Oro-facial pain and temporomandibular disorders classification systems: A critical appraisal and future directions

Is Muscle Pain in Temporomandibular Disorder a Hyperactivity Problem? A Clinical, Thermographic, and Electromyographic Analysis

ABSTRACT

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

LEVEL OF EVIDENCE

Level IV.

Does Liquid/Injectable Platelet-Rich Fibrin Help in the Arthrocentesis Treatment of Temporomandibular Joint Disorder Compared to Other Infusion Options? A Systematic Review of Randomized Clinical Trials

Temporomandibular joint disorders (TMDs) are prevalent musculoskeletal conditions involving pain and dysfunction of jaw mobility and function, which have proven difficult to treat satisfactorily. The present study aimed to assess the effectiveness of a liquid platelet-rich fibrin (i-PRF) infusion during arthrocentesis versus other options using coadjuvant materials to reduce TMD symptoms. A literature search was conducted using PubMed, EMBASE, Web of Science, Scopus, and ClinicalTrials.gov for RCTs published before January 2024, comparing i-PRF to any other TMD treatment. This systematic review was registered on PROSPERO (CRD42023495364). The searches generated several recent RCTs that compared i-PRF injection combined with arthrocentesis (AC) to AC-only or AC with platelet-rich plasma (PRP). The outcomes analyzed included measures of pain (visual analog scale, VAS), maximum mouth opening, joint sounds, and MRI-verified changes in joint structure. Across the RCTs, the addition of i-PRF injection to AC resulted in significant improvements in pain relief, joint function, mouth opening, and structural changes compared to AC-only or with PRP over follow-up periods ranging from 6 to 12 months. Current clinical evidence favors using i-PRF as an adjunct to AC rather than AC-only or AC with PRP for the treatment of TMDs. The improvements in subjective and objective outcome measures are clinically meaningful. Still, additional high-quality RCTs with larger sample sizes and longer follow-ups are required to strengthen the evidence base and better define the role of i-PRF in TMD management guidelines.

Advancements in Understanding and Classifying Chronic Orofacial Pain: Key Insights from Biopsychosocial Models and International Classifications (ICHD-3, ICD-11, ICOP)

In exploring chronic orofacial pain (COFP), this review highlights its global impact on life quality and critiques current diagnostic systems, including the ICD-11, ICOP, and ICHD-3, for their limitations in addressing COFP's complexity. Firstly, this study outlines the global burden of chronic pain and the importance of distinguishing between different pain types for effective treatment. It then delves into the specific challenges of diagnosing COFP, emphasizing the need for a more nuanced approach that incorporates the biopsychosocial model. This review critically examines existing classification systems, highlighting their limitations in fully capturing COFP's multifaceted nature. It advocates for the integration of these systems with the DSM-5's Somatic Symptom Disorder code, proposing a unified, multidisciplinary diagnostic approach. This recommendation aims to improve chronic pain coding standardization and acknowledge the complex interplay of biological, psychological, and social factors in COFP. In conclusion, here, we highlight the need for a comprehensive, universally applicable classification system for COFP. Such a system would enable accurate diagnosis, streamline treatment strategies, and enhance communication among healthcare professionals. This advancement holds potential for significant contributions to research and patient care in this challenging field, offering a broader perspective for scientists across disciplines.

Single-rooted extraction socket classification: A systematic review and proposal of a new classification system based on morphologic and patient-related factors

Taxonomy and classification of a disease contributes to facilitating the diagnosis and treatment planning process and simplifies communication between clinicians. The aim of this study was to provide a critical appraisal based on a systematic review of the single-rooted extraction socket (ES) classifications and subsequently, introduce a new classification system combining the cornerstones of the previously proposed systems and based on the latest consensus in implant dentistry. Following the systematic search process in PubMed, EMBASE, and SCOPUS databases 13 ES classifications were detected. The most repeated hard and soft tissue factors in the previous classifications were buccal bone dehiscence, interproximal bone, gingival recession, and soft tissue phenotype. However, there was minimal attention to patient-related factors such as systemic conditions and smoking. Therefore, a new classification system based on the combination of patient-related factors, clinical and radiographical parameters was proposed. This divides an ES into three types. Class I and II sockets are candidates for receiving immediate implant placement and conversely, a class III socket includes a compromised condition that requires multiple-stage reconstruction mostly suitable for standard delayed implant placement with alveolar ridge preservation. Within the limitations of this study, the new classification system not only provides comprehensive inclusion of various crucial parameters in implant placement (such as prediction of future implant position and osteotomy difficulty, etc.) but also, in contrast to the previously introduced systems, is able to classify the ES prior to extraction and also, takes into the account the patient-related factors as the class modifiers following the extraction.

Graded exposure and orthopedic manual physical therapy for kinesiophobia and function in chronic temporomandibular dysfunction: A case report

BACKGROUND

This case report describes the successful use of multi-modal physical therapy (PT), including orthopedic manual physical therapy (OMPT) and graded exposure, in a patient with chronic temporomandibular dysfunction (TMD).

CLINICAL PRESENTATION

A 41-yr old female presented with a five-year history of bilateral chronic myofascial TMD and comorbid neck/right arm pain. The patient was treated for 12 weeks with a focus on OMPT and graded exposure. The patient demonstrated clinically significant improvements on the Tampa Scale of Kinesiophobia-TMD, maximal mouth opening, Global Rating of Change, and Jaw Functional Limitation Scale.

CLINICAL RELEVANCE

Mechanisms underlying chronic TMD are complex. Current evidence supports PT management of physical impairments; however, neglecting central drivers or psychosocial factors may result in suboptimal outcomes. Physical therapists are able to address both peripheral and central mechanisms of pain, and future research should examine the utilization of multi-modal PT to improve kinesiophobia and function in patients with chronic TMD.

Malocclusion Generates Anxiety-Like Behavior Through a Putative Lateral Habenula-Mesencephalic Trigeminal Nucleus Pathway

Malocclusion is an important risk factor for temporomandibular disorder (TMD), a series of disorders characterized by dysfunction in the orofacial region involving the temporomandibular joint (TMJ) and jaw muscles. We recently showed that experimental unilateral anterior crossbite (UAC) produced masseter hyperactivity through a circuit involving the periodontal proprioception, trigeminal mesencephalic nucleus (Vme), and trigeminal motor nucleus (Vmo). Anxiety is a common complication in patients with TMD. The lateral habenula (LHb) is involved in emotional modulation and has direct projections to the Vme. Therefore, the present research examined whether UAC facilitates excitatory input from the LHb to the Vme and, subsequently, anxiety-like behaviors in rats. The LHb activation was evaluated by the electrophysiological recording, assessment of vesicular glutamate transporter-2 (VGLUT2) mRNA expression, and measurement of anxiety-like behaviors. The effects of LHb activity on Vme were evaluated by electrophysiological recording from Vme neurons and local changes in VGLUT2 protein density. UAC produced anxiety in modeled rats and increased neuronal activity in the LHb. VGLUT2 mRNA expression was also increased in the LHb. Further, VGLUT2-positive boutons were observed in close apposite upon parvalbumin (PV)-labeled Vme neurons. VGLUT2 protein expression was also increased in the Vme. Significantly, injection of VGLUT2-targeted shRNA into the LHb reduced the expression of VGLUT2 protein in the Vme, attenuated UAC-associated anxiety-like behaviors, and attenuated electrophysiological changes in the Vme neurons. In conclusion, we show that UAC activates the LHb neurons as well as the periodontal proprioceptive pathway to provide excitatory input to the Vme and produce anxiety in rats. These findings provide a rationale for suppressing activity of the LHb to attenuate both the physical and psychological effects of TMD.

Non-invasive brain stimulation in chronic orofacial pain: a systematic review

Background

Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are non-invasive brain stimulation techniques that are being explored as therapeutic alternatives for the management of various chronic pain conditions.

Objective

The primary objective of this systematic review is to assess the efficacy of TMS and tDCS in reducing clinical pain intensity in chronic orofacial pain (OFP) disorders. The secondary objectives are to describe adverse effects, duration of relief, and TMS/tDCS methodologies used in chronic OFP disorders.

Methods

A search was performed in MEDLINE, Embase, Web of Science, Scopus, and Google Scholar. Inclusion criteria were 1) population: adults diagnosed with chronic OFP including neuropathic and non-neuropathic disorders; 2) intervention: active TMS or tDCS stimulation regardless of the used protocol; 3) comparison: sham TMS or tDCS stimulation; and 4) outcome: primary outcome was patient reported pain intensity. Secondary outcomes were duration of pain relief, adverse effects, and methodological parameters. Risk of bias and quality of study reporting were also assessed.

Results

A total of 556 individual citations were identified by the search strategy, with 14 articles meeting selection criteria (TMS=11; tDCS=3). Data were obtained for a total of 228 patients. Included OFP disorders were trigeminal neuralgia, trigeminal neuropathy, burning mouth syndrome, atypical facial pain, and temporomandibular disorders. Significant pain reductions were obtained in both techniques. More number of sessions yielded to more durable effects. Overall, high risk of bias and poor study quality were found.

Conclusion

TMS and tDCS appear to be safe and promising alternatives to reduce pain intensity in different chronic OFP disorders. Additional research effort is needed to reduce bias, improve quality, and characterize optimal brain stimulation parameters to promote their efficacy.