Cows do not have upper front teeth and their lower bottom incisors never stop growing.
Cows don't have teeth on the top in the front of their mouths, but they do have molars on the top for grinding. Instead of teeth in the top front, they have a dental pad. This is a feature of ruminant* dental anatomy that results from the lack of the upper front teeth (incisors). It allows the animal to gather large quantities of grass and other plant matter. In cattle, the tongue is used to grasp food and pinch it off between the dental pad and the lower incisors. However, since they cannot bite grass off, they are inefficient at grazing more closely than 6 inches (15 cm) from the ground. Once they gather a length of grass, however, they can use their molars to grind it up.
(*) Ruminants are animals who chew their cud, like cattle, goats, sheep, camels, deer and giraffes, to name a few.