Subject: How can I kept an egg from rotting?

For Science Fair I determined to do the question, Does time effect how white 
your teeth will become when brushing?  I've done some research and came to the 
conclusion that eggs would be the best representive for the teeth.  I am 
afraid though that the eggs might rot, and I am not sure if I should 
refrigerate the eggs because it might effect the outcome.  If you have any 
suggestions it would be apreciated greatly! Thanks!

Re: How can I kept an egg from rotting?