[A study of how to distinguish the side on which TMJ noise is occurring]

Many patients with TMJ dysfunction suffer from TMJ noise. The measurement of TMJ noise is an important factor in assessing the state of the TMJ dysfunction. Consequently we measured the TMJ noise using electrical techniques in order to make an accurate record. However, determining the side on which the noise occurs is not always easy in auscultation or when picking up the noise electrically, because the sound is carried across the bony structure and picked up on both sides. To solve this problem, we used a three-directional accelerometer, measuring the sound on both sides in the hope that a difference in measurements would allow us to identify the side of the noise. In this study, we vibrated one side of the TMJ with pulse waves, and we compared the vibrated side to the unvibrated side. The height of the pulses was held at 4 volts. In addition, we changed the rising time from 0 volt to 4 volts within a range of 0.6-2.0 msec. The following results were obtained. 1. The time difference between the peaks of the three directions was from 0.32 msec to 3.22 msec on the vibrated side, and from 2.92 msec to 18.2 msec on the unvibrated side. 2. Whenever the time was increased within the selected range, the time difference between the peaks of the three directions on the vibrated side was shorter than that on the unvibrated side. 3. These results suggest that the use of a three-directional accelerometer is a reliable method of distinguishing on which side the TMJ noise is occurring.