Journal of Oral & Facial Pain and Headache, 01/1997

The purpose of this study was to determine the structural interrelationship between the temporomandibular joint (TMJ) and the middle ear, in terms of fibrous continuity between the sphenomandibular ligament (SML) of the mandible and the anterior malleolar ligament (AML) of the middle ear. Thirty-seven specimens of the TMJ and middle ear were obtained from adult human cadavers. The temporal bone, petrotympanic fissure, mandibular fossa, and middle ear were dissected en bloc, fixed, sectioned, stained, and observed microscopically. Of the 37 specimens, 67.6% had a continuity of the SML through the fissure passing near the malleus of the middle ear. The AML was present at the fissure in 64.9% of the specimens, with 58.3% passing through and not stopping at the fissure. Results indicated a fibrous ctontinuity between the SML and the AML. Structural differences between the two ligaments were also noted. The sML contained randomly arranged firbous connective tissue with numerous interposed blood vessels. The AML had a smooth arrangement of fibers within the connective tissue, and few blood vessels were apparent. The cl ear anatomic relationship observed strongly supports the contention of a functional interrelationship between the TMJ and the middle ear.

Controversy continues to exist over the putative role of bruxism in the etiology of temporomandibular disorders. A commonly held concept is that bruxism leads to signs and symptoms characteristic of one or more of the subdiagnoses of temporomandibular disorders, while another hypothesis suggests that bruxism is a temporomandibular disorder itself that sometimes coexists with other forms of temporomandibular disorders. Following a thorough review of the literature in this article, it is concluded that the relationship between bruxism and temporomandibular disorders is still unclear. Future research should examine longitudinal epidemiologic and clinical/experimental data to establish or refutre a cuase-and-effect relationship. In doing so, the existence of various subgroups of temporomandibular disorders should be taken into account, bruxism should be discriminated from its daytime variant

Chewing performance can be defined in terms of the reduction in food particle size after 15 chewing strokes. In this study, the relationship between chewing performance and electromyographic activity was investigated to develop optimal values of electromyographic v ariables, based on their ability to predict chewing performance. Electrognathographic and electromyographic recordings from surface electrodes over the digastric (abductor), masseter, and temporalis (adductors) muscles were made from 24 subjects while they chewed a hard fruit gum. A moderate negative correlation was found between the food particle size and the root mean square calculation for masseter activity (-.48; P .01). Weaker postive correlations were found between particle size and the asynchrony of ipsilateral and contralateral anterior temporalis muscles. (.36; P .05). A multiple regression model of electromyographic and electrognathographic varioables was able to predict chewing performance with an R(to the 2nd power) value of .66. If chewing performance is used as an output measure of masticatory function, it may be possible to determine optimal ranges for electromyographic variables and jaw movements.

The purpose of this investigation was to determine a possible association between disc displacement and temporomandibular disorders (TMD). Fifty-six Brazilian asymptomatic volunteers (25 males and 31 females) and 181 symptomatic TMD patients (112 females and 69 males) participated. Volunteers did not have temporomandibular joint pain, limited jaw opening, joint sounds, or previous TMD treatment. Bilateral temporomandibular joint magnetic resonance imaging scans were obtained from all subjects. Joints were classified as normal or having disc displacement. Asymptomatic volunteers had 28 (25%) joints with disc displacement; 10 (18%) had unilateral and 9 (16%) had bilateral disc displacement. Of the TMD patients, 25 (13.8%) had bilateral symptomatic but normal joints. Fifty-one (28.2%) had unilateral and 105 (58%) had bilateral disc displacement. Odds ratios (12.2 [95% confidence interval = 6.1 to 24.4, P = .001]) suggest a strong association between disc displacement and TMD. This study suggests that disc displacement is relatively common (34%) in asymptomatic volunteers and is highly associated with patients (86%) with TMD.

Recent evidence suggests that a past history of physical and/or sexual abuse is more frequently reported among chronic pain populations; however, the prevalence of reported abuse has not been examined in patients with chronic orofacial pain caused by temporomandibular disorders (TMD). This study compares reported physical/sexual abuse among female TMD subjects recruited from the general population with that of age-matched female control subjects. The association of reported abuse with clinical pain, experimental pain responses, and psychologic variables was examined in the TMD group. Results indicated that a slightly but not statistically greater percentage of TMD subjects (44.8%) reported a history of sexual or physical abuse compared to control subjects (33.3%). Reported abuse among TMD subjects was not re lated to clinical pain or psychologic variables. Regarding experimental pain responses, TMD subjects reporting a history of abuse exhibited longer ischemic pain tolerances compared to those not reporting abuse; however, the groups did not differ on other experimental pain measures. Results indicate that the reported prevalence of physical/sexual abuse is similar among tMD subjects compared to other chronic pain populations; however, the relationship of abuse to clinical and psychosocial variables remains unclear.

Variability in the assessment methods of patients seeking treatment for musculoskeletal disorders of the masticatory system confounds comparative assessment of different studies. In this study, presenting symptom profiles were assessed in 40 Australian and 42 Finnish patients with temporomandibular disorders. The symptom parameters of these patients were compared with those of 40 Australians reporting acute dental pain and were assessed with reference t o response to conservative management. A self-administered anamnestic questionnaire was used in a standard, systematic, and comparative way to assess demographi c data, general health status, and symptom parameters according to type, frequency, severity, duration, location, impact on the patients' lives, urgency for need of treatment, and possible initiating factors. It was found that the two nationalities studied had similar presentations of cardinal symptom profiles. Statistically significant differences in major presenting symptoms were found between patients with temporomandibular disorders and those with acute dental pain, but not between patients who responded rapidly as opposed to slowly to conservative therapy. It was concluded that the presenting symptom profiles were similar for the two nationalities and were not related to treatment outcome.

It has been suggested that stabilization appliances and mandibular anterior repositioning appliances work by decompressing the temporomandibular joint. To indirectly test this assumption, tomograms of right temporomandibular joints of seven subjects were taken during comfortable closure and maximum clenching in maximum intercuspation and on the two types of occlusal appliances. Outlines of the condyle and the temporal fossa were automatically determined by an edge detection protocol. Upon comfortable closure, the anterior joint space dimension was reduced with stabilization appliances and mandibular anterior repositioning appliances. Upon maximum clenching, the minimum joint space dimension on stabilization appliances was equivalent to that seen in maximum intercuspation, while that on mandibular anterior repositioning appliances was substantially less (P .05). Findings do not indicate that these appliances induce an increase in joint space during clenching.

The Dental Practice Act Committee of the American Academy of Orofacial Pain was convened in 1995 for the purpose of studying the scope of temporomandibular disorders (TMD)/orofacial pain and dental practice acts. The committee concluded that the scope of clinical practice of TMD/orofacial pain is expanding beyond the teeth and oral cavity to include the diagnosis and treatment of disorders aff ecting the entire head and neck. The expansion of clinical practice is consistent with historical precedent in dentistry and within the scope of current dental practice acts. The present report represents the posiiton of the American Academy of Orofacial Pain.