Temporomandibular disorders: associated features

Phenotyping of somatosensory tinnitus and its associations: An observational cross-sectional study

BACKGROUND

Somatosensory tinnitus (ST) is associated with activation of the auditory pathway by trigeminal or cervical afferents.

OBJECTIVE

This is a cross-sectional observational study that aims to verify the association of ST with TMD, bruxism, migraine and psychosocial aspects.

METHODS

This study was conducted at the Tinnitus Outpatient Clinic of the Clinical Hospital Complex of the Federal University of Paraná. Specific ST characteristics, were evaluated according to the last consensus for the diagnosis of ST. Two groups with 39 individuals each one were formed, the ST group (STG) and the comparison group (CG). TMD was classified according to the Diagnostic Criteria for Temporomandibular Disorders and migraine by the International Classification of Headaches. The presence of probable sleep and awake bruxism was associated with individual's reports and clinical inspections. The applied questionnaires investigated oral behaviours (OB), sleep quality (SQ), psychosocial aspects (PA), central sensitization (CS), tinnitus impact on quality of life (TIQF), and graded chronic pain scale (GCPS).

RESULTS

The STG showed a significant association with modulation manoeuvres and trigger points; myalgias and arthralgia; disc displacement with and without reduction; subluxation; bruxism; and presence of migraine. For the same group, we found a significant association with OB, PA, CS, TIQF and GCPS. There was no significant difference between groups regarding SQ.

CONCLUSION

There is a significant association between the presence of ST and the occurrence of TMD, probable sleep and awake bruxism, and migraine. There is also a greater impairment of OB, PA, CS and TIQF.

Analysis of the Effect of Exams on Perceived Stress and Temporomandibular Joint Status in Physiotherapy Students: A Pilot Study

Background and Objectives: Temporomandibular disorders or dysfunction (TMDs) encompass a range of complex conditions that impact the temporomandibular joint (TMJ), chewing muscles, teeth, and/or their supporting tissues. Stress is one of the most associated factors studied as a TMD predictor. The aim is to figure out the influence of stress on TMJ status and salivary cortisol in university students during and before exams. Materials and Methods: The study was non-experimental, employing a longitudinal, analytical, observational cohort design. The study population consisted of students enrolled in the physiotherapy degree program at the Alfonso X El Sabio University (Madrid, Spain). Data were collected during two distinct academic periods: the first period was characterized by low academic stress and no exams, and the second period coincided with the high academic stress of final course exams. The collected results included sociodemographic data, assessment of TMJ status (Fonseca Index), evaluation of muscle evaluation (masseter, upper trapezius, and sternocleidomastoid) using a MOXY Monitor (muscle oxygenation) and Neurotrac® (surface EMG, sEMG), assessment of perceived stress (PSS-14), and measurement of salivary cortisol (enzyme immunoassay with Elisa). The statistical analysis was conducted with a confidence level of 95% (p ≤ 0.05) and asymptotic or bilateral significance. Results: 70 students were analyzed during two different measurement periods. According to the Fonseca Index, initially, 37.14% of the analyzed students showed mild TMDs, 17.14% moderate TMDs, and 45.72% showed no TMDs. In general terms, stress increased with age and is related to female sex, maximum mouth opening decreased with age, oxygen saturation decreased with age and academic stress, and myoglobin concentration was related to age. Furthermore, muscle contraction decreased during higher academic stress and increased with age. For women, age was a risk factor for suffering from TMDs, and stress worsened the transition from having TMDs to having no TMDs in both sexes. Conclusions: Academic stress influences TMJ status and muscle outcomes such as oxygen saturation, myoglobin concentration, and muscle contraction, although more research is needed.

Repetitive nociceptive stimulation increases spontaneous neural activation similar to nociception-induced activity in mouse insular cortex

Recent noninvasive neuroimaging technology has revealed that spatiotemporal patterns of cortical spontaneous activity observed in chronic pain patients are different from those in healthy subjects, suggesting that the spontaneous cortical activity plays a key role in the induction and/or maintenance of chronic pain. However, the mechanisms of the spontaneously emerging activities supposed to be induced by nociceptive inputs remain to be established. In the present study, we investigated spontaneous cortical activities in sessions before and after electrical stimulation of the periodontal ligament (PDL) by applying wide-field and two-photon calcium imaging to anesthetized GCaMP6s transgenic mice. First, we identified the sequential cortical activation patterns from the primary somatosensory and secondary somatosensory cortices to the insular cortex (IC) by PDL stimulation. We, then found that spontaneous IC activities that exhibited a similar spatiotemporal cortical pattern to evoked activities by PDL stimulation increased in the session after repetitive PDL stimulation. At the single-cell level, repetitive PDL stimulation augmented the synchronous neuronal activity. These results suggest that cortical plasticity induced by the repetitive stimulation leads to the frequent PDL stimulation-evoked-like spontaneous IC activation. This nociception-induced spontaneous activity in IC may be a part of mechanisms that induces chronic pain.

Evaluation of orofacial pain and psychological comorbidities in health sciences university students

Introduction: Orofacial pain (OP) is a common public health problem among the general population however, its distribution among the young population like students has not been evaluated so far. The objectives of this study were to investigate the self-reported prevalence, and characteristics of OP, and to evaluate its association with psychological comorbidities such as anxiety and depression. Materials and Methods: A questionnaire-based study was conducted on students studying health sciences programs at SEGi University, Malaysia. A well-designed, structured questionnaire was utilized to assess the prevalence and characteristics of OP. Hospital Anxiety and Depression (HAD) scale was used to evaluate the psychological status of the students. The collected data was subject to statistical analysis by using the SPSS version 22 software. Results: Overall 494 university students had participated in the study of which, 78% (n = 375) of students had suffered from OP and it was significantly higher among the female students (p < 0.03). Headache was the most common type of OP (66.2%) followed by pain in temple region (47.2%), in and around eyes (29.1%), facial region (23.3%), and tooth/gingival pain (20.9%). The association between the prevalence of OP and anxiety was statistically significant (p < 0.019). About 35.4% of the health sciences students had first OP episode started three months ago, 4.2% had daily pain, 14.3% suffered from continuous pain, and only 14% of the students had consulted professionals and 36.1% of them took medication. Conclusion: A significantly higher prevalence of self-reported OP was evident among the health sciences university students and students with different types of OP had higher anxiety and depression scores. Early recognition of OP symptoms and associated comorbidities must be considered for the prevention and successful management of these conditions to circumvent its negative academic impact on the students.

Acupuncture in Temporomandibular Disorders Painful Symptomatology: An Evidence-Based Case Report

Temporomandibular dysfunction (TMD) is complex and multifactorial. Its etiology involves various factors, such as malocclusion, psychological patterns, parafunctional habits, and the temporomandibular joint anatomy. Symptoms include myofascial pain, joint clicking, mouth opening limitation, headaches, earaches, and neck pain, comprising one of the greatest causes of nondental pain. Acupuncture has been used to treat these conditions by acting locally both in muscle relaxation and pain management as well as reaching physical, mental, and emotional balance. The aim of this study is to present a brief literature review reporting the efficacy of acupuncture on TMDs and a case report in which the painful symptomatology of TMD was treated with a systemic protocol, based on scientific evidence and concepts of traditional Chinese medicine. Acupuncture may be a complementary treatment for TMD, and in this case report, it eliminated the patient's painful symptomatology.

Evaluation of skin sensitivity in individuals presented with temporomandibular disorder

ABSTRACT Purpose: to identify the occurrence of a difference in skin sensitivity between analogous points on the face in individuals with temporomandibular disorder. Methods: a total of 60 individuals of both genders, aged 18 to 73 years, participated in the study. People classified with TMD signs and symptoms with the Fonseca Anamnestic Questionnaire were included. The skin sensitivity was evaluated with a Semmes-Weinstein esthesiometer. Sensitivity change was defined in this study as the occurrence of a difference between analogous points on both hemifaces. The localization of the points followed the regional block anatomical description and was confirmed with a neuromuscular electrostimulation device. The collected data were analyzed statistically with a 5% significance level. Results: the occurrence of a difference in sensitivity between the analogous points had a significant association with age group and severity of TMD. However, no association was perceived between sensitivity change and gender. Conclusion: in the population studied, the more severe the temporomandibular disorder, the greater the skin sensitivity change on the face. Also, the older the person, the higher the number of analogous points with a difference in sensitivity.

Psychological factors in oral mucosal and orofacial pain conditions

The psychological aspects of chronic pain conditions represent a key component of the pain experience, and orofacial pain conditions are not an exception. In this review, we highlight how psychological factors affect some common oral mucosal and orofacial pain conditions (namely, oral lichen planus, recurrent aphthous stomatitis, burning mouth syndrome, and temporomandibular disorders) with emphasis on the significance of supplementing classical biomedical treatment modalities with appropriate psychological counseling to improve treatment outcomes in targeted patients. A literature search restricted to reports with highest relevance to the selected mucosal and orofacial pain conditions was carried out to retrieve data.

Temporomandibular disorders: improving outcomes using a multidisciplinary approach

Patients with temporomandibular disorders (TMD) can become very complex. This article aims to highlight the importance of the multimodal and multidisciplinary approach in this type of patients to improve clinical outcomes. At present we have innumerable techniques and tools to approach this type of patients from a biopsychosocial model where active and adaptive type treatments are fundamental. There are various health professions that have competence in the treatment of TMD, however, although in the most complex cases should be treated simultaneously, still too many patients receive unique treatments and only from one point of view. This review exposes the treatments available from a clinical-scientific perspective and also emphasizes the importance of working in specialized units with those professionals who have competencies on the different conditions that may occur.

A questionnaire-based study of sleep-wake patterns and sleep quality in a TMJ and orofacial pain clinic

OBJECTIVE

To determine the relationships among sleep quality, perceived pain, and psychological distress among patients with TMJ and orofacial pain.

METHODS

The authors examined 3276 patients with temporomandibular disorder (TMD) who visited the Orofacial Pain Clinic at Yonsei University College of Dentistry. The authors conducted a survey using the sleep-quality questionnaire and classified TMD patients into two groups based on Diagnostic Criteria for TMD. For statistical analysis, the authors calculated the correlations between pain intensity as measured using a numeric rating scale (NRS) and various factors.

RESULTS

The statistical analysis revealed correlations between pain intensity on the NRS and some of the factors in the sleep questionnaire. The pain intensity increased with age and for lower sleep efficiency (both p < 0.05).

CONCLUSION

These results imply that clinicians treating patients with orofacial pain should examine their sleep-wake patterns and sleep quality.

Exploring the Role of Negative Cognitions in the Relationship Between Ethnicity, Sleep, and Pain in Women With Temporomandibular Joint Disorder

Negative cognitions are central to the perpetuation of chronic pain and sleep disturbances. Patients with temporomandibular joint disorder (TMJD), a chronic pain condition characterized by pain and limitation in the jaw area, have a high comorbidity of sleep disturbances that possibly exacerbate their condition. Ethnic group differences are documented in pain, sleep, and coping, yet the mechanisms driving these differences are still unclear, especially in clinical pain populations. We recruited 156 women (79% white, 21% African American) diagnosed with TMJD as part of a randomized, controlled trial evaluating the effectiveness of interventions targeting sleep and pain catastrophizing on pain in TMJD. Analysis of baseline data demonstrated that, relative to white participants, African Americans exhibited higher levels of clinical pain, insomnia severity, and pain catastrophizing, yet there was no ethnic group difference in negative sleep-related cognitions. Mediation models revealed pain catastrophizing, but not sleep-related cognitions or insomnia severity, to be a significant single mediator of the relationship between ethnicity and clinical pain. Only the helplessness component of catastrophizing together with insomnia severity sequentially mediated the ethnicity-pain relationship. These findings identify pain catastrophizing as a potentially important link between ethnicity and clinical pain and suggest that interventions targeting pain-related helplessness could improve both sleep and pain, especially for African American patients. Perspective:Pain-related helplessness and insomnia severity contribute to ethnic differences found in clinical pain among woman with TMJD. Findings can potentially inform interventions that target insomnia and catastrophizing to assist in reducing ethnic disparities in clinical pain.

Temporal relationship between dysthymia and temporomandibular disorder: a population-based matched case-control study in Taiwan

Background

Numerous studies have reported a relationship between depression and temporomandibular disorders (TMD), but the conclusions remain undefined. The aim of this article was to examine the temporal relationship between depression and TMD.

Methods

In this retrospective matched case-control study, we recruited all samples from a randomsample sub-dataset of one million insured individuals for the year 2005 (Longitudinal Health Insurance Database (LHID2005)). All beneficiaries were enrolled in the National Health Insurance (NHI) programme in Taiwan. We used propensity scoring and matched the case and control groups (1:1) by ten confounding factors to detect the effect of different types of depression on TMD.

Results

The positive correlative factors of TMD included the total number of times medical advice was sought for an unspecified anomaly of jaw size plus malocclusion (TTSMA-JS, p = 0.045), the total number of times medical advice was sought for an anxiety state (TTSMA-AS, p = 0.000), and the total number of times medical advice was sought for a panic disorder (TTSMA-P, p = 0.009). Dysthymia (synonymous with chronic depression) had an effect on TMD. The odds ratio (OR) of dysthymia for TMD measured by multiple logistic regression was 1.91 (p = 0.008) after adjusting for demographic factors, psychiatric comorbidities, and maxillofacial confounders.

Conclusions

This study demonstrated the established temporal relationship between dysthymia and TMD. The inclusion of a psychiatrist on the TMD management team is appropriate.

Dysthymia increases the risk of temporomandibular disorder: A population-based cohort study (A STROBE-Compliant Article)

Numerous studies have investigated the relationship between depression and temporomandibular disorders (TMD), but the conclusions remain vague. The aim of this study was to examine the causal effect between depression and TMD.The reporting of this study conforms to the STROBE statement. In this retrospective cohort study, all samples were recruited from a representative subdataset of 1 million insured persons for the year 2005 Longitudinal Health Insurance Database, who were randomly selected from all beneficiaries enrolled in the National Health Insurance program of Taiwan. We used a propensity score and stratified 926,560 patients into 2 groups (propensity1 = 588,429 and propensity2 = 338,131) and 4 cohorts (propensity1 with depression = 18,038, propensity1 without depression = 570,391, propensity2 with depression = 38,656, propensity2 without depression = 299,475) to detect the development of TMD among the depressive and nondepressive patients between 2004 and 2013.The positive correlative factors of TMD included female, total number of times seeking medical advice (TTSMA) for anxiety state, TTSMA for generalized anxiety disorder, TTSMA for mandible fracture, and TTSMA for unspecified anomaly of jaw size. The propensity2 group was represented by elder and female-predominant patients who used more psychiatric health resources. Among 3 types of depression, only dysthymia (so-called chronic depression) had a causal impact on TMD in the propensity 2 group. In the propensity 2 group, the hazard ratio of dysthymia for TMD measured by Cox's regression was 1.64 (95% confidence interval 1.28-2.09), after adjusting for demographic factors, psychiatric comorbidities, and maxillofacial confounders. The first-onset mean time of TMD as the consequence of dysthymia was 3.56 years (sd = 2.74, min = 0.08, median = 2.99, max = 9.73).This study demonstrates that dysthymia increases the risk of TMD in elderly and female-predominant patients who use more psychiatric health resources.

Metabolic Changes in Masseter Muscle of Rats Submitted to Acute Stress Associated with Exodontia

Clinical evidence has shown that stress may be associated with alterations in masticatory muscle functions. Morphological changes in masticatory muscles induced by occlusal alterations and associated with emotional stress are still lacking in the literature. The objective of this study was to evaluate the influence of acute stress on metabolic activity and oxidative stress of masseter muscles of rats subjected to occlusal modification through morphological and histochemical analyses. In this study, adult Wistar rats were divided into 4 groups: a group with extraction and acute stress (E+A); group with extraction and without stress (E+C); group without extraction and with acute stress (NO+A); and control group without both extraction and stress (NO+C). Masseter muscles were analyzed by Succinate Dehydrogenase (SDH), Nicotinamide Adenine Dinucleotide Diaphorase (NADH) and Reactive Oxygen Species (ROS) techniques. Statistical analyses and two-way ANOVA were applied, followed by Tukey-Kramer tests. In the SDH test, the E+C, E+A and NO+A groups showed a decrease in high desidrogenase activities fibers (P < 0.05), compared to the NO+C group. In the NADH test, there was no difference among the different groups. In the ROS test, in contrast, E+A, E+C and NO+A groups showed a decrease in ROS expression, compared to NO+C groups (P < 0.05). Modified dental occlusion and acute stress - which are important and prevalent problems that affect the general population - are important etiologic factors in metabolic plasticity and ROS levels of masseter muscles.

Brain signature of chronic orofacial pain: a systematic review and meta-analysis on neuroimaging research of trigeminal neuropathic pain and temporomandibular joint disorders

Brain neuroimaging has been widely used to investigate the bran signature of chronic orofacial pain, including trigeminal neuropathic pain (TNP) and pain related to temporomandibular joint disorders (TMD). We here systematically reviewed the neuroimaging literature regarding the functional and structural changes in the brain of TNP and TMD pain patients, using a computerized search of journal articles via PubMed. Ten TNP studies and 14 TMD studies were reviewed. Study quality and risk of bias were assessed based on the criteria of patient selection, the history of medication, the use of standardized pain/psychological assessments, and the model and statistics of imaging analyses. Qualitative meta-analysis was performed by examining the brain regions which showed significant changes in either brain functions (including the blood-oxygen-level dependent signal, cerebral blood flow and the magnetic resonance spectroscopy signal) or brain structure (including gray matter and white matter anatomy). We hypothesized that the neuroimaging findings would display a common pattern as well as distinct patterns of brain signature in the disorders. This major hypothesis was supported by the following findings: (1) TNP and TMD patients showed consistent functional/structural changes in the thalamus and the primary somatosensory cortex, indicating the thalamocortical pathway as the major site of plasticity. (2) The TNP patients showed more alterations at the thalamocortical pathway, and the two disorders showed distinct patterns of thalamic and insular connectivity. Additionally, functional and structural changes were frequently reported in the prefrontal cortex and the basal ganglia, suggesting the role of cognitive modulation and reward processing in chronic orofacial pain. The findings highlight the potential for brain neuroimaging as an investigating tool for understanding chronic orofacial pain.

Time-dependent analysis of nociception and anxiety-like behavior in rats submitted to persistent inflammation of the temporomandibular joint

Temporomandibular disorder (TMD) is prevalent in dental clinics and can involve problems with the masticatory muscles or the temporomandibular joints (TMJ). The pain of TMD is frequently associated with inflammation in the TMJs, but it's etiology is considered to be multifactorial and includes biologic, behavioral, environmental, social, emotional and cognitive factors. The purpose of this investigation was to evaluate the anxiety-like behavior in rats exposed to temporomandibular inflammation via injection of Freund's Adjuvant (CFA) with the elevated plus maze (EPM) and light/dark box (LDB) tests and to evaluate nociceptive behavior with the von Frey test at different periods. Moreover, this study measured TMJ inflammation using plasma extravasation (Evans blue test) and the intraarticular infiltration of polymorphonuclear neutrophils (myeloperoxidase quantification). The results showed that rats that were submitted to TMJ inflammation exhibited a decreased number of entries into the open arms of the EPM and a decrease in the time spent in the light compartment and in the number of transitions in the LDB. Additionally, the number of entries in closed arms in the EPM, used as indicator of locomotor activity, did not alter between treatments. Furthermore, increases in mechanical sensitivity and increases in plasma extravasation in the joint tissue occurred throughout the inflammation process, along with an increase in myeloperoxidase in the synovial fluid of TMJ. Our results suggest that the temporomandibular inflammation induced by CFA produced anxiety-like behaviors in rats and induced nociceptive behavior across different periods of inflammation.

Influence of tinnitus on pain severity and quality of life in patients with temporomandibular disorders

Objective

The aim of this cross-sectional study was to evaluate the relationship among pain intensity and duration, presence of tinnitus and quality of life in patients with chronic temporomandibular disorders (TMD).

Material and Methods

Fifty-nine female patients presenting with chronic TMD were selected from those seeking for treatment at the Bauru School of Dentistry Orofacial Pain Center. Patients were submitted to the Research Diagnostic Criteria anamnesis and physical examination. Visual analog scale was used to evaluate the pain intensity while pain duration was assessed by interview. Oral Health Impact Profile inventory modified for patients with orofacial pain was used to evaluate the patients' quality of life. The presence of tinnitus was assessed by self report. The patients were divided into: with or without self report of tinnitus. The data were analyzed statistically using the Student's t-test and Pearson's Chi-square test, with a level of significance of 5%.

Results

The mean age for the sample was 35.25 years, without statistically significant difference between groups. Thirty-two patients (54.24%) reported the presence of tinnitus. The mean pain intensity by visual analog scale was 77.10 and 73.74 for the groups with and without tinnitus, respectively. The mean pain duration was 76.12 months and 65.11 months for the groups with and without tinnitus, respectively. The mean OHIP score was 11.72 and 11.74 for the groups with and without tinnitus, respectively. There was no statistically significant difference between groups for pain intensity, pain duration and OHIP scoreS (p>0.05).

Conclusion

Chronic TMD pain seems to play a more significant role in patient's quality of life than the presence of tinnitus.

Medical conditions and body pain in patients presenting orofacial pain

OBJECTIVE

To verify the frequency of self-reported medical conditions and pain areas in orofacial pain patients, comparing them with patients from the routine dental care.

METHODS

Data were collected from archives of the Orofacial Pain Clinic (Group A, n=319) and of the routine dental care clinics (Group B, n=84) at Faculdade de Odontologia de Araraquara, São Paulo, in Brazil. All individuals answered a standardized clinical questionnaire and completed a body map indicating their pain areas.

RESULTS

The Mann-Whitney's test demonstrated that Group A presented a higher mean number of medical reports than Group B (p=0.004). In both groups, Pearson's correlation test showed that the highest frequencies of medical conditions were positively correlated to highest frequencies of painful areas (0.478, p=0.001 and 0.246, p=0.000, respectively).

CONCLUSIONS

Group A tended to report more medical conditions and there was a positive correlation between the number of medical conditions and the one of pain areas for both groups.

Naturalistic changes in insomnia symptoms and pain in temporomandibular joint disorder: a cross-lagged panel analysis

An increasing number of prospective studies suggest a bi-directional association between the pain and sleep quality. Few of these investigations have controlled for synchronous correlations, an important source of extraneous variance in lagged associations, which may have confounded conclusions of prior investigations. Despite high rates of insomnia in temporomandibular joint disorders (TMD), no studies have examined temporal associations between naturalistic fluctuations in insomnia and pain in TMD. We conducted cross-lagged panel analysis to examine reciprocal temporal associations between 1-month changes in insomnia symptom severity and self-reported pain over 3 months among 53 TMD patients. This rigorous analytic strategy represents a comprehensive method to explore possible reciprocal temporal associations between insomnia and pain that controls for both auto- and synchronous correlations. Analyses revealed that initial-month increases in insomnia were associated with next-month increases in average daily pain, but not vice versa. The direction of the effect was such that initial-month increases in insomnia symptom severity were associated with next-month increases in average daily pain. These data suggest that naturally occurring fluctuations in insomnia symptom severity are prospectively associated with fluctuations in daily pain experience for persons with TMD. Potential mechanisms by which insomnia might influence pain in TMD and therapeutic implications of these findings are discussed.

Occlusion and brain function: mastication as a prevention of cognitive dysfunction

Research in animals and humans has shown that mastication maintains cognitive function in the hippocampus, a brain area important for learning and memory. Reduced mastication, an epidemiological risk factor for the development of dementia in humans, attenuates spatial memory and causes hippocampal neurons to deteriorate morphologically and functionally, especially in aged animals. Active mastication rescues the stress-attenuated hippocampal memory process in animals and attenuates the perception of stress in humans by suppressing endocrinological and autonomic stress responses. Active mastication further improves the performance of sustained cognitive tasks by increasing the activation of the hippocampus and the prefrontal cortex, the brain regions that are essential for cognitive processing. Abnormal mastication caused by experimental occlusal disharmony in animals produces chronic stress, which in turn suppresses spatial learning ability. The negative correlation between mastication and corticosteroids has raised the hypothesis that the suppression of the hypothalamic-pituitary-adrenal (HPA) axis by masticatory stimulation contributes, in part, to preserving cognitive functions associated with mastication. In the present review, we examine research pertaining to the mastication-induced amelioration of deficits in cognitive function, its possible relationship with the HPA axis, and the neuronal mechanisms that may be involved in this process in the hippocampus.

Distinct gender-related sleep pattern in an acute model of TMJ pain

Since it is recognized that acute inflammation of the temporomandibular joint results in sleep disturbances in male rats, and that the orofacial region may display a site-specific effect of ovarian hormones on nociception, we hypothesized that distinct genders would respond differently when subjected to this inflammatory acute orofacial pain. Sleep was monitored after injection of saline/Freund's adjuvant into the temporomandibular joint in male and female (proestrus and diestrus phases) rats. Progesterone and stress-related hormones were also assessed. In males, Freund's adjuvant induced a significant nociceptive response and sleep disturbances. Behavior and sleep architecture in the females remained unaffected. Our results suggest that females and males present distinct responses to an acute model of orofacial pain.

Sleep continuity and architecture: associations with pain-inhibitory processes in patients with temporomandibular joint disorder

Recent research suggests bi-directional interactions between the experience of pain and the process of sleep; pain interferes with the ability to obtain sleep, and disrupted sleep contributes to enhanced pain perception. Our group recently reported, in a controlled experimental study, that sleep fragmentation among healthy adults resulted in subsequent decrements in endogenous pain inhibition. The present report follows up that observation by extending this line of research to a sample of patients experiencing persistent pain. Patients with chronic temporomandibular joint disorder (TMD) pain were studied using polysomnography and psychophysical evaluation of pain responses. We assessed whether individual differences in sleep continuity and/or architecture were related to diffuse noxious inhibitory controls (DNIC), a measure of central nervous system pain inhibition. Among 53 TMD patients, higher sleep efficiency and longer total sleep time were positively associated with better functioning of DNIC (r=0.42-0.44, p<0.01; ps<0.05 for the multivariate analyses). These results suggest the possibility that disrupted sleep may serve as a risk factor for inadequate pain-inhibitory processing and hint that aggressive efforts to treat sleep disturbance early in the course of a pain condition might be beneficial in reducing the severity or impact of clinical pain.