In this video, we learn how to whiten yellow teeth at home with a lemon. You will need: a q-tip, baking soda, and a lemon. First, cut the lemon in half and squeeze out all the juice into a container, then add in baking soda to the juice to make a paste and mix together with the q-tip. Now, apply this mixture onto your teeth and leave on for around 10 minutes. After you have done this, you will have whiter teeth in just a few minutes! Only use this mixture a couple times a week, because it is bad for the enamel on the teeth if used too often.