Effect of mouth breathing on masticatory muscle activity during chewing food.

The aim of this study was to examine the effect of mouth breathing on masticatory muscle activity during chewing food. Masseter muscle activity during chewing of a rice ball was recorded in 45 adult volunteers (three women), identified as nose breathers. Surface electrodes were placed on the skin according to the orientation of the masseter muscle to record the activity of this muscle while the subjects chewed the food until swallowing. Each activity was recorded twice, once with nose breathing and once with mouth breathing induced by nasal obstruction. The integrated and mean electromyography values for mouth breathing were significantly lower than the values for nose breathing (P < 0·05). The resting and total duration of chewing were significantly prolonged (P < 0·05) and the active duration significantly shorter (P < 0·05) when breathing through the mouth compared with the nose. Significantly more chewing strokes were counted for mouth breathing compared with nose breathing (P < 0·05). Taken together, the results indicate that mouth breathing decreases chewing activity and reduces the vertical effect upon the posterior teeth.