This research was carried out to clarify the characteristics of the sounds of tooth tapping or percussion.
The external auditory meatus was selected as the site for monitoring of percussion sounds. The data concerning sounds recorded in a vertical and horizontal direction were processed in a microcomputer (Motorola MC-6809) and the FFT and cross correlation and analysis of the percussion sound wave were performed.
Spectral analysis of the percussion sound of each tooth revealed the following characteristics.
Concerning teeth on one jaw.
1) The group in which the maximum resonance frequency was single and identical in all teeth.
2) The group in which the resonance frequency of each tooth varied from each other but was the same in each individual tooth.
3) The group in which the resonance frequency of front teeth and molars differed, but the frequency of each existed within each spectrum.
Concerning bilateral teeth.
1) The group in which bilateral teeth had approximately equal spectra.
2) The group in which bilateral teeth had totally different spectra.
Furthermore the resonance frequency of vertical percussion ranged from 1, 100-2, 000Hz while that of horizontal percussion ranged from 500-1, 800Hz.
Percussion wave analysis
1) The percussion wave pattern until the maximum amplitude was reached possessed waves with a peak at the time of 1/4 and 3/4 of peculiar oscillation.
These 2 peaks appeared as positive and negative converse patterns. The oscillation in various modes showed the wave pattern added the wave with peaks at the above-mentioned times.
2) The percussion wave after the maximum amplitude showed a reducing sine wave oscillation.
3) The impulse added to the vibration due to the influence of the elastic component of the periodontal membrane showed a triangular wave with a direct linear increase until the maximum input is reached.
The characteristics of the wave pattern of this impulse greatly affects the resonance frequency.
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