Much like working out to stay in shape, tooth whitening maintenance needs to be done on a regular basis. If your habits that caused the staining remain the same, i.e, you still drink coffee, tea, red wine, or smoke or eat other staining foods on a regular basis, your teeth will restain. If your teeth were very dark to begin with, they may require more regular maintenance to maintain their new bleached shade. The good news is that for most people, if they have an in-office treatment (for the best results, it should be more than just ONE in-office treatment and it should be combined with an at-home bleaching protocol during the initial treatment), maintenance can be as simple as using their take home bleach in their custom whitening trays one day/night every few months. Wouldn't that be great if that would work with personal training as well!