Like most mammals, elephants have teeth called incisors. The differences between most mammals and elephants, however, is that elephants' incisors eventually become tusks as they grow into full-grown adults! This is the case for all elephants except female Asian elephants.
Elephants have a total of 26 teeth, their tusks counting for two. Unlike humans, elephants lose their molars--not once in their lives--but six times! Each time they lose these teeth, the new ones that come in a larger, allowing them to chew even tougher vegetation (like roots, shoots, and tree bark). They chew their food for long amounts of time--this is why they are eating 22 hours of the day!
Though their tusks are long, come out of their mouths, and are important for digging up roots, breaking off bark, and moving away unwanted vegetation, they are basically made of the same ivory as the rest of their teeth! Unfortunately this precious ivory is what has resulted in the deaths of thousands of these beautiful animals.