Come to think of it, I agree. Regarding the experiment with eggs, I distinctly remember the soda laden egg being submerged in the liquid for 24/7, where as the other egg received water and toothpaste. Perhaps a more accurate and interesting experiment would be to wash the tooth with soda and every morning/ evening wash it with toothpaste? Theoretically this can still show how important brushing is, if toothpaste really helps combat the acids from cola.

One of the most infamous experiments is submerging the tooth in cola, to show the importance of brushing. In primary school, it was done on white eggs though, but using a tooth would be more authentic. Ironically, while the tooth should completely rot in cola, the liquid is perfect for washing household things (the sink or a toilet bowl for example).