I figure you probably mean Incisors, the teeth right at the front, and Canines, the two pointy teeth next to them.
They are called cuspids. (Kus-pids).
Incisors
The front two teeth are called Incisors. They are used for biting off food.
Biting
If I am reading your question correctly, then you mean the anterior teeth. There are only six teeth that are considered anterior teeth, though. The order, from outside to inside, goes canine to lateral incisor to central incisor.
To protect your teeth and prevent you from biting your tongue.
They need to eat obviously... Also teeth can be used for biting; so it is also a way of defense.
The larger back teeth are used for crushing and chewing things, which the narrower and sharper front teeth are for biting and cutting into food.
Incisors are used for biting into and molars are used to chew.
biting
the upper jaw has a row of pointed maxillary teeth , which r absent in the lower jaw. roof of buccal cavity has a pair of sets of vomerine teeth. teeth r not used fr eating or biting they r used fr grasping food ,they r replaced throughout their life.
Your teeth are for biting not breathing.