Development of Diagnosing system using TMJ sounds

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Abstract : This study was done to establish the methodology for analyzing synchronously the acoustic signals of temporomandibular joint sound with the jaw movement. The analyzing system consisted of the computerized acoustic analyzer and Sirognathograph analyzing system.Eight asymptmatic adults were served as the subjects. Three detecting methods for acquiring temporomandibular joint sounds using an electret condenser microphone were evaluated. Three types of detecting method were as follows.Method 1 : An electret condenser microphone was fixed in the external auditory canal using adhesive tapes. The external auditory canal was partially open in this method.Method 2 : An electret condenser microphone was fixed in the external auditory canal using impression material. The external auditory canal was tightly closed in this method.Method 3 : An electret condenser microphone was fixed using impression material with an air vent tube. The external auditory canal was tightly closed but keeping air vent in this method. Method 3 was evaluated to be the most suitable method for detecting the temporomandibular joint sounds because this method showed the greatest signal to noise ratio.Using this method, the acoustic characteristics of the temporomandibular joint sounds were evaluated.The results were as follows.Coefficient variance of the duration between the beginning of jaw movement and the point of the maximal amplitude of temporomandibular joint sound was smaller than that between the beginning of the jaw movement and the beginning point of the temporomandibular sound in both closing and opening phases of jaw movement. In the one octave band analyses, the frequency bands with the maximal magnitude were different among the subjects.However, the frequency bands with the maximal magnitude were nearly constant in both closing and opening phases of jaw movement in each subject.