Orofacial musculoskeletal pain: An evidence-based bio-psycho-social matrix model

Association between possible bruxism, sleep quality, depression, anxiety and stress by gender. A cross-sectional study in a Spanish sample

OBJECTIVE

To explore the associations between possible bruxism, sleep quality, depression, anxiety and stress, with a specific focus on gender differences.

MATERIAL AND METHODS

An online questionnaire was administered to 400 Spanish-speaking participants, without cognitive impairments. The survey included the possible bruxism self-perception test of Lobbezoo et al., the Pittsburgh Sleep Quality Index, and the Depression, Anxiety, and Stress Scale-21 (DASS-21). Participants were recruited using a "snowball" sampling technique over a five-month period in 2024. The Chi-square test and the Fisher-Freeman-Halton exact test were used for statistical analysis. The significance level was set at 0.05.

RESULTS

Possible bruxists made up 25.4 % of women (n = 67) and 14.7 % of men (n = 20), with a statistically significant difference (P = 0.019). Depression was present in 30.0 % of participants (33.0 % of women and 24.3 % of men; P = 0.072), anxiety in 30.7 % (36.0 % of women and 20.6 % of men; P = 0.002), and stress in 29.0 % (33.3 % of women and 20.6 % of men; P = 0.008). No significant association was found between possible bruxism and emotional disorders in men, whereas a strong association was observed in women (P < 0.001). Similarly, no statistically significant relationship was found between possible bruxism and sleep quality in either gender. However, poor sleep quality was more common among women than men (54.6 % vs 43.7 %; P = 0.040).

CONCLUSIONS

Poor sleep quality, anxiety, stress and depression and possible bruxism are more frequent among women. While no association between possible bruxism and emotional disorders was found in men, a significant relationship was observed in women. Furthermore, although no direct association between possible bruxism and sleep quality was detected, sleep quality was significantly associated with emotional disorders in both genders.

CLINICAL RELEVANCE

These findings suggest that emotional disorders may contribute to the development of possible bruxism in women but not in men. Therefore, women with emotional disorders should be closely monitored, as they are particularly susceptible to possible bruxism and poor sleep quality. Dentists play a crucial role in diagnosing possible bruxism and identifying patients who may benefit from psychological support.

Orofacial pain symptoms in sleep bruxer or non-sleep bruxer: Insights from a population-based survey of puerperal women

OBJECTIVE

This study aimed to investigate the prevalence of orofacial pain (OP) symptoms among a large sample of women who self-identified as sleep bruxers or non-sleep bruxers and who had given birth in 2019 in the municipality of Rio Grande, RS, Southern Brazil.

METHODS

A standardized self-questionnaire was administered to assess OP symptoms. Chi-square tests were employed to compare proportions, and multivariate Poisson regression analysis with robust variance adjustment was used to estimate associations with sleep bruxers and non-sleep bruxers.

RESULTS

A total of 2225 women were included in the study, with 78 (3.5 %) reporting OP symptoms. In the adjusted analysis, self-reported OP symptoms were significantly associated with non-sleep bruxer women living with three or more people in the household (PR=8.40; 95 % CI 1.85-38.11), as well as severe anxiety (PR= 4.73; 95 % CI 2.00-11.18). Among sleep bruxers, a significantly lower OP symptoms prevalence for those who were able to rely on their friends in times of distress (PR= 0.17; 95 % CI 0.10-0.30), while those with personality disorders exhibited significantly higher OP symptoms prevalence (PR= 3.30; 95 % CI 1.04-10.45).

CONCLUSIONS

The prevalence of OP symptoms was higher among non-sleep bruxer women living with three or more individuals in the household and among those experiencing severe anxiety. Indeed, sleep bruxer women with personality disorders had a higher prevalence of OP symptoms, while those with strong social support demonstrated a lower prevalence.

Nocturnal Autonomic Nervous System Dynamics and Chronic Painful Temporomandibular Disorders

OBJECTIVE

Chronic pain associated with temporomandibular disorders (TMDs) may reflect dynamic autonomic nervous system (ANS) effects. This pilot observational study tested the hypotheses that Characteristic Pain Intensity (CPI) scores correlated with 1) amplitude, 2) duration, and 3) power densities (amplitude/duration) of nocturnal ultradian cycling of the sympathetic and parasympathetic arms of the ANS.

MATERIALS AND METHODS

In accordance with institutional review board oversight and Strengthening the Reporting of Observational Studies in Epidemiology guidelines, adult subjects gave informed consent, completed Axis I and II components of Diagnostic Criteria for TMD (DC-TMD), and were trained in research protocols to record nocturnal heart rate data. Subjects were assigned to ± pain groups based on CPI scores (0 = no pain, >0 = pain). Nocturnal ultradian cycling of sympathetic and parasympathetic activities was characterized using heart rate variability measures of the percentage of the absolute value of the low-frequency power component (ms2) and normal-to-normal sinus node depolarizations >50 ms compared to total number (pNN50, %), respectively. Peaks and valleys of ultradian cycling were identified, where cycle amplitudes and durations were quantified, and sympathetic/parasympathetic power densities were calculated. The hypotheses were tested by nonparametric correlations and regression analyses, where significance was defined by P < 0.05.

RESULTS

Of 32 individuals screened and enrolled, 18 females and 11 males completed all study protocols. Subjects produced 87 nighttime electrocardiogram recordings with an average duration of 7.7 ± 1.0 h. CPI scores ranged from 0 to 70 and were significantly higher (P = 0.032) in females (30 ± 25) than in males (10 ± 17). Nocturnal ultradian sympathetic cycling in females compared to males showed significantly higher amplitudes (P = 0.011) and lower durations (P = 0.048). CPI scores were correlated with nocturnal cycling amplitude and duration (all |R| ≥ 0.80) and the log of sympathetic/parasympathetic power densities (R2 = 0.89).

CONCLUSION

Characteristic Pain Intensity scores were correlated with amplitudes, durations, and power densities of nocturnal ANS ultradian cycling.Knowledge Transfer Statement:Chronic myofascial pain may reflect autonomic nervous system (ANS) activity. Characteristic Pain Intensity scores of subjects were correlated with power densities of ANS ultradian cycling during sleep. Future research is needed to detect sex differences in ANS power densities in subjects with chronically painful temporomandibular disorders.

Language errors in pain medicine: An umbrella review

Errors in language are common in pain medicine, but the extent of such errors has not been systematically measured. This pre-registered umbrella review explored Embase, PubMed, Medline and CINAHL and seeks to quantify the prevalence of errors in language in review articles since the last IASP definition revision. To be eligible, studies must have met the following criteria: 1) Primary aim was stated as to provide neurophysiological explanations of nociception and/or pain in humans in context of a pathology/condition; 2) Any type of review article; 3) Written in English; 4) Published in a peer-reviewed journal. Studies were excluded if they met any of the following criteria: 5) Published prior to the last revision of the IASP definition; 6) Published after May 2023; 7) Published in a predatory journal. Out of 5470 articles screened, 48 review articles met the inclusion criteria. All articles contained at least one error in language, there were no differences in the proportions of errors in language in review articles between years of publication, and various predictors were mostly not associated with a higher or lower number of errors in language counts in articles. Our findings reveal the need for heightened awareness among researchers, clinicians, journals and editorial boards regarding the prevalence and impact of these errors. Given our findings and their limitations, further research should focus on examining the contextual influence of misnomer usage and replication of these results. PERSPECTIVE: This umbrella review explored the main biomedical databases to see how many review articles contained language errors. Our findings underscore the imperative for prompt action in regulating pain medicine terminology. PRE-REGISTRATION: This umbrella review was pre-registered on OSF registries (https://doi.org/10.17605/osf.io/kau8m). ONLINE MATERIAL: https://osf.io/kdweg/.

Novel apocynin regulates TRPV1 activity in the trigeminal system and controls pain in a temporomandibular joint neurogenic model

OBJECTIVE

Herein, we investigate the potential analgesic effect of a newly synthesized chalcone-derived apocynin in a neurogenic pain model.

METHODS

Molecular docking was used to foretell the apocynin binding features and dynamics with the TRPV1 channel, and the activity was tested in vitro, using transfected HEK 293T cells with the rat TRPV1 receptor. The analgesic effect of apocynin was investigated using a capsaicin-induced pain model. The expression of TRPV1, TRPA1, TRPM8, and MAPKs was assessed by electrophoresis, and immunosorbent assays were performed to quantify the neurotransmitters Substance P, Glutamate, and CGRP. A survival assay using Galleria mellonella was carried out to determine the toxicity.

RESULTS

We observed that apocynin exhibits greater thermodynamic stability. Upon apocynin ligand binding, it changes the electrostatic potential for a predominantly electronegative state in the interior and neutral in its external vanilloid pocket. Treatment of apocynin induces antinociceptive effects against the noxious challenge of capsaicin. Histologically, apocynin decreased the number of TRPV1+ immunopositive cells. Electrophoresis showed reduced phosphorylation of p44/42 (ERK1/2) and decreased protein levels of substance P, and CGRP. In the survival assay, apocynin showed low toxicity.

CONCLUSIONS

In conclusion, we provide proof-of-principles that the newly synthesized apocynin compound effectively prevented nociception in a neurogenic model of orofacial pain.

Regulation of CeA-Vme projection in masseter hyperactivity caused by restraint stress

The overactivity of the masticatory muscles (bruxism or teeth clenching) is associated with stress exposure, and often leading to consistent muscle pain. However, the neural mechanism underlining it is not fully understood. The central amygdala (CeA), which is linked to stress-induced behaviors and physical reactions, projects directly to the mesencephalic trigeminal nucleus (Vme), which is crucial for oral-motor coordination. Thus, we hypothesized that the projections from the CeA to the Vme could be linked to stress-induced anxiety and overactivity of the jaw muscles. After establishing an animal model of restraint stress, we found that chronic stress could lead to noticeable anxiety-related behavior, increased masseter muscle activity, activation of GABAergic neurons in the CeA, and opposite changes in the excitability of multipolar GABAergic interneurons and pseudounipolar excitatory neurons in the Vme. Subsequently, through the utilization of anterograde and transsynaptic tracing in conjunction with immunofluorescence staining, we discovered that the neural projections from the CeA to the Vme were mainly GABAergic and that the projections from the CeA terminated on GABAergic interneurons within the Vme. Moreover, chemogenetically suppressing the function of GABAergic neurons in the CeA could effectively reduce anxiety levels and reverse the increase in the activity of the masseter muscles induced by stress. And, specifically inhibiting GABAergic projections from the CeA to the Vme via optogenetics could reduce the hyperactivity of the masseter muscles but not stress-induced anxiety. In conclusion, our findings indicate that GABAergic projections from the CeA to the Vme may play an important role in the masseter overactivity in response to chronic stress.

Correlation of Chronic Cervico-Cranio-Mandibular Pain in Individuals with Adverse Childhood Events: An Observational Study

OBJECTIVES

This cross-sectional observational study examines the relationship between chronic cervico-cranio-mandibular pain, a significant health concern associated with temporomandibular disorders, and adverse childhood experiences (ACEs). Given the high prevalence of cervical pain and the gap in adequate treatment for temporomandibular disorders, this research highlights the interplay between psychological, social factors, and musculoskeletal health.

METHODS

The study, conducted from January to June 2023, included 114 participants (mean age = 31 ± 12 years, 69.3% female) experiencing chronic cervico-cranio-mandibular pain. Pain severity and dysfunction were assessed, and exposure to ACEs was measured using validated questionnaires. Statistical analysis, performed using Jamovi (v 2.23.28) software.

RESULTS

Data revealed a significant correlation between the number of ACEs and both pain intensity (r = 0.254, p = 0.006, η2 = 0.062) and disability (r = 0.262, p = 0.005, η2 = 0.068). However, no significant association was found between ACEs and mandibular functional limitation (p = 0.222). These findings suggest that while early life stressors impact overall health, their specific influence on cervico-cranio-mandibular pain is limited.

CONCLUSION

The study emphasizes the importance of integrated early intervention strategies to mitigate the long-term musculoskeletal repercussions of adverse events, advocating for comprehensive mental health support and preventive measures. This research contributes valuable insights into the necessity of a multifaceted approach to understanding, diagnosing, and treating musculoskeletal disorders, highlighting the complexity of their causes and effects.

What has a year of social isolation due to the COVID-19 pandemic influenced oral parafunctional habits and temporomandibular disorders? A case-control study

OBJECTIVE

Few studies investigated the influence of oral parafunctional habits during the COVID-19 pandemic. Since some studies have demonstrated that signs and symptoms of temporomandibular disorder (TMD), as well as psychological alterations, increased during the COVID-19 pandemic lockdown, the aim of this study was to investigate whether social isolation is a situation that increases the prevalence of oral parafunctional habits.

METHODS

This was an observational case-control study. An online survey with questions about TMD symptoms (Diagnostic Criteria Symptom Questionnaire) and oral parafunctional habits (Oral Behaviours Checklist [OBC]) was administered to Brazilian residents at two different times (2020 and 2021). The participants were divided according to social isolation practices into study groups (GI: 2020, n = 507; GIII: 2021, n = 282) and control groups (GII: 2020, n = 98; GIV: 2021, n = 202).

RESULT

In each group, we evaluated the association of the frequency of oral parafunctional habits with the symptoms of TMD, and we observed that individuals with a greater presence of painful TMD present a greater number of oral parafunctional habits. Despite the literature showing that individuals who practiced social isolation developed more oral parafunctional habits, when analysing the association of the OBC questions in Groups GI × GII and GIII × GIV, only 'sustained talking' (p = .0022) and 'hold telephone between your hand and shoulders' (p = .0124) showed a significant difference in GI × GII. Kendall's coefficient of concordance revealed that there was a very strong concordance (GI × GII 0.9515 (p = .0087) and GIII × GIV 0.9655 (p = .0074)) between the ranks of the analysed oral parafunctional habits in all groups.

CONCLUSION

We can state that Individuals who practiced social isolation did not present more oral parafunctional habits than individuals who did not.

Oral behaviors and anxiety are significant predictors of jaw function limitation in patients with anterior disc displacement without reduction

OBJECTIVE

We aimed to describe jaw function characteristics in patients with anterior disc displacement without reduction (ADDWoR) using the jaw function limitation scale (JFLS), and to investigate the effects of biopsychosocial risk factors on limited jaw function.

DESIGN

In this cross-sectional study of 636 patients with ADDWoR (females, 568; males, 68), we used the JFLS to assess jaw function. Behavioral, psychological, sociodemographic, and biomedical data were collected. Multivariate logistic regression analysis was used to determine risk factors affecting limited jaw function. A receiver operating characteristic curve was used to evaluate the predictive effect of these risk factors.

RESULTS

ADDWoR-associated limitations included restricted jaw mobility and mastication, which exceeded median global functional limitations scale scores, especially mouth opening to bite an apple and chewing tough food. Females had greater limitations in jaw mobility, verbal and emotional communication, and overall. Multivariate logistic regression analysis findings indicated that oral behaviors, anxiety, sex, pain intensity, and maximal mouth opening (MMO) were predictive of limited jaw function (area under the curve, 72 %).

CONCLUSION

Patients with ADDWoR reported mastication and jaw mobility restrictions, with females having more pronounced limitations, and specific risk factors identified as significant predictors of jaw function limitations. Along with pain relief and improvement in MMO, appropriate psychological counseling and oral behavioral correction facilitates recovery of jaw function in such patients.

Temporomandibular Disorders in Relation to Mandibular Advancement Devices for Treating Obstructive Sleep Apnea

Mandibular advancement devices (MADs) keep the upper airways patent by holding the mandible and attached soft tissues forward via altered position of its condyles relative to the articulating surfaces of the temporal bones. During the first weeks of MAD therapy, pain may occur in the area of the temporomandibular joints, masticatory muscles, and/or teeth with a tendency of spontaneous resolution. In patients reporting temporomandibular disorder (TMD) symptoms prior to therapy, the MAD-related anterior condylar position during sleep may result in a reduction of TMD signs and symptoms.

Abnormal Functional Connectivity Intra- and Inter-Network in Resting-State Brain Networks of Patients with Toothache

Objective

To separate the resting-state network of patients with dental pain using independent component analysis (ICA) and analyze abnormal changes in functional connectivity within as well as between the networks.

Patients and Methods

Twenty-three patients with dental pain and 30 healthy controls participated in this study. We extracted the resting-state functional network components of both using ICA. Functional connectivity differences within 14 resting-state brain networks were analyzed at the voxel level. Directional interactions between networks were analyzed using Granger causality analysis. Subsequently, functional connectivity values and causal coefficients were assessed for correlations with clinical parameters.

Results

Compared to healthy controls, we found enhanced functional connectivity in the left superior temporal gyrus of anterior protrusion network and the right Rolandic operculum of auditory network in patients with dental pain (p<0.01 and cluster-level p<0.05, Gaussian random field corrected). In contrast, functional connectivity of the right precuneus in the precuneus network was reduced, and were significantly as well as negatively correlated to those of the Visual Analogue Scale (r=-4.93, p=0.017), Hamilton Anxiety Scale (r=-0.46, p=0.027), and Hamilton Depression Scale (r=-0.563, p<0.01), using the Spearman correlation analysis. Regarding the causal relationship between resting-state brain networks, we found increased connectivity from the language network to the precuneus in patients with dental pain (p<0.05, false discovery rate corrected). However, the increase in causal coefficients from the verbal network to the precuneus network was independent of clinical parameters.

Conclusion

Patients with toothache exhibited abnormal functional changes in cognitive-emotion-related brain networks, such as the salience, auditory, and precuneus networks, thereby offering a new imaging basis for understanding central neural mechanisms in dental pain patients.

Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets

Myogenous temporomandibular disorders is associated with an increased responsiveness of nerves innervating the masseter (MM), temporal (TM), and lateral pterygoid muscles (LPM). This study aimed to examine sensory nerve types innervating MM, TM and LPM of adult non-human primate-common marmosets. Sensory nerves were localized in specific regions of these muscles. Pgp9.5, marker for all nerves, and NFH, a marker for A-fibers, showed that masticatory muscles were primarily innervated with A-fibers. The proportion of C- to A-fibers was highest in LPM, and lowest in MM. All C-fibers (pgp9.5+/NFH-) observed in masticatory muscles were peptidergic (CGRP+) and lacked mrgprD and CHRNA3, a silent nociceptive marker. TrpV1 was register in 17% of LPM nerves. All fibers in masticatory muscles were labeled with GFAP+, a myelin sheath marker. There were substantially more peptidergic A-fibers (CGRP+/NFH+) in TM and LPM compared to MM. MM, TM and LPM NFH+ fibers contained different percentages of trkC+ and parvalbumin+, but not trkB+ fibers. Tyrosine hydroxylase antibodies, which did not label TG, highlighted sympathetic fibers around blood vessels of the masticatory muscles. Overall, masticatory muscle types of marmosets have similarities and differences in innervation patterns.

Psychological distress as a risk factor for the efficacy of chemotherapy in advanced gastric cancer patients

AIM

To assess the relationship between psychological distress and quality of life (QoL), cancer-related fatigue (CRF), and chemotherapy efficacy in advanced gastric cancer patients.

METHODS

Advanced gastric cancer patients (39 with psychological distress and 35 without psychological distress) completed the Distress Thermometer (DT), QoL, and CRF test before receiving chemotherapy and assessed the efficacy after completing 2 courses of chemotherapy.

RESULTS

Psychological distress was a significant factor in the efficacy of chemotherapy in advanced gastric cancer patients (χ2 = 6.324; p = 0.042). Compared to advanced gastric cancer patients with no psychological distress, advanced gastric cancer patients with psychological distress had a poorer QoL (50.41 ± 6.17 vs. 60.01 ± 7.94, t =  - 5.882, p < 0.01) and more pronounced CRF (5.75 ± 1.16 vs. 3.22 ± 0.75, t = 11.231, p < 0.01) while receiving chemotherapy. FACT-G (p = 0.0035, r =  - 0.4568), as well as PFS (p < 0.0001, r = 0.6599), correlated significantly with efficacy for patients in the psychological distress group. The FACT-G (p = 0.0134, r =  - 0.4139) of patients in the no psychological distress group correlated significantly with efficacy.

CONCLUSION

Psychological distress has a negative impact on QoL, CRF, and efficacy and may be a potential risk for the efficacy of palliative chemotherapy in advanced gastric cancer patients.

Experimental traumatic occlusion drives immune changes in trigeminal ganglion

We previously demonstrated that experimental traumatic occlusion (ETO) induces a long-lasting nociceptive response. These findings were associated with altered neuronal patterns and suggestive satellite glial cell activation. This study aimed to elucidate the activation of satellite glial cells following ETO in the trigeminal ganglion. Moreover, we explored the involvement of resident and infiltrating cells in trigeminal ganglion in ETO. Finally, we investigated the overexpression of purinergic signaling and the CX3CL1/CX3CR1 axis. RT-qPCR and electrophoresis showed overexpression of GFAP in the trigeminal ganglion (TG), and immunohistochemistry corroborated these findings, demonstrating SGCs activation. ELISA reveals enhanced levels of TNF-α and IL-1β in TG after 28 d of ETO. In trigeminal ganglia, ETO groups improved the release of CX3CL1, and immunohistochemistry showed higher CX3CR1+ -immunoreactive cells in ETO groups. Immunohistochemistry and electrophoresis of the P2X7 receptor were found in ETO groups. The mRNA levels of IBA1 are upregulated in the 0.7-mm ETO group, while immunohistochemistry showed higher IBA1+ -immunoreactive cells in both ETO groups. The expression of CD68 by electrophoresis and immunohistochemistry was observed in the ETO groups. For last, ELISA revealed increased levels of IL-6, IL-12, and CCL2 in the TG of ETO groups. Furthermore, the mRNA expression revealed augmented transcription factors and cytokines associated with lymphocyte activation, such as RORγt, IL-17, Tbet, IFNγ, FOXP3, and IL-10. The findings of this study suggested that ETO activates SGCs in TG, and purinergic signaling and CX3CL1/CX3CR1 axis were upregulated. We uncovered the involvement of a distinct subtype of macrophages, named sensory neuron-associated macrophage activation (sNMAs), and detected an expanded number of infiltrated macrophages onto TG. These findings indicate that ETO induces chronic/persistent immune response.

Soluble epoxide hydrolase inhibitor blockage microglial cell activation in subnucleus caudalis in a persistent model of arthritis

Rheumatoid arthritis (RA) is a chronic condition characterized by pain and infiltration of immune cells into the joint. Immune cells can be activated, producing inflammatory cytokines, leading to continuously degenerative and inflammatory reactions and the temporomandibular joint (TMJ) can be affected by RA. In this scenario, novel targets are needed to increase treatment efficacy with minimized side effects. The epoxy-eicosatrienoic acids (EETs), are endogenous signaling molecules, playing important roles in diminishing inflammation and pain but are promptly metabolized by soluble epoxide hydrolase (sEH), generating less-bioactive acids.Therefore, sEH inhibitors is an interest therapeutic target to enhance the beneficial effect of natural EETs. TPPU is a potent sEH inhibitor that is capable of dampening EETs hydrolysis. Thus, we aimed to assess the impact of pharmacological sEH inhibition on a persistent model of albumin-induced arthritis in the TMJ, in two scenarios: first, as post-treatment, in an installed arthritic condition, and second, the protective role, in preventing the development of an arthritic condition. In addition, we investigate the influence of sEH inhibition on microglia cell activation in the trigeminal subnucleus caudalis (TSC) and in vitro experiments. Finally, we examined the astrocyte phenotype. Oral administration of TPPU, acts in multiple pathways, in a protective and reparative post-treatment, ameliorating the preservation of the TMJ morphology, reducing the hypernociception, with an immunosuppressive action reducing neutrophil and lymphocytes and pro-inflammatory cytokines in the TMJ of rats. In TSC, TPPU reduces the cytokine storm and attenuates the microglia activated P2X7/Cathepsin S/Fractalkine pathway and reduces the astrocyte activation and glutamate levels. Collectively, our findings revealed that sEH inhibition mitigates hypersensitive nociception through the regulation of microglia activation and astrocyte modulation, demonstrating the potential use of sEH inhibitors as immunoresolvents in the treatment of autoimmune disorders.

Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets

Myogenous temporomandibular disorders (TMDM) is associated with an increased responsiveness of nerves innervating the masseter (MM), temporal (TM), medial pterygoid (MPM) and lateral pterygoid muscles (LPM). This study aimed to examine sensory nerve types innervating MM, TM and LPM of adult non-human primate - common marmosets. Sensory nerves are localized in specific regions of these muscles. Pgp9.5, marker for all nerves, and NFH, a marker for A-fibers, showed that masticatory muscles were predominantly innervated with A-fibers. The proportion of C- to A-fibers was highest in LPM, and minimal (6-8%) in MM. All C-fibers (pgp9.5+/NFH-) observed in masticatory muscles were peptidergic (CGRP+) and lacked mrgprD, trpV1 and CHRNA3, a silent nociceptive marker. All fibers in masticatory muscles were labeled with GFAP+, a myelin sheath marker. There were substantially more peptidergic A-fibers (CGRP+/NFH+) in TM and LPM compared to MM. Almost all A-fibers in MM expressed trkC, with some of them having trkB and parvalbumin. In contrast, a lesser number of TM and LPM nerves expressed trkC, and lacked trkB. Tyrosine hydroxylase antibodies, which did not label TG, highlighted sympathetic fibers around blood vessels of the masticatory muscles. Overall, masticatory muscle types of marmosets have distinct and different innervation patterns.

Myofascial Temporomandibular Disorders at a Turning Point: Pragmatic or Evidence-Based Management?

Unvalidated theories have been proposed for the etiopathogenesis of masticatory myofascial temporomandibular disorders (mTMD). Modalities such as cone-beam computed tomography/computed tomography and MRI contributes little to the diagnosis of mTMD. Diagnosing mTMD is based on the recognition of "familiar pain" presentation in the masticatory myofascial tissue. This assessment tool contributes little our understanding of the underlying disease process. Thus, management of mTMD is empirical and arbitrary. Exploring emerging technologies to identify biomarkers and objectively assess myofascial tissue physiology in disease and health may be key in moving the diagnosis of mTMD from the pragmatic paradigm to an evidence-based paradigm.

Efficiency of occlusal splint therapy on orofacial muscle pain reduction: a systematic review

BACKGROUND

This systematic review aims to examine the existing original studies to determine the effectiveness of occlusal splints (OSs) in the management of orofacial myalgia and myofascial pain (MP) in comparison with no treatment or other interventions.

MATERIALS AND METHODS

Based on the inclusion and exclusion criteria of this systematic review, randomized controlled trials were qualified, in which the effectiveness of occlusal splint therapy in the management of muscle pain was examined in comparison with no treatment or other interventions. This systematic review was conducted according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis 2020. The authors searched three databases (PubMed, CINAHL (The Cumulative Index to Nursing and Allied Health Literature) and Scopus) for English publications published between January 1, 2010, and June 1, 2022. The last database search was carried out on June 4, 2022. Data were extracted from the included studies and assessed for risk of bias using the revised Cochrane risk-of-bias tool for randomized trials.

RESULTS

Thirteen studies were identified for inclusion in this review. In total, 589 patients were diagnosed with orofacial muscle pain who underwent education and various forms of therapy including different types of OSs, light emitting diode therapy, acupuncture, low-level laser therapy, device-supported sensorimotor training, Kinesio Taping, myofunctional therapy, and physical therapy. All studies included demonstrated a high risk of bias.

CONCLUSIONS

There is insufficient evidence regarding whether OS therapy in the treatment of orofacial myalgia and MP offers an advantage over other forms of interventions or no treatment. Further reliable clinical studies in this area are needed to improve the quality of research, which should be performed with larger groups of blinded respondents and controls.

CLINICAL RELEVANCE

Due to the large-scale nature of orofacial muscle pain, it is assumed that each dental clinician will meet patients with orofacial muscle pain repeatedly in daily practice; hence, the review of the effectiveness of OSs in the management of orofacial myalgia and MP is necessary.

Psychological distress as risk factor for the efficacy of whole-brain radiotherapy in brain metastasis patients

Aim: To evaluate the relationship between psychological distress and the efficacy of whole-brain radiotherapy (WBRT) in advanced brain metastasis patients. Methods: Brain metastasis patients (40 with psychological distress and 47 without psychological distress) completed distress thermometer tests before WBRT, and progression-free survival (PFS) was acquired during the follow-up period. Results: Psychological distress was a risk factor for poorer PFS in patients treated with WBRT (p < 0.01). The PFS of survivors who underwent WBRT was superior for those without psychological distress (hazard ratio: 0.295; 95% CI: 0.173-0.500; p < 0.01). Conclusion: The survival of brain metastasis patients receiving WBRT was influenced by psychological distress, which negatively affected the treatment outcome and is likely to be a potential risk indicator in advanced cancer patients receiving WBRT.

CMD und Kieferorthopädie

Die Craniomandibuläre Dysfunktion (CMD) ist mit einer Prävalenz von über 30% die häufigste chronische Schmerzerkrankung im Kiefer- Gesichtsbereich. Die Therapie erfordert einen interdisziplinären, individuell angepassten Behandlungsansatz. Diese Fallvorstellung soll einen Einblick über das Behandlungskonzept eines posterior-lateralen Zwangsbisses mit Oberkiefer- Okklusionsschiene und OK/UK Alignern (Invisalign) geben.

Chronic Pain-Related Jaw Muscle Motor Load and Sensory Processing

Chronic pain associated with temporomandibular disorders (TMDs) may reflect muscle mechanoreceptor afferent barrage and dysregulated sensory processing. This observational study tested for associations between Characteristic Pain Intensity (CPI), physical symptoms (Patient Health Questionnaire-15 [PHQ-15]), and cumulative jaw muscle motor load (mV*s). In accordance with institutional review board oversight and Strengthening the Reporting of Observational Studies in Epidemiology guidelines, adult subjects gave informed consent and were identified via Diagnostic Criteria for TMD (DC-TMD) examination and research protocols. Subjects were assigned to ±Pain groups using DC-TMD criteria for myalgia. CPI scores characterized pain intensity. PHQ-15 scores were surrogate measures of dysregulated sensory processing. Laboratory tests were performed to quantify masseter and temporalis muscle activities (mV) per bite force (N) for each subject. In their natural environments, subjects recorded day- and nighttime electromyography from which cumulative jaw muscle motor loads (mV*s) were determined for activities consistent with bite forces of >1 to ≤2 and >2 to ≤5 N. Data were assessed using univariate analysis of variance, simple effects tests, K-means cluster classification, and 3-dimensional regression analyses. Of 242 individuals screened, 144 enrolled, and 125 with complete data from study protocols, there were 35 females and 15 males for +Pain and 35 females and 40 males for -Pain. Subjects produced 324 daytime and 341 nighttime recordings of average duration 6.9 ± 1.7 and 7.6 ± 1.7 h, respectively. Overall, +Pain compared to -Pain subjects had significantly higher (all P ≤ 0.002) CPI and PHQ-15 scores. Cumulative jaw muscle motor loads showed significant between-subject effects for time, diagnostic group, and sex (all P < 0.003), where motor loads tended to be higher for daytime versus nighttime, +Pain versus -Pain groups, and males versus females. Two clusters were identified, and regression relations showed associations of low-magnitude daytime masseter motor load, PHQ-15, and CPI scores for cluster 1 (n = 105, R2 = 0.44) and cluster 2 (n = 18, R2 = 0.80). Furthermore, these regression relations showed thresholds of motor load and PHQ-15 scores, above which there were nonlinear increases in reported pain.

Biological and Molecular Docking Evaluation of a Benzylisothiocyanate Semisynthetic Derivative From Moringa oleifera in a Pre-clinical Study of Temporomandibular Joint Pain

Objective

Moringa oleifera possesses multiple biological effects and the 4-[(4′-O-acetyl-α-L- rhamnosyloxy) benzyl] isothiocyanate accounts for them. Based on the original isothiocyanate molecule we obtained a semisynthetic derivative, named 4-[(2′,3′,4′-O-triacetyl-α-L-rhamnosyloxy) N-benzyl] hydrazine carbothioamide (MC-H) which was safe and effective in a temporomandibular joint (TMJ) inflammatory hypernociception in rats. Therefore, considering that there is still a gap in the knowledge concerning the mechanisms of action through which the MC-H effects are mediated, this study aimed to investigate the involvement of the adhesion molecules (ICAM-1, CD55), the pathways heme oxygenase-1 (HO-1) and NO/cGMP/PKG/K⁺_ATP, and the central opioid receptors in the efficacy of the MC-H in a pre-clinical study of TMJ pain.

Methods

Molecular docking studies were performed to test the binding performance of MC-H against the ten targets of interest (ICAM-1, CD55, HO-1, iNOS, soluble cGMP, cGMP-dependent protein kinase (PKG), K⁺_ATP channel, mu (μ), kappa (κ), and delta (δ) opioid receptors). In in vivo studies, male Wistar rats were treated with MC-H 1 μg/kg before TMJ formalin injection and nociception was evaluated. Periarticular tissues were removed to assess ICAM-1 and CD55 protein levels by Western blotting. To investigate the role of HO-1 and NO/cGMP/PKG/K⁺_ATP pathways, the inhibitors ZnPP-IX, aminoguanidine, ODQ, KT5823, or glibenclamide were used. To study the involvement of opioid receptors, rats were pre-treated (15 min) with an intrathecal injection of non-selective inhibitor naloxone or with CTOP, naltrindole, or norbinaltorphimine.

Results

All interactions presented acceptable binding energy values (below −6.0 kcal/mol) which suggest MC-H might strongly bind to its molecular targets. MC-H reduced the protein levels of ICAM-1 and CD55 in periarticular tissues. ZnPP-IX, naloxone, CTOP, and naltrindole reversed the antinociceptive effect of MC-H.

Conclusion

MC-H demonstrated antinociceptive and anti-inflammatory effects peripherally by the activation of the HO-1 pathway, as well as through inhibition of the protein levels of adhesion molecules, and centrally by μ and δ opioid receptors.

Peroxisome proliferator-activated receptor-gamma (PPARγ) and its immunomodulation function: current understanding and future therapeutic implications

INTRODUCTION

: Pain is a multidimensional experience involving the biological, psychological, and social dimensions of each individual. Particularly, the biological aspects of pain conditions are a response of the neuroimmunology system and the control of painful conditions is a worldwide challenge for researchers. Although years of investigation on pain experience and treatment exist, the high prevalence of chronic pain is still a fact.

AREAS COVERED

: Peroxisome proliferator-activated receptor-gamma (PPARγ) is a ligand-activated transcription factor belonging to the nuclear hormone receptor superfamily. It regulates several metabolic pathways, including lipid biosynthesis and glucose metabolism, when activated. However, PPARγ activation also has a critical immunomodulatory and neuroprotective effect.

EXPERT OPINION

: This review summarizes the evidence of synthetic or natural PPARγ ligands such as 15d-PGJ₂, epoxyeicosatrienoic acids, thiazolidinediones, and specialized pro-resolving mediators, representing an interesting therapeutic tool for pain control.

Temporomandibular joint (TMJ) disorders prevalence and awareness of appropriate clinical practices, among Al-Madinah community in Saudi Arabia

Background:  Painful temporomandibular joint disorders (TMDs) are of musculoskeletal origin and are considered the most common cause of non-odontogenic pain in the orofacial region.  The purpose of this study was to investigate the prevalence and awareness of temporomandibular joint (TMJ) disorders in Almadinah Almunawwarah community. Methods: An observational cross-sectional study with convenience sampling was conducted. A translated Arabic version of Fonseca's questionnaire was employed. The questionnaire asked about the participant's personal information, if they thought they had TMDs, and who to visit for therapy if necessary. These were followed by 10 items from Fonseca's questionnaire, each with a three-point scale. Results: The questionnaire was completed by 598 people. Females made up 57.1% of the participants. TMDs were present in 61% of the population, with varying degrees of severity. Males (44.3%) were less affected than females (55.7%). The difference, however, was not statistically significant (P = 0.354). Out of the 61% TMDs Positive patients, 74.1% had mild TMDs symptoms, while 20.8% and 5.1%, respectively, had moderate and severe TMDs symptoms (P = 0.05). The severity of the symptoms was unaffected by demographic data (P > 0.05). Only 40% seek care, with 64.6% selecting for a dentist and 24.6% preferring for an orthopaedic specialist (P= 0.008). Conclusions: Participants from Al-Madinah had a greater prevalence of mild TMDs. The majority of the participants had no idea who to go to for treatment. The findings of this study highlight the importance of educational activities to enhance public awareness. Fonseca's Anamnestic Index could also be considered as a useful instrument for early identification and measuring the severity of TMDs in the general population.

Temporomandibular joint (TMJ) disorders prevalence and awareness of appropriate clinical practices, among Al-Madinah community in Saudi Arabia

Background:  Painful temporomandibular joint disorders (TMDs) are of musculoskeletal origin and are considered the most common cause of non-odontogenic pain in the orofacial region.  The purpose of this study was to investigate the prevalence and awareness of temporomandibular joint (TMJ) disorders in Almadinah Almunawwarah community. Methods: An observational cross-sectional study with convenience sampling was conducted. A modified version of Fonseca's questionnaire was employed. The questionnaire asked about the participant's personal information, if they thought they had TMDs, and who to visit for therapy if necessary. These were followed by 10 items from Fonseca's questionnaire, each with a three-point scale. Results: The questionnaire was completed by 598 people. Females made up 57.1% of the participants. TMDs were present in 61% of the population, with varying degrees of severity. Males (44.3%) were less affected than females (55.7%). The difference, however, was not statistically significant (P = 0.354). Out of the 61% TMDs Positive patients, 74.1% had mild TMDs symptoms, while 20.8% and 5.1%, respectively, had moderate and severe TMDs symptoms (P = 0.05). The severity of the symptoms was unaffected by demographic data (P > 0.05). Only 40% seek care, with 64.6% selecting for a dentist and 24.6% preferring for an orthopaedic specialist (P= 0.008). Conclusions: Participants from Al-Madinah had a greater prevalence of mild TMDs. The majority of the participants had no idea who to go to for treatment. The findings of this study highlight the importance of educational activities to enhance public awareness. Fonseca's Anamnestic Index could also be considered as a useful instrument for early identification and measuring the severity of TMDs in the general population.

Soluble epoxide hydrolase inhibition avoid formalin-induced inflammatory hyperalgesia in the temporomandibular joint

Epoxyeicosatrienoic acids (EETs) are endogenous molecules that exerts effective antinociceptive and resolutive actions. However, because of their rapid metabolism by the soluble epoxide hydrolase (sEH), EETs are unable to remain bioavailable. Therefore, the aim of this study was to investigate whether local sEH inhibition could prevent inflammatory hyperalgesia in the temporomandibular joint (TMJ) of rats. For that, rats were pre-treated with an intra-TMJ injection of TPPU, followed by the noxious stimulus (1.5% of formalin intra-articular) to evaluate nociceptive behavior. Histological analysis was conducted to explore the inflammatory exudate and mast cell degranulation. Periarticular tissue over the TMJ was used to measure inflammatory lipids and cytokines/chemokine by Enzyme-Linked Immunosorbent Assay (ELISA). We demonstrated that peripheral pretreatment with TPPU prevents formalin-induced inflammatory hyperalgesia in the TMJ, and this effect is strictly local. Moreover, TPPU mitigates the leukocyte exudate in the TMJ, as well as inflammatory lipids mediators. Mast cell number and degranulation were abrogated by TPPU, and the inflammatory cytokine levels were decreased by TPPU. On the other hand, TPPU up-regulated the release of interleukin 10 (IL-10), an anti-inflammatory cytokine. We provide evidence that locally sEH by intra-TMJ injection of TPPU produces an antinociceptive and anti-inflammatory effect on rats' TMJ.

Brain Mechanisms of Exercise-Induced Hypoalgesia: To Find a Way Out from "Fear-Avoidance Belief"

It is well known that exercise produces analgesic effects (exercise-induced hypoalgesia (EIH)) in animal models and chronic pain patients, but the brain mechanisms underlying these EIH effects, especially concerning the emotional aspects of pain, are not yet fully understood. In this review, we describe drastic changes in the mesocorticolimbic system of the brain which permit the induction of EIH effects. The amygdala (Amyg) is a critical node for the regulation of emotions, such as fear and anxiety, which are closely associated with chronic pain. In our recent studies using neuropathic pain (NPP) model mice, we extensively examined the association between the Amyg and EIH effects. We found that voluntary exercise (VE) activated glutamate (Glu) neurons in the medial basal Amyg projecting to the nucleus accumbens (NAc) lateral shell, while it almost completely suppressed NPP-induced activation of GABA neurons in the central nucleus of the Amyg (CeA). Furthermore, VE significantly inhibited activation of pyramidal neurons in the ventral hippocampus-CA1 region, which play important roles in contextual fear conditioning and the retrieval of fear memory. This review describes novel information concerning the brain mechanisms underlying EIH effects as a result of overcoming the fear-avoidance belief of chronic pain.

The Tongue and Mouth Imagery Questionnaire (TMIQ) for Assessing Motor Imagery vividness of the temporomandibular region: a reliability and validity case-control study

Background

To date, no validated assessment of motor imagery (MI) ability with temporomandibular disorders (TMD) exists preventing identification of good imagers and appropriate MI use during TMD rehabilitation.

Objective

To assess the reliability and construct validity of the previously developed Tongue and Mouth Imagery Questionnaire (TMIQ) compared with the gold‐standard Kinaesthetic and Visual Imagery Questionnaire (KVIQ‐10).

Methods

Both KVIQ‐10 and TMIQ assess MI ability using vividness (i.e. clarity/brightness for visual MI, _VMI; or intensity for kinesthetic MI, _KMI) of MI using a 5‐point Likert scale (1: no image/sensation, 5: clear/intense image/sensation). The KVIQ‐10 was administered once (test) and the TMIQ twice (test–retest) to heathy participants and patients with TMD. Questionnaire validity was investigated using concurrent validity (Pearson correlation and paired t test); TMIQ‐test–retest reliability (intraclass correlation coefficients, ICCs); internal consistency (Cronbach ⍺) and the factorial structure (principal factor extraction).

Results

A total of 94 participants were included (n = 47 per group). The mean vividness scores of the KVIQ‐10 and the TMIQ were significantly correlated, and not significantly different for both groups indicating concurrent validity. ICCs in the control group (range: 0.82‐0.90), and in the TMD group (range: 0.75‐0.82) indicated good reproducibility. The Cronbach ⍺ values were all above 0.94, indicating excellent reliability. Two factors were extracted corresponding to _VMI and _KMI, and explained 66% of total variance.

Conclusion

The TMIQ is a valid and reproducible MI questionnaire showing excellent internal consistency and, therefore, can be used to assess imagined movements of the TM region in healthy individuals and patients with TMD.

Occlusal Trauma Induces Neuroimmune Crosstalk for a Pain State

Temporomandibular joint (TMJ) disorder caused by occlusal trauma is one of the most controversial topics in dentistry. Experimental traumatic occlusion (ETO) induced by metal crowns cemented to mandibular first molars in rats causes a long-lasting nociceptive response. This study aimed to elucidate whether ETO generates an increase in inflammatory mediators in the TMJ. In addition, the impact of ETO on trigeminal ganglia, neurotransmitter release, and satellite glial cell (SGC) activation was investigated. ELISA revealed enhanced inflammatory mediators, including TNF-α, IL-1β, IL-6, CX3CL1, and ADAM-17 by Western blotting, in periarticular TMJ tissue after 28 d of ETO. In the trigeminal ganglia, ETO groups increased the release of the neurotransmitters substance P and glutamate. Overexpression of the AMPA receptor and upregulation of NMDA were observed in the 0.4- and 0.7-mm ETO groups, respectively, highlighting enhanced neuronal excitation. Increased IL-1β and COX-2 mRNA levels in the 0.7-mm ETO group confirmed trigeminal ganglia SGC activation. Immunofluorescence and electrophoresis of SGC revealed increased pERK expression in the 0.7-mm ETO group. ERK phosphorylation was shown to be nociceptive specific, with its upregulation occurring in cases of chronic inflammatory pain. Increased PKA mRNA levels were observed in the 0.4-mm ETO group, while CREB mRNA levels were upregulated for both ETO groups. Electrophoresis showed overexpression of sodium channel Nav 1.7 in the 0.7-mm ETO group, while immunofluorescence revealed that Nav 1.7 is expressed in sensory trigeminal ganglia cells. The results of this study suggest that occlusal trauma induces neuroimmune crosstalk, with synthesis of proinflammatory/pronociceptive mediators, which increases neuronal activity in trigeminal ganglia via the activation of an inflammatory response cascade to develop a persistent neuroinflammatory state that leads to central sensitization.

Photobiomodulation inhibits inflammation in the temporomandibular joint of rats

Photobiomodulation (PBM) has been applied as a non-invasive technique for treating temporomandibular joint symptoms, especially on painful condition's relief, however the anti-inflammatory mechanism underlying the effect of PBM remains uncertain. This study aims to evaluate the mechanisms of action of PBM (808 nm) in a carrageenan-induced inflammation on temporomandibular joint (TMJ) of rats. In this study male Wistar rats were pre-treated with irradiation of a low-power diode laser for 15 s on TMJ (infra-red 808 nm, 100 mW, 50 J/cm² and 1.5 J) 15 min prior an injection in the temporomandibular joint of carrageenan (100 μg/TMJ). 1 h after the TMJ treatments, the rats were terminally anesthetized for joint cavity wash and periarticular tissues collect. Samples analysis demonstrated that PBM inhibit leukocytes chemotaxis in the TMJ and significantly reduces amounts of TNF-α, IL-1β and CINC-1. In addition, Western blotting analysis demonstrated that PBM significantly decreased the protein levels of P2X3 and P2X7 receptors in the periarticular tissues. On the other hand, PBM was able to increase protein level of IL-10 (anti-inflammatory cytokine). In summary, it is possible to suggest that PBM inhibit inflammatory chemotaxis, modulation the balance of the pro- and anti-inflammatory characteristics of inflammatory cells.