Mouth-closing disturbance caused by yawning in a patient with anterior disk displacement without reduction: Report of a case

Abstract

We report a case of mouth-closing disturbance caused by yawning. A 29-year-old man suddenly noticed mouth-closing disturbance and pain in the left temporomandibular joint after yawning. Magnetic resonance imaging (MRI) showed that the relation between the condyle and the disk was normal, but these structures were anteriorly displaced when the mouth was closed. An unsuccessful attempt was made to reduce the displaced condyle by manipulation. Then, the mandible was retracted elastically. The patient noticed that his occlusion was reduced the following morning. MRI showed anterior disk displacement without reduction, with enlargement of the posterior part of the disk. Therefore, we concluded that the mouthclosing disturbance was caused when the anteriorly displaced disk was reduced on yawning, and backward movement of the condyle was restricted by the deformed posterior part of the disk on closing the mouth.