Journal of Oral & Facial Pain and Headache, 03/2004

The collection of conditions affecting the temporomandibular joint (TMJ) and masticatory muscles, the so-called temporomandibular disorders, can be classified according to the Research Diagnostic Criteria for Temporomandibular Disorders. Of the 3 subgroups-muscle disorders (Group I); disc displacements (Group II); and arthralgia, arthritis, and arthrosis (Group III)- the muscle disorders are most frequently seen in community samples; Group II and Group III diagnoses are less prevalent. This may explain the relative scarcity of studies involving intracapsular TMJ disorders. In this review, new insights into the functional anatomy, imaging, and pathology of disorders of the TMJ are presented. Studies of TMJ dynamics may provide insight into the functional anatomy of the TMJ and thereby into the consequences of Group II and Group III disorders. The clinical use of imaging modalities such as computed tomography and magnetic resonance imaging for the TMJ and related structures remains controversial. Nevertheless, imaging is regularly used in the diagnosis of some Group II and Group III disorders. Magnetic resonance imaging may be of use not only for the visualization of disc displacements but also for the study of bone mineral density of the condyle. Cytokines such as interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFα) play an important role in TMJ pathology. For example, IL-1ß, which has been associated with TMJ pain, hyperalgesia, and anterior bite opening, is mostly absent in the synovial fluid of healthy joints. Since both IL-1 and TNFα are involved in the development of chronic pain and joint destruction, they may be the targets for specific treatments. While the advances reviewed in this paper are significant, multidisciplinary efforts and formation of international research collaborations will be necessary to continue advancement in the understanding of TMJ pathology and diagnosis. Keywords: cytokines, imaging, functional anatomy, temporomandibular disorders, temporomandibular joint

Aims: To consider temporomandibular joint (TMJ) anatomic interactions in order to refine hard tissue models differentiating (1) joints diagnosed with disc displacement with reduction (DDwR) or without reduction (DDw/oR) from asymptomatic joints (Normals), and (2) DDwR joints from DDw/oR joints. Methods:TMJ tomograms of 84 women with unilateral DDwR and 78 with unilateral DDw/oR were compared against each other and against those of 42 female Normal joints through the use of 14 linear and angular measurements, 8 ratios, and 34 interactions. A classification tree model for each comparison was tested for fit with sensitivity, specificity, accuracy, and log likelihood and compared to logistic regression models. Results: In the classification tree model comparison, the DDwR model versus the Normal model realized 35.9% log likelihood (88.0% sensitivity, 66.7% specificity); the DDw/oR model versus the Normal model realized 38.8% log likelihood (69.6% sensitivity, 85.7% specificity). The DDwR model versus the DDw/oR model realized 33.3% log likelihood (76.0% sensitivity, 73.1% specificity). In the logistic regression model comparison, the DDwR model versus the Normal model realized 40.8% log likelihood (82.1% sensitivity, 78.6% specificity) and the DDw/oR model versus the Normal model realized 61.1% log likelihood (85.9% sensitivity, 90.5% specificity). The DDwR model versus the DDw/oR model realized 21.5% log likelihood (60.3% sensitivity, 79.8% specificity). The addition of interactions to the logistic regression models improved the previously published log likelihood from 99% to 149%. Conclusion: The interactions improved logistic regression models and the data suggest that anatomic characteristics influence joint functional status. Because the models incorporated nearly all considered anatomic measurements, no anatomic factor is redundant in the closed TMJ biological system. Keywords: disc displacement with reduction, disc displacement without reduction, multifactorial analysis, temporomandibular joint anatomy

Aims: To evaluate short-term patient compliance with 5 conservative temporomandibular disorder (TMD) treatments (jaw relaxation, jaw stretching, heat application, cold application, and occlusal splint use) and the association of compliance with changes in pain intensity, pain-related activity interference, and jaw use limitations. Methods: Eighty-one TMD patients were given 1 to 5 treatment recommendations as part of usual care in a TMD specialty clinic. Compliance with each recommendation and pain, pain-related activity interference, and jaw use limitation measures were calculated from electronic interviews conducted 3 times daily for 2 weeks. Results: Median compliance with individual treatment modalities ranged from 7.7% for heat application to 92.7% for jaw relaxation; median overall compliance was 54.8%. Participants with higher initial pain intensity and jaw use limitations were significantly more compliant with their recommended treatment regimen (P .05). The authors controlled for age, gender, education, and initial jaw use limitations. Overall compliance was associated significantly and positively with 2-week jaw use limitations (P = .03). A trend toward a statistically significant positive association was found between compliance and 2-week pain intensity (P = .09). Conclusion: Compliance varied widely across patients and therapies. Patients with higher initial pain and jaw use limitation levels were more compliant with treatment recommendations. Although compliance was associated with slight increases in pain and jaw use limitations in this preliminary study, further research is needed to evaluate the longer-term effects of compliance with recommended therapies. Keywords: compliance, limitation of activities, limitation of jaw use, pain, temporomandibular disorders

Aims: To determine the construct validity of algometry and to compare it with that of palpation, and to compare tenderness of masticatory muscle sites and the temporomandibular joint (TMJ) on palpation and on algometry. Methods: Two hundred fifty subjects, 148 with temporomandibular disorder (TMD) pain complaints, underwent a standardized blinded physical examination that included pain-intensity measures on palpation and pressure pain threshold measures on algometry of masseter muscle sites, temporalis muscle sites, and the TMJ. Results: Logistic regression analysis indicated that the recognition of TMD pain complaints based on pressure algometry was comparable to that of palpation (R2 = 0.22 and R2 = 0.21, respectively). The masseter muscles were most tender to palpation and algometry, followed by the TMJs and the temporalis muscles. Conclusion: Construct validity of algometry in the recognition of TMD pain complaints is comparable to that of palpation, and differences in tenderness on palpation and on algometry are found between masticatory muscle sites and the TMJ. Keywords: algometry, construct validity, palpation, temporomandibular pain

Aims: To examine the relationship between depression and somatization and pain during muscle and joint palpation as well as limitations related to mandibular functioning (LRMF) in patients with temporomandibular disorders. Methods: The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) data for Axes I and II for 196 consecutive patients (56 men and 140 women) with a history of facial pain were obtained. The mean age of the predominantly Chinese patient population (83.2%) was 33.4 years (range 18 to 55 years). A computerized diagnostic system was used to collect the RDC/TMD history data. The Symptom Check List (SCL-90) depression and somatization scales were generated on-line and archived. The mean muscle pain (MP), joint pain (JP), and LRMF scores were computed with depression and somatization as main effects. Data were subjected to analysis of variance (Scheffé test) and Pearson's correlation at a significance level of .05. Results: Depression scores ranged from 4.03 to 8.16 (MP), from 0.67 to 1.03 (JP), and from 0.30 to 0.38 (LRMF); somatization scores ranged from 2.64 to 7.75 (MP), from 0.58 to 1.00 (JP), and from 0.30 to 0.41 (LRMF). Interaction effects between depression and somatization were not significant. Patients with severe depression had significantly higher MP scores than normal patients or patients with moderate depression. Patients with moderate and severe somatization had significantly higher MP scores than normal patients. LRMF scores of patients with severe somatization were significantly greater than those who were normal or suffered from moderate somatization. No significant difference in JP scores was observed for depression and somatization scales. Correlations between depression/somatization and MP, JP, and LRMF scores were significant and positive but weak; coefficients ranged from 0.15 to 0.41. Conclusion: The results suggest that depression and somatization are related to the self-report of MP. In addition, severe somatization may be associated with an increase in jaw disability. Keywords: depression, pain, somatization, temporomandibular disorders

Aims: To investigate whether secondary otalgia is associated with cervical spine disorder (CSD), temporomandibular disorders (TMD), or both, and to describe the pain characteristics and the comorbidity of secondary otalgia in subjects with and without CSD and TMD. Methods: A mailed questionnaire was sent to a random sample of 2,500 people aged 25 to 65 years. Altogether 1,720 recipients responded. Inclusion criteria were pain inside or around the ear without infection, tumor, or trauma, of 6 or more months duration, and a pain frequency of at least once a month. Altogether 152 respondents fulfilled the criteria, and of these 100 participated in the clinical examinations and interviews. Results: Based on standardized examinations and interviews, 91 subjects had secondary otalgia and 9 had primary otalgia. Most (85%) of the 91 subjects with secondary otalgia also had signs and symptoms of TMD and/or CSD and were therefore classified into 3 groups: CSD (35%), TMD (20%), or "Combination," ie, signs and symptoms of both TMD and CSD (30%). Subjects without CSD or TMD (15%) reported the same level of intensity and impact of otalgia on daily living and psychological distress as the others but less frequent head and neck pain and fewer sleeprelated problems. Conclusions: Most of the subjects reporting secondary otalgia also suffered from CSD or TMD or both. Thus, in patients with secondary otalgia, an examination of the cervical spine and the stomatognathic system should be routinely performed. Keywords: cervical spine disorder, epidemiology, questionnaire, temporomandibular disorder

Aims: To test the effects of occlusal force (OF) angle on the variations in predicted muscle and temporomandibular joint (TMJ) forces during unilateral molar bites. Methods: The craniomandibular (CM) geometries of 21 individuals were determined from lateral and posteroanterior cephalometric radiographs. These geometries were used in a numerical model based on minimization of muscle effort. This model was previously validated for this subject group through the use of jaw tracking and electromyographic data. The model predicted muscle and TMJ forces associated with static OFs on the right mandibular first molar. OF angle was varied from vertical to 40 degrees in the buccal and lingual directions, in increments of 10 degrees. Results: Intra- and intersubject variations in predicted muscle and TMJ forces for unilateral molar biting were dependent on OF angle and CM geometry. Nonvertical OFs were associated with either large anterior temporalis muscle forces (> 100% of applied OF in 3 subjects) or large inferior lateral pterygoid muscle forces (> 90% of applied OF in 3 subjects). On average, vertically and buccally directed OFs were associated with higher mean contralateral TMJ forces (60% of applied OF, SD 12%). Two subjects had large ipsilateral or contralateral TMJ forces (> 90% of applied OF). Conclusion: In a group of healthy subjects, depending on the individual CM geometry, large muscle and/or TMJ forces were predicted to be associated with specific unilateral molar OF angles. Propensities to increased muscle or joint forces may be predisposing factors in the development of myofascial pain or intracapsular disease. The results may explain, in part, the variation in location of symptoms in individuals who first present with temporomandibular disorders. Keywords: biting, modeling, muscles, occlusal forces, temporomandibular joint

Aims: To investigate changes in calcitonin gene-related peptide (CGRP)-like immunoreactivity (CGRP-LI) in the rat masseter muscle and brain after the unilateral experimental induction of masseter myositis. Methods: Ipsilateral and contralateral changes of the CGRP were examined in rat masseter muscle after the induction of unilateral myositis on the right side with an intramuscular injection of 0.01 mL Freund's adjuvant. The left masseter, and left and right masseters of control rats, were injected with 0.01 mL saline (0.9%). After 21 days, tissue samples from the masseter muscles and the hypothalamic-pituitary-adrenal (HPA) axis were analyzed for the presence of CGRP by immunohistochemistry, radioactive immunoassay, and high performance liquid chromatography. Hematoxylin-eosin staining was used to confirm inflammation in the masseter muscles. Results: Elevated CGRP-LI was detected bilaterally in the masseter muscles (P .001) in the myositis group. CGRP-immunoreactive nerve fibers were mainly detected in close proximity to muscle cells and in the walls of the blood vessels. Compared to the control rats, a significant difference in scratching behavior was seen in the myositis group from day 9 until day 21. In the myositis group, CGRP-LI was increased in the pituitary gland concomitant with the increase in CGRP-LI in the masseter muscles but was decreased in the hypothalamus. A possible explanation for these changes could be that rats with chronic myositis develop an abnormal function of the HPA axis triggered by masseter muscle inflammation. Conclusion: The results of this study demonstrate that CGRP may play an important role both peripherally and centrally in masseter muscle myositis in association with presumed nociceptive behavior. Keywords: calcitonin gene-related peptide, Freund's adjuvant, inflammation, masseter muscles, myositis, neurogenic inflammation, neuropeptides, scratching

Maxillofacial fractures in general and mandibular fractures in particular seem to be less common in children than in adults; however, this finding might be influenced by the fact that condylar fractures in children are often undiagnosed and so the true incidence is likely to be higher than that reported in literature. Traumatic lesions of the temporomandibular joint often are overlooked as they can apparently occur with relatively little pain, few clinical signs, and insufficient reaction by the child to alert an adult to the seriousness of the injury. Only 1 to 2 years later, when growth disturbances appear, are they perceived as a problem, but by that time, the dysplastic growth pattern has stabilized and will continue over a period of years. The problem is frequently underestimated because of the difficulties inherent in pediatric pain assessment. The fact that the mechanisms of pain perception in children differ somewhat from adult pain perception mechanisms is one factor that can make pediatric pain assessment difficult. This paper outlines 2 case reports that draw attention to pain in children in the case of temporomandibular joint injury. The inability to assess pain adequately may lead to a delay in diagnosis and treatment and possibly result in future growth disturbances and facial asymmetries. Keywords: children, pain assessment, pain perception, pain sensitivity, temporomandibular joint fractures