Sven-Erik Widmalm

The silent period in the masseter muscle of patients with TMJ dysfunction.

The silent period (SP) following a jaw jerk elicited during sustained contraction in the masseter muscles has been studied in two groups of subjects, one with and one without, acute and distinct symptoms of TMJ dysfunction. The subjects with acute TMJ dysfunction symptoms showed significantly shorter latency and longer duration of the silent period and the period of their depressed activity (DA) was also significantly longer than in the group without TMJ dysfunction. The duration of the SP of both muscles was symmetrical in about 60% of subjects in each group. This study validates that the duration of the silent period may be a useful diagnostic tool of clinical interest.

Temporomandibular joint pathosis related to sex, age, and dentition in autopsy material

The purpose of this autopsy study was to test the hypotheses that temporomandibular joint (TMJ) arthrosis is more common in women than in men, increases with age, and is more common in edentulous persons than in those with natural teeth. Two hundred forty-eight TMJs removed at autopsy from 224 fresh cadavers were investigated macroscopically with dissection or cryosectioning. Age was found to be a significant factor in prediction of TMJ arthrosis (p < 0.001) and of disk perforation (p < 0.05). No significant association was found between morphologic changes in the TMJ and the factor of sex for the whole group. Disk displacement and disk perforation were, however, more common in the joints of women than men in the group of persons 80 years of age or older (p < 0.05). There were significant associations (p < 0.001) between arthrosis, disk displacement, disk deformation, and disk perforation. There were no statistically significant differences in the prevalence of morphologic changes in the joints from persons with 10 or more natural teeth in each jaw compared with those from persons without natural teeth. The results of this study showed that TMJ arthrosis is more frequent in older than in younger persons. TMJ disk displacement generally appears necessary for the development of perforations. The findings of this study indicate that sex and dentition are not major factors for the development of TMJ pathosis in elderly individuals.

Clinical, radiographic, and electromyographic study of patients with internal derangement of the temporomandibular joint

Fifteen patients with internal derangement of the temporomandibular joint (TMJ) were examined clinically, radiographically, and electromyographically. Electromyographic recordings were also obtained from 11 subjects without signs or symptoms associated with their TMJs or masticatory musculature. All the patients with internal derangement demonstrated interferences on the ipsilateral side. This was interpreted as the result of disc displacement producing a reduced joint space and, consequently, a decreased vertical dimension on the symptomatic side. Slow opening and closing mandibular movements without clenching could be performed by healthy persons without noticeable EMG activity in the temporalis and masseter muscles. In association with disc displacement, electromyographic activity of the temporalis and masseter muscles occurred when the condyle slid over the posterior band of the disc and could be interpreted as an arthrokinetic reflex caused by distraction. Continuous muscle activity could be provoked by TMJ disc displacement and ceased when the disc position was normalized on mouth opening, only to occur again every time the disc became displaced on mouth closure. Anterior disc displacement without reduction (closed lock) could cause spastic activity in the temporalis muscle on the affected side. Spastic activity of the masseter and temporalis muscles occurring on the same side as a joint with anterior disc displacement hinders or inhibits the condylar movement necessary to achieve reduction.

A new method for recording temporomandibular joint sounds and electrical jaw muscle activity in relation to jaw opening degree

A system for continuously quantifying of jaw movements in terms of jaw angle was tested in combination with a previously tried method for simultaneous recording of temporomandibular joint (TMJ) sounds and electromyographic (EMG) activity. The system was used to measure the degree of rotation of the lower jaw in the sagittal plane in relation to the upper jaw. It was tested on a group of healthy subjects and patients with TMJ clicking and found useful to record EMG activity and TMJ clicking in relation to opening degree and velocity of jaw movement in open-close cycles.

Diagnostic Accuracy of TMJ Vibration Analysis for Internal Derangement and/or Degenerative Joint Disease

Lower joint arthrography and videofluoroscopy were used to diagnose 297 joints from temporomandibular disorders (TMD) patients. The surface vibrations of the temporomandibular joints (TMJs) were recorded by electrovibratography and a parameter set was derived through frequency analysis. Total vibration energies were used as the primary separating threshold for abnormal joints. The following conditions were statistically discriminated by multi-variate analyses: I) meniscal displacement with reduction; II) meniscal displacement with a partial disk reduction; III) meniscal displacement without reduction; and IV) degenerative joint disease and/or perforation of the disk. Using the total vibration energy as a threshold, the diagnostic sensitivity for the abnormal joints was 82%, while the diagnostic specificity for the joints with no evidence of internal derangement was 75%. Discriminant analysis for the above-mentioned four conditions revealed a diagnostic sensitivity of 79.0%, 85.7%, 77.1% and 76.3% for conditions I, II, III and IV, respectively. The diagnostic specificity was 76.2%, 79.9%, 59.0% and 77.9% for conditions I, II, III and IV, respectively. It was concluded that vibration analysis of the TMJ could be clinically useful as a screening examination for TMD patients.

New time-frequency analyses of EMG and TMJ sound signals

The use of the reduced interference distribution (RID) to obtain improved energy density representation of nonstationary signals in time and frequency is described. Two applications of clinical interest, namely, 3-D graphical presentations of motor unit action potentials (MUAPs) and of temporomandibular joint (TMJ) sounds, have been performed and are presented to show the advantages of using the RID. It is found that the RID gives more detailed and more accurate information about those signals when compared with other methods for time-frequency representation.<<ETX>>

Usefulness of proton density and T2-weighted vs. T1-weighted MRI in diagnoses of TMJ disk status.

ABSTRACT The aim of this study was to test the hypothesis that proton density and T2-weighted magnetic resonance (MR) images are more useful than T1-weighted MR images in the diagnoses of disk displacement, disk reduction, and disk shape. The subject group consisted of 92 patients referred for bilateral MRI imaging because of diagnosed signs of temporomandibular disorders (TMD). In the experimental group (52 patients), both T2-weighted and proton density images were made. In the control group (40 patients), only T1-weighted images were taken. The images were evaluated by two oral radiologists relative to their usefulness as a diagnostic aid and rated as either good or fair in each diagnostic category. The percentages of ratings that were good were higher (p<0.01) for T2-weighted and proton density images than for T1-weighted images in all three types of diagnoses (Fishers Exact test). In conclusion, T2-weighted and proton density-weighted images were found to be more useful than T1-weighted images in the diagnoses of disk status.