Cavity. That's the word no one wants to hear at the dentist's office. A cavity (say: KA-vuh-tee) develops when a tooth decays (say: dih-KAZE), or breaks down. A cavity is a hole that can grow bigger and deeper over time. Cavities are also called dental caries (say: KARE-eez), and if you have a cavity, it's important to get it repaired.
But why would your tooth develop a hole? Blame plaque. That's a sticky, slimy substance made up mostly of the germs that cause tooth decay. The bacteria in your mouth make acids and when plaque clings to your teeth, the acids can eat away at the outermost layer of the tooth, called the enamel (say: ih-NA-mul).
If you don't go to the dentist, the acids can continue to make their way through the enamel, and the inside parts of your tooth can begin to decay. If you've ever had a toothache or heard an adult complain about one, it may have been because there was a cavity that reached all the way inside a tooth, where the nerve endings are. Ouch!
Your dentist will carefully examine your teeth and may take X-rays. If your dentist discovers a cavity, he or she can repair it for you by first removing the rotted part of your tooth with a special drill. The dentist then fills the hole in your tooth with a special material. The result is called a filling.
Does it hurt? Sometimes it does, but your dentist can give you an anesthetic (say: an-es-THET-ick). That's a kind of medicine that will numb the area around the problem tooth while you're getting your new filling.