2 Hard boiled eggs (you may want to have extras on hand in case of breakage)
2 Clear jars (plastic may be safer to use around the children)
Water
Cola
Spoon

 

What to Do:

Invite the children to gently touch the eggs, so they can feel the hardness of the shell.
Explain to the children that the shell helps to protect the inside of the egg, just like the enamel on the outside of your teeth helps to protect the inside of the tooth.
Place one egg inside each of the jars.
Pour water into one of the jars and cola into the other jar (making sure the liquid covers the eggs).
Let the eggs stay in the jars for at least a couple of days.
Lift them out daily, using a spoon, to show the children the changes that are taking place.
Explain to the children that the sugar eats through the egg shell, just as it can eat through the enamel on their teeth, if they don't brush properly.