IT NEEDS TO BE STRONG ENOUGH. AND STAY ON LONG ENOUGH.
Bleaching requires a whitening chemical—in this case, hydrogen peroxide. But it’s not enough to just swipe it on. The bleach needs to remain on your teeth long enough to sink in.
“If you have a bleaching pen and you just rub it on your teeth, that’s not going to stay on,” says NYC-based cosmetic dentist Dr. Brian Kantor of Lowenberg, Lituchy & Kantor.
Proper bleaching systems, like the ones described here, are designed to deliver the one-two punch of concentrated peroxide and enough time.
IT WON’T WORK ON ALL TEETH.
For bleaching to make a difference, your teeth need to have become discolored over time. If your incisors were always a little off-white, that might be the shade you’re stuck with.
“There are teeth that will not bleach at all,” says Kantor. “If someone had white teeth and drank a lot of coffee and tea and wine, those teeth will bleach better than someone who was just born with darker teeth.”
As a rule, yellowed teeth bleach better than ones that have a grayish tint. Also, certain dental work such as crowns won’t bleach well.