Stress as a factor in muscle and temporomandibular joint pain

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

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

Enhanced cytokine-induced mechanical hyperalgesia in skeletal muscle produced by a novel mechanism in rats exposed to unpredictable sound stress

Stress exacerbates both experimental and clinical pain, most well-characterized in irritable bowel and fibromyalgia syndromes. Since it has been hypothesized that cytokines play an etiopathogenic role in fibromyalgia and other chronic widespread pain conditions, we investigated the relationship between stress and cytokines in a model of stress-induced chronic somatic pain. A series of experiments were performed to evaluate the impact of stress on the hyperalgesia-induced by endotoxin (lipopolysaccharide, LPS) and the role of two pro-inflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis α (TNFα). Fourteen days after exposure to a 4-day protocol of unpredictable sound stress, the ability of systemic LPS (100 μg/kg, i.p) to elicit cytokine-mediated mechanical hyperalgesia was measured in gastrocnemius muscle. LPS-induced hyperalgesia was significantly greater in stressed rats, but when rats were treated intrathecally with antisense oligodeoxynucleotide (ODN), to decrease either the gp130 subunit of the IL-6 receptor or the TNFα receptor, in nociceptors, skeletal muscle hyperalgesia in sound stressed, but not control, rats was prevented. These data suggest that chronic stress alters signaling in the primary afferent nociceptor for the hyperalgesia induced by endogenously produced pro-inflammatory cytokines.

TMD chronic pain and masseter silent period in psychiatric patients on antidepressive therapy

The aim of the study was to evaluate the long-term effects of antidepressive therapy on chronic pain and related disability, and masseter silent period in psychiatric depressive patients with temporomandibular disorders (TMD). The study included hospitalized psychiatric depressive patients on antidepressive therapy protocol (tetracyclic antidepressant-maprotiline and anxiolytic-diazepam) (n=30) and non-psychiatric patients seeking prosthodontic treatment (control group, n=38). TMD were diagnosed by Research Diagnostic Criteria for temporomandibular disorders proposed by Dworkin and LeResche. The surface electromyography was recorded from left and right masseter muscles and masseter inhibitory reflex (masseter silent period) was recorded after mechanical stimulation. The incidence of TMD appearance was very similar, of approximately 40% in both group of patients. The results of the study also indicated a higher prevalence of joint related TMD, a lower prevalence of muscular subtype of TMD and a lower grade of chronic pain and related disability in the psychiatric group of patients on antidepressive therapy in comparison with findings in the control group. In the patients on antidepressive therapy with TMD masseter silent period was not prolonged , while in the control group of patients with TMD the prolongation of the silent period was observed. The study provided evidence that long-term, combined therapy (maprotiline and diazepam) in psychiatric depressive patients significantly modulated signs and symptoms of TMD in comparison with the control group.

The lateral pterygoid muscle, a heterogeneous unit implicated in temporomandibular disorder: a literature review

Based on its anatomical relationships, the lateral pterygoid muscle is strongly linked with the temporomandibular joint (TMJ). It plays a major role in mastication. Embryological, histological, and anatomical knowledge define the lateral pterygoid muscle as a single muscle with a penniform structure. The various results of electromyographic (EMG) studies describe a complex physiology with a chronological contraction of the layers during the masticatory cycle. The sequential contraction of the layers of the lateral pterygoid muscle is the result of a selective neuronal activation induced by the masticatory Central Pattern Generator (mCPG). This neurophysiological theory highlights the essential role of the reticular formation in oral motor control. The sensitivity of those neurological structures to chronic emotional stress is one of the possible explanations for the appearance of oral parafunctions accompanied by a modification of pain perception and a disorganized muscular activation, determining factors in temporomandibular disorders.

Condylar and disk position and signs and symptoms of temporomandibular disorders in stress-free subjects

BACKGROUND

The authors conducted a study in subjects who tested free of psychological stress to determine the position of the condyle and whether that position was related to signs and symptoms of temporomandibular disorders (TMDs).

METHODS

Forty subjects underwent psychological evaluation to ensure freedom from psychological stress. The authors evaluated tenderness of the masticatory muscles and temporomandibular joints (TMJs) by means of bimanual digital palpation, and they determined the positions of the condyle and disk by using magnetic resonance imaging.

RESULTS

A total of 23.75 percent of the condyles were displaced away from the centric position either anteriorly (3.75 percent) or posteriorly (20.00 percent). chi(2) analysis showed a relationship between the position of the condyle and displacement of the disk, as well as a relationship between the position of the condyle and tenderness of the TMJs.

CONCLUSION

Although these relationships proved significant, it cannot be assumed that displacement of the condyle away from the centric position is predictive of TMD.

CLINICAL IMPLICATIONS

Only two subjects were judged to have had TMJ internal derangement. Thus, the absence of psychological stress seems to have played a role in this finding.

The Role of Tooth-Grinding in the Maintenance of Myofascial Face Pain: A Test of Alternate Models

OBJECTIVE

While mechanisms of myofascial face pain are poorly understood, bruxism has been implicated in the maintenance of this painful disorder. This study evaluates whether evidence of one aspect of bruxism, tooth-grinding, is positively associated with pain severity, as predicted by a psychophysiological model, or negatively associated, as predicted by an adaptation model of face pain.

PATIENTS

Participants were 51 women who met Research Diagnostic Criteria for the myofascial subtype of temporomandibular disorder.

OUTCOME MEASURES

Tooth-grinding was quantified by changes in microwear features of the molar teeth over 2 weeks. Palpated pain severity was quantified on an 11-point scale in response to palpation of the skin overlying the masseter and temporalis muscles bilaterally. Other measures included validated scales of spontaneous pain severity, stress, distress, and psychological symptoms. Association was quantified as Pearson correlation coefficients.

RESULTS

Data showed an inverse correlation (r = -0.37, P < 0.05) between palpated pain severity and the index of tooth wear, supporting the adaptation model. This correlation provided a weighted average of a strong effect (r = -0.80, P < 0.01) seen in those women reporting pain only the right side of their face with an effect that approximated zero in those reporting bilateral pain. Tooth wear measures were negatively associated with ratings of pain severity only over the right masseter.

DISCUSSION

While these data do not address the role of clenching, they cast serious doubt on the theory that myofascial face pain is maintained by tooth-grinding.

Comparison of inter-twin concordance in symptoms of temporomandibular disorders: a preliminary investigation in an adolescent twin population

There is controversy as to the genetic contribution to the pathogenesis of temporo-mandibular disorders (TMD). Several reports reveal a marked familial aggregation in the signs and symptoms of TMD, while others do not. Therefore, our goal was to investigate the hypothesis using a sophisticated research design, which was a well-known genetic survey inter-twin concordance assessment in the symptoms of TMD. This study is the first step to survey TMD symptoms of a twin group in junior and high schools as a preliminary trial. The 63 twins were asked to participate in this study in junior and senior high schools affiliated with the University of Tokyo, Japan, schools which kept ten twins in each grade for the purpose of several genetic survey programs. After excluding incomplete filling out of questionnaire sheets and data from male-female pairs, 43 monozygotic (MZ) (15.3+/-1.7 yrs, male/female = 17/26 pairs) and nine dyzygotic (DZ) (15.2+/-1.8 yrs, male/female = 6/3 pairs) twins were studied. Outcomes consisted of a prevalidated 14-item self-administered questionnaire, which assessed proband- and pair-wise concordance levels in the MZ and DZ twins. These results demonstrated that the MZ twins had a higher tendency of inter-twin concordance than DZ twins in terms of jaw pain in wide mouth opening (proband-wise concordance = 66.7% in MZ, 0% in DZ), difficulty in mouth opening (20% in MZ, 0% in DZ) and difficulty in mouth closing (50.0% in MZ, 33.3% in DZ), while there was no significant difference between the MZ and DZ concordance levels in other general health-related and behavior-related items, except toothache. However, the pair-wise concordance rates of jaw pain in wide mouth opening and difficulty in mouth opening in the MZ twins were not significantly higher compared to the DZ rate. Possibly, a genetic factor contributed to the pathogenesis of TMD in an adolescent population. The sample size needs to be increased, and there are plans to survey the next sample in the same schools.

Tooth abrasion in workers exposed to noise in the Montenegrin textile industry

A cross-sectional study was performed on 225 textile workers from a wool production company in Montenegro to test the hypothesis of a relationship between exposure to intense industrial noise and tooth abrasion. The group exposed to intense noise (104 dB (A) Leq) consisted of 111 weavers (82 males and 29 females), while the control group (81 dB (A) Leq) consisted of 114 blue-collar workers (32 males and 82 females) in preparation departments. A specialist in dental prosthetics clinically examined all the subjects and additionally analyzed tooth statuses on hard plaster models. Gender, age, socioeconomic status and tooth brushing habits of workers were controlled as confounding factors. Significantly high adjusted odds ratios for tooth abrasion of 3.74 (95% CI = 1.42-7.85; p < 0.01) were found among female workers exposed to intense noise in comparison with the control group. The analysis of the subclass of male workers with severe tooth abrasion (grades III-IV) revealed significantly high adjusted odds ratios for tooth abrasion of 5.48 (95% CI = 1.76-14.50; p < 0.01) among the noise exposed group compared to the control group. This study suggests that extremely high levels of occupational noise might be related to tooth abrasion in exposed textile workers.

Anxiety and personality traits in patients with muscle related temporomandibular disorders

This study tested the hypothesis that muscle related temporomandibular disorder patients with cervical muscle pain exhibit greater degree of psychological distress compared with patients without cervical muscle pain and controls. Thirty-eight muscle related temporomandibular disorder patients including 10 patients with cervical muscle pain and 41 healthy individuals as controls participated in the study. State and trait anxiety levels were assessed with the Spielberger's state and trait anxiety inventory. Personality traits (extroversion, neuroticism, psychoticism and social desirability) were assessed using the Eysenck's personality questionnaire, and the pain intensities described over the muscles were recorded using a 100 mm visual analogue scale. The muscle related temporomandibular disorder patients, in general, exhibited significantly higher degrees of neuroticism and trait anxiety. The patients with cervical muscle pain demonstrated a significantly higher level of psychoticism compared with the patients without cervical muscle pain and the controls and a significantly higher state anxiety level than the controls. They also demonstrated higher pain intensities in masseter and temporalis muscles compared with patients without cervical muscle pain. It has been suggested that either subjects with psychological distress are prone to temporomandibular disorders, or psychological distress is a manifestation of existing chronic pain conditions. The present findings demand further investigations and broader approach in management, as muscle related temporomandibular disorder patients with cervical muscle pain were both physically and psychologically compromised to a greater degree compared with patients without cervical muscle pain.

Prevalence of post-traumatic stress disorder symptoms in orofacial pain patients

OBJECTIVE

There is a high comorbidity between symptoms of post-traumatic stress disorder (PTSD) and chronic pain incidence. The objective of this investigation was to determine the prevalence of PTSD symptoms in chronic orofacial pain patients.

STUDY DESIGN

The study included 1478 adult patients (mean age 36.4 +/- 12.7 years) with primary diagnoses of masticatory/cervical muscle pain or temporomandibular joint pain. Patients completed a battery of psychometric questionnaires including a screening for PTSD symptoms. The sample was divided into a PTSD-positive group (n=218, 15%) a PTSD-negative group (n=551, 37%), and a no-stressor group (n=709, 48%) according to stressor incidence and symptom severity.

RESULTS

The current prevalence of PTSD symptomatology was considerably higher than that reported in surveys from the general population. Patients in the PTSD-positive symptom group reported significantly higher psychological distress, sleep dysfunction, and pain severity compared to patients in the other groups. Psychological distress as measured by the SCL-90-R reached clinically significant levels only in those patients with PTSD symptomatology.

CONCLUSIONS

The results of this study performed at a tertiary care center suggest that TMD patients without PTSD symptomatology show low levels of psychological distress, if any. Clinically significant levels of psychological distress are likely indicators for PTSD. PTSD screening should be included as part of a routine psychometric test battery in TMD patients.

Prevalence of traumatic stressors in patients with temporomandibular disorders

PURPOSE

The aim of the present study was to identify the prevalence of significant traumatic stressor(s) reported by chronic temporomandibular disorder patients, and to describe the nature of these stressors. A second aim of this study was to evaluate and compare the behavioral and psychological domains of patients who reported 1 or more significant traumatic stressors to those who did not.

PATIENTS AND METHODS

Twelve hundred twenty-one patients with chronic temporomandibular disorder pain completed a battery of psychometric measures including the Symptom Check List-90-Revised, Multidimensional Pain Inventory, Pittsburgh Sleep Quality Index, and a check list of major traumatic stressors.

RESULTS

The prevalence of major traumatic stressors among our chronic pain patients was high (49.8%). Traumatic stressors were related to increased pain severity, affective distress, and disability among patients with chronic pain. Patients admitting to major traumatic stressors also scored higher on most psychometric measures and more often had pain from myogenous origin. It is argued that possible significant contributors to chronic orofacial pain may be anxiety, depression, and dysregulation of the hypothalamic-pituitary-adrenal axis.

CONCLUSION

Prevalence of major traumatic stressors in chronic temporomandibular disorder patients is high. The greater distress on all psychological domains in patients endorsing major traumatic events may be a reflection of inadequate coping skills in these individuals. Therapy should be oriented toward the resolution of accompanying stressors such as depression, anxiety, and dysregulation of the hypothalamic-pituitary-adrenal axis.

Temporomandibular disorders, occlusion, and neck pain in subjects with facial pain: a case-control study

The etiology of facial pain is multifactorial. Based on the results of a questionnaire included in the study of the 1966 Northern Finland Birth Cohort, performed in 1997-98, we found an association of facial pain with subjective symptoms of temporomandibular disorders (TMD), neck pain and with occlusal factors reported by 5,696 subjects. The aim of the present study was to examine these associations clinically. In the year 2000, a new inquiry was sent to the following subjects living in Oulu: 1. all subjects who had reported facial pain in the former questionnaire (n=162) (case group); and 2. to a randomly selected group of nonpain controls (n=200), group matched for gender. Those who reported willingness to participate were invited to a clinical examination. Finally, the total number of subjects was 104, including 52 (10 men, 42 women) cases and 52 (10 men, 42 women) controls. Anamnestic data were collected, and clinical stomatognathic and musculoskeletal examinations were performed, both the clinicians and the subjects being unaware of the case-control status. Anamnestically, stress was the most often reported provoking factor for facial pain. Facial pain associated significantly with reported TMD symptoms and allergies. Based on clinical findings, most of the cases were classified in the myogenous subgroup of TMD. The risk for facial pain was six-fold in subjects with clinically assessed TMD, defined as moderate (DiII) or severe (DiIII) by Helkimo's clinical dysfunction index, almost six-fold in subjects with protrusion interferences and approximately three-fold in subjects with clinically assessed tenderness of distinct fibromyalgia (FM) points in the neck. According to the adjusted logistic regression analyses, TMD had the strongest influence on facial pain, followed by protrusion interferences, anamnestically reported allergies and "other headaches". The present study shows that as well as being connected with TMD, facial pain is associated with pain and muscle tenderness in the neck area.

Risk factors for diagnostic subgroups of painful temporomandibular disorders (TMD)

Temporomandibular Disorders (TMD) encompass several entities, which may have differing etiologies. To test this hypothesis, we investigated risk factors for three diagnostic subgroups of painful TMD. Ninety-seven subjects with myofascial pain only, 20 with arthralgia only, 157 with both myofascial pain and arthralgia, and 195 controls without TMD pain met criteria for study eligibility. Investigated risk factors included both physical and psychological variables. Adjusted odds ratios were calculated by multiple logistic regression analyses. Myofascial pain occurring alone was significantly associated with trauma (Odds Ratio [OR] = 2.0), clenching (OR = 4.8), third molar removal (OR = 3.2), somatization (OR = 3.7), and female gender (OR = 4.2). Myofascial pain with arthralgia was significantly associated with trauma (OR = 2.1), clenching (OR = 3.3), third molar removal (OR = 4.0), somatization (OR = 5.1), and female gender (OR = 4.7). No significant associations were found for the small-arthralgia-only group.

Depression, pain, exposure to stressful life events, and long-term outcomes in temporomandibular disorder patients

PURPOSE

This study investigated the role of psychological factors in temporomandibular disorders (TMD). Orofacial pain patients' pretreatment levels of depression, disability caused by pain, and exposure to stressful life events were measured, and differences on these variables between temporomandibular joint (TMJ) disease patients and patients whose pain was of muscular origin (MPD) were evaluated. The use of these variables and patient diagnostic status in predicting response to treatment in a subsample of these patients was also evaluated.

PATIENTS AND METHODS

Before undergoing treatment, 258 patients were administered the Beck Depression Inventory (BDI), the Pain Disability Index (PDI), and the Social Readjustment Rating Scale (SRRS). Follow-up data on pain disability, current level of pain, depression, and satisfaction with treatment were obtained on 48 of these patients who were contacted at varying intervals after completing treatment.

RESULTS

BDI scores obtained at the outset of treatment were significantly elevated and were positively correlated with SRRS and PDI scores. MPD patients had higher SRRS, BDI depression, and PDI pain disability scores than TMJ patients, and differences between the 2 groups in pain disability were greatest in areas that are often sources of interpersonal stress. Among follow-up patients, PDI scores declined after treatment, with MPD patients showing greater decreases than TMJ patients. Independent of patients' diagnostic status, their pretreatment PDI scores were predictive of their pain level at follow-up and were inversely related to their degree of satisfaction with treatment at follow-up; their pretreatment BDI scores were predictive of their depression level at follow-up.

CONCLUSIONS

The findings are consistent with previous research indicating a link between emotional dysfunction and TMD and are largely supportive of the conclusion that psychological factors play a more pronounced role when pain is of muscular origin. Promising behavioral interventions are available for TMD patients in whom psychological factors appear to be playing a significant role.

Psychological distress in chronic craniomandibular and cervical spinal pain patients

Recent studies to chronic pain have shown that the number of painful body areas is related to the level of psychological distress. Therefore, the first aim of this study was to analyse differences in level of psychological distress between craniomandibular pain patients with or without cervical spinal pain. In this analysis, the number of painful body areas below the cervical spine was also taken into account. The second aim was to determine psychological differences between subgroups of craniomandibular pain patients. In this study, 103 out of 250 persons with or without craniomandibular pain were included in the final analyses. Patients who suffered from both craniomandibular and cervical spinal pain showed higher levels of psychological distress, as measured with the Symptom Checklist 90 (SCL-90) than patients with local craniomandibular pain and persons without pain. Further, a positive relationship was found between the number of painful body areas below the cervical spine, as measured on a body drawing, and the SCL-90 scores. No psychological differences were found between myogenous and arthrogenous craniomandibular pain patients. In conclusion, chronic craniomandibular pain patients with a coexistent cervical spinal pain showed more psychological distress compared to patients with only a local craniomandibular pain and asymptomatic persons.

Elevation of histidine decarboxylase activity in skeletal muscles and stomach in mice by stress and exercise

The effects of different types of stress (water bathing, cold, restraint, and prolonged walking) on histidine decarboxylase (HDC) activity in masseter, quadriceps femoris, and pectoralis superficial muscles, and in the stomach were examined in mice. All of these stresses elevated gastric HDC activity. Although water bathing, in which muscle activity was slight, was sufficiently stressful to produce gastric hemorrhage and to increase gastric HDC activity, it produced no detectable elevation of HDC activity in any of the muscles examined. The other stresses all elevated HDC activity in all three muscles. We devised two methods of restraint, one accompanied by mastication and the other not. The former elevated HDC activity in the masseter muscle, but the latter did not. These results suggest that 1) HDC activity in the stomach is an index of responses to stress, 2) the elevation of HDC activity in skeletal muscles during stress is induced partly or wholly by muscle activity and/or muscle tension, and 3) stress itself does not always induce an elevation of HDC activity in skeletal muscles.

Cognitive factors associated with facial pain

Most well-accepted etiological models of facial pain (e.g., temporomandibular disorders and headache) implicate emotional distress as an important factor in the development and maintenance of pain. Data exists to support the notion that some facial pain sufferers are more emotionally distressed than no pain controls. However, many of these dependent measures of emotional distress are either lengthy assessment batteries, lack clear cut psychotherapeutic treatment implications, or focus exclusively on pain related sequela. As cognitive-behavioral interventions become more integrated into the treatment of chronic pain conditions, including various facial pain conditions, it becomes more imperative that the tools used to assess psychological functioning provide the clinician with specific cognitive/behavioral targets for change. The purpose of this study was to assess the degree to which symptomatic treatment seeking facial pain sufferers (N = 25), symptomatic non-treatment seeking facial pain sufferers (N = 48), and healthy pain-free controls (N = 70) differed on the Rational Beliefs Inventory (RBI). The RBI is a reliable, valid questionnaire assessing rational beliefs that are operationalized within a Rational Emotive Therapy (RET) framework. RET is a cognitive-behavioral treatment paradigm that focuses on how an individual's maladaptive cognitive errors or distortions exacerbate emotional distress. Group differences were assessed using a oneway Analysis of Covariance (ANCOVA) with the total RBI score serving as the dependent measure, and a Multivariate Analysis of Covariance (MANCOVA) using individual RBI belief subscales as dependent measures. These results indicated that groups differed significantly on the total score and several of the individual belief subscales. These findings indicated that facial pain sufferers generally hold maladaptive beliefs that may be of clinical significance for cognitive/behavioral treatment approaches.

Schedule-induced masseter EMG in facial pain subjects vs. no-pain controls

Empirical reports suggest that oral habits (e.g., teeth clenching) may be behavioral mediators linking stress to muscle hyperreactivity and the development of facial pain. Another report suggests that excessive behavioral adjuncts develop in conjunction with fixed-time stimulus presentation. The present study assessed the extent to which the oral habits exhibited by facial pain patients are schedule-induced. Subjects with Temporomandibular Disorder (TMD) symptomatology (n = 15) and pain-free controls (n = 15) participated in a 4-phase experiment (adaptation, baseline, task, recovery) designed to elicit schedule-induced behaviors. Self-report of oral habits and negative affect were recorded after each phase. Objective measures of oral habits were obtained via behavioral observation and masseter EMG recordings. Results revealed that negative arousal significantly increased during the fixed-time (FT) task and was also associated with increased oral habits among the TMD subjects. Moreover, 40% of the TMD subjects and none of the controls exhibited a pattern of EMG elevations in the early part of the inter-stimulus interval that met a strict criteria for scheduled-induced behavior per se. Taken together, these results suggest that the TMD subjects were engaging in schedule-induced oral habits. The adjunctive behavior literature seems to provide a plausible explanation as to how oral habits develop and are maintained in TMD patients, despite their painful consequences.

Epidemiology of temporomandibular disorders: implications for the investigation of etiologic factors

Epidemiology is the study of the distribution, determinants, and natural history of disease in populations. Epidemiology has several uses in addition to its traditional role of documenting the public health significance of a condition. Notably, epidemiologic methods and data can be used to identify and verify causes of disease. This article reviews the epidemiologic data on pain in the temporomandibular region, and on signs and symptoms associated with specific subtypes of temporomandibular disorders, with the aim of identifying possible etiologic factors for these conditions that deserve further study. Despite methodologic and population differences, several consistencies are apparent in the epidemiologic literature. Pain in the temporomandibular region appears to be relatively common, occurring in approximately 10% of the population over age 18; it is primarily a condition of young and middle-aged adults, rather than of children or the elderly, and is approximately twice as common in women as in men. This prevalence pattern suggests that etiologic investigations should be directed at biologic and psychosocial factors that are more common in women than in men, and diminish in older age groups. Most signs and symptoms associated with particular temporomandibular disorders (e.g., joint sounds, pain in the joint) also appear to be more prevalent in women than in men, although age patterns for these signs and symptoms are not as clear as for temporomandibular pain. The available data highlight the need for further research on etiologic factors associated with temporomandibular pain and with specific diagnostic subtypes of temporomandibular disorders.

Vibrotactile threshold is elevated in temporomandibular disorders

Experimental pain can elevate vibrotactile threshold, a phenomenon attributed in the literature to the operation of a 'touch gate.' It is not known, however, whether clinical pain produces similar effects. To explore this possibility, we measured vibrotactile threshold in patients with temporomandibular disorders (TMD) whose pain had a prominent myalgic component. Two-interval forced-choice tracking was used to determine threshold for a 25-Hz vibratory stimulus presented on the cheek. Threshold was found to be significantly elevated in the TMD group, compared to an age- and gender-matched control group of pain-free individuals. Within the TMD group, those with a supra-median level of muscle tenderness (corrected for background levels of spontaneous pain) had significantly higher threshold than those with lower levels of palpation pain. These findings are consistent with the idea of a touch gate, and suggest the usefulness of further research in this area with clinical pain populations. The effects of an adapting stimulus (25 Hz, 20 dB SL) were also studied, and found to produce parallel elevations in vibrotactile threshold in the TMD and pain-free groups. This result indicates that at least some adaptation occurs at a higher (subsequent) level of somatosensory information processing than does the touch gating implied by the unadapted thresholds.

Pain severity, negative affect, and microstressers as predictors of life interference in TMD patients

The purpose of this study was to examine the relationships among negative affect (depression, anxiety, and anger), microstressors (hassles), temporomandibular disorder (TMD) pain severity, and life interference, using structural equations modeling. One hundred four subjects were recruited from the Parker Mahan Facial Pain Clinic at the University of Florida. Significant positive direct effects were found for paths between pain severity and life interference; pain severity and negative affect; and negative affect and life interference. These results are consistent with a learning or behavioral model of suffering and suggest that negative affect is an important mediating variable in the relationship between pain and life interference. Microstressors were not a significant predictor and may not be a relevant issue in the TMD population. The results suggest that the impact of chronic pain conditions is influenced by both pain and negative affect, and assessment and treatment of chronic TMD disorders may better benefit from a multidisciplinary approach.

Interexaminer reliability of six orthopaedic tests in diagnostic subgroups of craniomandibular disorders

Interexaminer reliability is defined as the degree of consistency among examiners when making observations of the same clinical variable. In the present study, the interexaminer reliability of six orthopaedic tests was determined in a group of 79 patients with signs and/or symptoms of craniomadibular disorders (CMD), subdivided into three subgroups of patients with a mainly myogenous, a mainly arthrogenous, and a combined myogenous and arthrogenous disorder. Multi-test scores were composed for each test and combinations of tests for the three main symptoms of CMD, viz. pain, joint noises and restriction of movement. Although the orthopaedic tests showed different reliability scores, overall reliability of the determination of these three main symptoms of CMD was satisfactory. In the subgroups, arthrogenous signs and symptoms could be determined reliably with the set of six tests, whereas the reliability of the tests in determining pain and joint noises in the myogenous group was rather low. It may be concluded that the tests are well suited to evaluate arthrogenous signs and symptoms, but that the clinician should be aware of erroneous results of the tests in evaluating pain of a myogenous origin.

Psychosocial aspects of craniomandibular dysfunction. An assessment of clinical and community findings

This study was performed to assess whether subgroups of patients with signs and symptoms of craniomandibular dysfunction (CMD) and a control group of dental patients with and without signs of CMD can be characterized by psychosocial variables, and whether there is evidence of stress-induced muscle hyperactivity as a contributing factor in the development of signs and symptoms of CMD. A group of 127 care-seeking patients and a control group of 158 dental patients completed a Questionnaire Battery (QB) designed to measure external stressors, stress-related emotional reactions (anxiety and depression) and personal factors such as coping styles, health locus of control and personality. Patients with CMD with both a myogenous and an arthrogenous component reported more stress and stronger stress-related emotional reactions than patients with either an arthrogenous or a myogenous CMD. However, patients with arthrogenous CMD did not differ on psychosocial variables from patients with myogenous CMD. In contrast to expectations, controls with signs of CMD reported more stress than patients with CMD. Compared with controls, CMD-patients experienced less personal control over their health and they considered health to be determined by chance or fate. CMD-patients also reported to cope differently with stress than controls. Analyses of covariance showed that the results were not influenced by differences in age, sex or pain reported in the head, neck and/or shoulders. Results were interpreted with regard to the psychophysiological theory of the development of signs and symptoms of CMD as a consequence of the progression of stress-induced muscle hyperactivity. Differences between patients and controls in personal factors were interpreted with regard to treatment need for CMD.

Temporomandibular disorders: assessment of psychological factors

Factors such as psychological stress, anxiety, depression, oral habits, and chronic pain behaviors have been found in subgroups of Temporomandibular Disorders (TMD) patients. This paper reviews the current status of diagnostic methods and instruments designed to identify various psychological factors. The authors offer the following general conclusions: Although the DSM-III-R has significant limitations, it is currently the most common gold standard with which other psychological instruments are compared. There are several specific assessment instruments, such as the Beck Depression Inventory and the Zung Self-Rating Depression Scale, which have been found to have acceptable sensitivity and specificity scores. In addition, certain simple screening questions may be cost-effective for the identification of psychological factors. Because of studies indicating that the dentists' recognition of psychological factors is inaccurate, a brief screening questionnaire may be useful in TMD patients. The literature does not support the routine use of the MMPI. A major conclusion of this review is that there are several psychological instruments available which have demonstrated reasonable validity through a blind comparison with a gold standard. There is need for further development and testing of brief screening instruments using clinical decision methods.

The relationship of occlusion, parafunctional habits and recent life events to mandibular dysfunction in a non-patient population

This study investigated the association between occlusion, oral habits and stress relative to the level of mandibular dysfunction in the total population and in specific diagnostic subgroups (normal, joint disorder, muscle disorder and joint/muscle disorder). A total of 269 nursing students were given a questionnaire and examination. The questionnaire included items to calculate an oral habit index and a social readjustment rating scale. The examination included items to calculate an occlusal index, two craniomandibular indices and a diagnostic criteria for specific subgroups. In the total population there was a positive association between mandibular dysfunction and three postulated risk factors. The total population was then divided into diagnostic subgroups. There was a positive association between the degree of mandibular dysfunction and parafunctional habits for normals, muscle disorders and joint/muscle disorders. There was a positive association between mandibular dysfunction and occlusion for normals only. Finally there was a positive association between mandibular dysfunction and stress for muscle disorders only. The results suggest that associations between postulated aetiologic factors and mandibular dysfunction vary depending on whether the subjects have a muscle and/or joint disorder. Since all associations were weak, other possible risk factors need to be investigated.

Bruxism: a review of the literature. Part I

A review of the literature on bruxism--a condition which has been clinically recognized since the late nineteenth century--is presented. It will be seen that there is not complete agreement on the definition of this activity, and its aetiology and treatment remain controversial.

A dynamic model of etiology in temporomandibular disorders

A dynamic model is proposed to depict the etiology of temporomandibular disorders. A balance is described between destructive factors in the masticatory system that result in dysfunction, and adaptive factors that tend to return it homeostatically to normal. Five factors that cause or potentiate muscle hyperfunction are included on one side of the model with five other factors that affect the ability of the system to adapt on the other side. Relationships among the etiologic factors are discussed, and literature support for each is cited.

Stress in patients with pain in the muscles of mastication and the temporomandibular joints

This study examined the role of stress in subjects having combined muscle and temporomandibular joint pain compared to subjects having only muscle pain or only joint pain. It was found that the combined pain (n = 39) and muscle pain (n = 24) groups had comparable levels of pain intensity and activity impairment. The combined pain group, however, had the lowest level of stress and was rated lower than the muscle group in clinicians ratings of psychological factors, stress and chronicity. The combined pain group and joint pain group (n = 28) were found to be comparable in terms of the clinician's ratings. This data does not support the concept of a progression of symptoms from muscle pain to combined muscle and joint pain that would be expected from a stress-induced muscle hyperactivity model of temporomandibular disorders.