You check your chair before you sit down. Or you think before you believe the crazy stories someone is telling you. Believe it or not, your eyes and brain can play tricks on you too. If you were a shark you would never need to go to the dentist.
Sharks have a set of teeth that stand up like our teeth do.
But in a shark's mouth, behind the teeth that are standing up, there are more teeth lying flat. If the shark loses or breaks a tooth, a new one will take its place. But you are not a shark. It's a pretty creepy feeling. Not too many people can make it through the summer without getting a mosquito bite.