At the first visit to the hospital, the optimal jaw position for each patient was determined to make the oral splint. Patients were asked to bite several pieces of wooden tongue depressors (each thickness was 1.0 mm) between their upper and lower molar teeth. Then, they selected the most comfortable depressor thickness when they felt that their motor and phonic tics were most suppressed during biting. A custom-made oral splint with the most comfortable thickness was created of acrylic resin (Fig. 1A). At the next visit, the oral splint was set in each patient's mouth (Fig. 1B). At the additional visits, we made any necessary readjustments of the splint to increase comfort.