Is it adequate to brush my teeth with just water?

Yes: Yes you can. The action of the toothbrush bristles disrupts the bacterial growing on your teeth and gums. Toothpaste acts as a lubricant and slight detergent with some flavoring to make the experience a little more palatable (no pun intended). You can also use a baking soda paste on your brush if you wish.

Yes: The only reason to use toothpaste is to carry Fluoride to the teeth. A dry toothbrush or a wet one will be just as effective at removing the real culprit...Dental plaque.