[An acoustical analysis of TMJ sounds and its clinical importance].

The aim of this report was to establish a method for objective examination of TMJ sounds which is required for preventive care of the TMJ dysfunction, and to confirm its clinical importance by means of analysis of mandibular border movement and EMG. The subjects for the acoustical analysis of TMJ sounds consisted of 13 temporomandibular joints as the clicking group, 4 as the crepitus group, and 11 as the control group. The subjects for the analysis of the mandibular movement and EMG consisted of 8 adults with clicking as the clicking group and 11 without TMJ sounds as the control. The results obtained were as follows: 1. Clear and stable TMJ sounds waves could be recorded from the external auditory meatuses. 2. Clicking sounds waves showed a sharper rising and shorter duration than crepitus sounds waves. Comparing the three groups on the basis of the data of power spectrum analysis of frequencies using FFT, the spectrum of frequencies of the crepitus group was the highest and broadest, and that of control group was the lowest. 3. The deviation of the trace of mandibular border movement in the clicking group tended to be larger than in the control group. 4. In the clicking group, the frequency of occurrence of the silent period of EMG bursts during tooth tapping was lower and the duration of the silent period was shorter than in the control group. Duration, interval and cycle of EMG bursts during gum chewing in the clicking group was longer than in the control group. 5. From the above, it was suggested that the ones with TMJ sounds had the TMJ dysfunction latently, therefore it was considered valuable to use an analysis of TMJ sounds in the examination for the preventive care of the TMJ dysfunction.