Such products for teeth whitening are available in 2 forms

The first is gel which is applied for a restricted number of days till you can see the desired effect on your teeth.
The results of the gel normally last for a few months after which, your teeth will begin to yellow and stain as before.

Of course, you may use natural teeth whitening remedies to continue the effect of this gel for a slightly longer
period of time. Gels usually do not cost more than $20 or so but they must be applied at least twice a day.

Teeth whitening strips are another option costing about $50 and containing peroxide. You may also consider the more
expensive and more permanent procedures like in-office whitening and tray- based whitening.