Association between the Thickness or Area of the Temporal Muscle and Skeletal Muscle Mass in Bioimpedance Analysis.

INTRODUCTION: Sarcopenia associated with stroke can significantly impact patient prognosis; however, the current standard diagnostic methods for sarcopenia are rarely used in stroke patients. Therefore, the aim of the current study was to investigate whether the temporal muscle thickness (TMT) or area (TMA) could serve as a surrogate marker for measuring skeletal muscle mass. METHODS: This retrospective chart review study was conducted on 244 participants from March 2018 to February 2020. The TMT and TMA were measured at the supraorbital roof level using brain CT or T1-weighted MR imaging obtained from participants. The skeletal muscle mass and skeletal muscle index (SMI) and whole-body phase angle (WBPA) at 50 kHz were collected. Pearson correlation analysis was used to assess the relationship between the TMT or TMA and the results of the bioimpedance analysis. RESULTS: The mean TMT showed significant positive correlations with skeletal muscle mass (male, r = 0.520; female, r = 0.706), SMI (male, r = 0.426; female, r = 0.582), and WBPA (male, r = 0.295; female, r = 0.232). The mean TMA showed significant positive correlations with skeletal muscle mass (male, r = 0.490; female, r = 0.657), SMI (male, r = 0.289; female, r = 0.473), and WBPA (male, r = 0.232; female, r = 0.243). CONCLUSION: We observed moderate to strong positive correlations between body composition analysis measured by BIA and TMT or TMA, suggesting that TMT or TMA could serve as a reliable surrogate marker for identifying low skeletal muscle mass in cerebrovascular disease.

Muscle oxygenation and pain in different types of temporomandibular disorders.

OBJECTIVES: Studies exploring variations in peripheral muscle oxygenation and pressure pain thresholds (PPT) of masticatory muscles in individuals with Temporomandibular Disorders (TMDs) are limited. The purpose of this study was to compare variations in peripheral oxygenation of the masseter muscle; PPT of the masseter and temporal muscles and correlate peripheral muscle oxygenation and PPT of the masseter muscle in individuals with different types of TMDs. MATERIALS AND METHODS: Cross-sectional study involving 116 participants classified into three groups: muscle group (MG, n = 32), joint group (JG, n = 30) and muscle-joint group (MJG, n = 54). Individuals aged 26.97 ± 6.93, 68.97% female, 31,03% males were included. All participants were evaluated using the Diagnostic Criteria for Temporomandibular Disorders, Near-infrared spectroscopy (NIRS) for peripheral muscle oxygenation and pressure algometer for PPT. RESULTS: There was no difference in masseter muscle oxygenation among groups. In the masseter muscle, a weakly positive correlation was observed between PPT and variation in tissue saturation index in the MG (rho = 0.365) and JG (rho = 0.317). In addition, the MJG expressed lower PPT (p = 0.004) than JG, demonstrating that MJG had more pain in this muscle. CONCLUSIONS: MJG have lower PPT in the masseter muscle. Although the PPT is dependent on the type of TMDs, the correlation between PPT and oxygenation is weak. All TMDs groups evaluated (MG, JG, MJG) showed hemodynamic similarities of the masseter muscle. CLINICAL RELEVANCE: Understanding pain thresholds and the hemodynamic behavior of the masticatory muscles contributes to a more assertive physiotherapeutic assessment in TMDs, serving as a basis for careful and individualized interventions.

Reliability of an intraoral extension for intraoral palpation and assessment of mechanical sensitivity of the temporal tendon.

BACKGROUND: The temporal tendon is a structure often compromised in patients suffering from temporomandibular disorders (TMD), yet its intraoral location makes a standardised assessment difficult. OBJECTIVES: To evaluate the variability and accuracy to target force of a newly designed intraoral extension for a palpometer device (Palpeter, Sunstar Suisse) when compared to manual palpation, in addition to clinically assessing the mechanical sensitivity and referred sensations of the temporal tendon in healthy individuals. METHODS: Experiment 1: 12 individuals were asked to target on a scale 0.5, 1 and 2 kg, for 2 and 5 s by using five different methods (Palpeter, Palpeter with three different extension shapes and manual palpation). Experiment 2: 10 healthy participants were recruited for a randomised double-blinded assessment by applying pressure of 0.5, 1 and 2 kg to the right temporal tendon with the three extensions and manual palpation. Participants rated the intensity of their sensation/pain on a 0-50-100 numeric rating scale (NRS), unpleasantness on a 0-100 NRS, and if present, they rated and drew the location of referred sensations. Repeated measures analysis of variance (ANOVA) was used in both experiments to compare differences between palpation methods. Tukey's HSD tests were used for the post hoc comparisons, and p values below .05 were considered significant. RESULTS: Experiment 1: The extensions showed no significant differences between them regarding reliability and accuracy for all forces and durations (p > .05). The manual method was significantly less reliable and accurate when compared to the other methods (p < .05). Experiment 2: There were no significant differences between the Palpeter extensions regarding pain intensity or unpleasantness NRS scores (p > .05), but all the extensions had significantly increased pain intensity and unpleasantness when compared to manual palpation (p < .05). Similarly, the frequency of referred sensations was similar between extensions but increased when compared to manual palpation. CONCLUSIONS: The new Palpeter extensions proved to be significantly more accurate and have lower test-retest variability than the manual method in a non-clinical setting. Clinically, they showed no significant differences in NRS scores for pain intensity nor unpleasantness, with no major differences in referred sensations, making any of the extensions suitable for clinical testing of the temporal tendon in future studies.

Hypervigilance to pain and sleep quality are confounding variables in the infrared thermography examination of the temporomandibular joint and temporal and masseter muscles.

OBJECTIVES: Verify whether hypervigilance to pain (HP) and sleep quality (SQ) are confounding variables in the infrared thermography (IT) examination of the temporomandibular joint and temporal and masseter muscles. METHODS: A cross-sectional and analytical study was conducted, collecting HP and SQ data from 80 participants without temporomandibular disorders (TMD), performing their IT and another 40 participants with TMD. For the selection of participants with and without TMD, the TMD Pain Screener questionnaire and axis I of the Diagnostic Criteria for Temporomandibular Disorders were applied. SQ was verified using the Pittsburgh Sleep Quality Index (PSQI) questionnaire. For the HP assessment the Pain Vigilance and Awareness Questionnaire (PVAQ) was applied. And the IT was performed through a FLIR infrared sensor camera, model T650 Infrared. RESULTS: No significant correlations were found between SQ and the temperatures of the areas of interest (P > .05), and regarding HP, a statistically significant positive correlation was found with the dimensionless (ρ = 0.289) and non-dimensionless (ρ = 0.223) asymmetries of temporal muscle temperatures. In the temperature comparisons between the participants without TMD and the participants with TMD, significant differences were found (P < .05), also when the group without TMD was controlled according to both HP and SQ (P < .05), with higher temperatures found in the TMD group. CONCLUSIONS: HP and SQ can be considered confounding variables in IT examination of the temporomandibular region.

The preliminary study of the effects of individual musculoskeletally stable position in the treatment of temporomandibular disorders.

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.

Rheumatoid Arthritis and Osteoarthritis in Adult Women: A Functional Approach to the Stomatognathic System.

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<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.

Bite Force, Thickness, and Thermographic Patterns of Masticatory Muscles Post-Hemorrhagic Stroke.

OBJECTIVE: Stroke is a neurological deficit of cerebrovascular origin, considered a 21st-century epidemic that causes functional changes in the human body. This study aimed to evaluate the stomatognathic system of patients after hemorrhagic stroke through the bite force, thickness, and skin temperature in the region of the masseter and temporalis muscles. MATERIAL AND METHODS: Twenty-four subjects were divided into groups: post-hemorrhagic stroke; with right side of the affected body (n = 12) and without the neurological disorder (n = 12). Maximum molar bite force was verified using a digital dynamometer. Muscle thickness was measured using ultrasound images obtained at rest and during maximal voluntary contraction of the masseter and temporalis muscles. Thermographic camera was used to record the thermographic patterns of the masseter and temporalis muscles. Data were subjected to Student's t-test (P < .05). RESULTS: The maximum molar bite force showed significant differences in the right (P = .04) and left (P = .03) sides, with a reduction in force in the post-hemorrhagic stroke group on the affected and unaffected sides. There was a significant difference (P < .05) in the thickness of the left temporal muscle at mandibular rest (P = .01) between groups. The post-hemorrhagic stroke group clinically presented greater muscle thickness in almost 100% of the muscles evaluated in both clinical conditions. There were no significant differences in skin temperature in the masseter and temporal muscles between the groups. CONCLUSIONS: Our results suggest functional changes in the stomatognathic system of subjects after a hemorrhagic stroke, especially concerning molar bite force and masticatory muscle thickness in the temporal muscle (unaffected side).

Analysis of Masticatory Muscle Activity Based on Presence of Temporomandibular Joint Disorders.

BACKGROUND This study was conducted to analyze the activity of masticatory muscles depending on the presence of temporomandibular joint disorders (TMD) when foods of various hardness are masticated. MATERIAL AND METHODS We enrolled 20 subjects (13 men and 7 women) who met our selection criteria, and they were divided into 3 groups (the Disorder Group, the Malalignment Group, and the Control Group) based on surveys and screening inspection. The average of reference voluntary contraction (RVC) was used to measure masticatory muscle activity. Using surface electromyography (SEMG) for each group during masticatory activity, the activities of the masseter muscle and temporalis muscle were measured based on the hardness of 3 different foods (soft, sticky, and hard). RESULTS Characteristics of these 3 groups prior to the experiment were identical, and subsequent findings were as follows: First, when masticating sticky food, the Disorder Group and Malalignment Group showed significant differences from the Control Group in activities of the masseter muscle and temporalis muscle (p<0.05). Second, when masticating hard food, the Malalignment Group and Control Group showed significant differences from the Disorder Group in the masseter muscle and temporalis muscle activities (p<0.05). Based on these findings, the study showed that malalignment affects movement of the temporomandibular joint during mastication of sticky food, and the temporomandibular joint movement was affected by the presence of pain during mastication of hard food. CONCLUSIONS Our results provide basic data useful in the diagnosis of temporomandibular joint disorder, as well as guiding future studies on this topic.

Effects of 4-Week Diacutaneous Fibrolysis on Myalgia, Mouth Opening, and Level of Functional Severity in Women With Temporomandibular Disorders: A Randomized Controlled Trial.

OBJECTIVE: The purpose of this study was to assess the effects of 4-week protocol of diacutaneous fibrolysis (DF) compared with simulated DF (sham-DF) on myalgia and mouth opening. METHODS: In a sham randomized controlled trial, 34 women with temporomandibular disorders and myofascial pain were randomly divided as intervention group (IG) and sham-DF group (SG). The IG received 4 weeks of real DF, and the SG received sham. Pain was assessed through the visual analog scale and pressure pain thresholds (PPTs) on the temporomandibular joint (TMJ), and over the temporal and masseter muscles. The Mandibular Function Impairment Questionnaire was used to classify the participants regarding to the severity of the functional limitation related to TMD. RESULTS: Pain scores decreased for both groups, but the IG showed lower values at week 4, with between-group differences. Bilateral temporal PPT showed higher values at week 4, with between-group differences. The SG had lower PPTs but the IG had higher PPTs, both compared to baseline results. The time-by-group interaction and the frequency of participants above 40 mm of mouth opening showed a significant difference for the IG over time with higher results at the 4-week assessment compared to its own baseline. Both groups showed lower MFIQ scores from baseline to 4-week assessment. There was a lower frequency of a moderate level of severity for the IG. No differences were observed for TMJ or for the masseter muscles PPT. CONCLUSION: Improvements were observed for visual analog scale scores and PPTs on temporal muscles. There was a group-by-time interaction in the IG, suggesting a possible potential use of DF for mouth opening.

Chronic stress and temporalis muscle activity in TMD patients and controls during sleep: a pilot study in females.

OBJECTIVES: The aim of this study was to assess the correlation between chronic stress and temporalis muscle activity during four nights. MATERIAL AND METHODS: Forty-four female subjects were recruited in five dental practices located in different areas of the federal state of Saarland, Germany (dental practice network in Saarland). The following inclusion criteria were used: female, aged between 18 and 65, no somatization or depression, and no pain medication, graded chronic pain status < 3. Both subjects reporting about sleep bruxism and subjects negating sleep bruxism during anamnesis were included. Anamnestic issues, sleep bruxism, anxiety, and chronic stress were assessed using validated questionnaires. Temporalis muscle activity was measured for four nights using a portable electromyographic device. Correlation coefficient was used to assess the correlation (Spearman-correlation) between chronic stress and number of temporalis muscle episodes/hour and between anxiety and the number of episodes/hour. RESULTS: The analysis showed that the factors "work overload" (adulthood chronic stress because of too many demands at work) and "pressure to perform" (necessity to be successful at work) were significantly correlated with the number of temporalis muscle episodes per hour. In contrast, anxiety was not correlated with temporalis muscle episodes per hour. CONCLUSIONS: Work-related chronic stress seems to be associated with an increased level of temporalis muscle activity during sleep. CLINICAL RELEVANCE: During anamnesis, work-related aspects should be assessed in females presenting with sleep-bruxism.

The Electrical Activity of Masseter and Anterior Temporal Muscles in Patients With Unilateral Cleft Lip and Palate.

This study aimed to determine the electrical activity of masseter and anterior temporal muscles in patients with unilateral cleft lip and palate (CLP) and compare it with healthy volunteers. The study involved 20 female patients (mean age 20 ±â€Š4 years) with unilateral cleft lip and palate who had undergone lip and palate surgery in childhood and finished the first-phase orthodontic therapy with level and align teeth. Twenty age- and sex-matched volunteers with no cleft lip and palate were involved as controls. Electromyographic (EMG) signals of masseter and anterior temporal muscles were recorded at rest position, during swallowing and during maximum bite force (MBF). EMG signals at different test conditions were compared between the cleft and noncleft sides of CLP patients and between CLP patients and healthy individuals. The EMG potentials of masseter (rest, swallowing, MBF) and temporal (rest, MBF) muscles were significantly higher in the cleft than the noncleft side of CLP patients (P value <0.001). Generally, patients with unilateral cleft lip and palate experienced a significant increase in the electrical activity of the masseter and temporal muscles in both sides compared to the control group (P <0.05). In conclusion, patients with unilateral cleft lip and palate exhibit overall greater masticatory muscle activity compared to healthy individuals. The asymmetric masticatory function in subjects with unilateral cleft lip and palate may be associated with severe consequences such as asymmetric facial growth, implying the importance of early diagnosis and orthodontic treatment to achieve a favorable environment for balanced facial growth in CLP affected patients.

Evaluation of masticatory muscle activity in patients with unilateral posterior crossbite before and after rapid maxillary expansion.

Objectives: The relationship between unilateral posterior crossbite (UPCB) and the possible asymmetric activation of the jaw muscles in children is still under debate. This study aimed at evaluating the jaw muscle activity of children with UPCB before and after rapid maxillary expansion (RME) by means of surface electromyography and a standardized sampling protocol. Subjects and methods: Twenty-nine children with UPCB (UPCB-group, mean age 9.6 ± 1.6 years) and 40 UPCB-free controls (Control-group, 10.5 ± 1.1) were recruited. The activity of the left and right anterior temporalis (AT) and superficial masseter muscles (MM) was recorded during maximum voluntary clenching and a chewing task (T0). In the UPCB-group, data were collected, also, after the correction of the UPCB with RME (T1) and 6 months later (T2), without any further treatment. Electromyographic indices comparing the activity of paired muscle were computed via software to estimate the extent of asymmetric AT and MM activity. Paired and unpaired t-test or Wilcoxon-signed rank and Mann-Whitney U test, ANOVA or Friedman test and chi-squared test were used in the statistical analysis. Results: Both groups presented with asymmetric activity of the muscles, which did not differ between groups (T0, all P > 0.05). The treatment determined a decrease in muscular activity (T1, P = 0.040), and a more asymmetric pattern of muscle activation during chewing (T1, P = 0.040), which returned similar to baseline values at T2 (all P > 0.05). Conclusions: UPCB does not contribute to an asymmetric activation of AT and MM during functional tasks. The treatment of UPCB by RME did not determine a more symmetric activity of the assessed muscles.

Spinocerebellar ataxia: Functional analysis of the stomatognathic system.

BACKGROUND: Neurodegenerative diseases that affect the cerebellum, especially in elderly individuals, cause impairment of motor coordination and quality of life. The presente study evaluated the electromyographic activity and thickness of the right and left masseter and temporal muscles, and the maximum molar bite force of individuals with spinocerebellar ataxia. MATERIAL AND METHODS: Twenty-eight individuals were divided into two groups: those with (n=14) and without (n=14) spinocerebellar ataxia. Data on the masticatory muscles obtained from the electromyographic activity (resting, right and left laterality and protrusion), muscle thickness (maximal voluntary contraction and tensile strength) and maximum bite force (right and left) were tabulated and descriptive analysis using Student's t-test (P ≤ 0.05). RESULTS: In the comparison between groups, greater electromyographic activity was demonstrated for individuals with spinocerebellar ataxia, with a statistically significant difference in protrusion and laterality for the temporal muscles (P = 0.05). There was no statistically significant difference between the groups for masticatory muscles thickness in the conditions evaluated. For maximum molar bite force, the group with spinocerebellar ataxia showed lower bite force (P ≤ 0.05). CONCLUSIONS: The data obtained suggest that spinocerebellar ataxia promotes functional reduction in the stomatognathic system, mainly affecting the electromyographic activity and bite force, hindering chewing, with a resultant alteration of nutritional intake and a decrease of quality of life.

Electromyographic Activity of the Masseter and Temporal Muscles in Patients With Nonsyndromic Complete Unilateral Cleft Lip and Palate: 2-Stage Versus 1-Stage Palate Repair.

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.

The electrical activity of the masticatory muscles in children with cleft lip and palate.

BACKGROUND: Information regarding masticatory muscle function in children with cleft lip and palate (CLP) is limited. As a consequence, research on masticatory muscle activity in cleft subjects is needed. AIM: To assess masticatory muscle activity in children surgically treated for CLP as well as identify the possible factors associated with this activity. DESIGN: The sample comprised 82 children with mixed dentition and Class I occlusions (25 children with unilateral CLP and 57 subjects with no cleft abnormalities). A DAB-Bluetooth Instrument (Zebris Medical GmbH, Germany) was used to take electromyographical (EMG) recordings of the temporal and masseter muscles both in the mandibular rest position and during maximum voluntary contraction (MVC). RESULTS: Patients with clefts showed a significant increase in temporal muscle activity at rest compared with the controls. The presence of clefts and unilateral posterior crossbites are factors strongly associated with increased temporal muscle EMG potentials during rest position. CONCLUSIONS: Children with clefts have altered temporal muscle function. The presence of posterior crossbites affects the temporal muscle activity in cleft subjects. Early diagnosis and orthodontic treatment of malocclusions are necessary to achieve functional improvement in these patients.

[Electromyographic characteristics of temporal and masticatory muscles in patients with compression-dislocation dysfunction of temporomandibular joints of different severity].

OBJECTIVE: Introduction: The main causes of dysfunctional conditions of the temporomandibular joints (TMJ), are occlusal, neurogenic, orthodontic disorders. The muscular component of TMJ is determines the dynamic anatomical and functional state of the mandible Therefore, in the diagnosis of dysfunctions and understanding of their pathogenesis belongs to the electromyographic method of investigation. The aim of the work was a comparative assessment of the bioelectrical activity of the actual chewing and temporal muscles in patients with musculo-articular compressiondislocation dysfunction of the TMJ of various severity. PATIENTS AND METHODS: Materials and methods: Electromyographic studies of temporal and masticatory muscles were performed in 43 patients. Was assess maximal parameters were recorded with the greatest compression of teeth and in the periods of chewing on the side of the pain symptom and on the opposite side (µV), the frequency of filling the myogram (Hz), the time of activity (Ta) and the resting time (Tc), coefficient "K", which determines the ratio of the processes of activity and rest with functional samples (K = Ta / Tc). RESULTS: Results and conclusions: The main feature of the functional properties of the studied muscles in the compression-dislocation dysfunction of the TMJ is the prevalence of the maximum indices of their bioelectrical activity on the side of the joint with the dislocation of the articular head of the mandible in comparison with the joint, which is in a compression state both during periods of compression of the teeth and mastication. This kind of discoordination in the work of the muscular masticatory apparatus is reflected in the severity of the course of dysfunction.

Sleep deprivation sensitizes human craniofacial muscles.

It is unknown whether and how sleep deprivation influences craniofacial muscle sensitivity in healthy humans. We investigated whether total sleep deprivation (TSD) and one night of recovery sleep (RS) can alter mechanical pain sensitivity in temporal and masseter muscles. Fifteen healthy volunteers participated in three consecutive sessions. Pressure pain thresholds were measured on the temporal and masseter muscles. Both temporal and masseter muscles became sensitized after 24 h of TSD. RS reversed the muscle sensitization.

Evaluation of genetic factors involved in nocturnal electromyographic activity of masticatory muscles in twins.

OBJECTIVES: The objectives of this study were to assess sleep bruxism events by directly recording electromyographic activity during sleep and to reveal the relative importance of genetic and environmental factors involved in sleep bruxism in twins. MATERIAL AND METHODS: The subjects consisted of 108 twins (mean age 22.2 ± 6.4 years). Electromyographic activity of temporalis muscles during sleep was evaluated using a portable automatic sleep bruxism analyzer (Grindcare 3.0, Medotech A/S), and recordings were carried out for at least three consecutive nights. Quantitative genetic statistics based on structural equation modeling was utilized to estimate variance components. RESULTS: Monozygotic twin-pair correlation for the number of nocturnal electromyographic activities recorded in this study (r = 0.463, P = 0.009) was higher than dizygotic twin-pair correlation (r = 0.103, P = 0.725). The proportion of total phenotypic variance in the liability of sleep bruxism to attribute to genetic influences, related to the electromyographic activities, was 48 % (95 % CI 17-95 %) and to unique environmental influences was 52 % (95 % CI 28-82 %). CONCLUSIONS: Additive genetic effects may be a contributing factor to the occurrence of nocturnal EMG activity associated with sleep bruxism. CLINICAL RELEVANCE: A greater understanding of the contribution of genetic factors could have beneficial uses, including enhanced accuracy of sleep bruxism diagnosis, management of sleep bruxism, and enhanced estimation of the prognosis for patients suffering from sleep bruxism. In addition, it could be also important to adequately evaluate the environmental factors in patients with sleep bruxism.

A pilot study of nocturnal temporalis muscle activity in TMD diagnostic groups of women.

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.

Comparison of Pressure Pain Thresholds in Upper Trapezius and Temporalis Muscles Trigger Points Between Tension Type Headache and Healthy Participants: A Case-Control Study.

OBJECTIVE: To date, the minimum clinical differences (MCDs) in the pressure pain thresholds (PPTs) of the upper trapezius and temporalis muscles have not yet been established in participants with tension-type headache (TTH). The purpose of the study was to evaluate the MCDs of the PPTs of the upper trapezius and temporalis in participants with TTH and those without TTH. METHODS: The sample comprised 120 participants with TTH (n = 60; mean [standard deviation] years = 38.30 [10.05]) and without TTH (n = 60; 34 [8.20]). The participants were recruited from an outpatient clinic in Spain from 2014 to 2016. The PPTs of the most hyperalgesic trigger points of the upper trapezius and temporalis were assessed. RESULTS: There were statistically significant differences, mean (standard deviation) kg/cm2, for the right upper trapezius PPT (P < .001; 1.52 [0.35] vs 2.37 [0.49]), the left upper trapezius PPT (P < .001; 1.53 [0.36] vs 2.29 [0.49]), the right temporalis PPT (P = .008; 1.56 [0.31] vs 1.72 [0.33]), and the left temporalis PPT (P = .001; 1.57 [0.27] vs 1.74 [0.30]) between participants with and without TTH, respectively. CONCLUSIONS: The PPT MCDs for the right and left upper trapezius and the right and left temporalis were 0.85, 0.76, 0.16, and 0.17 kg/cm2, respectively, for the clinical management of trigger points in participants with TTH.