Biology: Which toothpaste works best?

This week we wrapped up our unit on acids and bases by testing which toothpaste works best. The bacteria in your mouth need food to live and multiply. When you eat sugary foods and other carbohydrates, the bacteria use them as food, too. Bacteria in your mouth turn the sugars in these foods into acids that can dissolve tooth enamel (the outer layer of the tooth). Brushing your teeth can help by getting rid of the sugar, but it also functions to reduce the acid-attack on your teeth.

Using chalk to represent teeth (chalk is made of calcium carbonate which is chemically similar to teeth), the kids tested each toothpaste as follows: They set up 4 test tubes, each one with some vinegar, a piece of chalk, and some dissolved toothpaste from one of the brands being tested. Immediately after combining these materials, a balloon was placed over the opening of each test tube. Without toothpaste protection, the balloon inflated as a result of the carbon dioxide produced by the acid-base reaction. Therefore we concluded that the toothpaste that resulted in the least-inflated balloon was the MOST effective.