Teeth

November 23, 2012 11:13 am

Teeth
They can bite, chomp, chew, crush, nibble, and gnaw. They can be cleaned, crowned, drilled, filled, pulled, capped, and straightened. You can crack them, break them, brush them, and floss them. You can even replace them if you lose them. What are they?
They’re your teeth.
WHAT TEETH ARE
Teeth are the hardest parts of the human body. They often survive long after the bones, or skeleton, have decayed. Scientists have discovered ancient teeth from animals and humans. These remains help scientists learn about the past. For example, they can tell whether a dinosaur ate other animals or plants from the kind of teeth it had.
Teeth are hard because they are made mainly of dentin and covered in a thin layer of enamel. Dentin is like bone only harder. Enamel is the hardest material in the body. Within this hard structure is a soft pulp full of blood vessels and nerves. If you have a toothache, it’s probably because something is irritating a nerve in the pulp.
Yet hard as they are, teeth can decay. Have you ever had a cavity? A cavity is a hole in a tooth. It develops when tiny bacteria eat away at the enamel and dentin. Luckily, a dentist can fill the holes that bacteria make.
Once a tooth decays, it can more easily crack and break. That’s why it’s so important to keep teeth clean. Brushing your teeth helps get rid of bacteria and the bits of food that bacteria feed on.
WHAT TEETH DO
Teeth do lots of things. They help you eat by tearing, grinding, and chewing food. It’s step one in the process of digestion.
Teeth also help you talk. Say the word thistle. Did you feel your tongue touch your upper front teeth? You should have felt it twice, on the th and on the l. You need your teeth to create certain sounds in speech.
Teeth help determine how you look. They support muscles in your face. If you didn’t have teeth, your lips would collapse inward.
KINDS OF TEETH
Teeth are specialists. That’s why your teeth don’t all look alike. If your adult teeth have grown in, you’ve got four different kinds of teeth.
Your front teeth, or incisors, are flat and sharp. You use these teeth like knives to cut into food. Next to the front teeth are your canines (your fangs!). You use these sharp, pointy teeth for tearing and shredding food. Beyond the canines are the bicuspids and the back teeth, or molars. You use these flatter teeth to chomp and grind.
ANIMAL TEETH
Animals have even more specialized teeth. They use their teeth for more than just eating.
Beavers use their front teeth to gnaw down whole trees. A beaver’s front teeth keep on growing. They would lengthen by about 4 feet (1.2 meters) every year if the beaver didn’t chisel them down by gnawing.
Walruses use their huge canines as hooks when they climb up onto ice. Elephant tusks are the largest teeth in the world. Elephants use them for digging or as weapons.
Piranhas are fish that have scissor-like teeth. They use these teeth to cut flesh off prey. Sharks have rows and rows of razor-sharp teeth. If they lose a tooth, a new one grows quickly in its place. The narwhal is a whale that has only two teeth. In male narwhals, one tooth grows forward like a long, twisted sword. Scientists are unsure about the purpose of these teeth, but they have seen narwhals dueling with them.
Some poisonous snakes have fangs for teeth. They use their fangs like needles for injections. These snakes bite and deliver deadly poison through their fangs!
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