PreparationThis experiment takes five to six days. If you are doing this experiment at home, we recommend you start on a Thursday or Friday afternoon, so that you can perform all the steps right after school or supper.
This experiment uses eggs to represent teeth and vinegar to represent the acids that are made by plaque bacteria, which cause tooth decay and cavities. Both eggshells and teeth can be weakened by acid, which is why good dental hygiene is so important.
What you will need:
- 4.6 oz tube of Crest Cavity Protection toothpaste (active ingredient: sodium fluoride)
- glass measuring cup
- fresh eggs without cracks (use several in case one gets broken by accident)
- ordinary vinegar
- plastic wrap
- clear nail polish
- paper towels
Conducting the EggsperimentFollow these easy steps:
- Allow eggs to warm to room temperature. With clean hands, wash the egg with water and dry with the paper towel.
- Empty the entire tube contents of Crest Cavity Protection toothpaste into the measuring cup and pat down with a teaspoon to level toothpaste and remove any air bubbles.
- Mark one side of the egg with a marker and cover this mark with clear nail polish to protect it from the vinegar.
- After the nail polish has dried, place the egg into the measuring cup, marked side down so the Crest toothpaste covers half the egg. Make sure the egg does not touch the bottom of the cup.
- Cover the cup tightly with plastic wrap and leave it in a safe place at room temperature for at least four full days (96 hours).
- After the treatment, with clean hands, rinse the Crest toothpaste off the egg with warm tap water and let the egg dry overnight.
- Pour enough vinegar into the clean measuring cup to cover the egg, and then carefully place the egg into the vinegar with the spoon. Rest the spoon on top of the egg to keep it submerged under the vinegar, and cover the cup with plastic wrap. You’ll notice bubbles starting to form on the side of the egg that was not treated with Crest.
- Leave the egg in the vinegar until the untreated side (the unmarked side) of the egg softens. This will take 7 to 13 hours.
- After 7 hours in the vinegar, remove the egg and check if the side not treated with Crest has softened by tapping it very lightly with your finger or a pen. If soft, go on to step 11.
- If the untreated side is still hard, put the egg back into the vinegar. Check the egg every hour or two afterwards until the untreated shell has softened.
Note: If you are not going to be home after the egg has soaked for 7 hours, take the egg out of the vinegar and wash it in warm water. Write down how many hours it was in the vinegar. As soon as you return, put the egg back into the vinegar and continue checking it every hour or so for softness. But be sure not to leave the egg out of the vinegar for more than 12 hours.
- When the untreated side is soft, remove the egg and gently wash it with warm tap water. The egg is very fragile now so be careful.
The ConclusionBy gently tapping both sides of the egg, you can now see two effects:
- Acid has made the side of the shell not treated with Crest soft and weak.
- Crest Cavity Protection (with sodium fluoride) has protected the shell and kept it hard and strong.