Vibration of the temporomandibular joints with normal radiographic imagings: comparison between asymptomatic volunteers and symptomatic patients.

In order to estimate the effect of a background noise during temporomandibular joint (TMJ) vibration analysis, 40 recordings from sensors not attached to subjects and sensors attached to subjects without any jaw movement were evaluated. Both of them showed very small energy density, close to 0, throughout 0 to 600 Hz and flat frequency distributions. To evaluate the vibration energy of asymptomatic TMJs with normal joint anatomy and symptomatic TMJs with normal arthrographic imagings, 20 TMJs from 10 clinically normal and asymptomatic volunteers with bilateral normal TMJ computerized tomography (CT) scanning (N-control) were analyzed at four mandibular positions. Results from intercuspal position and maximal opening were identical to the background noise. Results from closing and opening phase showed higher energy, especially below 150 Hz, than the background noise. Surface vibrations of 83 TMJs from patients with arthrographically normal imagings but having symptoms (NID) showed significantly higher energy than the N-control group above 300 Hz. When the total vibration energy (I(T)) is used to set the threshold for the separation of internal derangement, at I(T) = 2.06, the diagnostic specificity for the NID group is 75%, while the diagnostic sensitivity is 82.4% for internal derangement. At the same time, 98.3% of the N-control group was involved below the threshold.