Answer:
They have many rows of teeth in each jaw.
Shark teeth quickly fall as they are not firmly attached to the jaws. Therefore they replace the falling teeth with the ones in the row behind.
Links to other pages in this site
What Color Is The Hammerhead Shark?
How Many Feet Long Is A Shark?
What Is Scientific Name For A Great White Shark?
How Long Do Sharks Live?
What Are The Tiger Shark Enemies?