Reginald Ford, age 9, of Charlotte, N.C., for his question:

WHAT IS IN TOOTHPASTE?

Toothpaste and toothpower are both substances which are used with a toothbrush to clean the teeth. Both products contain a mildly abrasive substance, such as finely powdered calcium carbonate, or chalk, together with a soaplike material called a detergent.

Some toothpastes contain a sweetening agent other than sugar, along with various flavoring oils which are used to make the toothpaste taste pleasant.

Glycerin or a similar material is added to the basic ingredients of toothpaste.

Some toothpastes contain stannous fluoride, a chemical that some scientists believe helps prevent decay.

Most dentists urge this simple rule: Brush your teeth well after 'every meal.