Cynthia Burke, age l0, of Whitesboro, N.Y., for her question:

What are our teeth made of?

An up to date dentist can ,.fill a cavity or even extract a tooth without hurting you. But you would rather keep your teeth healthy and free of cavities. You can help make this possible by learning about your teeth and by following a few rules. Then the dentist will give them an expert cleaning, which is no strain on you at all.

Your teeth should look like a double row of milky white pearls, hard and spanking clean. When you look in a mirror and open your mouth, you see just the coating of only part of your teeth. When you run your finger over their tops, you are touching the hardest material in your body. It is tooth enamel, much harder than bones, and it forms a jacket over the crown or top part of each healthy tooth.

The enamel.  covered crown is above the gum where you can see it. every tooth has roots that reach right down into the jaw bone, and the biggest part of a tooth is buried out of sight. In a healthy tooth the material under the enamel of the crown also is out of sight. These hidden parts of each tooth are made of three different materials. Most of the tooth is hard, ivory colored dentine. This durable dentine fills part of the crown and most of the roots that reach Me prongs down into the jaw bone.

Neither enamel nor dentine is alive, but a healthy tooth is alive with blood vessels to feed it and nerves to warn you when it is damaged. The center of the tooth is a pocket of living pulp with nerves and blood vessels. A strip of this dental pulp reaches down each root and connects with living cells and blood vessels in the jaw. Though the roots have no enamel, they do have a protective coat of material called cementum.

The hard enamel on the crowns is meant to last through a life time of cheating and chomping. The roots of the teeth are built to stay healthy  but as we all know, things go wrong. Flaky tarter collects around the crowns, then cavities form. Twice a year the dentist should clean off the tarter and check for cavities. And the dentist usually says that he has fewer cavities to fill for people who brush Well and often and fewer still for those who eat a balanced diet of sensible meals.

The body builds its durable teeth from the various materials we eat. Young teeth that are still growing need lots of the calcium and phosphorus chemicals from such foods as meat and milk and leafy vegetables. snacks of sugary treats are not food for the teeth, especially when We have them betWeen our regular meals. Brushing must be done well and often  and twice a year the dentist should give your pearly teeth an expert cleaning job.