Effect of Mouth Breathing on Chewing Activity in Daily Life

Objectives: We evaluated the effect of the breathing through the mouth on chewing of usual foods. Materials and methods: We confirmed that the all subjects are real normal nasal breather by examining with CO2 sensor. EMG activity of the masseter muscle and expiratory airflow from the nose or mouth are recorded during chewing and swallowing a cup noodle and a rice ball. For the mouth breathing, the nostrils were obstructed with nose-clip. The duration of chewing, and the number and cycle of chewing stroke were evaluated, and compared when breathing through the nose and mouth using paired t-test. Results:Duration of chewing was prolonged when breathing through the mouth as compared when breathing through the nose. The significant difference was not found in the number of chewing at nasal breathing and mouth breathing. However, the chewing cycle at mouth breathing showed a significant smaller value as compared with nasal breathing. The duration of EMG activity of the masseter muscle above the threshold was significantly shorter when breathing through the mouth as compared when breathing through the nose. Conclusion: It is suggested that the mouth breathing brings the effect on chewing activity of usual food in daily life, and results in reducing the chance of occlusal contact.