Can I Use Whitening Gel for 1 Month? Or Only 2 Weeks? Desperate, Please Answer!

44% bleaching (usually carbamide peroxide, but there are others) is a very high concentration of bleach and is usually used in-office for a short period of time and then rinsed off so that no damage to soft tissue is done.

I would say that it is not a problem to use a lower concentration bleach for a longer period of time as long as you are careful and don't let the sensitivity get severe.  You can use some sensitivity toothpastes or a product called "Gel-Kam" that can be put directly in the trays that helps with sensitivity (I tell patients to rotate one night with the bleach and one night with the gel-kam if they are having sensitivity). Good luck with the bleaching and try to be patient, it does take time (longer for some) in order to get the results that you want.

It all depends on the cause and severity of your staining.  Tetracycline stains usually require at least a month or more