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Science experiment failed -What did we do wrong?


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I think I misunderstood something in the directions for the experiment we are trying.


It's an experiment to show how flouride protects teeth, so we coated one egg with toothpaste, let it sit for 24 hours, then we took it and an uncoated egg and soaked them in vinegar. I thought the uncoated egg was supposed to fall apart, but the toothpaste one is disintegrating. What's going on?

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Fluoride helps in building up and strengthening the developing tooth enamel and protects it against being demineralized.

Your experiment might have failed for several reasons:

1. I would suspect that the makeup of an egg shell is very different from tooth enamel. Egg shell is 95% calcium carbonate - tooth enamel is not.

2. I do not think that there is any process happening in a layed egg that constantly reinforces the shell and uses fluoride (our teeth reform enamel constantly).

3. the time span would be too short - it is the continuous application of fluoride and the building into the enamel that helps; a one-time-exposure to fluoride does not protect the tooth against a massive onslaught of acid.


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We did this experiment in REAL Science Odyssey Chem last year. We put 1/2 the egg in toothpaste for 5 days and left the other half untreated. We were then supposed to wipe off the egg and let it sit overnight to dry. Then we soaked the egg for 12 hours in vinegar. The question for the lab was: "Will the fluoride bond with the calcium to make a stronger shell (or in your case, stronger teeth)? If it does, the vinegar will not soften the eggshell."


My guess would be that in your experiment 24 hours wasn't long enough time for the fluoride to bond with the calcium? Another possibility could be that there was not enough fluoride in the toothpaste you chose to use for the experiment.


Our experiment worked and the kids thought it was really cool how half of the egg was squishy and gross and the other half was still hard.

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We did this experiment, too, but for our science fair so we tried several kinds of toothpaste. We found that some toothpastes "protect" the shell better than others, but one brand made the shell disintegrate much faster than our control.


Interestingly, the toothpaste that protected the shell the best was a natural one that had no flouride in it at all.

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