As soon as you see your new whiter teeth, you'll be hit with what I call "The WOW" experience. Your teeth will now have become as many as 12 shades whiter, so you won't be able to stop checking them out in the mirror. You'll feel like a new person. It is a great high.
But, within a few days, you'll most likely see the whiteness fade somewhat. You can minimize this regression, though. Out-of-office whitening (the do-it-yourself follow-up work) means more contact time of the active ingredients (hydrogen peroxide) on the teeth, and that will subdue regression.
Your dentist might send you home with a tray-and-gel system to use twice a day for three to seven days. Any longer wearing time will cause sensitivity, so its use should be limited - and monitored.
More Answers from Jonathan B. Levine, DMD