[Relationship between occlusal interference and hearing ability]

Clicking sounds are one of the symptoms that appear in the temporomandibular joint dysfunction at a high rate. But they are sometimes found in healthy subjects also, so that clicking sounds are seldom recognized as an pathologic condition. Study reports on clicking sounds in the past concentrated mainly on their cause, process of their appearance and their spectral properties. These studies were, however, all based on the understanding that clicking sounds were a kind of symptom or signals that accompanied the unbalanced jaw relationship. They did not examine pathologic conditions or functional change caused by the very existence of clicking sounds. This author has been reporting on the influence of clicking sounds on hearing abilities. This time the author considered it necessary to study the cause for rise of the hearing level of the clicking subjects in relation to the unbalanced positions of their jaws. The author therefore examined the relationship between the phases of occlusal contact and hearing abilities of the clicking subjects. From the results, we obtained the following conclusions: 1. As for the frequency of appearance of clicking sounds, 28 out of the 175 healthy subjects (aged either 21 or 22) had clicking sounds on one side, accounting for 16.0%, at the hazard rate of 1%. There was no differences between the sexes and between the right and left sides. 2. Of the 37 subjects, the cases in which the centric position fall on the intercuspal position were only three among the 17 non-clicking subjects (Group I), accounting for 17.6% and none, among the 20 clicking subjects.(ABSTRACT TRUNCATED AT 250 WORDS)