stable group (0.5 mm)., Conclusion: A larger sagittal relapse of mandibular setback occurred in patients with greater masticatory muscle activity. Modifications in surgical design and overcorrection should be considered in patients with greater masticatory muscle activity before OGS., (Copyright © 2013 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Objective swallowing assessment is indicated in the management of patients with Duchenne muscular dystrophy (DMD). Surface electromyography (sEMG) provides a non-invasive, objective method of quantifying muscle activity. It was hypothesised that the measurement of sEMG activity during swallowing would distinguish between preserved and disordered swallow function in DMD. This comparative study investigated the peak, duration, and relative timing of muscle activity during swallowing of four muscle groups: orbicularis oris, masseter, submental, and infrahyoid. The study included three groups of participants: Nine DMD patients with dysphagia (mean age = 21.7 ± 4.2 years), six DMD patients with preserved swallow function (21.0 ± 3.0 years), and 12 healthy controls (24.8 ± 3.1 years). Dysphagic DMD participants produced significantly higher normalised peak amplitude measurements than the healthy control group for masseter (61.77 vs. 5.07; p ≤ 0.01) and orbicularis oris muscles (71.87 vs. 26.22; p ≤ 0.05). Intrasubject variability for masseter peak amplitude was significantly greater for dysphagic DMD participants than the other groups (16.01 vs. 5.86 vs. 2.18; p ≤ 0.05). There were no differences in timing measurements between groups. Different characteristic sEMG waveforms were observed for the three groups. sEMG provides useful physiological information for the evaluation of swallowing in DMD patients, justifying further study.

Aim: The purpose of this case report is the concurrent evaluation of the masticatory pattern and the electromyographic activity, recorded during mastication, before and after therapy of deep bite malocclusion., Case Report: An 11-year-old boy, affected by deep bite (overbite = 5 mm) was treated by the use of a functional appliance (Function Generating Bite for Deep bite correction = FGB-D). Mandibular movements during mastication of a soft and a hard bolus were recorded both before and 10 months after correction of the malocclusion. Electromyographic activity (EMG) of the masseters and anterior temporalis muscles were recorded at the same time. Chewing cycles and EMG activity were recorded with the K7 I kinesiograph (Myotronics Inc., Seattle, WA-USA). Before therapy a higher EMG activity was recorded for both masseters and anterior temporalis muscles in comparison with the results after therapy., Results: The results showed a great decrease of the EMG activity of masseter and anterior temporalis muscles. Moreover, the height and width of the chewing cycles in the frontal plane increased after therapy., Conclusion: The functional improvement showed after therapy with FGB-D showed that the functional appliance is able to correct the dental malocclusion and the masticatory function. The orthodontic treatment should consider not only the repositioning of teeth within the dental arches but also the effects on function, especially when the malocclusion involves the muscular and skeletal structures.

The third part of this literature review on the clinical relevance of surface electromyography (EMG) of the masticatory muscles summarizes the results of clinical studies in patients with temporomandibular disorders (TMD), preferably randomized controlled trials, examining the impact of changes to the dynamic occlusion. Clenching in left and right laterotrusive positions results in decrease in EMG activity of masseter and temporalis muscles on both working and non-working side. Masseter muscle exhibits largely uniform bilateral activity in laterotrusive positions, independent of canine guidance or group function with and without non-working side contacts. There is a dominance of temporalis muscle activity on the working side and, in case of posterior contacts and balancing contacts, temporalis muscle activity increases and changes from an unilateral to a symmetrical pattern.

Increased resting electromyographic activity (EMG), reduced EMG during maximum voluntary clenching, and a shift to lower frequencies of the mean/median power frequency (MPF) of the EMG power spectrum have been reported for patients with temporomandibular disorder pain. It is unclear, however, whether these electrophysiological phenomena can be correlated with symptom improvement during the follow-up of myofascial pain patients in treatment. The objective of this study was to monitor the therapeutic effects of two different splint concepts (standard method and a complex splint procedure assisted by transcutaneous electrical nerve stimulation, TENS) for a period of 12 weeks, by use of clinical outcome criteria and EMG recordings. We tested the hypotheses that both measures evaluated will change in parallel during treatment and that the different splint concepts will result in no outcome differences between the variables studied. For two randomly selected groups, each containing 20 non-chronic myofascial pain patients, the clinical course after splint insertion was documented over a period of 12 weeks on the basis of pain and pain on palpation ratings, in parallel with EMG recording. Baseline values were monitored for matched healthy subjects. Although there was no correlation between the course of symptom improvement and significant changes in EMG data, MPF differed significantly (p < 0.05) between healthy subjects and patients. The therapeutic effects of splints of different clinical complexity differed significantly (p < 0.05) between the patient groups, in favor of the complex oral appliances, and substantial (p < 0.001) but temporary pain relief was achieved by additional TENS. For non-chronic myofascial TMD pain patients treated with splints, the course of symptom improvement is not paralleled by significant changes in EMG data. MPF can, however, be used to distinguish between healthy subjects and patients. Splints of different clinical complexity differ in their therapeutic effects in non-chronic myofascial TMD patients, and substantial temporarily limited pain relief can be achieved by additional muscle stimulation by TENS.

Purpose: Small, self-contained electromyographic (EMG) detector/analyzer (D/A) devices have become available for the detection of jaw muscle activity events above threshold. These devices claim to be less intrusive to the subjects sleep so it is less prone to induce disturbed sleep. The objective of this study was to evaluate for night-to-night variability and examine for a systematic alteration on the first night in EMG levels., Methods: Ten asymptomatic healthy volunteers (mean age, 26.8 ± 3.78) were recorded for six sequential nights in their home environment using EMG D/A system. The device yields a nightly EMG level above threshold score on a 0-4 level. Because the data are categorical and nonparametric, the data of the ten subjects across six nights were submitted to a Friedman repeated measures ANOVA. The significant level was set as alpha equal to 0.05., Results: The median and mode values of the subjects were tabulated and analyzed and we did not find a significant difference in EMG D/A level across the six nights (p = 0.287, Kendall's coefficient of concordance = 0.124, Friedman two-way repeated measures ANOVA). The data did show clear and substantial night-to-night variability., Conclusion: Substantial night-to-night variability in masseter EMG activity levels was clearly observed in our subjects. There was no evidence of a suppressed or elevated first-night effect-like variability on masseter muscle EMG level seen in these subjects using a small portable self-contained EMG detector/analyzer. These data suggest that recordings should be at least 5-6-nights duration to establish a reasonable measure of an individual's average nightly masseter EMG level.

The purpose of this study was to determine if a statistically significant reduction in muscle activity (p<0.05) occurs when prolonged disclusion time (>0.4 sec/excursion) is shortened to <0.4 sec/excursion with the Immediate Complete Anterior Guidance Development (ICAGD) enameloplasty. Forty-five symptomatic, fully informed subjects (29 female, 16 male) had their right and left disclusion times recorded with T-Scan III, while simultaneously, the bilateral masseter and anterior temporalis muscle activity was recorded electromyographically with BioEMG III (n=180 muscles). This recording was done twice, once pretreatment and again posttreatment (same day) after undergoing the ICAGD enameloplasty on the same day without changing electrodes. The Student's paired t-test was utilized to detect any significant change in the muscle activity levels between the pre- and posttreatment lateral excursive muscle contractions. Highly significant reductions were found in all four muscles' activities after shortening the pretreatment prolonged disclusion time to less than 0.4 seconds (p<0.0014); after Bonferroni correction (p<0.006). When properly performed, such that the posttreatment disclusion time is <0.4 sec/excursion, the ICAGD enameloplasty predictably reduces excursive muscle activity levels in the bilateral anterior temporalis and masseter muscles. Excursive muscle hyperactivity can be a source of lactic acid accumulation, muscular ischemia, and chronic myalgic temporomandibular joint dysfunction (TMD) symptoms. The ICAGD enameloplasty significantly reduces excursive muscle contractions after completion of the first ICAGD treatment session.

Introduction: Fracture of the mandible occurs more frequently and the surgical anatomy of the mandible and adjacent structures is extremely important in understanding the pattern of fracture, the displacement of fractured fragments, and factors necessary for uncomplicated healing. In the field of dentistry, surface electromyography, electrokinesiography, and more recently, TMJ sound analysis have been particularly important developments. Previous electromyographic studies involving anterior temporalis and superficial masseter have been conducted in mandibular condylar fractures and in orthognathic and cosmetic procedures of the jaws., Materials and Methods: This experimental study was undertaken to measure the electrical activity of the anterior temporalis and superficial masseter muscles in mandibular angle fracture cases (n = 6) and the changes in the electrical activity over a period of 6 months., Results: The study shows that muscle activity increases significantly over a period of time but never matches the muscle activity of the normal subjects of same sex and age in a follow-up of 6 months post-trauma., Discussion: Electrodiagnostic testing is a potentially valuable tool for the management of patients who have suffered craniomaxillofacial trauma. Electromyography is being employed in clinical practice, and allows the inclusion of quantitative data on the qualitative aspects of a diagnosis. These data are often of significant importance in the correct management of therapy and patient follow-up, particularly if the subject is at risk of developing a different and/or more serious disease.