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    Testing the Texture of Toothpaste

    Kids, chemistry is so common that it can even be found in toothpaste. Chemists have worked hard to come up with the perfect stuff. Read the labels – you'll find out all kinds of interesting things. Here you'll find some information plus learn some tests you can do to compare different brands.

    Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

    What are the active ingredients in toothpaste? There is fluoride of course, either as sodium fluoride or sodium monofluorophosphate. Fluoride reverses the process of tooth decay where acids (especially from sugar) dissolve minerals right out of the teeth. There are antibacterial agents such as triclosan to control plaque and antitartar agents to control mineralized plaque. Other, inactive or inert, ingredients are water, detergents (to loosen plaque), binders (keeps solid and liquid ingredients together), humectants (to keep it moist in the tube), flavoring, preservatives (to stop bacteria from growing on the other stuff), and abrasives (for cleaning and polishing).

    Using the tests that follow, you will use inquiry to observe, collect data, and make informed decisions related to consumer choices. You'll need toothpicks, 4-5 brands of toothpaste, a toothbrush, and also a microscope would be great. Prepare a chart listing the brands of toothpaste with sections for texture by "touch", "taste", and "microscope". Rub a bit of each brand between your fingers and note whether it feels smooth, gritty, etc. Then brush your teeth with each brand and record the texture by taste. Next, using a toothpick, smear some toothpaste on a microscope slide, add a drop of water, and put on a coverslip. View the slide in a microscope and draw a picture on your chart of what it looks like. Now compare all the brands for texture, grit, and appearance. Which would you choose, and why? Why is this better than just using water to brush your teeth?

    What do you suppose the abrasives are? This grit is often silica, alumina, calcium carbonate or sodium bicarbonate. Chemists are able to make toothpaste clean, polish, and protect your teeth, plus make it taste good and sit up on your toothbrush, too!

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    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    June 2000

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