Myofascial Temporomandibular Disorder Research Articles

Investigation of masticatory muscle thickness and mechanosensitivity of cervical and masticatory muscles in myofascial temporomandibular disorder patients with bruxism: A cross-sectional study

ObjectiveBruxism is a common problem associated with temporomandibular disorders (TMD). The aim of this study was to compare a patient group with Myofascial TMD and bruxism and a healthy control group in terms of masseter and temporal muscle thickness (clenching and resting), mechanosensitivity of neck and jaw muscles, craniofacial pain, and disability and emotional stress status. MethodsThe study included 31 patients with myofascial TMD and bruxism (19 females, 12 males) with a mean age of 29.96 ± 8.12 years (range, 18–45 years), and a control group of 31 healthy subjects (19 females, 12 males) with a mean age of 27.58 ± 9.39 years years (range, 18–45 years). Masseter and temporal muscle thicknesses were evaluated with a mobile ultrasound device both at rest and when clenching the jaw. The mechanosensitivity values between the upper trapezius, obliquus capitis inferior, masseter and temporal muscles were measured with a digital algometer device. Craniofacial pain and disability level were evaluated with the Craniofacial Pain and Disability Index (CFPDI), and emotional stress levels with the Perceived Stress Scale-14 (PSS-14). ResultsNo difference was determined between the two groups in respect of the clenching and resting ratios of muscle thickness in any muscle (p > 0.05). The mechanosensitivity values in all muscles were lower in the myofascial TMD group than in the healthy group (p < 0.05). The CFPDI and PSS-14 scores were higher in the myofascial TMD group (p < 0.05). There was a moderate positive correlation between CFPDI, PSS-14 and Bruxism Frequency Score (p < 0.05). ConclusionThe difference in mechanosensitivity and CFPDI values between the myofascial TMD patients with bruxism and the healthy control group indicates that the problem in this patient group has effects in the craniocervical and cervical regions. In addition, the correlation between CFPDI, PSS-14 and Bruxism Frequency Score in myofascial TMD patients suggests that this problem may be affected by the interaction of different parameters.

Effectiveness of an 8-week neck exercise training on pain, jaw function, and oral health-related quality of life in women with chronic temporomandibular disorders: a randomized controlled trial

To test the effectiveness of an 8-week exercise program targeted to the neck muscles compared to manual therapy, and placebo treatments on orofacial pain intensity, jaw function, oral health-related quality of life (OHRQoL), and jaw range of motion (ROM) in women with Temporomandibular Disorders (TMD). In this randomized controlled trial, fifty-four women (between 18–45 years old) with a diagnosis of myofascial or mixed TMD according to the Research Diagnostic Criteria for TMD (RDC/TMD) were randomized into three groups: Neck motor control training (NTG), Manual Therapy Group (MTG), and Placebo Group (PG). All patients were evaluated with the Visual Analog Scale, Mandibular Function Impairment Questionnaire, Oral Health Impact Profile-14, and jaw Range of Motion (ROM) at baseline, immediately after treatment (after 8 weeks of treatment), one month, and three-month follow-up. For all outcomes, a mixed analysis of variance (ANOVA) with repeated measures was conducted with a Bonferroni post hoc test. NTG was significantly better than the PG group on pain and jaw function at the end of treatment, one- and three-month follow-up (Effect Size (ES) &gt;0.7). For OHRQoL, NTG was significantly better than MTG and PG at the end of treatment and at three-month follow-up (ES &gt;0.7). The results of this project are encouraging, and they could be used to guide clinical practice in this field. Exercises targeted to the neck (which require low therapeutic supervision) could be a simple and conservative way to improve pain and disability for women with TMD with neck involvement.

Examination of Conditioned Pain Modulation in Myofascial TMD With Consideration of Temporal Summation

Research on myofascial temporomandibular disorder (mTMD) has often focused on potential dysfunction in endogenous pain modulation. However, studies on the specific inhibitory and facilitatory components of endogenous pain modulation using conditioned pain modulation (CPM) and temporal summation of second pain (TSSP) have shown mixed results. This study aimed to 1) examine whether women with mTMD demonstrated efficient CPM compared to controls; 2) explore the association between independent measures of CPM and TSSP in women with mTMD relative to controls; and 3) determine whether resulting modulatory profiles differentially predicted pain intensity among cases. All participants were recruited from dental clinics. Cases were women who met the research diagnostic criteria for mTMD. Controls did not have facial pain on exam and were selected to be sociodemographically similar to cases. CPM and TSSP were assessed via independent psychophysical protocols. CPM was examined in linear mixed models predicting pain thresholds adjusted for age and stratified by TSSP. Mean CPM was estimated at a 2.2 (SD = 2.8) degree increase in pain thresholds (P ≤ .001), similar in cases and controls (P = .67). CPM was less efficient in cases with enhanced TSSP (P = .031), but not in controls. Although the double-pronociceptive profile of both low CPM and high TSSP trended higher among cases than controls, it did not predict higher levels of pain intensity among cases. This study does not support deficient inhibitory endogenous pain modulation in mTMD, but results suggest that inhibitory and facilitatory pain modulation should be examined concomitantly in the study of endogenous pain modulation. PerspectiveThis manuscript presents a novel examination of inhibitory modulation by the level of facilitatory modulation in mTMD. The findings and approach may prove useful for mechanistic researchers studying endogenous pain modulation and clinical researchers seeking to jointly examine conditioned pain modulation and temporal summation in future research on chronic pain.

Effectiveness of Dry Needling versus Manual Therapy in Myofascial Temporomandibular Disorders: A Single-Blind Randomized Controlled Trial.

Dry needling (DN) is an invasive physiotherapy technique employed for reducing myofascial pain. To compare the effectiveness of dry needling (DN) versus manual therapy (MT) in improving pain, active maximal mouth opening (AMMO) and cervical disability in patients with myofascial pain from temporomandibular disorders (TMDs) were investigated against these treatments. A single-blind, randomized controlled trial was carried out. Individuals (n = 50) with TMDs were randomly allocated in a 1:1 ratio to the DN (n = 25) or MT group (n = 25). Each group received three sessions, separated by 4 days, of either DN or MT. Outcomes were assessed according to pain intensity (Numeric Pain Rating Scale), AMMO (cm), disability (Neck Disability Index), and pressure-pain threshold (PPT) (digital algometry) from the active myofascial trigger points. In both groups, pain and neck disability were significantly lower at the end of treatment compared with those measured at baseline (pain: -2.52 with 95% CI: -3.43 to -1.60 for DN group; pain: -2.92 with 95% CI: -3.77 to -2.07 for MT group; disability: -3.2 with 95% CI: -4.31 to -2.09 for DN group; disability: -2.68 with 95% CI: -3.56 to -1.79 for MT group), but not were not lower after the first session, without differences between the groups. AMMO was significantly higher after the first session (0.16 with 95% CI: 0.03 to 0.29 for DN group; 0.30 with 95% CI: 0.20 to 0.41 for MT group) and at the end of treatment in both groups (0.27 with 95% CI: 0.14 to 0.41 for DN group; 0.37 with 95% CI: 0.22 to 0.52 for MT group) compared with the baseline measurements. Finally, PPT results for the masseter and pterygoid muscles were significantly higher at the end of treatment in both groups (without statistically significant differences between groups), but not after the first session. The assessed therapies, DN and MT, are equally effective in improving pain, AMMO, cervical disability, and PPT in the muscles directly involved in the temporomandibular joint biomechanics of patients with myofascial TMDs.

Pressure release technique versus placebo applied to cervical and masticatory muscles in patients with chronic painful myofascial temporomandibular disorder: A randomised clinical trial.

The therapeutic approach to myofascial TMD should focus on pain relief and rehabilitation of function. This study investigated whether pressure release technique (PRT) is effective for reducing pain in people with chronic myofascial temporomandibular disorders (TMD). A single-blinded randomised parallel-group trial, with 3 months follow-up was conducted. A total of 72 patients were randomly allocated to receive PRT or sham PRT. Primary outcome was pain assessed with a visual analogue scale (VAS). Secondary outcomes included pressure pain thresholds (PPTs), range of opening of the mouth (ROM), Neck Disability Index (NDI), Pain Catastrophizing Scale (PCS), Tampa Scale for Kinesiophobia (TSK-11), State-Trait Anxiety Index (STAI) and State-Trait Depression Index (ST-DEP). All parameters were assessed at baseline, at the end of the treatment and at 3 months follow-up. Statistical analysis was performed by ANOVA. There were significant main effects of time, group and interaction between time and group (F ≥ 21.92; p < .001) on VAS pain. Post hoc tests showed a significant reduction in VAS pain scores in the PRT group (≥31.9%; p < .001). Effect sizes were moderate in the PRT group at all follow-up periods (≥1.25 Cohen's d). Also, there were significant effects of time in secondary outcomes (F ≥ 9.65; p < .001), and there were also interactions between time and group (F ≥ 3.82; p < .002) with better effects in the PRT group. The inclusion of PRT to conventional management with occlusal splints and self-care management appears to be effective to improve self-reported levels of pain in patients with chronic myofascial TMD pain. Retrospectively registered (ClinicalTrials.gov: NCT03619889).

Efficacy of different combinations of physiotherapy techniques compared to exercise and patient education in temporomandibular disorders: A randomized controlled study

ABSTRACT Objective This study aims to investigate the efficacy of different types of physiotherapy approaches in individuals with cervical myofascial painful temporomandibular disorders (TMDs). Methods Seventy-five participants with myofascial pain of jaw muscles and cervical myofascial pain were randomized into three groups: exercise group (E), low-level laser therapy group (LLLT), and manual pressure release group (MPR). All patients were assessed before treatment and after 12 sessions of treatment. Results Significant improvement was seen in all groups’ pressure pain threshold (PPT) values (p < 0.01). Some masticatory and neck muscles’ PPT changes in MRP and LLLT groups were significantly higher than the exercise group (p < 0.05). Conclusion Exercise therapy is an effective approach for treatment of TMDs. Additionally, LLLT combined with exercise and MPR combined with exercise have better effects than only exercise therapy. Multimodal treatment approaches should include exercise to achieve better results in clinical practice.

Morphological Changes of the Suboccipital Musculature in Women with Myofascial Temporomandibular Pain: A Case-Control Study.

Temporomandibular disorder (TMD) is an umbrella term including pain problems involving the cranio-cervical region. It has been suggested that patients with TMD also exhibit cervical spine disturbances. Evidence suggests the presence of morphological changes in the deep cervical muscles in individuals with headaches. The objective of this study was to compare the morphology of the suboccipital muscles between women with TMD and healthy controls. An observational, cross-sectional case-control study was conducted. An ultrasound examination of the suboccipital musculature (rectus capitis posterior minor, rectus capitis posterior major, oblique capitis superior, oblique capitis inferior) was conducted in 20 women with myofascial TMD and 20 matched controls. The cross-sectional area (CSA), perimeter, depth, width, and length of each muscle were calculated by a blinded assessor. The results revealed that women with myofascial TMD pain exhibited bilaterally reduced thickness, CSA, and perimeter in all the suboccipital muscles when compared with healthy women. The width and depth of the suboccipital musculature were similar between women with myofascial TMD and pain-free controls. This study found morphological changes in the suboccipital muscles in women with myofascial TMD pain. These changes can be related to muscle atrophy and are similar to those previously found in women with headaches. Future studies are required to investigate the clinical relevance of these findings by determining if the specific treatment of these muscles could help clinically patients with myofascial TMD.

Effectiveness of manual therapy and cervical spine stretching exercises on pain and disability in myofascial temporomandibular disorders accompanied by headaches: a single-center cohort study

BackgroundPrevious studies have demonstrated a relationship between headaches and temporomandibular disorders (TMDs). Moreover, recent studies have shown functional, anatomical, and neurological associations between the temporomandibular joint (TMJ) and upper cervical spine. This study aimed to investigate the effectiveness of manual therapy and cervical spine stretching exercises for pain and disability in patients with myofascial TMDs accompanied by headaches.MethodsThirty-four patients recruited from Gyeryong Hospital with headaches and diagnosed with TMDs were randomly assigned to the experimental (n = 17) and control (n = 17) groups. Headache impact was assessed using the Korean Headache Impact Test-6. Masseter myofascial pain was measured using the visual analog scale, and TMJ pressure pain threshold levels were evaluated using an algometer. Neck pain intensity was assessed using the numerical rating scale. Once per week for 10 weeks, the experimental group received cervical spine-focused manual therapy and stretching exercises alongside conservative physical therapy, and the control group received conservative physical therapy alone. Patients were evaluated at baseline and 5 and 10 weeks post-intervention.ResultsAfter the intervention, the experimental group exhibited significant reductions in the cervical kyphotic angle, Korean Headache Impact Assessment score, neck pain intensity, TMJ pain pressure threshold, Neck Disability Index score, and Jaw Functional Limitation Scale level compared with the control group (p < 0.01).ConclusionManual therapy and stretching exercises could help resolve TMDs accompanied by headaches through biomechanical changes in the cervical spine. These findings may guide protocols and clinical trials involving manual therapy that align morphological structures.

Application of Botulinum Toxin in Temporomandibular Disorders: A Systematic Review of Randomized Controlled Trials (RCTs)

Temporomandibular disorders (TMDs) are multi-factorial and polysymptomatic pathologies and their management must be customized for every patient. Numerous therapy techniques are available to treat temporomandibular disorders-related muscular discomfort and persistent orofacial pain. Botulinum toxin (BoNT) has emerged as a popular option for patients with myofascial TMD who do not completely recover from their condition after receiving conservative care and medication. A systematic search of the literature, from January 2000 until 1 April 2022, was performed in the MEDLINE (PubMed), Web of Science, and Lilacs databases. The following search terms combination: (temporomandibular disorders) OR (botulinum) OR (toxin) was employed. A total of 357 articles were initially found in the electronic search. After screening, 11 full-text articles satisfied the inclusion criteria. The Cochrane risk of bias tool (RoB 2) tool, which uses seven domains of bias to assess random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment of self-reported outcomes, blinding of outcome assessment of objective measures, incomplete outcome data, selective reporting, and other biases, was employed to analyze randomized controlled trials. The aim of this systematic review of randomized controlled trials is to provide an overview of the use of BoNT for TMDs by comparing the application of BoNT with other therapeutic approaches. BoNT-A could help patients that do not respond to conservative treatments. Low doses are recommended when BoNT-A is considered for persistent orofacial pain related to TMD. Future research should, however, conduct clinical trials with a stricter design. The results of BoNT-A could be confirmed by more randomized controlled trials with larger sample sizes, less bias, and longer follow-up times.

Pain Management and Rehabilitation for Central Sensitization in Temporomandibular Disorders: A Comprehensive Review.

Temporomandibular disorders (TMD) are a group of musculoskeletal diseases affecting masticatory muscles and temporomandibular joints (TMJ). In this context, the chronic TMD could be considered as a condition with chronic primary orofacial pain, presenting as myofascial TMD pain or TMJ arthralgia. In this context, myogenous TMD may present overlapping features with other disorders, such as fibromyalgia and primary headaches, characterized by chronic primary pain related to dysfunction of the central nervous system (CNS), probably through the central sensitization. This phenomenon could be defined as an amplified response of the CNS to sensory stimuli and peripheral nociceptive, characterized by hyperexcitability in the dorsal horn neurons in the spinal cord, which ascend through the spinothalamic tract. The main objectives of the management of TMD patients are: decreasing pain, increasing TMJ function, and reducing the reflex masticatory muscle spasm/pain. The first-line treatments are physical therapy, pharmacological drugs, occlusal splints, laser therapy, extracorporeal shockwave therapy, transcutaneous electrical nerve stimulation, and oxygen–ozone therapy. Although all these therapeutic approaches were shown to have a positive impact on the central sensitization of TMD pain, there is still no agreement on this topic in the scientific literature. Thus, in this comprehensive review, we aimed at evaluating the evidence on pain management and rehabilitation for the central sensitization in TMD patients.

Temporal Summation and Aftersensations of Second Pain in Women with Myofascial Temporomandibular Disorder Differ by Presence of Temporomandibular Joint Pain.

PurposeMechanisms underlying myofascial temporomandibular disorder (mTMD) are poorly understood. One theory is dysfunction in the central mediation of pain, specifically in enhanced facilitatory pain modulation. Because mechanisms leading to central sensitization may differ for joint and muscle pain, this study of mTMD addressed phenotypic heterogeneity by temporomandibular (TM) joint pain in the examination of quantitative sensory testing (QST).Patients and MethodsThe stimulus dependent increase in second pain (temporal summation (TS)) and associated aftersensations (AS) were examined across groups of women with mTMD with TM joint pain and without, and a demographically matched control group.ResultsTS was slightly more evident in mTMD without joint pain vs with (p = 0.035), but AS were most robustly persistent in the group with joint pain vs without (p < 0.002).ConclusionWhile both subgroups demonstrated evidence of central sensitization relative to controls on one of two measures, differences in QST results, if replicated, may point to possible differences in the mechanisms that yield central sensitization. Alternatively, it may represent methodological artifacts that need to be addressed. Therefore, greater consideration should be given to symptom-based phenotypes in studies examining TS and AS.

Clinical identification of the stimulus intensity to measure temporal summation of second pain

Temporal summation of second pain (TSSP) has been suggested as a psychophysical index for central sensitization, one of the critical mechanisms in the chronification of pain. However, there is no gold standard for protocols to measure TSSP. The purpose was to establish the stimulus intensity for measuring TSSP. Female patients with chronic myofascial temporomandibular disorders pain (n = 16) and healthy female volunteers with no pain (n = 15) participated. Pain thresholds (PT °C) were measured, and repetitive heat stimuli at three stimulus intensities (PT °C, PT + 1 °C, PT + 2 °C) were applied. TSSP parameters were quantified as TSSP magnitude (TSm) and TSSP frequency (TSf). In healthy female volunteers, pain ratings significantly decreased at PT °C (p < 0.050), besides TSm and TSf at PT + 2 °C were significantly higher than those at PT °C (p < 0.025). In chronic pain patients, pain ratings significantly increased at PT + 1 °C and PT + 2 °C (p < 0.050). At PT + 2 °C, TSm and TSf in chronic pain patients were significantly higher than those in healthy volunteers (p < 0.050). It could be helpful to measure TSSP with the stimulus intensity adjusted individually to the patient’s pain thresholds + 2 °C for assessing central sensitization.

Association among headache, temporomandibular disorder, and awake bruxism: A cross-sectional study.

To evaluate the association between headache, myofascial temporomandibular disorder (TMD), and awake bruxism (AB). Bruxism seems to act as a risk factor for TMD and its associated comorbidities, such as headaches. In total, 406medical records of individuals who sought care at a university dental clinic were screened. The Research Diagnostic Criteria for Temporomandibular Disorders was used to assess and diagnose TMD, as well as to obtain self-reports of AB and headache. The sample consisted of 307medical records. About 72.5% (221/305) of the sample reported having headaches, and 67.4% (180/267) and 68.4% (210/307) were diagnosed with AB and TMD, respectively. Individuals who reported having AB (odds ratio [OR], 2.28; 95% confidence interval [CI], 1.09-4.7) and who were diagnosed with myofascial TMD (OR, 2.53; 95% CI, 1.15-5.5) were more likely to have had headaches in the past 6months when compared with patients without myofascial TMD and bruxism. Also, individuals who self-reported headache were 2.27 times (95% CI, 1.09-4.7) more likely to have AB and 2.45 times (95% CI, 1.13-5.34) more likely to have myofascial pain than individuals without headaches. Individuals with myofascial TMD, headaches, or AB were more likely to have at least one of the other conditions.

Comparison of factors affecting patients with a myofascial temporomandibular disorder with and without sleep bruxism.

The aim of the present study was to evaluate the relationship between jaw function, neck disability, sleep quality, fatigue, and headache in patients with myofascial temporomandibular disorder (TMD) with sleep Bruxism (SB) and without it (non-SB). This case-control study was conducted with a total of 200 myofascial TMD patients, comprising 91 identified as SB and 109 as non-SB. The Jaw Function Limitations Scale (JFLS), Neck Disability Index (NDI), Pittsburgh Sleep Quality Index (PSQI), Fatigue Severity Scale (FSS), and Headache Impact Test-6 (HIT-6) scales and indexes were used. In the group with SB compared to the non-SB group, JFLS, NDI, PUKI, and FSS scores were statistically significantly higher (P < 0.001). No statistically significant difference was found between the groups in terms of visual analog scale (VAS) (P = 0.127) and HIT-6 scores (P = 0.365). The probability of having JFLS in patients with SB compared to those without was folded 3.551 times (P = 0.002), and the probability of having NDI increased 3.473 times (P = 0.002). In addition, SB was observed to trigger poor sleep quality (P < 0.001). There was no statistically significant determinant of bruxism on FSS (P = 0.196), and on HIT-6 (P = 0.488). It can be concluded that SB causes limitation of the jaw's functional activities, neck problems, and decreased sleep quality in myofascial TMD. These findings emphasize the importance of considering SB when evaluating and treating patients with myofascial TMD problems.

Investigation of Snoring and Obstructive Sleep Apnea Using Portable Polysomnography in Patients with Temporomandibular Disorder.

ObjectiveTo investigate snoring and obstructive sleep apnea (OSA) in patients with temporomandibular disorder (TMD) using portable polysomnography and identify sex-based differences in clinical features and sleep-related resultsMethodsSeventy consecutive patients (44 female; mean age, 46.6918.18 years) with myofascial pain-associated TMD, diagnosed based on the criteria for TMD Axis I, were enrolled. Sleep quality and quantity were measured using portable polysomnography. Clinical characteristics were investigated using well-structured standardized reports on clinical signs and symptoms, questionnaires, and clinical examination by TMD specialists.ResultsAmong 70 TMD patients, 50.0% had OSA and 15.7% had snoring, with no sex-based differences. The mean Mallampati scores for OSA prediction (2.69±1.12 vs. 1.70±0.82, p<0.001), mean body mass index (BMI) (24.94±1.78 vs. 22.02±2.24, p<0.001), and ratio of overweight patients (57.7 vs. 11.4%) with BMI ≥25 were significantly higher in males than in females (all p<0.001). Conversely, the mixed sleep apnea index was significantly higher in females than in males (0.81±0.80 vs. 0.44±0.54, p=0.022). Female sex was associated with the absence of snoring (OR=0.146, p=0.022). Based on the area under curve (AUC) value for snoring prediction, Mallampati score was the strongest predictor (AUC>0.932, p<0.001), followed by BMI, overweight, and obstructive sleep apnea index (AUC>0.8, all p<0.001).ConclusionsOur results support the necessity of investigating sex-based differences when examining sleep problems, including snoring and OSA, in TMD patients. Mallampati scoring could be a useful tool for physical examination prior to polysomnography. Sleep and biopsychosocial factors are important for the diagnosis and treatment of TMD.

Effectiveness of low-level gallium aluminium arsenide laser therapy for temporomandibular disorder with myofascial pain: A systemic review and meta-analysis.

Purpose:Temporomandibular disorder (TMD) causes masticatory muscle pain and mouth opening limitations and affects patients’ ability to eat, practice oral health and perform other activities of daily living. Although the benefits of low-energy lasers in treating TMD have been reported, the results vary greatly depending on the equipment used and the energy output. This study systematically evaluated the efficacy of a low-level gallium aluminium arsenide (GaAlAs) laser treatment for TMD with myofascial pain and maxillary pain.Methods:We searched the PubMed, EMBASE, Cochrane Library, Web of Science, and ClinicalTrials.gov databases for randomized controlled trials (RCTs) published since database inception to April 5, 2020, that compared low-level laser treatment to sham/placebo treatment or no intervention in patients suffering from TMD with myofascial pain. Three reviewers independently screened the literature, extracted data, and assessed the quality of the included studies according to the risk-of-bias tool recommended by the Cochrane Handbook V.5.1.0 (Cochrane Collaboration, London, UK). Then, a meta-analysis was performed using RevMan 5.3 and Stata 15.1 software.Results:The data from 8 randomized controlled trials including 181 patients were analyzed. The severity of myofascial TMD pain (measured on a visual analogue scale, VAS) at the end of treatment was significantly different between the control laser therapy and the low-level GaAlAs laser therapy (weighted mean difference [WMD] = −0.76, 95% confidence interval [CI] −1.51 to 0.01, P = .046); at 3 to 4 weeks after treatment, there was no significant difference (WMD = 1.24, 95% CI −0.04 to 2.51, P = .057). In addition, there was no significant improvement in maximum mouth opening (MMO) at the end of treatment (WMD = −0.03, 95% CI −4.13 to 4.06, P = .987) or at 3 to 4 weeks after treatment (WMD = 1.22, 95% CI −2.94 to 5.39, P = .565).Conclusions:The results of this study suggest that there is insufficient evidence to indicate an efficacy of low-level GaAlAs laser therapy in improving TMD pain and maximal oral opening. These results suggest that clinicians should make appropriate recommendations to inform patient decision-making.

Stress-evoked muscle activity in women with and without chronic myofascial face pain.

Amplified muscle activity in reaction to daily life stressors might explain chronic pain in temporomandibular disorder (TMD). To assess whether patients with myofascial TMD pain (MFP) react to standardised stressors with greater masticatory muscle activity than demographically matched controls. A total of 124 female MFP patients and 46 demographically matched and pain-free controls rated distress while performing a series of standardised stress-reactivity tasks (viz., cold pressor test, mental arithmetic test, speech stressor test and reaction time/startle response test) as well as a vanilla baseline control task. Blood pressure was measured before and after each task, and electromyographic (EMG) activity was continuously recorded over the jaw-closing muscles and several non-masticatory muscles during each task. Linear mixed model analyses were used to test the hypothesis that case status, stress-reactivity task and muscle recording site influenced EMG activity. Stress induction was successful, as evidenced by distress ratings and blood pressure measurements that were significantly elevated during performance of the stress tasks. Participants reported that some of the tasks were stressful in a way that resembled stressors experienced in their daily lives. Elevated muscle activity could be confirmed only for the reaction time/startle response task, where mean EMG activity was elevated more in cases than in controls, specifically in the jaw-closing muscles. These data could not provide clear support for the theory that psychological stressors produce a differential increase in masticatory muscle activity in MFP patients than pain-free controls.

Nerve growth factor and glutamate increase the density and expression of substance P-containing nerve fibers in healthy human masseter muscles

Nocifensive behavior induced by injection of glutamate or nerve growth factor (NGF) into rats masseter muscle is mediated, in part, through the activation of peripheral NMDA receptors. However, information is lacking about the mechanism that contributes to pain and sensitization induced by these substances in humans. Immunohistochemical analysis of microbiopsies obtained from human masseter muscle was used to investigate if injection of glutamate into the NGF-sensitized masseter muscle alters the density or expression of the NMDA receptor subtype 2B (NR2B) or NGF by putative sensory afferent (that express SP) fibers. The relationship between expression and pain characteristics was also examined. NGF and glutamate administration increased the density and expression of NR2B and NGF by muscle putative sensory afferent fibers (P < 0.050). This increase in expression was greater in women than in men (P < 0.050). Expression of NR2B receptors by putative sensory afferent fibers was positively correlated with pain characteristics. Results suggest that increased expression of peripheral NMDA receptors partly contributes to the increased pain and sensitivity induced by intramuscular injection of NGF and glutamate in healthy humans; a model of myofascial temporomandibular disorder (TMD) pain. Whether a similar increase in peripheral NMDA expression occurs in patients with painful TMDs warrants further investigation.

Effects of myofascial release applied to neck muscles and craniocervical flexor training in patients with chronic myofascial TMD: A single arm study

ObjectiveTo evaluate the effects of myofascial trigger point release applied to superficial neck muscles and strengthening of the deep flexor muscles in subjects with myofascial temporomandibular disorders (mTMD). MethodsFourteen women (23.4 ± 3.32 years old) presenting with mTMD and trigger points (TrPs) in the sternocleidomastoid, suboccipital, and upper trapezius muscles were included in this study. They were evaluated on two occasions during a baseline period (3 weeks apart) with no intervention and a third time after a 5-weeks intervention protocol. Outcome measures included pressure pain threshold (PPT) over the masticatory muscles, mandibular function, orofacial pain intensity, maximum mouth opening, and the craniocervical flexion test. All women received 10 treatment sessions that included strain-counterstrain technique applied to TrPs found in the prior listed superficial neck muscles and stabilization exercise using a pressure biofeedback for the deep neck flexor muscles. One-way ANOVA or correspondent non-parametric tests as well as effects sizes were used to compare the outcomes at baseline and after the treatment. ResultsStatistically significant improvements were found in the PPT over left masseter and temporalis (p < 0.05) (mean difference (MD) of 0.50 and 0.42 kg/cm2), orofacial pain intensity (MD = −3.39 points), mandibular function (MD = −7.22 points) and performance of the deep cervical muscles (MD = 130.42 points) compared to baseline period. Effect sizes were moderate or large. ConclusionThe protocol intervention may have positive effects in patients with mTMD. However, studies with better methodological quality need to be performed to confirm those effects. Registrationensaiosclinicos.gov.br (RBR-7x828q);

Aberrant Brain Signal Variability and COMT Genotype in Chronic TMD Patients

The analysis of brain signal variability is a promising approach to understand pathological brain function related to chronic pain. This study investigates whether blood-oxygen-level–dependent signal variability (BOLDSV) in specific frequency bands is altered in temporomandibular disorder (TMD) and correlated to its clinical features. Twelve patients with chronic myofascial TMD and 24 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging. The BOLDSV was measured as the standard deviation of the BOLD time series at each voxel and compared between groups. We also examined the potential relationship between the BOLDSV and the catechol-O-methyltransferase (COMT) Val158Met polymorphism. We assessed sensory-discriminative pain in the craniofacial region, pain sensitivity to sustained masseteric pain challenge, and TMD pain frequency for clinical correlation. Patients displayed reduced BOLDSV in the dorsolateral prefrontal cortex (dlPFC) as compared with HC in all frequency bands. In the slow-3 band, patients also showed reduced BOLDSV in the medial dorsal thalamus, primary motor cortex (M1), and primary somatosensory cortex (S1) and heightened BOLDSV in the temporal pole. Notably, we found a significant correlation between lower BOLDSV (slow-3) in the orofacial M1/S1 regions and higher clinical pain (intensity/area) and higher sensitivity of the masseter muscle pain. Moreover, lower BOLDSV (slow-3) in the dlPFC and ventrolateral PFC was associated with a higher TMD pain frequency. Participants who had the COMT 158Met substitution exhibited lower BOLDSV in the dlPFC and higher BOLDSV in the temporal pole as compared with participants without the COMT 158Met substitution. An increasing number of Met alleles was associated with lower dlPFC and greater temporal pole BOLDSV in both HC and TMD groups. Together, we demonstrated that chronic TMD patients exhibit aberrant BOLDSV in the top-down pain modulatory and sensorimotor circuits associated with their pain frequency and severity. COMT Val158Met polymorphism might affect clinical symptoms in association with regional brain signal variability, specifically involved in cognitive and emotional regulation of pain.