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What makes teeth hurt?

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HealthWiki > Where There Is No Dentist > Chapter 4: School Activities for Learning about Teeth and Gums > What makes teeth hurt?


A tooth will hurt if it is broken, loose, or if it has a cavity. Cavities are the usual cause of toothaches.

Healthy teeth are alive.

Two thin strings enter each tooth. One, the nerve, comes from the brain and carries the message of pain. The other is the blood vessel. It comes from the heart and carries blood to the tooth.

a person's jaw, showing the 2 strings described above.

If you could peel away the gum and look inside the bone, you would see that a nerve and a blood vessel go into each one of a tooth’s roots.

They give the tooth life and feeling.

The hard cover of the tooth protects the nerve and blood vessel inside it. But when tooth decay eats through that cover, the nerve and blood vessel are unprotected. A cavity lets food, water and air get closer to the nerve, and that can make the tooth hurt.

The sugar in food makes tooth decay possible. Sweet food that is also sticky is the worst of all because it glues itself to the teeth. Germs inside your mouth use the sugar to grow and to work harder at making cavities.

teeth. + sweet foods. causes cavities.

See the next section for more discussion of how germs and sugar combine to cause cavities.

A cavity may look small on the outside, but it is much bigger inside. Decay spreads more easily in the soft part under the hard cover of the tooth.

A tooth with a cavity may hurt, but it usually does not hurt all the time. This is because the bottom of the cavity is close, but not yet on the nerve inside the tooth.

illustration of the above: a tooth with a small cavity.

Fill a small cavity and save a tooth.

A small cavity that is not treated grows bigger and gets deeper. When the cavity finally touches the nerve, it causes a tooth abscess. Infection from the tooth decay going inside the tooth causes the tooth to ache all the time, even when you try to sleep.

Infection can pass from the tooth to the bone. As it spreads under the skin, there will be swelling of your face.

illustration of the above: a tooth with an abscess.

A tooth with an abscess must either be taken out or have its nerve treated.

An abscessed tooth is dying. When it dies the tooth changes color from white to dark yellow, grey, or even black. Pus from the end of its root can pass to the gum, making a sore called a gum bubble.

DENT Ch4 Page 47-3.png

A tooth is like a light bulb.

When the bulb is alive from power inside, it is bright and useful.

The little wires inside the bulb are like the nerves inside the tooth. When the bulb burns out, it is dark and not useful any more.


  1. Have each student look inside a partner’s mouth. Look for black spots that may be cavities, for dark teeth that are dead, and for sores on the gums, especially near a bad tooth.
  2. Discover how sweet food sticks to teeth.
    a knife cutting chocolate
    • Cut several different kinds of food with a knife.
    • Vegetables and meat do not stick to the knife.
    • Sweet foods, like chocolate and jam buns, do stick to the knife. They stick to your teeth the same way.

    DENT Ch4 Page 48-2.png

    Pour some cola or juice in a dish, and leave it outside overnight.

    As water is lost, the juice left in the dish becomes sticky. It attracts flies.

    The air you breathe dries the cola and causes a sticky, very sweet coating to form on your teeth. It attracts germs.

    DENT Ch4 Page 48-3.png

    Try to find some old teeth. Ask the students to keep their own baby teeth when they fall out. (Note: in some countries this is not acceptable.) Your dental worker can save you some teeth that were taken out at the clinic.

    Scrape the outer cover of the root with a knife. Feel how hard and smooth it is.

    illustration of the below: teeth in glasses of milk, cola, and water.

    Then find out what happens when the students leave a tooth in cola, milk, or plain water.

    After 3 days scrape each tooth again with a knife. Students will discover that sweet cola drinks make teeth softer and darker in color.

  3. Look inside a tooth for the space where the nerve and blood vessel used to be. See how close they were to the tooth’s hard outer cover. Look for a small hole at the end of the root. That is the place where the nerve and blood vessel enter the tooth. Ask your dental worker to find an old tooth with a cavity and cut it for you.
    a tooth with a cavity.
    breaking a tooth with a hammer.
    a rotten yam.
    • Take a hammer.
    • Gently break open a tooth.
    • Look inside.

    See how much bigger the cavity is on the inside. It spreads under the hard cover.

    Cut through a rotten yam. See how the rotten part spreads
    under its skin in the same way.

  4. Do a project in class.
    • Count the number of students with cavities.
    • Count the number of teeth having cavities. Show the students how to look for them on the tops, sides and between the teeth.
    • Find out the person’s age.
    Have the students write on the blackboard what they counted. Then make a chart or graph.

    2 students writing numbers of cavities on a blackboard.
    • Decide if tooth decay is a serious problem in your school. Ask your dental worker to look at your results and to come and treat the students, and help you prevent the problem from returning.
    • Do the same with brothers and sisters at home. Find out if tooth decay is a problem with these young children. Tell your dental worker what you find.

This page was updated:19 Feb 2018