Through a chemical reaction inside your tooth, it changes the colour to a whiter shade.
Professional whiteners tend to be more concentrated, so they work faster, says Dr. Wolff.
You could have white teeth in one hour with a light-based whitening treatment, which uses a special light to speed up the bleaching process.
Your dentist can also custom make you retainer-like trays that you wear for anywhere from 15 minutes to overnight for one to two weeks, Dr. Wolff says.
Over-the-counter whitening kits - like the strips, gels, and paint-on liquids you see in the drugstore - can also work well, he says. But since they’re typically less concentrated, your results may be less dramatic.
It comes down to how much you’re willing to spend: Professional bleaching can cost $200 to $600, Dr. Wolff says, while over-the-counter products like Crest Whitestrips or Rembrandt 2-Hour Whitening Kit may cost as little as $20.
Ready to splurge? Just make an appointment with your dentist.
But if you want to DIY your smile, heed these precautions.
Don’t bleach if your teeth are grey.
Bleach works on teeth with yellow or brown discolouration, which is usually caused by food stains, Dr. Wolff says.
But it won’t do much for grey teeth, which may be genetic or due to antibiotics. Talk to your dentist to find a solution—veneers may be your only option.
Don’t bleach if your teeth are already sensitive.
Over-the-counter products will probably just lead to more pain. See your dentist: He or she may be able to give you a treatment that is safe for sensitive teeth, Dr. Wolff says.
Stop after two weeks or if you experience side effects.
Bleaching has possible side effects. The peroxide can irritate your gums or make your teeth sensitive to hot and cold. If either of those things happen, stop bleaching immediately, says Dr. Wolff. The problems usually subside when you stop bleaching.
Bleaching too much increases your risk for side effects, so if you’ve used over-the-counter whiteners for two weeks and your teeth aren’t as bright as you want them, see your dentist.
This article originally appeared on MensHealth.com