Time-frequency analysis of temporomandibular joint (TMJ) sounds

Temporomandibular joint (TMJ) sounds and motion were recorded during clinically-derived two movements-simple jaw opening and jaw protrusion followed by opening-from ten patients. A new time-frequency method-radially Gaussian kernel (RGK) distribution-was applied to classify the TMJ clicking sounds into six groups, type I to type VI, based upon time-frequency patterns of energy distribution. The number of clicks and percentage of each type were examined. During the two movements, type I and type IV patterns were most frequently observed and type II and type III were rarely found. Type V and type VI were rarely found during opening movements. However, they were frequently observed during the protrusion phase of the second movement. Relations between the two movements were examined by the prevalence of each type. It was found that some patients tended to have the same types of clicks during the same movements