http://planetgreen.discovery.com/fashion-beauty/homemade-minty-toothpaste.html
Ingredients
1 tsp baking soda
1/2 tsp finely ground sea salt
A drop of peppermint, spearmint, etc. (Pick what you would like your toothpaste to taste like and use that flavor.)
A splash of tap water
Mix all the ingredients until it forms a paste thick enough to put on your toothbrush.