Journal of Oral & Facial Pain and Headache, 02/1998

Neuropeptides are considered mediators and modulators of inflammatory joint disease. Substance P (SP) has been proposed as a mediator of pain, and its vasoactive properties are well documented. In this study, the presence of SP-like immunoreactivity in the synovial fluid was correlated to intra-articular temperature (IAT) and pain from the arthritic temporomandibular joint (TMJ) 3 to 5 weeks after one intra-articular injection of glucocorticosteroids. Eighteen TMJs were investigated for IAT and the presence of SP-like immunoreactivity in the synovial fluid in 12 patients with systemic inflammatory joint disease. After arthrocentesis, the aspirates were analyzed for SP-like immunoreactivity by means of competitive radio immunoassay. A visual analogue scale and an algometer determining the rpessure pain threshold and tolerance level assessed arthritic pain and hyperalgesia in the TMJ. Our results indicate that SP-like immunoreactivity is associated with IAT and that increased concentrations of joint fluid SP-like immunoreactivity correspond to increased pain threshold and tolerance and a concomitantly decreased visual analogue scale. These findings suggest that SP is implicated in the vascular and nociceptive response of the arthritic joint and that SP, possibly assisted by the antinociceptive effect of local corticosteroids, has a modulatory role in arthritic pain and hperalgesia.

The aim of this investigation was to determine the temporal effect of an intra-articular injection of capsaicin to the temporomandibular joint on the levels of calcitonin gene-related peptide-like immunoreactivity (CGRP-ir) in the trigeminal ganglion of the rat. The temporomandibular joints of 26 adult female rates were injected on one side with capsaicin and contralaterally with a control vehicle. Another 8 animals served as an untreated control group and received no injections. Animals were sacrificed at time intervals of 4 hours, 48 hours, 10 days, and 21 days following treatment. The trigeminal ganglia were extirpated, and CGRP-ir levels were quantified using a radioimmunoassay. Results demonstrated that when the capsaicin-treated side and teh vehicle-treated side were compared, CGRP-ir levels decreased initially at 4 hours and increased at 48 hours. At 10 days, CGRP-ir levels had again dropped below control lev els, followed by an increase at 21 days. CGRP-ir levels for the first two time periods investigated, which simulate an acute inflammatory state, mimic results observed in studies using limb joints, while the other time pe riods, which represent an intermediate and a chronic condition, respectively, suggest a more complex interaction with capsaicin-sensitive primary afferents.

Patients with chronic orofacial pain often report disturbances in sleep, leading to the hypothesis that nocturnal motor hyperactivity of the muscles of mastication may contribute to the nociceptive process. This hypothesis was tested in a controlled study to evaluate the relationship between sleep stages, patient self-report of pain in the orofacial region, and nocturnal masticatory muscle activity. Twenty subjects participating in a two-period, within-subject, crossover study received triazolam or placebo for 4 nights. Sleep, pain, and mandibular range of motion were assessed at baseline, following the first period, and again following the second period; a 3-day washout period separated the two treatments. Subjective report of sleep quality was significantly improved following triazolam in comparison to placebo as measured by category scales for sleep quality, restfulness, and sleep compared to usual. The amount of time spent in stage-2 sleep was also significantly increased by triazolam. No improvement was seen in pain as measured by palpation with an algometer, in scales for sensory intensity and the affective component of pain, or in daily pain diaries. Mean facial muscle electromyographic activity for 30-second epochs averaged over the entire period of sleep did not reveal any differences in muscle activity across the three conditions. These data indicate that improvements in sleep quality and alterations in sleep architecture do not affect nocturnal facial muscle activity or subsequent pain report in temporomandibular patients, thereby failing to support the hypothesized relationship between sleep disturbances and chronic orofacial pain.

The purposes of this study were to compare disabilities and health status associated with temporomandibular disorders (TMD) to other musculoskeletal disorders, to describe the types of physical therapy administered to patients with TMD, and to evaluate health-related quality of life (HRQOL) as an index of clinical change following physical therapy treatment. Outcomes for 56 patients (mean age 40 years, SD 13 years; 89% female) were evaluated from a large database generated by the Focus on Therapeutic Outcomes network. A generic assessment of HRQOL - the Medical Outcomes Study (MOS) 17 - was used to evaluate the physical and mental aspects of disability associated with TMD, and the results were compared descriptively to three groups of patients with different cervical pain syndromes. The results showed that patients with TMD had limitations in social function, emotional well-being, and energy level similar to patients with cervical disorders. Physical function (ie, walking, carrying loads, or lifting), however, was much more limited in cervical disorder patients and bodily pain interfered more with daily work. Large positive effect sizes (> 0.80) in the areas of social function and bodily pain indicated clinical improvement for patients with TMD at the completion of physical therapy. The results suggest that the MOS-17 may be useful as one measure of clinical change for patients with TMD who receive physical therapy.

The aim of this study was to compare somatic complaints and psychologic distress in a group of whiplash patients with temporomandibular disorders (TMD) and a group of patients with TMD only, and to assess the outcome after conservative TMD treatment consisting of counseling, muscle exercises, and a stabilization splint. Each group consisted of 16 patients (12 women and 4 men) with a mean age of 42 years. The duration of the symptoms was from 1 to 3 years. In addition to a functional clinical examination and a recording of headache frequency and intensity, the patients answered three questionnaires: a Somatic Complaints Questionnaire (SCQ); the trait portion of Spielberger's State-Trait Anxiety Inventory; and the Symptom Checklist-90-Revised (SCL-90-R). The whiplash patients had higher scores than the TMD patients on the SCQ muscle score and on the following subscores of SCL-90-R: obsession, somatization, depression, and anger/hostility. The treatment outcome as assessed by the change of self-reported frequency of headache, number of tender muscles upon palpation, and change of values on a visual analogue scale for headache intensity showed that the whiplash patients obtained only a decrease in the proportion of tender muscles, while those in the TMD only group showed improvement on all treatment criteria.

Parafunctional activities are assumed to play an important role in temporomandibular disorders (TMD), but experimental data in support of this hypothesis are lacking. This study examined the role of parafunctional clench ing on various measures of TMD pain. Five subjects participated in daily 17-minute electromyogram biofeedback training session structured in three phases. Subjects were instructed to maintain temporalis and masseter muscle activity below 2 uV in the first (decrease) phase of training (10 sessions), above 10 uV in the second (increase) phase (1 to 8 sessions), and below 2 uV in the third (decrease) phase (10 to 15 sessions). Preliminary screening examinations showed that none of the subjects had TMD. Two subjects reported intolerable pain during increase training, and both were diagnosed with a TMD during this phase. No subject was diagnosed with TMD pain during either decrease training phase. The authors conclude that chronic, low-level parafunctional clenching may be a factor in the cause of TMD pain.

The aim of this study was to determine the shear stress of the human postmortem temporomandibular joint (TMJ) disc. Correlation of shear stress with age or with the region of the disc was determined. Nine discs were removed unilaterally from postmortem humans, ages 36 yo 76 years. Disc s were sectioned into lateral (eight), central (eight), and medial (eight) specimens. Each specimen was attached by cyanoacrylate adhesive to a servohydraulic test system aparatus within 48 hours of retrieval. Shear properties were measured under quasistatic conditions with a linear increase of displacement until the specimen failed to maintain maximum resistance to the applied force. The shear moduli were analyzed by means of the Wilcoxon's signed ranks test. The results shoed that values of shear moduli on peripheral portions (lateral and medial) were significantly higher than on central portions (P = 0.0013). The correlation between the shear moduli of TMJ discs and age showed a regression slope for shear module of -0.326 + 0.0341 x age (r = 0.769; P 0.01). Periphe ral portions (lateral and medial) have a higher shear moduli and are stiffer than the central portions of discs and shear moduli or stiffness of TMJ discs increase with age.