Get a thorough cleaning of your teeth before whitening. So, long as you follow the directions for whitening and don't do it more than 2 x a year you'll be fine. If you're wanting a professional whitening, just listen to your dentist. Be aware that "at home" whitening kits are safe, but can cause irritation of the gums, but this goes away once you're done whitening. If it becomes bothersome, just skip a day between whitening.