Journal of Oral & Facial Pain and Headache, 02/1993

Muscle fatigue has been thought to be one of the causes of pain associated with temporomandibular disorders. A multitude of variables could contribute to neuromuscular fatigue when a subject attempts to sustain a given force. In studies of jaw muscles the endurance limit has been related to a failure in electrical conductivity (transmission fatigue), an increasing imbalance in the intracellular contents of muscle fibers (contraction fatigue), and the onset of pain. This review describes the principles that underlie fatigue and the results of studies of jaw muscle fatigue. Attempts are made to explain why various studies may have produced different results.

Research efforts have been directed to determine whether temporomandibular disorder (TMD) patients have psychological problems and whether these factors influence treatment outcome. Because there is no consensus about the best way to quickly assess psychological problems in TMD patients, this study was designed to evaluate a simple method for identifying psychological factors that may need to be addressed as part of a comprehensive treatment program. This method involved having TMD patients systematically rate themselves, using a brief screening questionnaire, for the presence or absence of psychological problems. These ratings were then compared to results from extensive psychological testing. Sensitivity, specificity, and ordinal rank-based association model analyses showed moderate to strong associations between patients' ratings and the corresponding psychometric measures. These results provide evidence that the brief self-ratings of psychological factors utilized in this study may be a useful first step to screening for psychological difficulties in TMD patients.

The reproducibility and predictive power of MRI diagnosis was evaluated in a group of 70 patients with limited mouth opening. The predictive reliability of the MRI findings was assessed by comparing the images with a final clinical diagnosis that was based on the initial clinical diagnosis, adjusted and refined, when possible, by findings made during the treatment period (conservative treatment in 51 patients, conservative and surgical treatment in 19 patients). The overall reproducibility of the MRI interpretation by the radiologist appeared very good. The predictive reliability was excellent for normal disc position and fair for anterior disc displacement with reduction. For disc displacement without reduction, however, the predictive power was questioned because of false-positive MRI findings.

The association between malocclusion and the prevalence of temporomandibular disorders (TMD) was studied in an orthodontic patient population before orthodontic treatment was started. A total of 305 patients, 232 with general malocclusion and 73 who also had cleft lip or palate, were given a questionnaire about the subjective symptoms of TMD. Clinical examinations for type of malocclusion and TMD signs were also conducted. No significant differences in the prevalence of TMD were observed between the sexes or between the two patient groups. Temporomandibular joint sounds and difficulty of jaw movement were the most common of the TMD signs and symptoms. Open bite, posterior crossbite, and deep bite were the most prevalent types of malocclusion in both groups. Thus, some specific types of malocclusion were significantly associated with the occurrence of TMD.

The range of mandibular movements was studied on 600 randomly selected people. Mandibular mobility varied widely from subject to subject. There were considerable age and sex differences but no differences were found between the mobility values of persons who were functionally healthy and those with dysfunctions. These factors make it difficult to construct cutoff values that reflect normalcy in mandibular mobility and thus render the clinical utility of such values questionable. The use of age- and sex-corrected border values for mandibular mobility is proposed. The clinical utility of patients' opinions concerning mouth-opening capacity is stressed. On the basis of statistically significant differences, the use of different border values for the protrusive and laterotrusive movements seems to be necessary.

Ten anatomic territories, including both lateral pterygoid muscle and temporomandibular joint heads, were explored with magnetic resonance imaging in subjects with no dysfunctional disorders. The sequence used was one of inversion-recovery, supplemented with image contrast reversal for better visualization. The muscles were observed in the resting position and in dynamic relation. Slice plane definition provided information on the anatomic variations of the superior head and on the muscle-articular junction, in particular on the fascicular aspect of the superior lateral pterygoid muscle and on the differentiation between condyle insertions under effort. The choice of technique and the results are discussed. Avenues are opened for the exploration of muscles utilizing magnetic resonance imaging.

The prevalence of oromandibular dysfunction was studied in 735 subjects from a random sample population of 1,000 subjects aged 25 to 64 years. A diagnosis of oromandibular dysfunction was based on criteria established by the International Headache Society, as a subgroup to tension-type headache. Tenderness in pericranial or jaw muscles was not included. The most common symptoms were clenching (22%) and grinding of teeth (15%). The most common sign was irregular jaw movements on opening and closing (29%). The ratio of men to women for most symptoms and signs ranged from 2:3 to 1:3. This study serves as a base in evaluating the importance of oromandibular dysfunction as a causative factor for tension-type headache.

Clinical assessment of function impairment associated with temporomandibular disorders should not only comprise diagnostic assessment of symptoms and signs but also function impairment assessment in the patient's value system. Regarding clinical assessment methods, the range of opening movement has been demonstrated to be one of the few variables that can be measured reliably. However, this variable allows no distinction to be made between articular and muscular causes of movement restriction. To assess joint mobility, a combination of indirect and direct assessments is proposed, including the range of opening movement after passive stretch, the range of horizontal excursion toward the opposite side, and the condylar translatory capacity by palpation. In clinical practice, signs and symptoms needed for diagnosis are frequently used as the only basis for mandibular function assessment. Function assessment in the patient's value system, however, is a neglected area in outcome assessment. The main objective of this study was to design and clinimetrically evaluate a mandibular function impairment questionnaire. The relationship between jaw function impairment and measures of pain, movement restriction, and psychological distress was assessed. The questionnaire appears to be a reliable and valuable complementary tool for assessing mandibular function impairment.

Dental attrition severity as the cumulative record of parafunctional and functional wear was graded from study cast analysis using established methodology. Attrition severity was compared in anterior, posterior mediotrusive, and posterior laterotrusive segments. Attrition scores in 48 female and 100 male totally asymptomatic controls were compared to 239 female and 31 male patients differentiated into five patient groups of temporomandibular disorders: (1) disc displacement with reduction, (2) disc displacement without reduction, (3) osteoarthrosis with a history of prior derangement, (4) osteoarthrosis without a history of prior derangement, and (5) myalgia only. All the male patients were in the myalgia-only group. Age was controlled in the analysis to control for functional wear. Comparisons between patients and controls were made according to 10-year age intervals. Analysis included ANCOVA confirmed by a Games-Howell post-hoc test, with P .01 interpreted as a significant difference in the attrition score. Only 1 of 112 ANCOVAs showed a significant difference, with younger men from 20 to 29 years of age in the myalgia-only group having lower mediotrusive attrition than the male controls. It would therefore be difficult if not impossible to differentiate patients from nonpatients based on the severity of dental attrition. Consequently, a major peripheral occlusal etiologic role for attrition in TMD is questioned. Some clinical implications are elaborated.

Forty consecutive patients with a cervical whiplash injury were examined and compared with 40 matched controls. The incidence of signs and symptoms was high in both groups. Temporomandibular joint pain (P .001), limitation of mouth opening (P .01), and masticatory muscle tenderness (P > .01) were found significantly more frequently in the patient group, while the presence of joint sounds, deviation during mouth opening, and the overall presence of a symptom were not significantly different between groups. When asked whether they would seek treatment for the observed signs and symptoms, a significantly higher number of the whiplash group responded positively when compared to the control group. These findings warrant further study and suggest the benefit of a routine examination of the temporomandibular joint and masticatory system in patients with cervical whiplash injury.

This paper describes a patient in whom a huge osteochondroma of the mandibular condyle was mistakenly treated as temporomandibular joint syndrome for approximately 6 months before an accurate diagnosis was made. While clinical and pathologic features of this lesion are discussed, further emphasis is placed on the surgical management and immediate reconstruction with autogenous costochondral grafting.