Dava Kay Riccioni, age 12, of Peoria, Illinois, for her question:

What are teeth made of?

The body goes to a lot of trouble to build permanent teeth from the foods we eat. But sad to say, many young persons have a lot more dental trouble than they should. A lot of this can be avoided if we understand how our teeth are made and how to protect them. However, it does not help to know all these things unless we promise ourselves to follow the rules of tooth care    every single day of our lives.

The two main tooth building ingredients are calcium and phosphorous, but a lot of other food substances are needed to build them and still more are needed to keep them healthy. All of the materials required for tooth building and maintenance are extracted from the foods we eat. But the best possible diet can fail if we also consume a lot of tooth¬ destroying foods or neglect regular dental care.

Calcium is a chalky white mineral which is very plentiful in milk. When we drink plenty of milk, we also get phosphorous and small amounts of several other tooth building minerals. We also get more phosphorous from eggs and fish and from vegetables of the pea family.

Vitamins also are necessary for the building and care of teeth, especially vitamins A and C. We get vitamin A from green and yellow vegetables, especially carrots, from fish oils and eggs, liver and certain fruits, especially apricots. Vitamin C is plentiful in citrus fruits, cabbage and cantaloupe.

Since the permanent teeth are meant to last, you may wonder why the dental foods are needed to maintain them. It is true that the outside of a tooth is made from durable dentine and enamel, meant to last a lifetime. The body cannot rebuild or repair it. But this is not the whole story.

The inside of the tooth is a pulpy wad of living tissue, fed by nerves and blood vessels. The roots of the tooth are anchored in the living jaw bone and surrounded by the living gums. When the pulp and the surrounding tissues are unhealthy, a sturdy tooth is weakened and most likely decays.

For example, vitamin C helps to maintain healthy gums. Unhealthy gums tend to become sore and infected    and there goes a tooth. A well balanced diet is needed to keep the pulpy core healthy. Just about all nutritious foods play some role in rebuilding and maintaining our teeth.

But there are a few habits that ruin them. For example, chewing on hard items, such as ice cubes, can crack the enamel and encourage decay. Candies and sugary pop provide food for bacteria that cause tooth decay. Between meal snacks also leave crumbs for bacteria.

Teeth require brushing after eating. At least once a day, it is sensible to remove fragments from between the teeth with a thread of dental floss. And, even with all the proper care, twice a year we take our teeth to visit a dentist. He gives them a super cleaning and fills any small cavities before they become big ones.