Got a month? Try this 2-step solution

Four weeks is the optimal amount of time to whiten teeth, says Las Vegas cosmetic dentist Michaela Tozzi, D.M.D. That’s because you can spend the first two weeks prepping teeth to prevent the discomfort that bleach can cause and the second two weeks whitening. For weeks 1 and 2: Brush teeth twice a day with a toothpaste infused with arginine and calcium carbonate, like Tom’s of Maine Rapid Relief Sensitive Toothpaste (Walmart.com). “Arginine blocks the little ‘highways’ in the tooth that lead to sensitive nerve pain, and mildly abrasive calcium carbonate buffs away external stains so teeth look whiter,” says Dr. Tozzi.

For weeks 3 and 4: Use a whitening pen with 3% hydrogen peroxide like Colgate Optic White Overnight Teeth Whitening Pen (Target.com) each night before bed. “The lower dose can sit on teeth for a longer period of time, breaking up stains as you sleep for teeth that are five shades whiter—pain-free.”