Apple cider vinegar is an acid and can be used as an effective tooth whitening treatment.
More Info: Vinegar is also known as acetic acid, and as with most home treatments of this nature, overly aggressive use can damage the tooth enamel. If you are going to try this treatment you should discuss with your dental health provider first and minimally follow these precautions:
It is safest to dilute the apple cider vinegar first.
Mix a teaspoon of vinegar in a glass of water and use this solution as a mouthwash, swishing it around your mouth for one or two minutes.
After spitting out the solution, clean off any residue with a rinse of clean water. Otherwise the acid will erode the enamel and weaken the teeth.
The teeth will be softer after this treatment, so its best to wait an hour before brushing.
This method should not be used frequently.
Apple cider vinegar is a popular home remedy though many of the claims are not confirmed by research. Remember, vinegar is an acid. It is strong enough to eat through tooth enamel, and can cause burns to the skin. If used, it should be prepared in a diluted form, and followed by rinsing.