Some sports players use dental mouth guards to reduce the risk of orofacial trauma. Althoug mouth guard have been shown to protect against orofacial injury, many players do not use them during training and playing because of discomfort and breathing problems. This study was performed to measure the alteration of respirotory volume during wear the mouth guard. I checked 5 D university male students ventlation with and without mouth guard in steady state. Air flow and volume were decreased during wearing Mouth guards compare to not wering. It suggested that mouth guard would have change the ventilation patterns.