How may stressful experiences contribute to the development of temporomandibular disorders?

Association Between Temporomandibular Disorders and Irritable Bowel Syndrome: A Scoping Review

Temporomandibular disorders (TMDs) encompass various clinical conditions associated with the temporomandibular joint (TMJ) and the masticatory muscles. TMD symptoms include pain in the orofacial region, restricted or altered mandibular movement, and sounds associated with the temporomandibular joint (TMJ). This condition adversely affects quality of life, social functioning, and daily activities, and may also contribute to widespread pain syndromes and comorbidities, including irritable bowel syndrome (IBS). IBS is a common chronic functional disorder of the lower gastrointestinal tract, characterized by recurrent abdominal pain associated with impaired bowel symptoms. Previous studies indicate an association between TMD and IBS. This scoping review examined the correlation between TMD and IBS concerning their pathology, frequency, and severity, and the potential similarities in how the nervous and endocrine systems influence them. PubMed, SCOPUS, Web of Science, and Google Scholar search engines were utilized to identify suitable studies for this article. Following the application of selection criteria, a total of 58 clinical papers met the eligibility requirements for inclusion in the systematic review. Research showed that both conditions significantly enhance the development of one another and have mutual comorbidities. Both ailments were proven to modify central nervous system processing, leading to high comorbidity in patients. Combining dental and gastroenterological treatments, including a simultaneous therapeutic approach, can significantly enhance patients' quality of life, but further research is needed for a holistic approach.

Neurofeedback Technology Reduces Cortisol Levels in Bruxismitle Patients: Assessment of Cerebral Activity and Anxiolytic Effects of Origanum majorana Essential Oil

Cerebral activities were measured during 21 essions in NeurOptimal (NO)-trained patients with bruxism. Salivary cortisol levels were quantified for each six training sessions (session 1, 6, 12, 18, 21) in 12 patients with bruxism after performing their pre- and post-NeurOptimal sessions. Their cortisol levels were compared with controls (without stress). We evaluated whether NO overtraining could reduce stress in bruxism after 21 repeated sessions with/without Origanum majorana inhalation by using nasal impregned filters with this essential oil (n = 12). This study enrolled 89 participants (590 salivary samples for cortisol assessment by ELISA ng/mL). Salivary samples were collected at several NO learning sessions (session 1, 6, 12, 18, and 21). In the present study, we assessed whether Origanum majorana essential oil exposure during 21 NO training sessions can promote anxiolytic effects by reducing cortisol levels in Bruxismitle patients or modulate their brain activities. The experimental design also included control subjects without NO training (n = 30) and unstressed participants without bruxism, as well as trained NeurOptimal (n = 5) participants during the 21 sessions, also including control subjects without stress. In our study, NeurOptimal post-training decreased cortisol levels in Bruxismitle patients, reducing stress scores on the Hamilton II scale after 21 NO sessions; finally, Origanum majorana essential oil exposure during NO training could enhance anxiolytic effects of repeated NO in Bruxismitle patients. The parameter divergence as an index of cerebral activity evaluates the reached difference between cerebral activity at pre-learning (PRE) minus post-training (POST) values in Bruxismitle participants with/without Origanum majorana odor exposure during each NO training sessions. As a consequence of NO overtraining, these cerebral activities fluctuate reaching a calm state while anxious states are associated with high divergences. The reduction in divergences when they are close to zero by habituation means a final calm state is reached by NO overtraining, while higher divergences mean anxiogenic states. Collectively, Origanum majorana essential oil inhalation during NO training could decrease salivary cortisol levels after 21 NO training sessions in Bruxismitle.

Manual therapy and dry needling improve mobility, pain and reduce fear of COVID-19 in temporomandibular disorder patients: Randomized controlled trial

BACKGROUND AND PURPOSE

The COVID-19 pandemic exacerbated pain and joint mobility outcomes in patients with temporomandibular disorders (TMD), being that effective treatments are of clinical interest. We aimed to evaluate the effects of manual therapy (MT) and dry needling (DN), compared to cognitive-behavioral therapy/control (CO), on pain, articular mobility, and fear of COVID-19 in patients with TMD.

MATERIALS AND METHODS

Sixty participants with myofascial TMD were randomly assigned to three groups: MT, DN, and CO. Participants received four weeks of treatment (30 min per week). The participants completed the Fear of COVID- 19 Scale, the Visual Analog Scale, and mandibular mobility was assessed. Data were collected before the intervention (T1), after the last treatment session (T2), and 30 days after the end of treatment (T3). The data were analyzed using two-way Mixed-Design ANOVA, considering the group effect (DN x MT x CO), time (T1, T2, and T3), and the interaction time × group in the observed variance of outcomes.

RESULTS

We observed an interaction effect of time × group for maximum mouth opening, protrusion, and pain. The maximum mouth opening increased in the DN and MT groups (p = 0.005), while protrusion increased in the DN group (p = 0.007; test power = 97%, large effect size). A decrease in pain scores over time was observed in the DN and MT groups (p < 0.001; test power>99%, large effect size). The fear of COVID-19 score decreased in the DN and MT groups after 30 days (p = 0.033).

CONCLUSION

DN and MT improve pain, joint mobility, and fear of COVID-19 in patients with TMD.

The Potential of Percent Agreement as an Adjunctive Diagnostic Tool for Acute Temporomandibular Disorder

Background/Objectives: It is well established that individuals with chronic temporomandibular disorder (TMD) exhibit differences in their physical and psychosocial characteristics from those with acute TMD. However, few studies have analyzed the physical and psychosocial characteristics of patients with acute TMD. The objective of this cross-sectional study is twofold: first, to ascertain whether there are differences in physical and psychosocial factors among patients with acute TMD based on the percent agreement between patient-reported pain sites and pain sites identified through standardized palpation and, second, to determine the potential of percent agreement as a diagnostic and prognostic factor. Methods: We analyzed physical and psychosocial factors in 309 patients diagnosed with acute TMD. Of these, 171 patients were selected for an analysis of their response to treatment. These patients were divided into three groups based on their percent agreement: Group A (agreement under 80%), Group B (agreement 80-89%), and Group C (agreement 90% or over) in the initial analysis and Group a (agreement under 80%), Group b (agreement 80-89%), and Group c (agreement 90% or over) in the subsequent analysis. This study was approved by the Ethics Committee of Pusan National University Dental Hospital (IRB No. 2023-05-011, 25 May 2023). Results: The lower the percent agreement, the greater the parafunctional oral habits, stress, chronicity, somatization, depression, anxiety, and number of painful sites. A lower percent agreement was associated with poorer treatment outcomes. The percent agreement demonstrated a 41.2% capacity to predict residual pain after treatment. Conclusions: Clinicians can utilize percentage agreement as an adjunctive diagnostic tool to provide more suitable treatments to patients.

Comparative Evaluation and Correlation of Hyoid Bone Position, Airway Dimension, and Psychological Status in Class II Vertical and Horizontal Malocclusion Cases With Temporomandibular Disorder Compared to Class I Non-Temporomandibular Disorder Cases

Introduction Temporomandibular disorder (TMD) involves discomfort and impaired function in the masticatory muscles and temporomandibular joint (TMJ), with a multifaceted etiology that includes biomechanical, neuromuscular, psychological, and biological factors. This research aims to assess and correlate the hyoid bone position, airway dimensions, and psychological status in class II Hz (horizontal) and Vt (vertical) malocclusion cases with TMD in contrast to non-TMD class I cases. Methodology This research was carried out at the Orthodontics Department, Sharad Pawar Dental College and Hospital, Sawangi, with consent obtained from the ethical committee. A total of 63 adult patients with class I, class II horizontal, and class II vertical malocclusions were selected. TMD was diagnosed using the Helkimo index, and patients were categorized accordingly. Psychological status was evaluated using the Warwick-Edinburgh scale, while the placement of hyoid bone and airway dimensions were assessed using lateral cephalograms. Statistical analysis involved descriptive and inferential statistics using SPSS version 27.0, with a significance level of p < 0.05. Results The research showed a noteworthy difference in the hyoid bone's location, airway dimensions, and psychological status among the three groups. Class II TMD patients (both vertical and horizontal) exhibited higher hyoid bone positions and larger Go-Hy-Me angles (angle formed by the gonion-hyoid line and the hyoid-menton line) compared to class I patients. In addition, class II vertical TMD patients showed the most reduced airway dimensions. Psychological assessments indicated higher stress, anxiety, and depression levels in class II TMD patients, particularly in the vertical group, compared to class I non-TMD patients. Conclusion This study highlights the intricate relationships between hyoid bone position, airway dimensions, and psychological status in TMD patients. TMD patients present with hyoid bones positioned closer to the cranium and mandible, larger Go-Hy-Me angles, and reduced airway dimensions. Psychological distress exacerbates TMD symptoms, negatively impacting overall well-being and quality of life. Orthodontists should consider these interrelated factors when devising treatment plans to improve patient outcomes. Future longitudinal studies with larger samples and advanced imaging techniques are recommended to further elucidate these interactions.

Oral issues and childhood stress in eight-to-ten-year-old schoolchildren: a case-control study

OBJECTIVE

The aim of the present study was to investigate whether oral problems, harmful oral habits, and sociodemographic factors are associated with the occurrence of stress in schoolchildren.

MATERIALS AND METHODS

A case-control study nested within a cross-sectional study was conducted with a sample of 375 schoolchildren eight to ten years of age in the city of Diamantina, Brazil. The case group (with childhood stress) and control group (without childhood stress) were matched for age and sex at a 1:4 ratio (75 cases to 300 controls). Data collection involved the self-administration of a questionnaire by parents/caregivers addressing sociodemographic characteristics and the child's history of harmful oral habits. The children answered the Child Stress Scale (CSS) and underwent a clinical oral examination to determine the presence/absence of dental caries, malocclusion, and traumatic dental injuries. Data analysis involved the calculation of frequencies, the chi-square test, and conditional logistic regression (95% CI; p ≤ 0.05).

RESULTS

The final adjusted conditional logistic regression model showed that dental caries (OR = 1.78, 95% CI: 1.01 - 3.14, p = 0.044) and biting objects (OR = 1.81, 95% CI: 1.02 - 3.22, p = 0.041) remained associated with stress in the schoolchildren analysed.

CONCLUSION

The present results showed that children with dental caries and the habit of biting objects were more likely to have childhood stress.

CLINICAL RELEVANCE

The study allows paediatric dentists to expand their knowledge with regards to the influence of oral problems and harmful habits on the occurrence of childhood stress and serves as a guide for decision-making related to oral problems in schoolchildren.

Is There a Relationship between Salivary Cortisol and Temporomandibular Disorder: A Systematic Review

BACKGROUND

This systematic review examines and evaluates the relationship between salivary cortisol levels and temporomandibular disorder (TMD) in young adult patients.

METHOD

Six databases-PubMed, Scopus, Web of Science, Google Scholar, ProQuest, and Cochrane Library-were utilized to screen eligible studies. A systematic search was performed based on PECO questions and eligibility criteria. The research question for this review was "Do salivary cortisol levels correlate with TMD in individuals aged 18-40?" The risk of bias for quality assessment was determined by the Cochrane tool. PRISMA guidelines were followed while performing this review.

RESULT

A total of fourteen studies were included in this review. Of these, eleven were observational studies (four cross-sectional and seven case-control), and three were randomized control trials. Eleven of the included studies presented a low to moderate risk in the qualitative synthesis. The total sample size of the included studies was 751 participants. The included studies suggest higher salivary cortisol levels in TMD patients than in healthy individuals.

CONCLUSIONS

The findings of this review indicate higher salivary cortisol levels in adult patients with TMD than in healthy controls. Thus, supportive psychological treatment and clinical modalities should be provided to patients with TMD. Moreover, higher-quality studies with low heterogeneity are required to support this finding.

COVID-19 pandemic and the psyche, bruxism, temporomandibular disorders triangle

OBJECTIVE

To investigate the effect of the Coronavirus pandemic on the report of psychological status, bruxism, and TMD symptoms.

METHODS

An online survey was drafted to report the presence of psychological status, bruxism activities, and reported symptoms of TMDs perceived during the COVID-19 pandemic in a population of 506 individuals.

RESULTS

Mental health is not positive during the Coronavirus pandemic: almost half the subjects reported an increase in bruxism behaviors, while up to one-third reported an increase in their symptoms involving the TMJ and jaw muscles. Specifically, 36% and 32.2% of participants reported increased pain in the TMJ and facial muscles, respectively, and almost 50% of the subjects also reported more frequent migraines and/or headaches.

CONCLUSION

Increased psychosocial distress during the COVID-19 pandemic can increase the frequency of TMD symptoms and bruxism behaviors, which, in turn, constitute a triangle of mutually interacting factors with the psychological and emotional status.

Neuroscience contributes to the understanding of the neurobiology of temporomandibular disorders associated with stress and anxiety

OBJECTIVE

This review proposes a neurobiological model for temporomandibular disorders (TMD) associated with stress and anxiety.

METHODS

An electronic search was performed in the PubMed, Embase, and Web of Science databases. Articles published up to 2020 were selected. The search terms were the following: temporomandibular disorders, anxiety, stress, neurobiology of stress and anxiety, and orofacial pain.

RESULTS

In total, there were 100 studies, which presented a total of 10 different analyses. The results were described, demonstrating the type of analysis that was performed on each item analyzed for a better understanding of the context.

CONCLUSION

The conclusion is that the interactions between the masticatory system, temporomandibular joints (TMJs), and stomatognathic apparatus with "stress neuromatrix," "pain neuromatrix," "limbic system," and "neuroimmunoendocrine system" would produce the range of changes observed in neural connectivity and the diversity of symptoms presented in TMD.

The association of T102C (rs6313) polymorphism in the 5-HT2A receptor gene with temporomandibular disorders and anxiety in a group of Turkish population

OBJECTIVE

To investigate the relationship between T102C (rs6313) polymorphism in the 5-hydroxytryptamine receptor-2A (5HTR2A) gene and temporomandibular disorder (TMD) and anxiety.

METHODS

This observational case-control study included 80 patients and 70 healthy controls. TMD was diagnosed using the criteria for TMD (DC/TMD). Anxiety was assessed with the Beck anxiety scale. A genotyping study of HTRR2A T102C (rs6313) gene polymorphism was performed from genomic DNA isolated from blood.

RESULTS

The TMD group had higher anxiety scores than the control group (p < .05). The TMD group was similar to the control group regarding genotype and allele frequencies. However, the polymorphic CC genotype was more common in those with high anxiety (p < .05).

CONCLUSION

There was no clear evidence of an association between TMD and the T102C polymorphism in HTR2A and TMD. However, anxiety is closely related to the T102C polymorphism in HTR2A.

Forced swim stress exacerbates inflammation-induced hyperalgesia and oxidative stress in the rat trigeminal ganglia

This study investigates the impact of combining psychophysical stress, induced by forced swim (FSS), with masseter inflammation on reactive oxygen species (ROS) production in trigeminal ganglia (TG), TRPA1 upregulation in TG, and mechanical hyperalgesia. In a rat model, we demonstrate that FSS potentiates and prolongs CFA-induced ROS upregulation within TG. The ROS levels in CFA combined with FSS group surpass those in the CFA-only group on days 4 and 28 post-treatment. FSS also enhances TRPA1 upregulation in TG, with prolonged expression compared to CFA alone. Furthermore, CFA-induced mechanical hyperalgesia is significantly prolonged by FSS, persisting up to day 28. PCR array analyses reveal distinct alterations in oxidative stress genes under CFA and CFA combined with FSS conditions, suggesting an intricate regulation of ROS within TG. Notably, genes like Nox4, Hba1, Gpx3, and Duox1 exhibit significant changes, providing potential targets for managing oxidative stress and inflammatory pain. Western blot and immunohistochemistry confirm DUOX1 protein upregulation and localization in TG neurons, indicating a role in ROS generation under inflammatory and stress conditions. This study underscores the complex interplay between psychophysical stress, inflammation, and oxidative stress in the trigeminal system, offering insights into novel therapeutic targets for pain management.

Exploring the Relationship between Psychoneuroimmunology and Oral Diseases: A Comprehensive Review and Analysis

The relationship between psychoneuroimmunology (PNI) and oral health has recently garnered increasing attention due to the intricate interaction among psychological factors, the nervous system, immune responses, and oral diseases. This comprehensive review aims to elucidate the multifaceted connections between PNI and various oral conditions and conduct an in-depth analysis. Psychological factors, such as stress, anxiety, and depression, have been linked to oral microbiome alterations and immune function and the development and progression of oral diseases, such as periodontal disorders, oral ulcers, and temporomandibular disorders. Conversely, oral health conditions, particularly chronic periodontitis, have been associated with systemic inflammation, affecting mental health and overall well-being through neuroendocrine-immune pathways. Moreover, neural mechanisms, including the brain-gut axis and the autonomic nervous system, significantly influenced oral health through immune modulation and inflammatory responses. Understanding these complex interactions has implications for therapeutic interventions that target both psychological well-being and oral health outcomes. This review synthesizes current research findings from various disciplines, including immunology, neuroscience, dentistry, and psychology, to offer a comprehensive understanding of the bidirectional relationship between PNI and oral diseases. The implications of these interactions on treatment strategies, preventive measures, and interdisciplinary approaches underscore the need for integrated healthcare models that address psychological and oral health aspects to improve outcomes and quality of life in patients.

Loss of Slc39a12 in hippocampal neurons is responsible for anxiety-like behavior caused by temporomandibular joint osteoarthritis

Background

An evident association between mood disorders and TMJ dysfunction has been demonstrated in previous studies. This study observed both the behavioral changes and the pathological changes in hippocampal tissue of rats in an animal model of TMJ-OA by injecting MIA into TMJ.

Methods

Eighteen SD rats were randomly assigned to the NC group and the MIA groups. A TMJ-OA model was established to assess the HWT in the TMJ region, and the rats were subjected to the OFT and EPM. HE, O-fast green staining, qRT-PCR and immunofluorescence were used to detect condylar damage. Serum and hippocampal oxidative stress levels were detected. Functions of genes obtained by RNA-Seq were investigated using H2O2, ZnCl2 and transfection of siRNA on HT22 cells.

Results

Injection of MIA resulted in disorganization of the chondrocyte layer on the condylar surface of rats, with reduced synthesis and increased degradation of the condylar cartilage matrix and reduced HWT. The results of the OFT and EPM showed that the rats in the MIA group developed anxiety-like behavior during the sixth week of MIA injection. Increased Nox4 expression, decreased SOD2 expression, elevated MDA level, and reduced GSH level were detected in serum and hippocampal neurons in the MIA group, with nuclear pyknosis and reduced Nissl bodies observed in neurons. The expression of Slc39a12 in hippocampal neurons of rats in the MIA group decreased. Slc39a12 knockdown in HT22 cells induced increased Nox4 expression, decreased SOD2 expression, increased MDA level, and reduced GSH and intracellular Zn2+. Oxidative stress in HT22 cells after transfection and H2O2 stimulation was reversed when ZnCl2 was added.

Conclusion

Loss of Slc39a12 in hippocampal neurons results in cellular oxidative stress, further leading to neuronal damage. This may potentially explain how TMJ-OA triggers anxiety-like behavior in rats.

Effect of propranolol on temporomandibular joint pain in repeatedly stressed rats

Stress substantially increases the risk of developing painful temporomandibular disorders (TMDs) by influencing the release of endogenous catecholamines. Propranolol, an antagonist of β-adrenergic receptors, has shown potential in alleviating TMD-associated pain, particularly when the level of catecholamines is elevated. The aim of this study was to explore whether intra-articular propranolol administration is effective in diminishing temporomandibular joint (TMJ) pain during repeated stress situations. Additionally, we investigated the effect of repeated stress on the expression of genes encoding β-adrenoceptors in the trigeminal ganglion. In the present study, rats were exposed to a stress protocol induced by sound, then to the administration of formalin in the TMJ (to elicit a nociceptive response), followed immediately afterward by different doses of propranolol, after which the analgesic response to propranolol was evaluated. We also assessed the levels of beta-1 and beta-2 adrenergic receptor mRNAs (Adrb1 and Adrb2, respectively) using reverse transcription-quantitative PCR (RT-qPCR). Our findings revealed that propranolol administration reduces formalin-induced TMJ nociception more effectively in stressed rats than in non-stressed rats. Furthermore, repeated stress decreases the expression of the Adrb2 gene within the trigeminal ganglion. The findings of this study are noteworthy as they suggest that individuals with a chronic stress history might find potential benefits from β-blockers in TMD treatment.

Machine learning analysis with population data for the associations of preterm birth with temporomandibular disorder and gastrointestinal diseases

This study employs machine learning analysis with population data for the associations of preterm birth (PTB) with temporomandibular disorder (TMD) and gastrointestinal diseases. The source of the population-based retrospective cohort was Korea National Health Insurance claims for 489,893 primiparous women with delivery at the age of 25-40 in 2017. The dependent variable was PTB in 2017. Twenty-one predictors were included, i.e., demographic, socioeconomic, disease and medication information during 2002-2016. Random forest variable importance was derived for finding important predictors of PTB and evaluating its associations with the predictors including TMD and gastroesophageal reflux disease (GERD). Shapley Additive Explanation (SHAP) values were calculated to analyze the directions of these associations. The random forest with oversampling registered a much higher area under the receiver-operating-characteristic curve compared to logistic regression with oversampling, i.e., 79.3% vs. 53.1%. According to random forest variable importance values and rankings, PTB has strong associations with low socioeconomic status, GERD, age, infertility, irritable bowel syndrome, diabetes, TMD, salivary gland disease, hypertension, tricyclic antidepressant and benzodiazepine. In terms of max SHAP values, these associations were positive, e.g., low socioeconomic status (0.29), age (0.21), GERD (0.27) and TMD (0.23). The inclusion of low socioeconomic status, age, GERD or TMD into the random forest will increase the probability of PTB by 0.29, 0.21, 0.27 or 0.23. A cutting-edge approach of explainable artificial intelligence highlights the strong associations of preterm birth with temporomandibular disorder, gastrointestinal diseases and antidepressant medication. Close surveillance is needed for pregnant women regarding these multiple risks at the same time.

Type of correlation between bite force and EMG activity of the temporalis and masseter muscles during maximal and submaximal clenching

INTRODUCTION

Maximal bite force is an important determinant of masticatory function and is essential for the estimation of dental status. Bite force is usually measured by gnathodynamometry.

Nutrient insufficiencies and deficiencies involved in the pathogenesis of bruxism (Review)

Stress has been well-documented to have a significant role in the etiopathogenesis of bruxism. Activation of the hypothalamic-pituitary-adrenal axis (HPA) and subsequent release of corticosteroids lead to increased muscle activity. Neurological studies have demonstrated that chronic stress exposure induces neurodegeneration of important neuronal structures and destabilization of the mesocortical dopaminergic pathway. These disruptions impair the abilities to counteract the overactivity of the HPA axis and disinhibit involuntary muscle activity, while at the same time, there is activation of the amygdala. Recent evidence shows that overactivation of the amygdala under stressful stimuli causes rhythmic jaw muscle activity by over activating the mesencephalic and motor trigeminal nuclei. The present review aimed to discuss the negative effects of certain vitamin and mineral deficiencies, such as vitamin D, magnesium, and omega-3 fatty acids, on the central nervous system. It provides evidence on how such insufficiencies may increase stress sensitivity and neuromuscular excitability and thereby reduce the ability to effectively respond to the overactivation of the sympathetic nervous system, and also how stress can in turn lead to these insufficiencies. Finally, the positive effects of individualized supplementation are discussed in the context of diminishing anxiety and oxidative stress, neuroprotection and in the reversal of neurodegeneration, and also in alleviating/reducing neuromuscular symptoms.

The association of self-reported awake bruxism and sleep bruxism with temporomandibular pain and dysfunction in adult patients with temporomandibular disorders

OBJECTIVE

To investigate the association of the severity of temporomandibular disorders (TMD) pain and dysfunction with the frequency of self-reported awake bruxism (AB), sleep bruxism (SB), and stress in an adult TMD-patient population.

MATERIALS AND METHODS

This cross-sectional study included 237 TMD patients based on the Diagnostic Criteria for TMD. Age, sex, frequency of self-reported AB and SB, and stress were included as independent variables. TMD pain and TMD dysfunction were included as dependent variables in regression analyses. Univariate and multivariable linear regression analyses were used to predict TMD pain and TMD dysfunction in two separate models. Finally, network analysis was performed to investigate the associations between all variables.

RESULTS

In the univariate analyses, TMD pain was significantly associated with self-reported AB-frequent (unstandardized coefficient (B) = 3.196, 95%CI 1.198-5.195, p = 0.002). TMD dysfunction was significantly associated with AB-frequent (B = 2.208, 95%CI 0.177-4.238, p = 0.033) and SB-sometimes (B = 1.698, 95%CI 0.001-3.394, p = 0.050). In the multivariable analyses, TMD pain was significantly associated with TMD dysfunction (B = 0.370, p < 0.001), stress (B=0.102, p < 0.001). TMD dysfunction was significantly associated with TMD pain (B = 0.410, p < 0.001) only. Network analysis showed that TMD pain is a bridge factor between AB, stress, and TMD dysfunction.

CONCLUSIONS

TMD pain is directly associated with AB, stress, and TMD dysfunction, while TMD dysfunction is only associated with TMD pain.

CLINICAL RELEVANCE

Reducing pain may improve pain-related dysfunction, and the management of AB and stress may improve TMD pain and dysfunction, and vice versa.

Oral health quality of life is associated to jaw function and depression in patients with myogenous temporomandibular dysfunction

OBJECTIVE

To determine which factors influence and better differentiate between good and poor oral health-related quality of life (OHRQoL) in patients with myogenous TMD and which cut-off could predict a good/poor OHRQoL.

METHODS

Fifty-eight women with myogenous TMD were included. Factors of interest were collected (i.e., demographic variables, depression symptoms (Symptom Checklist-90 R (RDC/TMD)), pain intensity (Visual Analog Scale), jaw function (Mandibular Functional Limitation Questionnaire), and OHRQoL (Oral Health Impact Profile-14). A multivariable regression model, logistic regression, and receiver operating curve (ROC) analyses were conducted.

RESULTS

Depression symptoms (β = 0.139) and jaw function (β = 0.478) were significantly associated with OHRQoL in the multivariable model. The best model to discriminate between good/poor OHRQoL included only jaw function (AUC = 0.90), with the best cut-off of 17 points (sensitivity: 0.93; specificity: 0.79).

CONCLUSION

Depression symptoms and jaw function were significantly associated with OHRQoL. The best model and cut-off to discriminate good/poor OHRQoL included only jaw function.

Non-Pharmacological Pain Treatment of Patients with Myofascial Pain Syndrome of the Masticatory Muscles-Case Series

Myofascial pain is the most common cause of chronic pain in the masticatory region and can be assessed through clinical analysis and muscle palpation. Generally, it appears with headache and orofacial pain associated with sensitive points (trigger points) due to the excessive contraction of the masticatory muscle fibers. The study aims to evaluate how a correct treatment of myofascial pain can improve the life quality of affected patients. In this case series, 300 patients with myofascial pain were divided into two groups: 150 with intra- and extra-articular disorders and 150 with only extra-articular disorder. Each group included 75 males and 75 females. All the patients were treated with gnathological therapy through passive aligners and biofeedback exercises for four months. They underwent pain assessment (through a visual analogue scale and muscular palpation test) before, during, and after the treatment, as well as nuclear magnetic resonance of the temporomandibular joint before and after the gnathological treatment. The treatment considerably reduced the pain in all patients, without drugs, in four months according to the visual analogue scales and the palpation test. The temporomandibular magnetic resonance in each patient was similar before and after the gnathological treatment. The improvement in pain did not depend on a change in the relationship between the articular condyle and the disc.

Association of stress, anxiety, and depression levels with sleep quality in patients with temporomandibular disorders

OBJECTIVE

To examine the psychological symptoms of TMD and their effects on sleep quality in patients with temporomandibular disorders.

METHODS

The study was carried out with 425 consecutive TMD patients who sought care at the oral and maxillofacial surgery clinic of a faculty of dentistry. Perceived Stress Scale-14, Beck Anxiety Scale, and Beck Depression Scale were used to evaluate the psychological state. Sleep quality was evaluated with the Pittsburgh Sleep Quality Index.

RESULTS

The mean sleep score of all participants was 6.52. As the level of anxiety and depression increased, the scores of both total sleep quality and sleep quality components increased significantly p < 0.01. On the other hand, those with poor sleep quality had significantly higher stress, anxiety, and depression levels than those with good sleep quality p < 0.01.

CONCLUSION

Negative emotional situations such as stress, anxiety, and depression seriously impair sleep quality in TMD patients.

Effect of sound-induced repeated stress on the development of pain and inflammation in the temporomandibular joint of female and male rats

Temporomandibular disorder (TMD) is a common painful condition of the temporomandibular joint (TMJ) and associated structures. Stress is a significant risk factor for developing this painful condition that predominantly affects women. This study aimed to test the hypothesis that stress increases the risk of developing TMJ pain by facilitating inflammatory mechanisms in female and male rats. To test this hypothesis, we evaluated TMJ carrageenan-induced expression of pro-inflammatory cytokines and migration of inflammatory cells and TMJ formalin-induced nociception in female and male rats submitted to a repeated stress protocol induced by sound. We found that sound-induced repeated stress facilitates TMJ inflammation and contributes to TMJ nociception development equally in females and males. We conclude that stress is a risk factor for developing painful TMJ conditions in males and females, at least in part, by favoring the inflammatory process similarly in both sexes.

Impact of COVID-19 on Portuguese Dental Students: A Cohort Study

Introduction: The goal of this study was to assess the impact of COVID-19 on Portuguese dental students on their depression, anxiety, temporomandibular dysfunction, academic degree, and oral behaviors. Methods: The target of this population study was to enroll third-, fourth-, and fifth-year students of the Integrated Master’s degree in Dental Medicine at the Universidade Católica Portuguesa—Faculty of Dental Medicine (Viseu, Portugal) in the academic year 2021–2022. Temporomandibular disorders (TMD) symptoms, oral behaviors, anxiety, and depression were assessed using validated questionnaires. The variables under study were (a) age, gender, marital status, academic level, academic degree, medication, and any existing pathologies; (b) questions related to taste changes or thoughts that would indicate (or not) worsening psychological conditions (anxiety and depression). After data collection (Google Forms®), data were transferred to an Excel file and entered into SPSS® software. A chi-square test allowed the independence between ordinal or nominal variables. The Spearman correlation test was used to analyze the relationship between variables in the study (significant if p ≤ 0.05). Results: 98.2% of the students answered the questionnaire. TMD had a prevalence of 35%, and anxiety and depression a prevalence of 29% and 24%, respectively. The results showed that the female gender was the most affected by psychological and temporomandibular disorders. Statistically significant correlations were identified between variables, such as gender and anxiety, TDM, and depression (respectively, p = 0.0001, p = 0.014, and p = 0.026); between TDM and anxiety and depression (respectively, p = 0.001 and p < 0.001); and between performing oral behaviors and TMD, anxiety, and depression (respectively, p = 0.0001, p = 0.0001, and p = 0.006). The variables, such as age and academic degree, did not establish a statistically significant relationship with TMD, oral behaviors, and the two psychological conditions. Conclusions: It was possible to conclude that there was a moderate prevalence of TMD, anxiety, and depression in the period studied. Moreover, a statistically significant relationship was found between TMD, anxiety, and depression with gender and frequency of OBs; however, no significant association was found for TMD, anxiety, and depression with the age of students and with the academic degree.

Stroke: An electromyographic approach to the masseter and temporal muscles, orofacial soft tissue pressure, and occlusal force

Stroke is a cerebrovascular disease that triggers changes in the central and peripheral nervous systems, and can compromise human body function. This cross-sectional observational study aimed to analyze the electromyographic (EMG) activity of the masseter and temporal muscles, orofacial soft tissue pressure, and strength of occlusal contacts in patients who had suffered a stroke. Twenty-four patients were divided into two groups: stroke (n = 12) and control (n = 12). The EMG of the masseter and temporal muscles was evaluated during mandibular rest, protrusion, right laterality, left laterality, and maximal voluntary contraction. The Iowa Oral Pressure Instrument (IOPI) was used to measure pressure from the tongue, lips, and buccinator muscles. A computerized system for occlusal analysis (T-Scan III) was used to measure the occlusal contact points of the right and left hemiarches (upper and lower) and the upper and lower first molars. Data were subjected to Student's t-test (p < 0.05). The stroke group had lower normalized electromyographic activity, with a significant difference in the left temporal muscle during rest (p = 0.03) when compared to the control group. There was a significant difference between the groups in tongue pressure (p = 0.004) with a lower mean value in the stroke group. There was a significant difference between the groups in the evaluation of the occlusal contact points of the first permanent molars, with a lower mean percentage in the stroke group. The results indicate that stroke negatively affects functional performance of the stomatognathic system.

Temporomandibular disorder severity and its association with psychosocial and sociodemographic factors in Turkish adults

BACKGROUND

There is a lack of awareness regarding temporomandibular disorder (TMD) and its association with psychological and sociodemographic factors in the Turkish population. This study aimed to evaluate the relationship between signs/symptoms of anxiety-depression, sociodemographic factors, parafunctional habits, bruxism, and the presence and severity of the symptoms of TMD in Turkish adults.

METHODS

The participants completed an online questionnaire consisting of sociodemographic questions, the Fonseca Anamnestic Index, and the Patient Health Questionnaire-4.

RESULTS

The mean age of the 2580 participants was 35.29 ± 12.70 years, and 63.3% were women. The frequency of the participants who showed symptoms of TMD was 69.8%. The severity of TMD symptoms was significantly greater in participants who had signs/symptoms of anxiety and depression (p < 0.05). Sociodemographic and psychological data showed an association between the presence and severity of the symptoms of TMD and sex (OR 1.52, 95% confidence interval (CI) 1.26-1.85), parafunctional habits (OR 2.64, 95% CI 2.36-2.99), bruxism (OR 3.14, 95% CI 1.78-4.90), signs/symptoms of anxiety (OR 2.30, 95% CI 1.76-3.00), and signs/symptoms of depression (OR 1.90, 95% CI 1.48-2.42).

CONCLUSIONS

The results of the present study suggest that females and those who report bruxism, parafunctional habits, and signs/symptoms of anxiety-depression are more likely to show symptoms of TMD with different severity.

Prevalence of self-reported symptoms of temporomandibular disorders and associated factors in the period of distance learning

OBJECTIVE

Assess the prevalence of self-reported TMD symptoms and anxiety and check the quality of sleep and life during the distance learning period in university students at the University of Brasilia (UnB).

MATERIALS AND METHODS

The participants were students from the Health Sciences College and Medicine College at UnB. Self-administered questionnaires were used to evaluate symptoms of TMD, quality of life, and sleep quality. One-way analysis of variance, followed by Bonferroni test, and Kruskal-Wallis test, followed by Dunn's test, were performed (P < 0.05). For qualitative data analysis, the chi-square test was applied (P < 0.05).

RESULTS

Total 156 students were included; prevalence of TMD, anxiety, sleep disturbance, and poor sleep quality was 73.1%, 84%, 12.8%, and 62.8%, respectively. A greater prevalence of painful TMD was observed in students with severe anxiety (P = 0.007). Students with symptoms of painful TMD, severe anxiety, and sleep disorders had statistically worse quality of life.

CONCLUSIONS

The implementation of distance learning in health courses to replace classroom teaching during the COVID-19 pandemic has impacted TMD prevalence, anxiety, quality of life, and sleep quality.

CLINICAL RELEVANCE

Psychological factors are directly associated with TMD symptoms and quality of life, TMD conditions are related to quality of life as well. COVID-19 pandemic and the distance learning in health courses are new situations that can lead to a great impact on mental health and in consequence to TMD conditions and quality of life.

Psychological Profiles and Their Relevance with Temporomandibular Disorder Symptoms in Preorthodontic Patients

Background

Temporomandibular disorders (TMDs) refer to a group of heterogenous musculoskeletal diseases with diverse clinical symptoms and an undetermined aetiology. The psychological profiles were closely related to the onset and treatment outcomes of TMDs.

Objective

To examine the relevance between psychological profiles and different symptoms of TMDs in preorthodontic patients.

Methods

The study was conducted among 570 preorthodontic patients. TMDs symptoms were recorded by the Diagnostic Criteria for TMD (DC/TMD) symptom questionnaire. The seven-item Generalized Anxiety Disorder Scale (GAD-7), the nine-item Patient Health Questionnaire (PHQ-9), and the Pain Catastrophizing Scale (PCS) were used for the evaluation of anxiety, depression, and pain catastrophizing levels. The relevance of three psychological profiles with TMDs and subtypes was evaluated with Spearman's rank correlation test and logistic regression analysis (P < 0.05).

Results

34.56% of the enrolled preorthodontic patients were diagnosed with TMDs. Scores of GAD-7, PHQ-9, and PCS were significantly higher in the TMDs group than in the non-TMDs group. Participants with anxiety, depression, or high pain catastrophizing had a higher prevalence of both pain-related TMDs symptoms and intra-articular TMDs symptoms. The correlations among pain-related TMDs, intra-articular TMDs, and scores on the psychological scales were significant (P < 0.05). The adjusted logistic regression model revealed that anxiety, depression, and high pain catastrophizing were significant risk factors for TMDs with an odds ratio (OR) of 2.196, 1.741, and 1.601, respectively. Depression was associated with higher pain-related TMDs prevalence (OR = 2.136), while anxiety and depression were associated with higher intra-articular TMDs prevalence (OR = 2.341 and 1.473).

Conclusion

Anxiety, depression, and high pain catastrophizing were comorbid psychological conditions of TMDs. Depression was the top risk factor for pain-related TMDs, while anxiety rendered the highest risk for intra-articular TMDs. Inclusion of psychological assessments in preorthodontic evaluation might yield great benefits in TMDs screening.

Oral health-related quality of life and psychological states of dental students with temporomandibular disorders

PURPOSE/OBJECTIVES

This study investigates the frequency of temporomandibular disorders (TMD) in dental students, and evaluates the association between TMDs, psychological states, and oral health-related quality of life (OHRQoL). The presence of bruxism was also determined.

METHODS

Two hundred ninety-three dental students completed the Symptom Checklist 90-Revised (SCL-90-R) and Oral Health Impact Profile 14 (OHIP-14) questionnaires and underwent a clinical examination according to Diagnostic Criteria for TMDs.

RESULTS

TMDs were detected in 46.4% of the dental students. OHIP-14 scores of students with TMDs were significantly higher than scores for students without TMDs (p < 0.05). Significant differences were observed in all SCL-90-R scores among students with and without TMDs, except for phobic anxiety and additional SCL-90-R subscale scores (p < 0.05). The prevalence of myalgia was significantly higher in clinical students (26.6%) than in preclinical students (15.6%). OHIP-14 scores of clinical students were significantly higher than preclinical students (p < 0.05).

CONCLUSIONS

In dental students, there was a high frequency of TMDs and bruxism. OHRQoL was poorer in clinical students. Levels of anxiety, depression, and somatization were not different in clinical and preclinical students. SCL-90-R scores are higher in students with TMDs except for phobic anxiety and additional SCL-90-R subscale scores.

High Pain Intensity is a Risk Factor of Non-Resolving TMD: A Three-Year Follow-Up of a Patient Group in a Norwegian Interdisciplinary Evaluation Program

Purpose

To investigate the outcome of patients with long-term refractory temporomandibular disorders (TMD) three years after a Norwegian interdisciplinary evaluation program with attention to patient satisfaction, function, pain, and psychosocial variables.

Patients and Methods

The study population consisted of 60 long-term refractory TMD patients who were investigated by a Norwegian interdisciplinary team. A questionnaire that covered medical history, function, pain, lifestyle factors, TMD-status and follow-up from their general medical practitioner (GMP) was sent to the patients three years after the evaluation. Questionnaires that assessed function (Mandibular Functional Index Questionnaire [MFIQ] and Roland Morrison Scale [RMS]), pain intensity (General Pain Intensity questionnaire [GPI]) and psychosocial factors (Hospital Anxiety and Depression scale [HADS]); a 2-item version of the Coping Strategies Questionnaire [CSQ]) were included in the package.

Results

Thirty-nine out of 60 TMD patients completed the questionnaires. Improvements in TMD symptoms were reported in 10 patients (26%), were unchanged in 16 patients (41%) and worsened in 13 patients (33%). Only 8 patients (21%) were satisfied with the follow-up of the suggested treatments from their GMP. Significant improvements of symptoms were noted in MFIQ (jaw function), GPI (including pain intensity at maximum and suffering from pain), and CSQ (pain related catastrophizing), in all 39 TMD patients as one group. However, a subgroup analysis showed that the significant improvements were mostly within patients who reported improvement of TMD symptoms. A high pain intensity at baseline was a significant risk factor (OR = 5.79, 95% CI: 1.34, 24.96) for patients who reported worsening of TMD symptoms at follow-up.

Conclusion

High pain intensity at baseline was a significant risk factor for poorer recovery three years after an interdisciplinary evaluation. Our data support the notion that improved coping with TMD pain includes both decreased pain intensity, CSQ and MFIQ scores.

Activation of the Mesencephalic Trigeminal Nucleus Contributes to Masseter Hyperactivity Induced by Chronic Restraint Stress

Psychological stress is commonly accepted to be closely associated with masticatory muscle disorder, which is the main symptom of temporomandibular disorder (TMD). Previous studies have confirmed that exposure to stress may cause masticatory muscle hyperactivity. However, the central mechanism underlying this process remains unclear. The mesencephalic trigeminal nucleus (Vme), which resides in the brainstem, is the primary afferent center for masticatory proprioception and plays a key role in oral–motor movements by projecting to the trigeminal motor nucleus (Vmo). Therefore, the present study was designed to examine the role of Vme neurons in masseter overactivity induced by chronic stress. We found that subjecting mice to restraint stress (6 h/day) for 14 days caused significant anxiety-like behavior, obvious masseter overactivity, and markedly enhanced electrophysiological excitability of Vme neurons. By using anterograde tract tracing combined with immunofluorescence staining methods, we observed vesicular glutamate transporter 1 (VGLUT1)-positive glutamatergic projections from the Vme to the Vmo. Moreover, chronic restraint stress (CRS) elevated the expression of VGLUT1 and choline acetyltransferase (ChAT) in Vmo. Furthermore, administration of VGLUT1-targeted short hairpin RNA (shRNA) into the bilateral Vme significantly suppressed the enhanced overexcitability of Vme neurons, downregulated the overexpression of VGLUT1 and ChAT in the Vmo, and attenuated the elevated overactivity of the masseter caused by CRS. Taken together, we showed that CRS can excite neurons in the Vme, enhancing glutamatergic excitatory projections from the Vme to the Vmo and resulting in masseter muscle overactivity. These findings provide us with a novel central mechanism underlying the correlation between psychological factors and TMD.

DISFUNÇÕES TEMPOROMANDIBULARES E FATORES PSICOLÓGICOS: UMA REVISÃO DE LITERATURA

As disfunções temporomandibulares (DTM) são condições biológicas que envolvem sinais e sintomas como dores crônicas na articulação temporomandibular e nos músculos da mastigação. O presente estudo tem como objetivo identificar quais e como conceitos psicológicos são descritos em artigos de intervenções odontológicas relacionadas à DTM, em artigos de revisão sistemática. Para isto foram utilizadas três bases de dados na busca e seleção: PubMed, Scopus e Web of Science. Aplicou-se em todas estas bases de dados a mesma formulação de termos-chave. Foram selecionados os artigos de revisões, publicados entre 2000 e 2017, escritos em inglês. Dos 4.092 artigos encontrados, sete foram selecionados descrevendo intervenções psicológicas envolvidas com o tratamento da DTM. Todos os artigos selecionados foram analisados com base em seus objetivos e discussões, considerando as características de apresentação e compreensão das variáveis psicológicas relacionadas à disfunção temporomandibular e às intervenções utilizadas. Para tanto, foram realizadas análises qualitativas e quantitativas. Pode-se concluir que a compreensão e a definição das variáveis psicológicas relacionadas à DTM não são evidentes, o que dificulta a produção de resultados claros sobre a eficácia dos diagnósticos e intervenções para DTM. 

Painful Temporomandibular Disorders, Bruxism and Oral Parafunctions before and during the COVID-19 Pandemic Era: A Sex Comparison among Dental Patients

Aim: To evaluate the effect of the current coronavirus pandemic on the prevalence of bruxism, oral parafunctions and painful Temporo-Mandibular Disorders (TMDs) and to evaluate the influence of the pandemic on both sexes. Methods: This retrospective study included 288 dental patients who underwent complete anamnesis and examination according to the Diagnostic Criteria for TMD. The study evaluated two patient populations according to the date of examination: (a) pre-COVID-19 pandemic era (108 patients); (b) COVID 19 pandemic era, where 180 patients were examined during the pandemic. Results: A significant increase in parafunction activity was found in both men and women (p < 0.001) during the COVID-19 pandemic. Awake bruxism (AB) and sleep bruxism (SB) was more prevalent during the COVID-19 pandemic solely in women (AB-p < 0.001; SB-p = 0.014). Conclusions: Men and women were affected by the ongoing stress due to the COVID-19 pandemic, yet women showed a higher influence as compared to men. The long-term exposure to elevated levels of anxiety and stress may aggravate or trigger stomatognathic detrimental conditions. Dentists should be aware and regularly monitor their patients regarding the possible existence and consequences of bruxism and TMD.

Increased Risk of Temporomandibular Joint Disorder in Osteoporosis Patients: A Longitudinal Study

BACKGROUND

The objective of this study was to investigate the risk of temporomandibular joint disorder (TMD) in patients with osteoporosis.

METHODS

Data from the Korean National Health Insurance Service-Health Screening Cohort from 2002 to 2015 were collected. Participants ≥ 40 years old were enrolled, and the history of osteoporosis was evaluated. The 62,328 osteoporosis patients were matched for age, sex, income, and region of residence with 62,328 control participants. The occurrence of TMD was assessed in both the osteoporosis and control groups during the follow-up period. Stratified Cox proportional hazard analyses for TMD were conducted for the osteoporosis and control groups. The hazard ratios (HRs) of osteoporosis for TMD were further analyzed by age and sex subgroups.

RESULTS

A total of 1.2% (725/61,320) of the osteoporosis patients and 0.6% (339/61,320) of the control participants had TMD (P<0.001). Osteoporosis was associated with an elevated HR of TMD (adjusted HR=1.96, 95% CI=1.72-2.23, P<0.001). Among the age and sex subgroups, the < 60-year-old mal\e group demonstrated an adjusted HR of osteoporosis for TMD as high as 4.47 (95% CI=1.17-17.12, P=0.029). Other age and sex subgroups also showed a higher HR for TMD associated with osteoporosis (adjusted HR=2.30, 95% CI=1.90-2.78, P<0.001 for the ≥ 60-year-old female group).

CONCLUSION

Osteoporosis was related to a higher risk of TMD in the adult population. A prominent association of osteoporosis with TMD was noted in middle-aged men and older women.

Telemedicine for a Multidisciplinary Assessment of Orofacial Pain in a Patient Affected by Eagle’s Syndrome: A Clinical Case Report

Background:

Orofacial pain has a broad range of origins and a multidisciplinary approach occupies a relevant role.

Objective:

The aim of this study was to review the literature regarding the evolution of telemedicine and orofacial pain related to a case report of a patient affected by Eagle's syndrome.

Materials and Methods:

Two authors (RJM and SG) independently reviewed the literature up to March 2020. A case report was developed by including the interdisciplinary assessment and initial treatment of orofacial pain in a 38-year-old female patient affected by Eagle’s syndrome. The patient was interviewed by two different specialists (from Rome, Italy and Los Angeles, California) through an online meeting platform in order to evaluate her complex situation, demonstrating the possibilities that telemedicine offered during the COVID-19 pandemic.

Conclusion:

An interdisciplinary approach can be performed for future follow ups on patients as various advantages were found by the patient and by the clinicians themselves.

Coronavirus Lockdown as a Major Life Stressor: Does It Affect TMD Symptoms?

Temporomandibular disorders are multi-factorial conditions that are caused by both physical and psychological factors. It has been well established that stress triggers or worsens TMDs. This paper looks to present early research, still unfolding, on the relationship between COVID-19 as a major life stressor and TMDs. The main aims of this study were to: investigate the presence of symptoms related to TMDs and the time of onset and the worsening of painful symptoms in relation to the changes in social life imposed by the coronavirus pandemic; and to evaluate the perception of COVID-19 as a major stressful event in subjects who report worsening of painful TMD symptoms. One hundred and eighty-two subjects answered questionnaires-Axis II of the RDC/TMD, the PSS, and specific items about coronavirus as a stressful event-during the lockdown period for COVID-19 in Italy to evaluate the presence of reported symptoms of TMD and the level of depression, somatization, and stress perceived. The results showed that 40.7% of subjects complained about TMD symptoms in the past month. Regarding the time of onset, 60.8% of them reported that facial pain started in the last three months, while 51.4% of these subjects reported that their symptoms worsened in the last month and were related to the aggravation of pain due to the coronavirus lockdown as a major life event and to the stress experienced. The results of this study seem to support the hypothesis that stress during the pandemic lockdown influenced the onset of temporomandibular joint disorders and facial pain, albeit with individual responses.

COVID-19: Prosthodontic Challenges and Opportunities in Dental Practice

The coronavirus disease (COVID-19) has spread globally. Dentists, dental specialists, dental assistants, dental staff, and patients are potentially at higher risk of COVID-19 infection during dental treatments. The prosthodontic dental treatment procedures may range from low to very high risk of COVID-19. This article presents necessary recommendations regarding the prosthodontic dental treatment procedures with standards of care and infection control.

α1 adrenergic receptor activation has a dynamic effect on masticatory muscle afferent fibers

Temporomandibular Disorder (TMD) patients report amplification of pain in the masticatory muscles after psychological trauma or stressful conditions. The mechanisms underlying this phenomenon are yet to be elucidated. This study combined immunohistochemistry with single cell in vivo electrophysiology recordings of masticatory muscle afferent fibers to investigate the role of α₁-adrenergic receptors in muscle nociception. It was found that a subset of trigeminal afferent fibers which innervate the masseter and temporal muscles expressed α_1a, α_1b and α_1d receptors, including a smaller number of putative nociceptors which co-expressed TrpV₁ receptors. Local injection of the selective α₁ adrenergic receptor agonist phenylephrine into masticatory muscle decreased and increased the mechanical activation threshold of slow and fast conducting afferent fibers, respectively. This effect was reversed by co-administration of the α₁ selective antagonist terazosin. To rule out the possibility that local ischemia was responsible for the observed effect of phenylephrine on masticatory muscle afferent fibers, additional experiments were conducted where blood flow to the masticatory muscle was reduced by common carotid artery occlusion. This investigation found that muscle blood flow occlusion increased the mechanical activation threshold of the majority of masticatory muscle afferent fibers unrelated to conduction velocity. These findings suggest that under conditions of increased sympathetic tone, such as those related to stress, noradrenaline may sensitize masticatory muscle nociceptors to increase pain and desensitize muscle proprioceptors to alter muscle tone, through activation of α₁ receptors.

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.

Prevalence of Temporomandibular Disorder in Turkish University Students: a Questionnaire Study

Background/Aim: Temporomandibular dysfunction (TMD) might influence any individual with different signs and symptoms irrespective of gender or age. The aim of this study is to assess the prevalence of TMD in Oral and Dental Health Program students of İstanbul University-Cerrahpaşa.

Material and Methods: This study include a sample of 486 students with age ranging from18 to 24 years. The presence and severity of TMD was evaluated using the Fonseca’s Anamnestic Index (FAI) and its questionnaire. The data were analysed using SPSS Version 22. The chisquare test was used to compare the data from different groups and to determine whether the differences were statistically significant.

Results: The results showed that a total of 47,53% of students had some degree of TMD and females were generally more affected than males. These degrees were as follows: 33,95 % were classified as mild, 11,52 % moderate and 2,05 % severe signs and symptoms. The women exhibited some degree of TMD (51,8%) at a higher frequency than men (40,33%). No significant differences were observed between gender for a same TMD severity degree (p>0.05).

Conclusions: A high prevalence of mild TMD was found in this study population. In addition, tense personalities, headaches, and temporomandibular joint (TMJ) sounds were the most prevalent findings of TMD. The present study suggests that Fonseca’s Anamnestic Index (FAI) has been used in screening for TMD for prevention and management of TMD in a non-patient young population.

A comparative clinical and radiographic study on patients with chronic facial pain with and without temporomandibular disorder presenting to an otolaryngology clinic

Objective: Facial pain associated with temporomandibular disorder (TMD) is considered a component of Costen's syndrome. However, prior to the current study, no previous clinical and radiographic studies have addressed facial pain in patients with TMD. Methods: The study included 212 patients with chronic facial pain examined in an otolaryngology clinic. These were stratified into 132 patients with TMD and 80 patients without TMD. Clinical and radiographic findings were documented in both groups. Results: Forty-eight patients in the TMD group had normal endoscopic findings and clear CT scans and had their facial pain directly attributable to TMD. Conclusion: In patients presenting with facial pain, where nasal endoscopy reveals no abnormality, TMD should be specifically addressed, especially if CT scans of the paranasal sinuses are clear.

Updates in PTSD Animal Models Characterization

Post-traumatic stress disorder (PTSD) is a chronic, debilitating mental disorder afflicting more than 7% of the US population and 12% of military service members. Since the Afghanistan and Iraq wars, thousands of US service members have returned home with PTSD. Despite recent progress, the molecular mechanisms underlying the pathology of PTSD are poorly understood. To promote research on PTSD (especially its molecular mechanisms) and to set a molecular basis for discovering novel medications for this disorder, well-validated animal models are needed. However, to develop PTSD animal models is a challenging process, due to predisposing factors such as physiological, behavioral, emotional, and cognitive changes that emerge after trauma. Currently, there is no well-validated animal model of PTSD, although several stress paradigms mimic the behavioral symptoms and neurological alterations seen in PTSD. In this chapter, we will provide an overview of animal models of PTSD including learned helplessness, footshock, restraint stress, inescapable tail shock, single-prolonged stress, underwater trauma, social isolation, social defeat, early-life stress, and predator-based stress. We emphasize rodent models because they reproduce some of the behavioral and biotical phenotypes seen in PTSD. We will also present data showing that homologous biological measures are increasingly incorporated in studies to assess markers of risk and therapeutic response in these models. Therefore, PTSD animal models may be refined in hopes of capitalizing on the understanding of the molecular mechanisms and delivering tools in order to develop new and more efficacious treatments for PTSD.

Prevalence of signs and symptoms of temporomandibular disorders in college preparatory students: associations with emotional factors, parafunctional habits, and impact on quality of life

The aim of this study was to evaluate the prevalence of temporomandibular disorders (TMD) signs and symptoms, its correlation with gender, parafunctional habits, emotional stress, anxiety, and depression and its impact on oral health-related quality of life (OHRQL) in college preparatory students at public and private institutions in João Pessoa, Paraíba (PB). The sample consisted of 303 students. Presence of TMD symptoms was determined by an anamnesis questionnaire containing questions related to the presence of parafunctional habits and emotional stress. A simplified clinical evaluation protocol was used. Anxiety and depression were determined with the Hospital Anxiety and Depression (HAD) scale and the OHRQL using the short version contained in the Oral Health Impact Profile (OHIP-14). The Chi-square, Fisher Exact, Mann Whitney, and Kruskal-Wallis tests were performed. Presence of signs and symptoms of TMD was statistically associated (p ≤ 0,05) with female gender, parafunctional habits, emotional stress, and anxiety, and represented greater impairment of the OHRQL. The physical pain domain was the most affected. The increased prevalence of signs and symptoms of TMD among college preparatory students indicates that there is a need for education and clarification among teachers and students to improve early diagnosis and to prevent the problem.

The associations between work-related factors and temporomandibular disorders among female full-time employees: findings from the Fourth Korea National Health and Nutrition Examination Survey IV (2007-2009)

Background

The aim of this study was to investigate the association between work-related factors and temporomandibular disorders (TMD) among female full-time employees using representative data from a national population-based survey.

Methods

Data from the Fourth Korea National Health and Nutrition Examination Survey IV (2007–2009) were used to analyze 1,612 women. Complex samples logistic regression was applied for adjusting for general characteristics and work-related factors to examine the association between work-related factors and TMD.

Results

The prevalence of TMD was 12.8% in this study population. With respect to age, educational status, marital status, problem drinking, exercise, and stress, there were statistically significant differences in the prevalence of TMD. In logistic regression analyses on complex samples, based on 40 h or less per week, odds ratios (ORs) for respondents who worked 40–48 working hours, 49–60 working hours, and more than 60 h were 1.16 (95% confidence interval (CI) 0.69–1.94), 1.41 (95% CI 0.79–2.54), and 2.43 (95% CI 1.29–4.59), after adjusting for general characteristics, working schedule, employment status, and occupation.

Conclusions

This study found that long working hours were significantly associated with TMD in Korean female full-time employees.

Temporomandibular Disorders Related to Stress and HPA-Axis Regulation

Temporomandibular disorders (TMDs) are characterized by pain and dysfunction in the masticatory apparatus and the temporomandibular joint (TMJ). Previous trauma, stress symptoms, psychosocial impairment, and catastrophizing have been related to TMD. To assess if the hypothalamic-pituitary-adrenal (HPA) axis is upregulated in TMD patients, we performed a cross-sectional study with saliva from 44 TMD patients and 44 healthy sex- and age-matched controls for cortisol (F) and cortisone (E) with liquid chromatography-tandem mass spectrometry. Furthermore, we calculated the F/E ratio for the evaluation of 11β-hydroxysteroid dehydrogenase activity. We also assessed anxiety/depression and pain catastrophizing scores from a questionnaire that participants completed prior to the examination. We found that F (P=0.01), E (P=0.04), the F/E ratio (P=0.002), and the sum of glucocorticoids (E + E) in saliva (P=0.02) were significantly higher in the TMD group. Anxiety/depression and catastrophizing scores were also significantly higher in the TMD group (P < 0.0001). Our findings indicate that patients with TMDs may have an upregulated HPA axis with higher F secretion from the adrenal cortex. Anxiety/depression and pain catastrophizing scores were significantly higher in the TMD group, and psychological factors may contribute to chronic upregulation of the HPA axis.

Extracellular signal-regulated kinase activation in the spinal cord contributes to visceral hypersensitivity induced by craniofacial injury followed by stress

BACKGROUND

We previously developed an animal model to examine mechanisms that underlie the emergence of visceral hypersensitivity modeling pain characteristics of temporomandibular disorder (TMD) patients with comorbid irritable bowel syndrome (IBS). In ovariectomized (OVx) rats with estradiol (E2) replacement, visceral hypersensitivity developed subsequent to masseter muscle inflammation followed by repeated forced swim (FS) stress. The purpose of this study was to investigate whether activation of extracellular signal-regulated kinase (ERK) in the spinal cord contributes to visceral hypersensitivity in this overlapping pain model.

METHODS

In OVx with E2 replacement rats masseter muscle inflammation was followed by 3 day FS (comorbid condition). Depression-like behaviors were assessed by sucrose preference and in the elevated plus maze, and visceral sensitivity was measured by the visceromotor response (VMR) to colorectal distention. The protein level of ERK1/2 and phosphorylated ERK1/2 (p-ERK1/2) in the L6-S2 dorsal spinal cord was analyzed by western blot.

KEY RESULTS

FS stress decreased sucrose consumption in E2 replaced rats in sucrose preference test. The expression of p-ERK1/2 in the L6-S2 dorsal spinal cord increased significantly in E2 with comorbid rats. Intrathecal injection of mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor PD98059 blocked the visceral hypersensitivity induced by masseter muscle inflammation combined with FS stress.

CONCLUSIONS & INFERENCES

These data indicate that ERK1/2 activation contributes to the visceral hypersensitivity evoked by craniofacial inflammation pain combined with stress. The results may provide a new therapeutic avenue for alleviating overlapping pain conditions.

Metabolic and vascular pattern in medial pterygoid muscle is altered by chronic stress in an animal model of hypodontia

Psychological stress is an important perpetuating, worsening and risk factor for temporomandibular disorders of muscular or articular origin. Occlusion instability, by the way, is considered a risk factor of this pathology and can be reproduced in some experimental animal models. The exact physiologic mechanism underlying these relations however, remains unclear. Our purpose was to test the hypothesis that chronic stress and unilateral exodontia induce metabolic and vascular changes in the medial pterygoid muscle of rats. Adult Wistar rats were submitted to chronic unpredictable stress and/or unilateral exodontia and their plasma and medial pterygoid muscle were removed for analysis. The parameters evaluated included plasma levels of corticosterone, metabolic activity by succinate dehydrogenase, oxidative capacity by nicotinamide adenine dinucleotide diaphorase, capillary density by laminin and alfa-CD staining and reactive oxidative species production. Chronic unpredictable stress as an isolated factor, increased oxidative metabolism, capillary density and reactive oxygen species production at medial pterygoid muscle. Conversely, exodontia has a main effect in metabolism, promoting glycolytic transformation of muscle fibers. Association of both factors induced a major glycolytic pattern in muscle and vascular changes. Our findings provide insights into the mechanisms, possibly inducing metabolic and vascular alterations on medial pterygoid muscle of rats, by which chronic stress and occlusal instabilities might be involved as risk factors in the pathophysiology of temporomandibular disorders with muscular components.

A Study to Determine the Prevalence of Temporomandibular Disorders in a Young Adult Population and its Association with Psychological and Functional Occlusal Parameters

PURPOSE

To determine the prevalence of temporomandibular disorders (TMD) in medical university students and to analyze the relationship of TMD with psychological and functional occlusal parameters.

MATERIALS AND METHODS

200 students (mean age 21.81 ± 1.99) were screened for TMD with the TMD Pain Screener. Clinical examinations identified the participants with TMD. Based on their diagnostic criteria for TMD (DC/TMD) axis I diagnosis, participants were divided into three groups: group 1- non-TMD, group 2- pain related TMD and headaches, and group 3- intra-articular joint disorders. Further study was continued involving patients diagnosed with TMD as the study group, and an equal number of age- and sex-matched participants were selected in control group. Among these, emotional distress was evaluated using the "hospital anxiety and depression scale" (HADS). Occlusal evaluations were done by using the T-Scan computerized occlusal analysis system. Occlusion time, left lateral disclusion time, right lateral disclusion time, and protrusion disclusion time were measured with T-Scan III. These parameters were compared among the groups with ANOVA test at a significance level of 0.05.

RESULTS

17% of the population were affected by TMD. The mean HADSd (depression) and HADSa (anxiety) scores were significantly higher (p < 0.05) in group 2 (7.67 ± 3.68; 10.60 ± 3.33) and group 3 (6.89 ± 3.23; 9.26 ± 4.05) as compared to group 1 (3.18 ± 2.33; 5.29 ± 3.21). The mean values of occlusion time, left lateral disclusion time, right lateral disclusion time, and protrusion-disclusion time were also higher for group 2 and group 3 as compared to group 1.

CONCLUSIONS

This study found that the prevalence of TMD in this university student population was 17%. There were significant associations of TMD with psychological parameters and functional occlusal parameters.

Spared Nerve Injury Increases the Expression of Microglia M1 Markers in the Prefrontal Cortex of Rats and Provokes Depression-Like Behaviors

Pain and depression are frequently co-existent in clinical practice, yet the underlying mechanisms remain largely to be determined. Microglia activation and subsequent pro-inflammatory responses play a crucial role in the development of neuropathic pain and depression. The process of microglia polarization to the pro-inflammatory M1 or anti-inflammatory M2 phenotypes often occurs during neuroinflammation. However, it remains unclear whether M1/M2 microglia polarization is involved in the neuropathic pain induced by spared nerve injury (SNI). In the present study, the mechanical withdrawal threshold, forced swim test, sucrose preference test, and open field test were performed. The levels of microglia markers including ionized calcium-binding adaptor molecule 1 (Iba1), cluster of differentiation 11b (CD11b), M1 markers including CD68, inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), IL-6, tumor necrosis factor-a (TNF-α), 8-hydroxy-2-deoxyguanosine (8-OH-dG), and M2 markers including CD206, arginase 1 (Arg1), IL-4 in the prefrontal cortex were determined on day 14 after SNI. The results showed that SNI produced mechanical allodynia and depressive-like behaviors, and also increased the expressions of microglia markers (Iba1, CD11b) and M1 markers (CD68, iNOS, IL-1β, TNF-α, and 8-OH-dG) in the prefrontal cortex. Notably, minocycline administration reversed these abnormalities. In addition, minocycline also promoted M2 microglia polarization as evidenced by up-regulation of CD206 and Arg1. In conclusion, data from our study suggest that SNI can lead to depression-like behaviors, while M1 polarization and consequent overproduction of pro-inflammatory cytokines plays a key role in the pathogenesis of neuropathic pain. The data furthermore indicate that modulation of inflammation by inhibition of M1 polarization could be a strategy for treatment of neuropathic pain, and might prevent the induction of neuropathic pain-induced depression symptoms.