Sex, Gender, and Orofacial Pain

Associations of Gender Role and Pain in Musculoskeletal Disorders: A Mixed-Methods Systematic Review

Previous studies have investigated the association of gender roles with pain outcomes in healthy individuals. However, little is known about this association in those with musculoskeletal (MSK) disorders. Therefore, this mixed-methods systematic review aimed to investigate the association of sociocultural gender roles on pain outcomes in adults with MSK disorders. Literature from Medline, CINAHL, Web of Science, and Embase was reviewed from inception to February 2023. Eligibility criteria included studies of adults with an MSK pain disorder that explored the relationship between gender roles and pain for all primary qualitative and quantitative study designs. Exclusion criteria were grey literature, review articles, case studies, and conference proceedings. Risk of bias was assessed via the Quality Appraisal for Diverse Studies for quantitative studies and the McMaster Quality Appraisal Tool for qualitative studies. Eleven studies were included, nine qualitative, and two quantitative with a total of 540 participants (19.6% women, 80.4% men) with various MSK disorders. The convergent integrated approach was used to synthesize data from the qualitative and quantitative studies resulting in three themes and seven subthemes. Our findings identified differences in the way individuals explained the cause of their pain, were treated for their pain in a social and systemic context, and in describing the effect pain had on their lives based on gender roles. There is a need for pain management to evolve to acknowledge the individual pain experience through exploration of an individual's gender identity and roles. PERSPECTIVE: This article demonstrates that gender roles have a multidimensional influence on the pain experience in those with musculoskeletal disorders. These findings support the development of gender-sensitive, patient-centered approaches to pain management, acknowledging each individual's important roles and identities.

Aging is associated with sex-specific alteration in the expression of genes encoding for neuroestradiol synthesis and signaling proteins in the mouse trigeminal somatosensory input

Pain perception is influenced by sex and aging, with previous studies indicating the involvement of aromatase, the estradiol synthase enzyme, in regulating pain perception. Previous research has established the presence of aromatase in dorsal root ganglia sensory neurons and its role in modulating pain perception. The present study aims to explore the implications of aging and sex on the expression of aromatase and estrogen receptors in the trigeminal ganglion. The study examined mRNA levels of aromatase, ERs, and the androgen receptor (AR) in the trigeminal ganglion of 3-month-old and 27-month-old male and female mice, as well as 3-month-old mice from the four-core genotype (FCG) transgenic model. The latter facilitates the assessment of gonadal hormone and sex chromosome implications for sex-specific traits. Aromatase localization in the ganglion was further assessed through immunohistochemistry. Aromatase immunoreactivity was observed for the first time in sensory neurons within the trigeminal ganglion. Trigeminal ganglion gene expressions were detected for aromatase, ERs, and AR in both sexes. Aromatase, ERβ, and GPER gene expressions were higher in young males versus young females. Analyses of the FCG model indicated that sex differences depended solely on gonadal sex. The aging process induced an enhancement in the expression of aromatase, ERs, and AR genes across both sexes, culminating in a reversal of the previously observed gender-based differences. the potential impact of estrogen synthesis and signaling in the trigeminal ganglion on age and sex differences warrants consideration, particularly in relation to trigeminal sensory functions and pain perception.

Role of HDAC5 Epigenetics in Chronic Craniofacial Neuropathic Pain

The information provided from the papers reviewed here about the role of epigenetics in chronic craniofacial neuropathic pain is critically important because epigenetic dysregulation during the development and maintenance of chronic neuropathic pain is not yet well characterized, particularly for craniofacial pain. We have noted that gene expression changes reported vary depending on the nerve injury model and the reported sample collection time point. At a truly chronic timepoint of 10 weeks in our model of chronic neuropathic pain, functional groupings of genes examined include those potentially contributing to anti-inflammation, nerve repair/regeneration, and nociception. Genes altered after treatment with the epigenetic modulator LMK235 are discussed. All of these differentials are key in working toward the development of diagnosis-targeted therapeutics and likely for the timing of when the treatment is provided. The emphasis on the relevance of time post-injury is reiterated here.

Sleep, Caffeine, BMI, and Pressure Pain Threshold in Temporomandibular Disorder Patients: An Observational Study

BACKGROUND

Temporomandibular disorders (TMDs) represent a multifactorial condition involving a multitude of symptoms of the temporomandibular joint that emanates a series of distress. Understanding the relationship between these lifestyle factors and pain perception in TMD patients is essential for optimizing their management and care. This study delves into the intricate interplay between sleep, caffeine consumption, body mass index (BMI), and the potential effect on pressure pain threshold (PPT) values among individuals with TMDs.

MATERIALS AND METHODS

This is an observational study. Data were collected from a convenient sample of female patients at a single center in Riyadh city, between the ages of 20 and 50 years. The variables collected were based on an operator-designed questionnaire, the symptom questionnaire, and the Diagnostic Criteria for Temporomandibular Joint Disorders (DC/TMD).

RESULTS

A total of 139 participants were included in the study, appraising the occurrence of TMD and pain as per reports of caffeine intake and sleep duration. The observed outcomes indicate that the amount of sleep has a significant effect on the PPT values in TMD patients. This study highlights the substantial impact of sleep duration on lowering PPT values in individuals with TMDs. The findings highlight the importance of considering sleep duration and caffeine intake in the comprehensive management of TMD patients. There was no effect of BMI on this particular sample.

CONCLUSION

This study shows a positive correlation between sleep and pain and TMD, caffeine, and pain. A deeper understanding of these relationships could pave the way for more effective pain management strategies and personalized treatment approaches tailored to the unique needs of TMD patients. BMI had no effect.

Temporomandibular disorder patients with excessive daytime sleepiness present greater pain intensity and reduced jaw function

BACKGROUND

Sleep disorders are associated with temporomandibular disorders (TMDs). Limited studies have focused on excessive daytime sleepiness (EDS) and its impact on jaw functions in TMD patients.

OBJECTIVE

The aim of the present investigation was to identify the impact of EDS on pain and jaw function in TMD patients.

METHODS

A total of 338 TMD patients (50 males and 288 females) was included. The Epworth Sleepiness Scale (ESS) was used to classify patients into EDS group (score ≥ 10) and non-EDS group (score < 10). The Jaw Functional Limitation Scale 8-item (JFLS-8) was used to assess the severity of jaw dysfunction. Pain intensity was evaluated using the Visual Analogue Scale (VAS). Anxiety and depression were evaluated using the Generalised Anxiety Disorder 7-item (GAD-7) and the Patient Health Questionnaire 9-item (PHQ-9). All included patients were diagnosed with pain-related TMD (PT), intra-articular TMD (IT) or combined TMD (CT).

RESULTS

Compared with non-EDS patients, EDS patients exhibited more severe jaw dysfunction, greater pain intensity and higher PHQ-9 scores (p < .05). Multivariate analyses showed that EDS (B = 3.69), female gender (B = 3.69), and elevated GAD-7 score (B = 0.73) were significantly associated with an increased score on the JFLS-8 (p < .05). Moreover, bivariate logistic regression analysis indicated a significant relationship between EDS and PT (OR = 2.70, p = .007).

CONCLUSION

The presence of EDS was more closely related to PT, but the causal relationship between them needs to be further confirmed. More concern and intervention to alleviate poor sleep quality might be highlighted during the treatment of TMD, especially PT subtype.

Obstructive sleep apnea treatment improves temporomandibular disorder pain

PURPOSE

The existence of a bidirectional relationship between poor sleep and pain intensity has been studied, and good sleep quality has been found to be a key factor underlying pain control. The purpose of this prospective cohort study was to observe if OSA treatment provides a reduction in temporo-mandibular disorder (TMD) pain and headache attributed to TMD in patients with obstructive sleep apnea (OSA) after 18 months of OSA treatment.

METHODS

A prospective cohort study was conducted on consecutive patients suffering from OSA. Patients underwent polysomnography and TMD examination according to the DC/TMD protocol at baseline and after 18 months. Intensity of TMD pain and headache attributed to TMD were analyzed.

RESULTS

Of 40 patients (31 men, mean age 51.3 ± 10.3 years), 33 underwent OSA treatment. At the follow-up examination after 18 months, significant improvements in the intensity of pain-related TMD and headache attributed to TMD were observed (p < 0.05). Seven patients did not start treatment for OSA or discontinued treatment. These patients did not show any significant difference in intensity of TMD-pain or headache attributed to TMD after 18 months (p > 0.05).

CONCLUSIONS

Significant reductions in intensity of pain-related TMD and headache attributed to TMD were observed in patients with OSA after 18 months of OSA treatment onset, while no difference was observed in subjects not undergoing or discontinuing OSA treatment.

TRIAL REGISTRATION

The protocol was registered on ClinicalTrials.gov database with number NCT04948541.

Epigenetic HDAC5 Inhibitor Reverses Craniofacial Neuropathic Pain in Mice

Identifying and resolving molecular complexities underlying chronic neuropathic pain is a significant challenge. Among the numerous classes of histone deacetylases, Class I (HDAC 1-3) and Class III (sirtuins) have been best studied in experimental pain models where inhibitor pre-treatments but not post-treatments abrogate the development of pain-related behaviors. Post-treatment here in week 3 with less well-studied Class IIa HDAC4/5 selective inhibitor LMK235 diminishes the trigeminal ganglia increases of HDAC5 RNA and protein in two chronic orofacial neuropathic pain models to levels measured in naïve mice at week 10 post-model induction. HDAC4 RNA reported in lower limb inflammatory pain models is not evident in the trigeminal models. Many other gene alterations persisting at week 10 in the trigeminal ganglia (TG) are restored to naïve levels in mice treated with LMK235. Important pain-related upregulated genes Hoxc8,b9,d8; P2rx4, Cckbr, growth hormone (Gh), and schlafen (Slfn4) are greatly reduced in LMK235-treated mice. Fold increase in axon regeneration/repair genes Sostdc1, TTr, and Folr1 after injury are doubled by LMK235 treatment. LMK235 reduces the excitability of trigeminal ganglia neurons in culture isolated from nerve injured mice compared to vehicle-treated controls, with no effect on neurons from naïve mice. Electrophysiological characterization profile includes a shift where ∼20% of the small neurons recorded under LMK235-treated conditions are high threshold, whereas none of the neurons under control conditions have high thresholds. LMK235 reverses long-standing mechanical and cold hypersensitivity in chronic trigeminal neuropathic pain models in males and females (5,10 mg/kg), preventing development of anxiety- and depression-like behaviors. PERSPECTIVE: Data here support HDAC5 as key epigenetic factor in chronic trigeminal neuropathic pain persistence, validated with the study of RNA alterations, TG neuronal excitability, and pain-related behaviors. HDAC5 inhibitor given in week 3 restores RNA balance at 10 weeks, while upregulation remains for response to wound healing and chronic inflammation RNAs.

Characterization of head and neck pain symptoms of patients presenting to a tertiary care pain clinic

OBJECTIVE

To characterize the presentation and symptomatology of individuals presenting with pain in head and neck regions.

METHODS

A retrospective chart-review was performed on patients with pain in the HFN presenting to a tertiary pain center in Turkey between January 2016 and January 2017. Information regarding the characteristics of pain and medical and treatment history were extracted and reviewed.

RESULTS

Among 197 subjects, 135 (68.5%) were females. The average duration of pain was 60.13 ± 92.32 months. The pain was continuous in presentation and severe in intensity in 43.1% and 51.8% of the subjects, respectively. The pain was associated with at least one somatosensory symptom in 12.1% of subjects. Common diagnoses were trigeminal neuralgia, persistent idiopathic facial pain, and migraine headaches.

CONCLUSION

Painful disorders of the HFN are associated with varying and perplexing signs and symptoms. Such patients should undergo a comprehensive clinical assessment with a multidisciplinary team.

Factorial structure and measurement invariance of the Chinese version of the Oral Health Impact Profile-14 among clinical populations and non-clinical populations: an evidence for public oral investigations

OBJECTIVE

Oral health-related quality of life (OHRQoL) is a multidimensional concept that is commonly used to examine the impact of oral health status on quality of life. The purpose of this study was to examine the optimal factor model of the Chinese version of the Oral Health Impact Profile (OHIP-14) questionnaire in clinical populations, measurement invariance across clinical status and gender cohorts. This would ensure equal validity of the Chinese version of OHIP-14 in different populations and further support public oral investigations.

METHODS

The Chinese version of OHIP-14 was used to investigate 490 dental patients and 919 college students. Confirmatory factor analysis (CFA), item analysis and reliability, measurement invariance, and the t-test were used for data analyses.

RESULTS

We found that the 7-factor structure had the best-fit index in the sample (CFI = 0.970, TLI = 0.952; SRMR = 0.029, RMSEA = 0.052(0.040,0.063)). The reliability of the scales was satisfactory (Cronbach's α = 0.942). The error variance invariance fitted the data adequately in measurement invariance, indicating that measurement invariance is acceptable both across the clinical and non-clinical populations (∆CFI=-0.017, ∆RMSEA = 0.010) and across genders in the clinical population (∆CFI = 0.000, ∆RMSEA=-0.003). T-test for scores showed that the clinical populations scored significantly higher than the non-clinical populations, as did the overall score (t = 7.046, p < 0.001, d = 0.396), in terms of functional limitation (t = 2.178, p = 0.030, d = 0.125), physical pain (t = 7.880, p < 0.001,d = 0.436), psychological discomfort (t = 8.993, p < 0.001, d = 0.514), physical disability (t = 6.343, p < 0.001, d = 0.358), psychological disability (t = 5.592, p < 0.001, d = 0.315), social disability (t = 5.301, p < 0.001,d = 0.304), social handicap (t = 4.452, p < 0.001, d = 0.253), and that in the non-clinical populations, females scored significantly higher than males, as did in terms of physical pain (t = 3.055, p = 0.002, d = 0.280), psychological discomfort (t = 2.478, p = 0.014, d = 0.222), and psychological disability (t = 2.067, p = 0.039, d = 0.188).

CONCLUSION

This study found that the Chinese version of OHIP-14 has measurement invariance between the clinical and non-clinical populations and across genders in the clinical populations, and can be widely used in OHRQoL assessment for public oral investigations.

Involvement of Oxidative Stress and Nutrition in the Anatomy of Orofacial Pain

Pain is a very important problem of our existence, and the attempt to understand it is one the oldest challenges in the history of medicine. In this review, we summarize what has been known about pain, its pathophysiology, and neuronal transmission. We focus on orofacial pain and its classification and features, knowing that is sometimes purely subjective and not well defined. We consider the physiology of orofacial pain, evaluating the findings on the main neurotransmitters; in particular, we describe the roles of glutamate as approximately 30-80% of total peripheric neurons associated with the trigeminal ganglia are glutamatergic. Moreover, we describe the important role of oxidative stress and its association with inflammation in the etiogenesis and modulation of pain in orofacial regions. We also explore the warning and protective function of orofacial pain and the possible action of antioxidant molecules, such as melatonin, and the potential influence of nutrition and diet on its pathophysiology. Hopefully, this will provide a solid background for future studies that would allow better treatment of noxious stimuli and for opening new avenues in the management of pain.

Development of a model to investigate the effects of prolonged ischaemia on the muscles of mastication of male Sprague Dawley rats

OBJECTIVE

The aims of this study were to develop a novel rodent model of masticatory muscle ischaemia via unilateral ligation of the external carotid artery (ECA), and to undertake a preliminary investigation to characterize its downstream effects on mechanosensitivity and cellular features of the masseter and temporalis muscles.

DESIGN

The right ECA of 18 male Sprague-Dawley rats was ligated under general anaesthesia. Mechanical detection thresholds (MDTs) at the masseter and temporalis bilaterally were measured immediately before ECA ligation and after euthanasia at 10-, 20-, and 35-days (n = 6 rats/timepoint). Tissue samples from both muscles and sides were harvested for histological analyses and for assessing changes in the expression of markers of hypoxia and muscle degeneration (Hif-1α, VegfA, and Fbxo32) via real time PCR. Data were analyzed using mixed effect models and non-parametric tests. Statistical significance was set at p < 0.05.

RESULTS

MDTs were higher in the right than left hemiface (p = 0.009) after 20 days. Histological changes indicative of muscle degeneration and fibrosis were observed in the right muscles. Hif-1α, VegfA, and Fbxo32 were more highly expressed in the masseter than temporalis muscles (all p < 0.05). Hif-1α and, VegfA did not change significantly with time in all muscles (all p > 0.05). Fbxo32 expression gradually increased in the right masseter (p = 0.024) and left temporalis (p = 0.05).

CONCLUSIONS

ECA ligation in rats induced hyposensitivity in the homolateral hemiface after 20 days accompanied by tissue degenerative changes. Our findings support the use of this model to study pathophysiologic mechanisms of masticatory muscle ischaemia in larger investigations.

Sleep Bruxism in Puerperal Women: Data from a Population-Based Survey

OBJECTIVE

To evaluate the self-reported SB prevalence and explore associated risk factors in puerperal women who had given birth in Rio Grande, Southern Brazil.

METHODS

A single, standardized questionnaire was given within the 48 h postpartum period. Self-reported SB was the main outcome investigated. Chi-square test was used to compare proportions, and Poisson regression with robust variance adjustment was used in the multivariate analysis.

RESULTS

A total of 2225 women were included. Only 79 (3.6%) of these reported clenching or grinding their teeth during sleep. Adjusted analysis showed that the higher education level of the mothers (PR = 3.07; 95% CI 1.49-6.28; P = 0.006); living with three or more persons in the household (PR = 0.54; 95% CI 0.34-0.84; P = 0.007); medication intake during pregnancy (PR = 1.68; 95% CI 1.09-2.58; P = 0.017); smoking (PR = 1.93; 1.16-3.23; P = 0.024), or ever smoked (PR = 1.82; 95% CI 0.85-3.90; P = 0.024); severe anxiety (PR = 1.36; 95% CI 0.61-3.02; P = 0.005); and headache upon waking (PR = 4.19; 95% CI 1.95-9.00; P < 0.001) were significantly associated with self-reported SB.

CONCLUSION FOR PRACTICE

Our data pointed towards new factors in a specific group of women that may be relevant for preventing sleep-related behaviors in the pregnancy-puerperal cycle. The higher levels of education, medication intake, smoking or even smoked, severe anxiety, the higher the probability of puerperal woman to self-report SB. The nighttime tooth clenching strongly increased headache upon waking.

The Chinese version of the Oral Health Impact Profile-14 (OHIP-14) questionnaire among college students: factor structure and measurement invariance across genders

Background

The Oral Health-related Quality of Life (OHRQoL) is a multi-dimensional concept commonly used to examine the impact of health status on quality of life, and the Oral Health Impact Profile-14 (OHIP-14) questionnaire is a good self-assessment tool. This study was designed to investigate the factor structure of the OHIP-14 scale Chinese version, measurement invariance and latent mean differences across genders among college students.

Methods

The online survey was completed by 919 college students. This study used confirmatory factor analysis (CFA) to check the structural models of the OHIP-14 scale, The correlation of each item with the scale total score could test homogeneity, and Cronbach’s alpha (Cronbach’s α) could evaluate internal consistency. Multi-group CFA was used to explore whether the Chinese version of the OHIP-14 scale was used in male and female populations for measurement consistency. T-test compared scores between men and women. Regression analyses were used to evaluate the relationship between age, gender, education, subject, and the score on the OHIP-14 scale.

Results

We found that the 7-factor structure had the best fit index in the sample. According to Cronbach’s α, the overall score of OHIP was 0.958, and Cronbach’s α for 7 factors was: functional limitation was 0.800, physical pain was 0.854, psychological discomfort was 0.902, physical disability was 0.850, psychological disability was 0.768, social disability was 0.862, social handicap was 0.819 and the test–retest reliability interval was 0.723. Multi-group confirmatory factor analysis supported residual measurement invariance across gender. T-test for scores showed that females scored higher significantly than men as did the overall score, in terms of physical pain (p<0.001), physical disability (p<0.001), and psychological disability (p<0.001).

Conclusions

This study found the OHIP-14 Chinese version to be a good tool for assessing the college students' OHRQoL in China, allowing people to conduct self-assessments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02441-6.

Differentiating Gender and Sex in Dental Research: A Narrative Review

While in humans the term “sex” refers to the biological attributes that distinguish subjects as male, female, and intersex, the term “gender” refers to psychological, social, and cultural factors that strongly influence attitudes, behaviors, and relationships of individuals. Recently, it has been emphasized how the integration of these two terms in the design of the research can improve the methodology of the research itself. However, in dental research, the influence of gender has not gained enough consideration and it is often used indiscriminately as a synonym for sex. This narrative review discusses the usefulness of considering gender and sex in dental research, whose guidelines have been provided so far on this topic, and whether the top 20 dental scientific journals promote the analysis of sex and gender in their guidelines. Sex and gender analysis in dental research could be important both for analyzing biological differences such as those in the immune or neuro-immune system, cardiovascular physiology, developmental anomalies or deformities, and psychosocial differences such as lifestyle, pain experience and prevalence of chronic pain, eating behavior, and access to healthcare services. As for the specific policies for sex and gender analysis and reporting, only five out of 20 biomedical journals have included them in their editorial policy, which refers mainly to the correct use of the terms “sex” and “gender.” In conclusion, we found that no specific and differentiated sex and gender analysis and reporting are required in dental journals. Their integration, which is still not routinely applied, may be improved in the future by updating editorial guidelines and developing more specific methodological recommendations.

Glossopharyngeal Neuralgia: Epidemiology, Risk factors, Pathophysiology, Differential diagnosis, and Treatment Options

Purpose of Review

This is a comprehensive review of the most recent literature on glossopharyngeal neuralgia (GPN), a relatively rare form of neuropathic facial pain. It covers the epidemiology, risk factors, pathophysiology, and differential diagnosis given that glossopharyngeal neuralgia can often be confused with other facial pain syndromes. Finally, we extensively review recent findings regarding medical or conservative measures, minimally invasive, and surgical options for potentially treating and managing glossopharyngeal neuralgia.

Recent Findings

An in-depth analysis of the recent literature indicates that glossopharyngeal neuralgia is not only rare but its etiology and pathophysiology are complex and are often secondary to other disease processes. Regardless, current management options are shown to be effective in controlling pain. Conservatively, first-line management of GPN is carbamazepine, but gabapentin and eslicarbazepine acetate are suitable alternatives. In terms of current minimally invasive pain management techniques, pulsed radiofrequency ablation, nerve blocks, or percutaneous radiofrequency thermocoagulation are effective. Finally, surgical management involves microvascular decompression and rhizotomy.

Summary

While there are currently many viable options for addressing glossopharyngeal neuralgia pain ranging from conservative to surgical management, the complex nature of GPN etiology, pathophysiology, and involved anatomical structures prompts further research for more effective ways to treat the disease.

The Role of Pain Inflexibility and Acceptance among Headache and Temporomandibular Disorders Patients

Temporomandibular disorders (TMD) and headache are complex. This study aims to assess the association between TMD, headache, and psychological dimensions such as psychological inflexibility and pain acceptance. The sample consisted of 120 participants following a non-probabilistic convenience sampling strategy through a direct invitation to the patients attending our facilities and their relatives (n = 61 diagnosed with headache, n = 34 diagnosed with TMD-headache, n = 25 control group). Diagnostic Criteria for Temporomandibular Disorders (DC-TMD), International Classification of Headache Disorders (ICHD-3 beta version), Chronic Pain Acceptance Questionnaire (CPAQ-8), and Psychological Inflexibility in Pain Scale (PIPS) were used as assessment tools. One-way ANOVA, multiple regression analysis (MRA), and the Johnson-Neyman approach were run by IBM SPSS, version 27 (IBM^® Company, Chicago, IL, USA). The significance level was 0.05. One third of our sample presented with headache with TMD. Females were predominant. Males with headache, no systemic disease, less pain severity but higher frequency, living longer with the disease and having sensitive changes, showed higher pain acceptance. When headache occurs with TMD, women with higher education, no headache family history, less pain, and no motor changes showed higher pain acceptance. Patients with both conditions are more liable to have chronic pain and pain inflexibility. Pain intensity and willingness explain 50% of the psychological inflexibility in the headache group. In our sample, individuals suffering from both conditions show greater pain inflexibility, implicating more vivid suffering experiences, leading to altered daily decisions and actions. However, further studies are needed to highlight this possible association.

Sex Differences in the Amygdaloid Projections to the Ventrolateral Periaqueductal Gray and Their Activation During Inflammatory Pain in the Rat

Preclinical and clinical studies have reported sex differences in pain and analgesia. These differences may be linked to anatomical structures of the central nervous system pain modulatory circuitry, and/or hormonal milieu. The midbrain periaqueductal gray is a critical brain region for descending inhibition of pain. The PAG projects to the rostral ventromedial medulla (RVM), which projects bilaterally to the spinal cord to inhibit pain. In addition to pain, this descending circuit (or pathway) can be engaged by endogenous opioids (i.e., endorphins) or exogenous opioids (i.e., morphine), and we have previously reported sex differences in the activation of this circuit during pain and analgesia. Forebrain structures, including the amygdala, project to and engage the PAG-RVM circuit during persistent inflammatory pain. However, there are limited studies in females detailing this amygdalar-PAG pathway and its involvement during persistent inflammatory pain. The objective of the present study was to delineate the neural projections from the amygdala to the PAG in male and female rats to determine if they are sexually distinct in their anatomical organization. We also examined the activation of this pathway by inflammatory pain and the co-localization of receptors for estrogen. Injection of the retrograde tracer fluorogold (FG) into the ventrolateral PAG (vlPAG) resulted in dense retrograde labeling in both the central amygdala (CeA) and medial amygdala (MeA). While the number of CeA-vlPAG neurons were comparable between the sexes, there were more MeA-vlPAG neurons in females. Inflammatory pain resulted in greater activation of the amygdala in males; however, females displayed higher Fos expression within CeA-vlPAG projection neurons. Females expressed higher ERα in the MeA and CeA and the same was true of the projection neurons. Together, these data indicate that although the MeA-vlPAG projections are denser in females, inflammatory pain does not significantly activate these projections. In contrast, inflammatory pain resulted in a greater activation of the CeA-vlPAG pathway in females. As females experience a greater number of chronic pain syndromes, the CeA-vlPAG pathway may play a facilitatory (and not inhibitory) role in pain modulation.

Transcriptional Alterations of Mouse Trigeminal Ganglion Neurons Following Orofacial Inflammation Revealed by Single-Cell Analysis

Orofacial inflammation leads to transcriptional alterations in trigeminal ganglion (TG) neurons. However, diverse alterations and regulatory mechanisms following orofacial inflammatory pain in different types of TG neurons remain unclear. Here, orofacial inflammation was induced by injection of complete Freund’s adjuvant (CFA) in mice. After 7 days, we performed single-cell RNA-sequencing on TG cells of mice from control and treatment groups. We identified primary sensory neurons, Schwann cells, satellite glial cells, oligodendrocyte-like cells, immune cells, fibroblasts, and endothelial cells in TG tissue. After principal component analysis and hierarchical clustering, we identified six TG neuronal subpopulations: peptidergic nociceptors (PEP1 and PEP2), non-peptidergic nociceptors (NP1 and NP2), C-fiber low-threshold mechanoreceptors (cLTMR) and myelinated neurons (Nefh-positive neurons, NF) based on annotated marker gene expression. We also performed differential gene expression analysis among TG neuronal subtypes, identifying several differential genes involved in the inflammatory response, neuronal excitability, neuroprotection, and metabolic processes. Notably, we identified several potential novel targets associated with pain modulation, including Arl6ip1, Gsk3b, Scn7a, and Zbtb20 in PEP1, Rgs7bp in PEP2, and Bhlha9 in cLTMR. The established protein–protein interaction network identified some hub genes, implying their critical involvement in regulating orofacial inflammatory pain. Our study revealed the heterogeneity of TG neurons and their diverse neuronal transcriptomic responses to orofacial inflammation, providing a basis for the development of therapeutic strategies for orofacial inflammatory pain.

Motivation, Perception, and Behavior of the Adult Orthodontic Patient: A Survey Analysis

Purpose

The article is aimed at improving the understanding of the sociocultural profile of adult orthodontic patients and their expectations. In particular, it addresses three main aspects: the motivation and needs that underpin the decision to start orthodontic treatment, how it influences the patients' daily life, and the different oral hygiene demands.

Materials and Methods

An online survey was completed by 276 patients undergoing orthodontic treatment with different techniques. The questions asked concerned gender, age, type of appliance, any previous orthodontic treatments, type of any previous retainers, reasons for therapy, satisfaction, pain, problems in eating, daily number of teeth brushings and flossings before and during the treatment, perception of cost, sensation of visibility of the appliance, and if they would recommend orthodontic treatment.

Results

A significant role within our sample is played by gender; 87.94% consisted of female patients out of which 72.57% wanted to improve their aesthetics, while only 54.84% of male patients cited the same reason. Invisible aligners were preferred by 67.70% of the patients due to them being considered the least painful, causing the fewest problems with eating, and the least visible. Metal braces were perceived as the less expensive treatment. Over a third of the patients (33.85%) had previously undergone orthodontic treatment, among them 54.05% wore a mobile retainer, 31.08% a fixed one, and 14.86% both. Daily tooth brushing and flossing increased during therapy with clear aligners by 48.94% and 126.39%, respectively.

Conclusions

The greatest demand for orthodontic treatments comes from women, as they pay more attention to aesthetics, which makes the clear aligners the most common choice. The relapse after orthodontic treatment seems to cause a higher demand for retreatment, and oral hygiene habits significantly improve during orthodontic treatment, especially with the clear aligners.

Sigma-1 receptors and progesterone metabolizing enzymes in nociceptive sensory neurons of the female rat trigeminal ganglia: A neural substrate for the antinociceptive actions of progesterone

Orofacial pain disorders are predominately experienced by women. Progesterone, a major ovarian hormone, is neuroprotective and antinociceptive. We recently reported that progesterone attenuates estrogen-exacerbated orofacial pain behaviors, yet it remains unclear what anatomical substrate underlies progesterone's activity in the trigeminal system. Progesterone has been reported to exert protective effects through actions at intracellular progesterone receptors (iPR), membrane-progesterone receptors (mPR), or sigma 1 receptors (Sig-1R). Of these, the iPR and Sig-1R have been reported to have a role in pain. Progesterone can also have antinociceptive effects through its metabolite, allopregnanolone. Two enzymes, 5α-reductase and 3α-hydroxysteroid dehydrogenase (3α-HSD), are required for the metabolism of progesterone to allopregnanolone. Both progesterone and allopregnanolone rapidly attenuate pain sensitivity, implicating action of either progesterone at Sig-1R and/or conversion to allopregnanolone which targets GABAA receptors. In the present study, we investigated whether Sig-1 Rs are expressed in nociceptors within the trigeminal ganglia of cycling female rats and whether the two enzymes required for progesterone metabolism to allopregnanolone, 5α-reductase and 3α-hydroxysteroid dehydrogenase, are also present. Adult female rats from each stage of the estrous cycle were rapidly decapitated and the trigeminal ganglia collected. Trigeminal ganglia were processed by either fluorescent immunochemistry or western blotting to for visualization and quantification of Sig-1R, 5α-reductase, and 3α-hydroxysteroid dehydrogenase. Here we report that Sig-1Rs and both enzymes involved in progesterone metabolism are highly expressed in a variety of nociceptive sensory neuron populations in the female rat trigeminal ganglia at similar levels across the four stages of the estrous cycle. These data indicate that trigeminal sensory neurons are an anatomical substrate for the reported antinociceptive activity of progesterone via Sig-1R and/or conversion to allopregnanolone.

Analgesic effects of Phα1β toxin: a review of mechanisms of action involving pain pathways

Phα1β is a neurotoxin purified from spider venom that acts as a high-voltage-activated (HVA) calcium channel blocker. This spider peptide has shown a high selectivity for N-type HVA calcium channels (NVACC) and an analgesic effect in several animal models of pain. Its activity was associated with a reduction in calcium transients, glutamate release, and reactive oxygen species production from the spinal cord tissue and dorsal ganglia root (DRG) in rats and mice. It has been reported that intrathecal (i.t.) administration of Phα1β to treat chronic pain reverted opioid tolerance with a safer profile than ω-conotoxin MVIIA, a highly selective NVACC blocker. Following a recent development of recombinant Phα1β (CTK 01512-2), a new molecular target, TRPA1, the structural arrangement of disulphide bridges, and an effect on glial plasticity have been identified. CTK 01512-2 reproduced the antinociceptive effects of the native toxin not only after the intrathecal but also after the intravenous administration. Herein, we review the Phα1β antinociceptive activity in the most relevant pain models and its mechanisms of action, highlighting the impact of CTK 01512-2 synthesis and its potential for multimodal analgesia.

Impact event and orofacial pain amid the COVID-19 pandemic in Brazil: a cross-sectional epidemiological study

Objectives

This study aims to assess the impact of social isolation, due to the Covid-19 pandemic, on mental health, Temporomandibular Disorder (TMD) and orofacial pain in men and women.

Methodology

Individuals living in Brazil answered an online questionnaire on their sociodemographic and behavioral aspects, emotional scale (DASS-21), Impact of Event Scale, and Pain Screener in Temporomandibular Disorders (TMD-Pain Screener) during June 2020. Descriptive statistical analyses and logistic and linear regressions were applied (5% significance).

Results

Overall, 2301 individuals were included, 89.1% practiced social isolation, 72.6% were employed/studying, at least 15% presented severe or extremely severe levels of emotional distress and presence of powerful (34.1%) and severe impact event (15%). During the outbreak, 53.2% perceived feeling worse and 31.8% reported that orofacial pain started or worsened after the pandemic outbreak. Gender was associated with “social class” (P=0.036), “pain/stiffness in the jaw on awakening” (P=0.037), “change of pain during jaw habits” (P=0.034) and “perception of change in the situations mentioned in the TMD-Pain Screener” (P=0.020), “depression” (P=0.012), “anxiety” (P=0.006) and “impact of the event” (P=8.3E-11). Social isolation had a lesser chance to change the routine, to be practiced by the unemployed/not studying, and to be practiced by men (all with P<0.001). Associations were found between social class and all subscales of the DASS-21 and IES, all with P<0.001.

Conclusions

The practice of social isolation has social determinants. High levels of psychological and event impacts were detected. The presence of orofacial pain seemed to increase during the health crisis, and there were gender differences in the response to the COVID-19 pandemic.

Social determinants of seeking emergency and routine dental care in Saudi Arabia during the COVID-19 pandemic

Background

Between March and June 2020, closing dental clinics during the COVID-19 pandemic except for emergency dental care was recommended. It is documented that health-seeking behaviors change during pandemics. The objective of this study was to examine social determinants associated with decisions to seek dental care in Saudi Arabia during the COVID-19 pandemic.

Methods

A total of 4372 participants were invited to this cross-sectional web-based survey distributed from April 21 to June 20, 2020. The survey included a list of emergency, urgent, and routine dental procedures. Participants were asked if they would seek dental care for these conditions during the pandemic, and what pain severity would make them seek dental treatment. Logistic regression models were performed for predicting variables that explain the decision to go or not to go to the dental clinic during the pandemic for each dental condition.

Results

A total of 3443 responded to this survey. The emergency dental situation participants were most willing to go to the dental clinic for was trauma involving facial bones compromising the airway (94.5%). Only 65.8% were willing to seek care for facial cellulitis compromising the airway. On average 35.2% reported seeking teleconsultation as the first step. Eighteen percent of participants were still willing to go to the dental clinic during the pandemic for routine dental procedures. Multiple logistic regression showed that females (Odds Ratio (OR): 1.6, OR 95% CI 1.3, 1.9), people who had never visited a dentist (OR: 1.8, OR 95% CI 1.3, 2.5), and people living in metropolitan regions (OR: 1.8, OR 95%: 1.4, 2.3) had higher odds for not seeking emergency dental care during this pandemic. The pain threshold for seeking dental care during the pandemic was 7 out of 10. Female, those who never visited a dentist, and those from urban regions reported higher pain threshold before seeking dental care (P value < 0.001).

Conclusion

Social disparities were found in emergency dental care seeking decision-making in Saudi Arabia during the COVID-19 pandemic. It was alarming that some people were afraid to seek dental care for life-threatening dental emergencies as cellulitis during this pandemic. This reflects the importance of increasing public health awareness and governmental regulations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01577-1.

Is there a difference in treatment effect of different intra-articular drugs for temporomandibular joint osteoarthritis? A systematic review of randomized controlled trials

A systematic review based on the PRISMA guidelines was conducted to investigate and compare treatment with hyaluronic acid (HA), corticosteroids, and blood products in patients with temporomandibular joint osteoarthritis (TMJOA). The MEDLINE/PubMed, Embase, and Cochrane Library databases were searched for articles published until September 25, 2019. Articles met the inclusion criteria if they reported patients with TMJOA, a comparison group, and a follow-up period of at least 6 months. The mean and standard deviation for TMJ pain and maximum mouth opening (MMO) were reported. Nine studies involving 443 patients were included. Injectables and Ringer's lactate solution or normal saline were reported to significantly improve TMJ pain and MMO. Regarding TMJ pain, two studies showed a significant superiority of plasma rich in growth factors (PRGF)/platelet-rich plasma (PRP) injections with or without arthrocentesis over HA, but HA showed a significant improvement compared to corticosteroids. For MMO, no injectable was found to be superior to Ringer's lactate or a normal saline control, but arthrocentesis + PRP resulted in MMO improvement compared to arthrocentesis + HA. Overall, all injectables in conjunction with arthrocentesis were efficient in alleviating pain and improving MMO in TMJOA patients; however, a meta-analysis was not possible due to heterogeneity across studies.

Effects of sex on placebo effects in chronic pain participants: a cross-sectional study

ABSTRACT

Sex-related differences can influence outcomes of randomized clinical trials and may jeopardize the effectiveness of pain management and other therapeutics. Thus, it is essential to understand the mechanistic and translational aspects of sex differences in placebo outcomes. Recently, studies in healthy participants have shed light on how sex-related placebo effects might influence outcomes, yet no research has been conducted in a patient population. Herein, we used a tripartite approach to evaluate the interaction of prior therapeutic experience (eg, conditioning), expectations, and placebo effects in 280 chronic (orofacial) pain patients (215 women). In this cross-sectional study, we assessed sex differences in placebo effects, conditioning as a proxy of prior therapeutic effects, and expectations evaluated before and after the exposure to positive outcomes, taking into account participant-experimenter sex concordance and hormonal levels (estradiol and progesterone assessed in premenopausal women). We used mediation analysis to determine how conditioning strength and expectations impacted sex differences in placebo outcomes. Independent of gonadal hormone levels, women showed stronger placebo effects than men. We also found significant statistical sex differences in the conditioning strength and reinforced expectations whereby reinforced expectations mediated the sex-related placebo effects. In addition, the participant-experimenter sex concordance influenced conditioning strength, reinforced expectations, and placebo effects in women but not in men. Our findings suggest that women experience larger conditioning effects, expectations, and placebo effects emphasizing the need to consider sex as a biological variable when placebo components of any outcomes are part of drug development trials and in pain management.

The Impact of SARS-CoV-2 Outbreak on the Polish Dental Community's Standards of Care-A Six-Month Retrospective Survey-Based Study

Currently, SARS-CoV-2 is the primary pathogen worldwide, disrupting most of our everyday activities. The study aim was to evaluate its impact on the Polish dental community, standards of care, health, and welfare. Methods: A Google Forms survey was conducted among 303 dental practitioners. Results: Of respondents, 54.93% curbed the number of patients in the last six months, 34.21% declared no changes, and 10.86% reported an increase; whereas 70.7% of the respondents reported a treatment price increase within the same period (27.96% and 1.32% reported no changes and a decrease, respectively). Of the respondents, 15.5% did not close their businesses during the first wave of the pandemic. Most declared 1 or 2 month break, 30.7% and 34.7%, respectively. Some reported 3, 4, or 5 month breaks (15.84%, 1.32%, and 0.99%, respectively), and only two respondents (0.66%) did not admit patients at all. Headache episodes were more frequent among female dentists before the pandemic; after the pandemic, headache frequency increased among both sexes. Temporomandibular disorders (TMDs) were more frequent among women (p = 0.017). Conclusions: Most Polish dentists followed SARS-CoV-2 recommendations and restricted their practices to admitting only patients with pain or incomplete treatment. Decreased sleep parameters, head, back, and neck pain, were observed. This situation may affect dental health conditions in Polish society over time.

Comparison of emotional disturbance, sleep, and life quality in adult patients with painful temporomandibular disorders of different origins

OBJECTIVES

This study compared the differences in emotional disturbance, sleep, and life quality among adult patients with temporomandibular (TMD) muscle and/or joint pain.

MATERIALS AND METHODS

The study involved an analytical cross-sectional design. A total of 420 consecutive patients diagnosed with pain-related TMDs based on the Diagnostic Criteria for TMDs (DC/TMD) were recruited from a TMD referral centre and stratified into three groups, namely muscle pain (MP; n = 50), joint pain (JP; n = 329), and combined muscle-joint pain (CP; n = 41). Emotional disturbance, sleep quality, and oral health-related quality of life (OHRQoL) were assessed with the Depression, Anxiety, and Stress Scale-21 (DASS-21), Pittsburgh Sleep Quality Index (PSQI), and Oral Health Impact Profile-TMDs (OHIP-TMDs) respectively. Statistical analyses were performed using the chi-square test, one-way ANOVA, and Pearson's correlation (p < 0.05).

RESULTS

Mean age for the three pain groups (females = 349; males = 71) ranged from 37.15 ± 14.91 to 38.60 ± 14.37 years (p = 0.973). Ranking of depression, anxiety, and stress scores was as follows: CP > MP > JP. Significant differences in emotional disturbances were observed (p < 0.001). CP patients had significantly poorer sleep quality than those with JP (p = 0.004). Moreover, OHRQoL was also significantly more impaired as compared to both MP (p = 0.006) and JP (p < 0.001) patients. Correlations between global PSQI and OHIP-TMDs scores were weak to moderate (r_s = 0.30-0.47).

CONCLUSIONS

Patients with combined muscle-joint pain presented higher levels of emotional disturbance than those with only MP or JP. They also had significantly poorer sleep quality and lower OHRQoL.

CLINICAL RELEVANCE

Emotional and sleep health must be considered in the management of painful TMDs.

The Pain-to-Well-Being Relationship in Patients Experiencing Chronic Orofacial Pain

Introduction: Orofacial pain features may negatively influence a person's well-being and vice versa. Some aspects of well-being can be measured with axis II instruments that assess patients' psychosocial and behavioral status. The aim of this study was to investigate associations between pain features and psychosocial variables as indicators of well-being. Materials and Methods: Seven hundred ninety-nine anonymized datasets collected using the Web-based Interdisciplinary Symptom Evaluation (WISE) of patients reporting to the Interdisciplinary Orofacial Pain Unit, University of Zurich, between March 19, 2017 and May 19, 2019, were analyzed. Pain features including intensity, number of locations, impact, and duration were evaluated. Psychometric measures assessed pain-related catastrophizing and disability, illness perception, distress, anxiety, depression, injustice experience, dysmorphic concerns, and insomnia. Results: Most patients were between 30 and 59 years old (58.3%), female (69.8%), working (66.0%), and experienced pain for more than 6 months (68.5%). Pain intensities were higher in women than men and higher in disabled than working patients. Scores indicating elevated stress and depression were also observed in disabled patients. The sample prevalence rates of clinically relevant axis II instrument scores were as follows: Graded Chronic Pain Scale for the Head (GCPS-H), 27%; Patient Health Questionnaire 4 (PHQ4), 21%; PHQ9, 21%; Pain Catastrophizing Scale (PCS), 20%; General Anxiety Disorder 7 (GAD7), 15%; Insomnia Severity Index (ISI), 15%; Injustice Experience Questionnaire (IEQ), 14%; GCPS for the Body (GCPS-B), 13%; PHQ for Stress (PHQstr), 6%; and Dysmorphic Concern Questionnaire (DCQ), 2%. Noteworthy results of correlation analysis of the clinically relevant axis II scores and pain measures were as follows: the PHQstr had moderate associations (0.34-0.43) with the sum of pain intensity at rest and during function, number of pain locations, and typical pain intensity. The IEQ scores were moderately associated with typical pain intensity at 0.39. The DCQ scores were moderately associated with pain extension at 0.41. Conclusions: Moderate correlations of certain pain and well-being measures were found in patients reporting clinically relevant stress, injustice experience, and dysmorphic concern, all of which reflect impaired well-being. PHQ4 is suitable for routine distress screening in the clinical setting.

Age-related differences in diagnostic categories, psychological states and oral health-related quality of life of adult temporomandibular disorder patients

OBJECTIVES

The peak prevalence of temporomandibular disorders (TMDs) may occur in middle age. This study determined the proportion of matured adults seeking TMD treatment and compared their diagnostic, psychological and oral health-related quality-of-life (OHRQoL) profiles to younger patients.

METHODS

Adult subjects were recruited from a tertiary TMD centre and assigned to three age groups, namely 18-44 years (young adults [YA]), 45-64 (middle-aged adults [MA]) and ≥65 (old adults [OA]). TMD diagnoses were established with the Diagnostic Criteria for TMDs and categorised as pain-related (PT), intra-articular (IT) and combined (CT) TMDs. Psychological states and OHRQoL were assessed with the Depression, Anxiety, and Stress Scale-21 (DASS-21) and Oral Health Impact Profile-TMDs (OHIP-TMDs). Demographic, DASS-21, and OHIP-TMDs data were analysed using chi-square test, one-way ANOVA and Pearson's correlation (P < .05).

RESULTS

Middle-aged (19.7%; 136/692) and old (4.0%; 28/692) adults comprised about a quarter of the TMD patients. Although gender distribution was comparable, significant differences in TMD categories were observed (P < .001). Pain-related TMDs were more prevalent in the MA/OA groups while intra-articular TMDs were more frequent in the YA group. No significant difference in DASS-21 and total OHIP scores was noted among three groups. However, the MA and OA groups had significantly lower OHRQoL in the physical pain domain. Correlations between DASS-21 and OHIP-TMDs scores varied with age and ranged from r_s  = 0.47-0.92.

CONCLUSIONS

Matured patients constituted a quarter of TMD cohort and presented higher frequencies of painful TMDs. They have similar psychological profiles to younger patients but experienced lower OHRQoL in physical pain domain.

Glial cell activation and altered metabolic profile in the spinal-trigeminal axis in a rat model of multiple sclerosis associated with the development of trigeminal sensitization

Trigeminal neuralgia is often an early symptom of multiple sclerosis (MS), and it generally does not correlate with the severity of the disease. Thus, whether it is triggered simply by demyelination in specific central nervous system areas is currently questioned. Our aims were to monitor the development of spontaneous trigeminal pain in an animal model of MS, and to analyze: i) glial cells, namely astrocytes and microglia in the central nervous system and satellite glial cells in the trigeminal ganglion, and ii) metabolic changes in the trigeminal system. The subcutaneous injection of recombinant MOG_1-125 protein fragment to Dark Agouti male rats led to the development of relapsing-remitting EAE, with a first peak after 13 days, a remission stage from day 16 and a second peak from day 21. Interestingly, orofacial allodynia developed from day 1 post injection, i.e. well before the onset of EAE, and worsened over time, irrespective of the disease phase. Activation of glial cells both in the trigeminal ganglia and in the brainstem, with no signs of demyelination in the latter tissue, was observed along with metabolic alterations in the trigeminal ganglion. Our data show, for the first time, the spontaneous development of trigeminal sensitization before the onset of relapsing-remitting EAE in rats. Additionally, pain is maintained elevated during all stages of the disease, suggesting the existence of parallel mechanisms controlling motor symptoms and orofacial pain, likely involving glial cell activation and metabolic alterations which can contribute to trigger the sensitization of sensory neurons.

Craniofacial neuralgias

While non-headache, non-oral craniofacial neuralgia is relatively rare in incidence and prevalence, it can result in debilitating pain. Understanding the relevant anatomy of peripheral branches of nerves, natural history, clinical presentation, and management strategies will help the clinician better diagnose and treat craniofacial neuralgias. This article will review the nerves responsible for neuropathic pain in periorbital, periauricular, and occipital regions, distinct from idiopathic trigeminal neuralgia. The infratrochlear, supratrochlear, supraorbital, lacrimal, and infraorbital nerves mediate periorbital neuralgia. Periauricular neuralgia may involve the auriculotemporal nerve, the great auricular nerve, and the nervus intermedius. The greater occipital nerve, lesser occipital nerve, and third occipital nerve transmit occipital neuralgias. A wide range of treatment options exist, from modalities to surgery, and the evidence behind each is reviewed.

Orofacial antinociceptive activity and anchorage molecular mechanism in silico of geraniol

We aimed to evaluate the orofacial antinociceptive effect of geraniol in mice and its molecular anchorage mechanism. Seven mice per group (probabilistic sample) were treated with geraniol (12.5, 25 and 50 mg/kg, i.p.), morphine (6 mg/kg, i.p.) and vehicle (saline + Tween 80 at 0.2%, i.p.) 30 minutes prior to the beginning of the experiment. Injecting glutamate (25 μM), capsaicin (2.5 μg) and formalin (2%) into the right upper lip (perinasal) of the mouse induced nociception. Behavioral analysis of the animals considered the friction time (in seconds) of the mentioned region using hind or front paws by a researcher blinded to the treatment groups. The statistical analysis was performed blindly, considering α = 5%. The results showed that in the glutamate and capsaicin tests, concentrations of 25 mg/kg and 50 mg/kg presented antinociceptive activity (p < 0.005, power> 80%). In the formalin test, geraniol was able to reduce nociception at a concentration of 50 mg/kg (p < 0.005, power> 80%). In the molecular anchorage study, high values of binding between the evaluated substance and receptors of glutamate were observed (metabotropic glutamate receptor, -87.8501 Kcal/mol; N-methyl-D-aspartate, -86.4451 Kcal/mol; α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, -85.6755 Kcal/mol). Geraniol presented orofacial antinociceptive activity, probably by interacting with glutamate-related receptors.

Persistent post-traumatic headache: a migrainous loop or not? The preclinical evidence

Background

According to the International Classification of Headache Disorders 3, post-traumatic headache (PTH) attributed to traumatic brain injury (TBI) is a secondary headache reported to have developed within 7 days from head injury, regaining consciousness following the head injury, or discontinuation of medication(s) impairing the ability to sense or report headache following the head injury. It is one of the most common secondary headache disorders, and it is defined as persistent when it lasts more than 3 months.

Main body

Currently, due to the high prevalence of this disorder, several preclinical studies have been conducted using different animal models of mild TBI to reproduce conditions that engender PTH. Despite representing a simplification of a complex disorder and displaying different limitations concerning the human condition, animal models are still a mainstay to study in vivo the mechanisms of PTH and have provided valuable insight into the pathophysiology and possible treatment strategies. Different models reproduce different types of trauma and have been ideated in order to ensure maximal proximity to the human condition and optimal experimental reproducibility.

Conclusion

At present, despite its high prevalence, PTH is not entirely understood, and the differential contribution of pathophysiological mechanisms, also observed in other conditions like migraine, has to be clarified. Although facing limitations, animal models are needed to improve understanding of PTH. The knowledge of currently available models is necessary to all researchers who want to investigate PTH and contribute to unravel its mechanisms.

Sex difference in clinical presentation of patients with infectious mononucleosis caused by Epstein-Barr virus

INTRODUCTION

There are few studies on sex difference in patients with infectious mononucleosis caused by Epstein-Barr virus (EBV-IM). We performed a retrospective study to evaluate the sex difference in clinical presentation of patients with EBV-IM.

METHODS

We performed a single-center retrospective study evaluating >14-year-old patients with serologically confirmed EBV-IM during 2006-2017. We compared the patients' age, symptoms, physical findings, and laboratory data between male and female patients. To adjust for confounding factors, we performed a logistic regression analysis based on the results of univariate comparisons.

RESULT

Of the 122 eligible patients (56 male and 66 female, ratio: 1:1.2), the median ages were 26 years old (interquartile range [IR], 22-31.5 years old]) and 22 years old (IR, 20-25 years old) for males and females, respectively (p < 0.001). Headache was significantly more prevalent in males (25.0% vs. 10.6%, p = 0.036). Leukocyte count was also significantly higher in males (11,400/mm³ [IR, 7,600-14,100/mm³] vs. 9,400/mm³ [IR, 6,600-11,600/mm³], p = 0.021). The prevalence of periorbital edema (male: 3.6% vs. female: 18.1%, p = 0.012) and severity of transaminase elevation were significantly higher in females. The regression analysis evaluating clinical characteristics of male patients showed that age >30 years old, headache, and leukocyte >11,000/mm³ had high odds ratios.

CONCLUSION

Our single-center retrospective study suggests that older age of onset, headache, and leukocytosis are more likely to be characteristics of male patients with EBV-IM. Our study also underscores the importance of periorbital edema as a clue for early diagnosis of EBV-IM, especially in female patients.

The Usefulness of the Pressure Algometer in the Diagnosis and Treatment of Orofacial Pain Patients: A Systematic Review

Objectives

The pressure pain threshold (PPT) may be an efficient approach to screen and evaluate orofacial pain. However, the results of previous PPT studies have varied greatly. The aim of this paper was to determine whether the PPT is an efficient approach for screening and evaluating orofacial pain.

Methods

The search yielded 123 articles. After removal of duplicates and screening of abstracts, 32 articles were selected for further evaluation. The Cochrane Collaboration tool for assessing the risk of bias was used for the evaluation of the studies.

Results

The studies covered a total of 4403 adult patients, aged 16-62, and 30 children. The studies investigated the reliability and validity of the PPT (measured by a pressure algometer) in TMD patients. The PPT was investigated in relation to headache, menstrual cycle, oral contraception, occlusal interference, and occlusal appliances. Generally, the risk of bias was low to unclear. Some structural limitations were inherent in the studies, such as small samples and short duration of the testing involved. Also, the analyzed studies lacked consistency in study design and patient management. Pressure increase values differed from 20 kPa/s to 50 kPa/s and from 0.5 kg/cm²/s to 2 kg/cm²/s. Descriptions of the PPT examination points also varied, from very precise and repeatable to a simple listing of anatomical points. The number of measurements varied from 1 to 5 at each visit. The intervals ranged from 5 seconds to 15 minutes. However, some studies confirmed that the pressure algometer is an effective tool for determining the source of orofacial pain.

Conclusions

Based on the analyzed articles, the authors argue that the PPT is not an efficient approach for screening and evaluating orofacial pain. What is more, it should not be used as the only diagnostics tool for patients with orofacial pain. Importantly, however, additional factors should be considered in the future for the evaluation of the PPT, including body symmetry and posture, hormone levels and the menstrual phase in women, and the use of medications and its influence on the PPT. Further clinical trials should also be performed on the PPT, examining head and neck pain patients, with more precise study design and larger samples.

Effect of preemptive analgesia with ibuprofen in the control of postoperative pain in dental implant surgeries: A randomized, triple-blind controlled clinical trial

BACKGROUND

Preemptive analgesia has as its basic principle the administration of analgesics before the onset of painful stimuli, in order to reduce or prevent postoperative pain, but this question is little explored in implantology. Thus, this study was conducted in order to evaluate the clinical efficacy of ibuprofen in pain prevention after unit implant surgery.

MATERIAL AND METHODS

For this triple-blind, parallel, placebo-controlled and randomized clinical trial, 54 insertion surgeries of unitary implants were performed. Two groups have received two different protocols 1 hour before surgery: Ibuprofen group (IBU) 600 mg of ibuprofen; and (2) placebo group (maize starch). The intensity of the pain was evaluated through the visual analogue scale (VAS) in 6 times (1, 6, 12, 24, 48 and 72 hours after the surgery). Patients were instructed to take 750 mg of paracetamol as rescue medication, if necessary. The occurrence and the intensity of pain were analyzed by means of an analysis of variance ANOVA with repeated measurements using the general linear model procedure.

RESULTS

The IBU group had significantly lower VAS scores overall (IBU = 0.30, ± 0.57; placebo = 1.14, ± 1.07; p<0.001) and at all times in the intra, intergroup comparisons and time/group interaction than the placebo group (p<0.001). The use of rescue medication was significantly lower and the postoperative time was longer in the IBU group compared to placebo (p = 0.002).

CONCLUSIONS

The single use of ibuprofen was found to be significantly superior in reducing pain after unit implant surgery compared to placebo. Key words:Analgesia, dental implants, pain, surgery, oral.

Therapeutic Approaches for Peripheral and Central Neuropathic Pain

Neuropathic pain is a chronic secondary pain condition, which is a consequence of peripheral or central nervous (somatosensory) system lesions or diseases. It is a devastating condition, which affects around 7% of the general population. Numerous etiological factors contribute to the development of chronic neuropathic pain. It can originate from the peripheral part of the nervous system such as in the case of trigeminal or postherpetic neuralgia, peripheral nerve injury, painful polyneuropathies, or radiculopathies. Central chronic neuropathic pain can develop as a result of spinal cord or brain injury, stroke, or multiple sclerosis. As first-line pharmacological treatment options, tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and gabapentinoids are recommended. In trigeminal neuralgia, carbamazepine and oxcarbazepine are the first-choice drugs. In drug-refractory cases, interventional, physical, and psychological therapies are available. This review was structured based on a PubMed search of papers published in the field from 2010 until May 2019.