Deborah Jarrell, age 13, of Chesapeake, We Va.., for her question:

What causes teeth to decay?

One hot summer day. Andy was in a soda fountain when he heard a strange chomping noise, The fella next to him was chewing up the ice in his soft drink. Ha, thought Andy, this young man will soon have a perfect set of teeth   false ones. One of Andy's girl friends, age tons thinks that the best time to eat is between meals and that the best foods are candy and potato chips. She too will have perfect teeth   false ones.

It is true that tooth decay is actually caused by bacteria   but some of us certainly do all we can to help these little creatures along. It is also true that by using good sense we can do a lot to protect our teeth from decay bacteria, These minute creatures are always present in the mouth. But there are many do's and dont's we can use to stop them from eating holes in our teeth.

Our pearly teeth grow as we grow, during our early years. The body builds them from the food we eat. Certain foods are better tooth builders than others and if the body is short of this kind of nourishment it cannot build strong teeth. The tooth building foods are milk, meat and dairy products.  If that snack eating girl friend of Andy's drank milk and ate scraps of cheese between meals, she might keep her own teeth.

However, snack eaters have another trouble the stomach can digest only so much food. If we keep it busy with a lot of valueless food, it is not ready to digest its well balanced meals. The whole body then goes short of nourishment. In our growing years, this nourishment is needed to build not only teeth but bones and other tissues which must last us a lifetime.

So let's get back to the ice chewer and see what damage he is doing to his teeth. The main part of a tooth is made of hard dentine.  It is covered with a shell of even harder enamel,  the heart of the tooth is a pulpy mass of nerves and blood vessels. The bacteria in the mouth cling to the enamel shell and, so long as it remains whole, they cannot do much harm. In time, however, they form crusty little flakes of tartar. Every day we remove some by brushing. About every six months, sensible people have the dentist clean their teeth and scrape this tartar away.

Trouble begins when the hard pearly enamel cracks or wears thin. Chances are, it will not wear thin if you ate the proper foods while your teeth were growing,. But the strongest tooth can be cracked. You can crack or break a tooth while cracking a nut.  Enamel also cracks when made very hot or very cold. Chewing ice, then, is just murder on the tooth enamel. When cracks form in the enamel, the tiny bacteria walk right in. They settle down to feed on the dentine and pretty soon the nerves in the center of the tooth scream out that something is wrong