A great natural way is to swish with coconut oil. The first time I tried it, I swished for a few days and got compliments from people i never told I was doing anything to whiten.
You can buy coconut oil for $5 at most grocery stores, in the same aisle as all the other oils. It is solid at room temperature and will melt in your mouth or during cooking.
Take one teaspoon of coconut oil and put it in your mouth. I put the oil under my tongue until it melts (about a minute), because I don’t like the texture of it unmelted. Once it is liquid, swish vigorously, much like you would swish around a bit of mouthwash. Make sure you swish to reach your front teeth especially.
Swish for about 5 minutes. If you can’t swish that long, start with a minute and work up to 5 minutes.
When times up, spit the oil into the garbage. Not the sink. Remember, coconut oil is solid at room temperature, so when it cools again it will clog up your sink a bit. So spit into the garbage.
Now, brush your teeth. You’re done!
Do this once a day for as many days as you like. I noticed a difference after 3 days (that’s when I got complimented by a family member, saying my teeth looked really white). You can continue for as many days as you like.
