Adan:
You know, most animals don\'t have perfect teeth... far from it, they have cavities, missing teeth, and gum problems. Nature sometimes compensates (beaver teeth keep growing, shark teeth keep coming in), but if you ever look at a 10 year old buffalo\'s mouth, then you realize exactly why humans developed toothbrushes, paste, flouride, floss, and listerine.
As for killing the germs, I think that probably the boiling hot tapwater most people rinse their teeth with will kill the germs, and the toothpaste itself, probably.