First: put 5 big tablespoons of lemon juice into a small container.
Secondly: add in 3 to 4 tablespoons of baking soda into the lemon and mix until it is a paste like substance.
Thirdly: get your toothbrush and dip it into the paste making sure you have a good dollop of it on the brush.
Fourthly: brush your teeth with the paste for 2/3 minutes(warning it does not taste good)
Five: after you've swilled the substance out your mouth, then brush your teeth regularly as you would with toothpaste.