Kitchen science: Why do we clean our teeth?

 

So, answering the question "why do we need to clean our teeth?" seems easy, but there's nothing better than a demonstration, and we love a bit of kitchen science.  It doesn't take much time to actually do, but there is a LOT of waiting between steps.

Things you need:

2 eggs
2 cups big enough for the egg to fit in easily
2 nets / similar to support the eggs (we used the ones you get oranges in)
Something to hold the nets up with (we used kebab sticks, but elastic bands would work just as well)
Vinegar
Fluoride mouthwash

What to do:

Put one egg in each of the cups, inside a net so that it hangs and doesn't touch the bottom of the cup, then fill one cup with mouthwash (make sure it has fluoride in) and the other cup with water.
We've done this before with the egg just sitting in the cup at the bottom and it's fine, but the part of the egg which is touching the cup doesn't get the full effect of the mouthwash.
The egg soaking in the mouthwash is "cleaning its teeth", the one in the water is not.
Leave them like this for 24 hours.

The next day, take the eggs out, pour away the water and mouthwash, and fill each cup with vinegar, before putting the eggs back in.  The vinegar is the "acids in foods".
The one which didn't "clean its teeth" will immediately be covered in bubbles and you will shortly notice the shell starting to dissolve.  Wait at least 12, preferably another 24 hours.

After the wait, take the eggs out and investigate what has happened to them.  The one which was soaked in mouthwash will still have a relatively hard and intact shell, the one which was not will have lost its shell almost entirely and will be soft and baggy.

The shells represent the enamel on your teeth, and are a pretty good representation of why you should clean them regularly.