Temporomandibular Myofascial Pain Syndrome-Aetiology and Biopsychosocial Modulation. A Narrative Review

Effectiveness of Ultrasound Therapy, TheraBite Device, Masticatory Muscle Exercises, and Stabilization Splint for the Treatment of Masticatory Myofascial Pain: A Randomized Controlled Trial

BACKGROUND

Myofascial pain syndrome (MPS) is a particular type of temporomandibular joint disorder. Research findings comparing various treatment approaches are scarce and controversial. Therefore, this study aimed to compare the effectiveness of ultrasound therapy, stabilization splint, TheraBite device, and masticatory muscle exercises in reducing pain intensity and improving mandibular mobility in patients with MPS.

METHODS

It was a single-blind, randomized, parallel-group, active-controlled trial that took place between April 2023 and October 2023 at the Department of Fixed Prosthodontics, Damascus University. Patients older than 18 years old with myofascial pain accompanied by limited jaw opening and pain lasting for at least 6 months were included. Eighty patients were randomly assigned into four groups using online randomization software: ultrasound therapy, stabilization splint, TheraBite device, and masticatory muscle exercises. Only outcome assessors were masked to treatment allocation. The exercise regimen was the exercise program for patients with TMD. The following primary outcome measures were considered at the baseline (t0), at the first (t1), second (t2), and fourth (t3) week of treatment, and at the second (t4) and fifth (t5) month of follow-up: pain intensity using the visual analogue scale, maximum interincisal opening, right lateral movement, and left lateral movement measured in millimeters.

RESULTS

The pain level changed from severe to mild at t3 in ultrasound therapy, stabilization splint, and TheraBite device groups. In the masticatory muscle exercises group, it changed to moderate, with a significant difference between ultrasound therapy (p = 0.012) and stabilization splint (p = 0.013) groups. In addition, the mandibular mobility continued to improve at the subsequent follow-up periods (t4 and t5).

CONCLUSIONS

All therapies are equally effective after 5-month follow-up. However, ultrasound therapy and stabilization splints have the benefit of achieving rapid improvement.

TRIAL REGISTRATION

ISRCTN20833186.

β2-adrenergic receptor activation decreases the mechanical sensitivity of rat masticatory muscle afferent fibres

BACKGROUND

Activation of β2 adrenergic receptors reduces cutaneous mechanical pain thresholds in rats. While β2 adrenergic receptor activation may contribute to mechanisms that underlie temporomandibular joint pain, its effect on masticatory muscle pain sensitivity is uncertain.

OBJECTIVES

The current study sought to determine the extent to which β adrenergic receptors are expressed by masticatory muscle afferent fibres, and to assess the effect of local activation of these receptors on the mechanical sensitivity of masticatory muscle afferent fibres in rats.

METHODS

Trigeminal ganglion neurons that innervate the rat (n = 12) masseter muscle and lower lip were identified by tissue injection of fluorescent dyes and were then stained with antibodies against β1 or β2 adrenergic receptors. Extracellular recordings from 60 trigeminal ganglion neurons that innervate the masticatory muscle were undertaken in a second group of anaesthetised rats of both sexes (n = 37) to assess afferent mechanical activation thresholds. Thresholds were assessed before and after injection of the β adrenergic receptor agonists into masticatory muscle.

RESULTS

β1 and β2 adrenergic receptor expression was greater in labial skin than in masticatory muscle ganglion neurons (p < .05, one-way ANOVA, Holm-Sidak test). There was a higher expression of β2 adrenergic receptors in masticatory muscle ganglion neurons in males than in females. The mixed β agonist isoproterenol increased afferent mechanical activation threshold in male but not female rats (p < .05, Mann-Whitney test). In male rats, salbutamol, a β2 selective agonist, also increased afferent mechanical activation threshold but hydralazine, a vasodilator, did not (p < .05, Mann-Whitney test).

CONCLUSION

Activation of β2 adrenergic receptors decreases the mechanical sensitivity of masticatory muscle afferent fibres in a sex-related manner.

Anxiety mediates association between sex and jaw function limitation in temporomandibular disorder patients from China

Aim

The objective of this study is to explore the relationship between sex and jaw function and to test whether anxiety mediates the causal relationship between sex and jaw function in temporomandibular disorders (TMDs) patients.

Methods

A total of 488 participants with TMD were included in the analysis. Demographic data were collected. Generalized anxiety symptoms and anxiety severity were initially assessed using the GAD-7 questionnaire. And jaw function limitation was measured using the JFLS-8 scale. A directed acyclic graph (DAG) was used in this study to evaluate the hypotheses. Mediation analysis was conducted to explore causality and to calculate the total effect, natural direct effect (NDE) and natural indirect effect (NIE).

Results

In TMD patients, there was a significant association between female and jaw function (r = 0.17, p < 0.001), female and anxiety (r = 0.15, p = 0.002), anxiety and jaw function (r = 0.35, p < 0.001). In addition, sex can directly lead to differences in impaired jaw function (NDE: 3.719, 95% CI: 1.619-5.828, p < 0.001), and can also be causally related to jaw function through anxiety (NIE: 1.146, 95% CI: 0.267-2.024, p = 0.011). And the total effect was 4.865 (95% CI, 2.709-7.029, p < 0.001).

Conclusion

A causal mechanism was found that anxiety acts as a mediator of sex effects on jaw function. Therefore, psychological factors need to be taken into account in the treatment of female TMD patients. Further clinical trials are needed to explore whether psychotherapy is more beneficial to improve jaw function in female TMD patients.

Physical manifestations of stress in women. Correlations between temporomandibular and pelvic floor disorders

INTRODUCTION

Stress is characterized as a challenging occurrence that triggers a physiological and/or behavioral allostatic response, alongside the demands typically encountered throughout the natural course of life. A sustained state of stress gives rise to secondary effects, including insomnia and neck pain. Also, the risk of musculoskeletal problems in the cervical and lumbar spine can be increased due to a sustained state of stress. The present study main objective is to study the association between orofacial and pelvic floor muscles in women in Spain.

METHODOLOGY

An observational, cross-sectional, retrospective analytical study was designed and carried out in the laboratories of the European University of Madrid. Sixty-five participants were recruited with a mean age of 29.9 ± 7.69. Measurements were taken by myotonometry on natural oscillation frequency (Hz), dynamic stiffness (N/m), elasticity (N/m2), mechanical stress relaxation time (ms) and creep, for the following muscles: right and left masseter, right and left temporalis and central fibrous nucleus of the perineum (CFPF). On the other hand, the subjects completed the following questionnaires: perceived stress scale (PSS-14), anxiety scale (STAI), self-reported bruxism questionnaire (CBA), Fonseca Anamnestic Index and the Pittsburgh Sleep Quality Scale (PSQI).

RESULTS

Significant correlations were found in several parameters between the right temporalis and CFPF (p<0.05). Highlighting the correlation between TMDs and lubrication r = -0.254 (p = 0.041) and bruxism with pain in sexual intercourse r = 0.261 (p = 0.036).

CONCLUSION

The results support the proposed hypothesis. To the author's knowledge, this is the first study which relates both locations, and it is suggested to continue with the research and expand the knowledge of it.

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

OBJECTIVE

Bruxism 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.

METHODS

The 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).

RESULTS

No 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).

CONCLUSION

The 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.

Comorbid psychiatric conditions with temporomandibular disorders (TMD) in a tertiary referral clinic

Patients with chronic pain have a higher prevalence of mood disorders with depression and anxiety contributing to higher pain intensity, emotional allodynia, and neuro-anatomical changes. We sought to quantify the prevalence of psychiatric comorbidities (PCs) in a tertiary referral clinic for temporomandibular disorders (TMDs). Medical records of all patients attending clinics run by three tertiary temporomandibular joint (TMJ) surgeons for the period January to April 2022 inclusive were audited for the prevalence of concomitant psychiatric conditions. A total of 166 patients were identified with a female to male ratio of 5:1 and mean (SD) age of 45.1 (15.2) years. A total of 124 (89.9%) patients were tertiary referrals and 72 (43.4%) patients had concomitant psychiatric diagnoses, with 58 (34.9%) being on some form of psychotropic medication (PM) (patients on anticonvulsants for neuropathic pain were not included). A majority of 136 (81.9%) patients had some form of intervention (including Dysport® and minimally invasive surgery) which appeared more common in patients with co-existing psychiatric issues (p < 0.05). A higher proportion of mental health issues exist among TMD patients in a tertiary referral clinic than would be expected in the general population. We suggest a holistic approach to patients with multidisciplinary care taking into account this prevalence to ensure decision-making that contextualises the patient and not simply the pathology.

Do myofascial trigger points in masseter muscles affect the symptoms of disc displacement with reduction? A cross-sectional study

OBJECTIVE

The aim of this study was to demonstrate the effect of myofascial pain with referral from the trigger points in the masseter muscles on the clinical symptoms and functional limitations of the temporomandibular joint in participants with disc displacement with reduction.

METHODS

This prospective, cross-sectional study recruited participants aged 18-45 years with disc displacement with reduction with/without myofascial pain with referral in the masseter muscles based on the inclusion criteria. Maximum mouth opening and the presence of probable awake bruxism were assessed. The "Graded Chronic Pain Scale version 2.0" and "Jaw Function Limitation Scale-8" were used to evaluate Diagnostic Criteria for Temporomandibular Disorders Axis II. Pain levels were measured using the Visual Analog Scale.

RESULTS

A comparison between the disc displacement with reduction and disc displacement with reduction+myofascial pain with referral groups revealed statistically significant differences in Visual Analog Scale (p<0.001), the presence of awake bruxism (p=0.038), and Graded Chronic Pain Scale version 2.0 (p=0.010). However, no statistically significant difference was observed between the two groups concerning maximum mouth opening and Jaw Function Limitation Scale-8.

CONCLUSION

Participants with both disc displacement with reduction and myofascial pain with referral in the masseter muscle exhibited higher pain intensity, a higher prevalence of awake bruxism, and increased pain-related disability compared to those with disc displacement with reduction alone.

Allogenic umbilical cord tissue for temporomandibular joint injuries

The temporomandibular joint (TMJ) is crucial for functions of daily living such as mastication and articulation. Common TMJ issues include osteoarthritis, internal derangement, and myofascial pain dysfunction. Conservative methods such as physical therapy and medications are used, with surgical options such as arthroscopy and replacement for severe cases. Emerging regenerative medicine explores non-surgical treatments using human stem cells from umbilical cord derivatives, showing potential for tissue regeneration in TMJ disorders. A systematic search was conducted across PubMed, Embase, Scopus, and Web of Science databases, adhering to PRISMA guidelines, aiming to identify relevant articles published in English until August 2023. The search used specific terms to target in vitro, preclinical, and clinical studies on umbilical cord (UC)-derived tissue and mesenchymal stem cells (MSCs) for treating TMJ disorders. The search was extended to three clinical trial registries for on-going investigations related to UC tissue and MSCs for TMJ disorder management. The studies included in this article report the safety and efficacy profiles of allogenically acquired, umbilical cord-derived tissues and associated mesenchymal stem cells for temporomandibular joint ailments, future adequately powered, randomized controlled trials are warranted to conclusively justify the clinical use of this biologic therapy.

Effect of Botulinum Toxin on Masticatory Muscle Pain in Patients with Temporomandibular Disorders: A Randomized, Double-Blind, Placebo-Controlled Pilot Study

This study aimed to evaluate the efficacy of botulinum toxin type A (BoNT/A) in patients with temporomandibular disorders (TMDs) associated with masticatory muscle pain (MMP) and headaches. This randomized, double-blind, placebo-controlled pilot study is the first clinical trial to evaluate both disorders simultaneously. Twenty-one patients with myogenous TMD were randomly assigned to two groups. The experimental and control groups received injections of either BoNT/A or saline into the sites showing tenderness after palpation of a total of 16 muscle areas, including each masseter, a temporalis, splenius capitis, sternocleidomastoid, and trapezius muscle. During each visit, the clinical effects, based on the intensity of orofacial pain (OVAS), headache (HVAS), number of tender points (TPs), maximum mouth opening (MMO), and headache frequency (HF), were evaluated at four time points, namely, pre-injection and 4, 8, and 12 weeks after the injection, in both groups. Friedman and Mann-Whitney tests were used for the analyses. In the experimental group, the reductions in OVAS, TP, HVAS, and HF showed significant differences over time, excluding MMO, whereas there was no significant difference in any of the variables in the control group. In addition, the decline in TPs was significantly different between the experimental and control groups at all time points, especially after 4 and 12 weeks, compared to that during pre-injection. In conclusion, treatment with BoNT/A was relatively effective for masticatory muscle pain caused by TMDs and headache compared to the saline placebo.

Pharmacological Management of Orofacial Pain

Orofacial pain is a category of complex disorders, including musculoskeletal, neuropathic and neurovascular disorders, that greatly affect the quality of life of the patient. These disorders are within the fields of dentistry and medicine and management can be challenging, requiring a referral to an orofacial pain specialist, essential for adequate evaluation, diagnosis, and care. Management is specific to the diagnosis and a treatment plan is developed with diverse pharmacological and non-pharmacological modalities. The pharmacological management of orofacial pain encompasses a vast array of medication classes and approaches. This includes anti-inflammatory drugs, muscle relaxants, anticonvulsants, antidepressants, and anesthetics. In addition, as adjunct therapy, different injections can be integrated into the management plan depending on the diagnosis and needs. These include trigger point injections, temporomandibular joint (TMJ) injections, and neurotoxin injections with botulinum toxin and nerve blocks. Multidisciplinary management is key for optimal care. New and safer therapeutic targets exclusively for the management of orofacial pain disorders are needed to offer better care for this patient population.

Temporomandibular disorders in immune-mediated rheumatic diseases of the adult: A systematic review

OBJECTIVE

To systematically review the literature concerning temporomandibular disorders (TMDs) in immune-mediated rheumatic diseases (IMRDs) of the adult. The temporomandibular joint (TMJ) outcomes used in clinical studies, the prevalence of TMDs in IMRDs and the risk factors for their development were qualitatively synthetized.

METHODS

A literature search on PubMed Central, Embase and Cochrane Library databases was performed for studies including TMJ outcomes in IMRDs patients compared with healthy controls, other rheumatic diseases or in the assessed IMRDs patients after follow-up and treatment. Among the IMRDs of the adult, original articles investigating TMJ involvement in inflammatory polyarthritides and/or autoimmune connective tissue diseases were considered. The quality of the studies was scored using the Newcastle-Ottawa scale (NOS).

RESULTS

Of the 3259 screened abstracts, 56 papers were included in the systematic review. Most of the papers (77%) investigated TMDs in rheumatoid arthritis (RA) with a prevalence of signs and symptoms varying from 8% to 70%. The risk factors for TMDs development in RA were female sex, younger age, anti-citrulline peptide autoantibodies (ACPA) positivity, higher disease activity, cervical spine involvement, cardiovascular and neuropsychiatric comorbidities. Ten papers (18%) evaluated TMDs in spondylarthritides (SpA) reporting a prevalence of symptoms and signs in 12%-80% of patients with higher TMDs prevalence in patients with radiographic spine involvement, skin psoriasis and HLADRB1×01 positivity. Among autoimmune connective tissue diseases (CTDs), systemic sclerosis (SSc) displayed the highest evidence of TMDs patient-reported outcomes (PROs) and clinical findings (20-93%), followed by systemic lupus erythematosus (SLE) in 18-85%, primary Sjogren's syndrome (24-54%) and idiopathic inflammatory myopathies (4-26%). In SSc and SLE, TMDs were more frequent in patients with higher disease activity and duration, correlating with the extent of skin fibrosis in SSc and with renal involvement in SLE.

CONCLUSION

TMDs in IMRDs display a significant relevance in the rheumatological clinical practice even if often misdiagnosed. This burden is epidemiologically important in terms of PROs and clinical findings which correlate with disease activity in RA, SpA, SSc and SLE. The early recognition and multidisciplinary management of TMDs is warranted and should be aimed at hindering the TMJ structural damage maximizing the quality of life of patients.

Temporomandibular Joint Disorders: Functional and Conservative Treatment

Temporomandibular joint disorders (TMDs) represent a group of conditions that cause pain and dysfunction in the joints and muscles responsible for jaw movement [...].

Outcomes of IncobotulinumtoxinA Injection on Myalgia and Arthralgia in Patients Undergoing Temporomandibular Joint Arthroscopy: A Randomized Controlled Trial

BACKGROUND

Several studies have considered Botulinum Neurotoxin Type A injections effective in treating temporomandibular joint disorder (TMD) symptoms. A double-blind, randomized, controlled clinical trial investigated the benefit of complementary incobotulinumtoxinA (inco-BoNT/A) injections in the masticatory muscles of patients submitted to bilateral temporomandibular joint (TMJ) arthroscopy.

METHODS

Fifteen patients with TMD and an indication for bilateral TMJ arthroscopy were randomized into inco-BoNT/A (Xeomin, 100 U) or placebo groups (saline solution). Injections were carried out five days before TMJ arthroscopy. The primary outcome variable was a Visual Analogue Scale for TMJ arthralgia, and secondary outcomes were the myalgia degree, maximum mouth opening, and joint clicks. All outcome variables were assessed preoperatively (T0) and postoperatively (T1-week 5; T2-6-month follow-up).

RESULTS

At T1, the outcomes in the inco-BoNT/A group were improved, but not significantly more than in the placebo group. At T2, significant improvements in the TMJ arthralgia and myalgia scores were observed in the inco-BoNT/A group compared to the placebo. A higher number of postoperative reinterventions with further TMJ treatments were observed in the placebo group compared to inco-BoNT/A (63% vs. 14%).

CONCLUSIONS

In patients submitted to TMJ arthroscopy, statistically significant long-term differences were observed between the placebo and inco-BoNT/A groups.

Stress Experience, Depression and Neck Disability in Patients with Temporomandibular Disorder-Myofascial Pain with Referral

The etiology of temporomandibular disorders (TMDs) is firmly anchored in the biopsychosocial model in which a special role is attributed to the stress, depression, somatic symptoms, and anxiety. The aim of the study was to assess the level of stress, depression and neck disability in patients with temporomandibular disorder-myofascial pain with referral. The study group enrolled 50 people (37 women and 13 men) with complete natural dentition. All the patients underwent a clinical examination according to the Diagnostic Criteria for Temporomandibular Disorders and were diagnosed as individuals with myofascial pain with referral. The questionnaires were associated with stress, depression, and neck disability; Perceived Stress Scale (PSS-10), Beck Depression Inventory(BDI), and Neck Disability Index (NDI) were evaluated. Of the individuals evaluated, 78% showed elevated levels of stress, and the average value of the PSS-10 in the study group was 18 points (Me = 17). Furthermore, 30% of the subjects presented depressive symptoms, with the average value of BDI was 8.94 points (Me = 8), and 82% of the subjects showed neck disability. The multiple linear regression model revealed that BDI and NDI allowed explanations for the 53% differentiation of PSS-10. In conclusion, stress, depression, and neck disability coexist with temporomandibular disorder-myofascial pain with referral.

The Role of Maxillofacial Structure and Malocclusion on Condylar Displacement in Maximum Intercuspation and Centric Relation in Patients Seeking Orthodontic Treatment-A Scoping Review

BACKGROUND

Available knowledge about malocclusion and cephalometric variables and their connection with an increased risk of condylar displacement (CD) is scarce. This article aims to present current information on the relationship between centric relation-maximum intercuspal position discrepancies and maxillofacial morphology and malocclusion in patients seeking orthodontic treatment as well as to identify those who require expanded diagnostic evaluation for this disorder.

METHODS

This review analyzed the PubMed, Cochrane Library, Web of Science, and Scopus electronic databases up to February 2022. Keywords and additional manual searches were performed. Literature selection was based the PRISMA-ScR checklist. The JBI Critical Appraisal Tool assessed the methodological quality of included studies.

RESULTS

The databases search provided 2321 studies. A total of 10 studies were included in this review after eligibility criteria and JBI assessment. This review was separated into five parts that evaluated CD correlations depending on the following: maxillofacial structure in different vertical and sagittal skeletal patterns, vertical, horizontal, and transverse malocclusions.

CONCLUSIONS

A hyperdivergent facial skeletal structure is a risk factor for increased CD, particularly in the vertical dimension. The condylar processes are usually displaced in a posteroinferior direction. Further studies are warranted to elucidate the relationship among remaining skeletal and dental malocclusions and the occurrence of CD.

Preclinical models of deep craniofacial nociception and temporomandibular disorder pain

Chronic pain in temporomandibular disorder (TMD) is a common health problem. Cumulating evidence indicates that the etiology of TMD pain is complex with multifactorial experience that could hamper the developments of treatments. Preclinical research is a resource to understand the mechanism for TMD pain, whereas limitations are present as a disease-specific model. It is difficult to incorporate multiple risk factors associated with the etiology that could increase pain responses into a single animal. This article introduces several rodent models which are often employed in the preclinical studies and discusses their validities for TMD pain after the elucidations of the neural mechanisms based on the clinical reports. First, rodent models were classified into two groups with or without inflammation in the deep craniofacial tissues. Next, the characteristics of each model and the procedures to identify deep craniofacial pain were discussed. Emphasis was directed on the findings of the effects of chronic psychological stress, a major risk factor for chronic pain, on the deep craniofacial nociception. Preclinical models have provided clinically relevant information, which could contribute to better understand the basis for TMD pain, while efforts are still required to bridge the gap between animal and human studies.

The Prevalence and Overlaps of Temporomandibular Disorders in Patients with Myofascial Pain with Referral-A Pilot Study

The aim of the study was to evaluate the temporomandibular joint, the prevalence of single and multiple diagnosis and potential sided domination of temporomandibular dysfunction in patients with temporomandibular disorder-myofascial pain with referral. The study group enrolled 50 people-37 females and 13 males between 18 and 25 years old with an average age of 23.36 ± 2.14. The patients underwent joint vibration analysis. Sixty seven percent of all examined tem-poromandibular joints were classified as group I according to Mark Piper's classification. Class IIIA appeared in 17% of joints. Eight percent of temporomandibular joints were classified as class IVA. There were no statistically significant differences in the prevalence of temporomandibular disorder with respect to gender (p = 0.838639). The relatively high prevalence of multiple diagnoses proved the overlapping nature of muscle and intraarticular disorders. Twenty eight percent of the subjects suffered from a combination of myofascial pain with referral and bilateral temporoman-dibular dysfunction. In 62% of the patients a lack of intraarticular disorders was reported. The suggestion that there exists sided domination in the occurrence of temporomandibular disorders has not been confirmed. Due to the small sample size, such differences cannot be excluded. Fur-ther research is needed.