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3 also help people to speak clearly and to give shape to the face. Each tooth is covered in a shiny, hard coating called enamel, which resists wear and decay. Although enamel is the hardest material in the human body, it can be eroded by bacterial acid produced in the mouth. Regular teeth brushing will prevent build-up of bacterial acid.

2 EIN-O'S INTRO

Even though there is an incredible variation in body shapes and sizes, all humans share common features and the same working parts. The human body is built from trillions of cells. Similar cells group together to form tissues (a Latin word that means “woven”). Types of tissues include nervous tissue, muscle tissue, connective tissue and epithelial tissue. And when tissues group together, they can make organs that pump blood (heart), digest food (stomach) and breath air (lungs). The Bio Signs series is an assortment of 6 human anatomy models. The detailed models are the: Brain and Skull, Eye, Head and Torso, Heart, Skin, and Teeth and Gums.

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wisdom tooth can prove to be extremely uncomfortable and may have to be removed.

Different Kinds of Teeth There are four main kind of teeth shaped to do different jobs.

Inside each tooth is soft pulp made of blood vessels and nerves surrounded by a semi-hard material called dentine. Roots hold teeth firmly inside the jawbone.

At the front of each jaw there are chisel-shaped incisors to cut food just like scissors.

Ein-O Fact

The canines are longer and more pointed, to help tear and rip food such as meat.

When the jawbone is already crowded with teeth, the arrival of a

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The Development of Teeth

The Structure of the Tooth

In humans, the 20 milk teeth usually begin to erupt when a baby is about 6 months old. These are pushed out gradually as the adult or permanent teeth develop beneath them. When the child is about 6 years old, their milk teeth start to be replaced by the permanent teeth. By the age of 20 years, most adults have a full set of 32. Although the third molars (called wisdom teeth) may never erupt.

A tooth has an outer layer of hard enamel, over a layer of bone-like dentine, which encloses the soft pulp cavity.

TEETH AND GUMS Our teeth are important for tearing, cutting and grinding food. This prepares food into smaller pieces ready for swallowing and digestion. We need to eat food because our energy comes from food. The obvious function of teeth is for biting, tearing and chewing food. However, teeth also

The premolars and molars at the back have uneven surfaces and are like nutcrackers. They crush and grind food into smaller pieces.

Q: How do permanent teeth develop? A: Permanent teeth begin to develop inside the gums as soon as the first milk teeth appear. As a permanent tooth grows, it slowly cuts away at the root of the milk tooth. So when the milk tooth’s root is completely eroded, it falls out and is replaced by the permanent tooth.

Try this! Q: Why do milk teeth fall out? A: Milk teeth, or baby teeth, fall out because as the jawbone grows, the teeth become too small for it. However, milk teeth are important because they help the jawbone grow properly.

If you want to know how acid can break down the tough outer surface (enamel) of teeth, place one of your milk teeth that has fallen out into a glass of soft drink. Leave it for a few days and then examine it. What do you see?

• Underneath the crown is dentine, which is slightly softer. This helps to absorb knocks and great pressure. • Inside the tooth is the pulp cavity, which is the living part of the tooth. This region contains the nerves and blood vessels. • The gum seals the lower side of the tooth to prevent infection. • The tooth’s lower part, the root, anchors it to the jawbone.

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This I Know Guide provides an introduction to: Teeth and Gums

• A tooth’s upper part, the crown, is covered by the hardest material in our bodies. This material is enamel.

Dentine

carnivores have sharp, cutting teeth. Rabbits’ teeth grow all their lives, unlike ours. Rabbits must wear away their front teeth to keep them sharp, otherwise the teeth grow too long.

Gum

Jawbone Pulp Cavity

Milk teeth and permanent teeth have similar structures, but the crowns and roots are weaker in milk teeth than in permanent teeth. Also, there are no premolars in milk teeth.

Ein-O Fact

Root

The shape and type of teeth depends on an animal’s natural diet. Herbivores have large, ridged, grinding teeth and carnivores have sharp, cutting teeth.

Brushing and flossing helps to keep teeth and gums strong and healthy in order to avoid toothache and tooth decay. Tiny pieces of food may stick on the surface of teeth. When this happens, bacteria will make acid from it and this is what decays teeth. Too much sugary food and drink can rot teeth if they are not cleaned.


Teeth