Gray hairs and fine lines aren’t the only signs of aging; teeth lose their luster as the years pass, too. So in the quest for eternal youth, a stunning smile is just as important as shiny strands and smooth skin. With that in mind, Crest is encouraging women to “keep them guessing” with its new Crest Whitestrips Renewal ($30; drugstore.com). Like the original Whitestrips, Renewal strips are worn twice a day for 30 minutes at a time. That means you can still shower, check your email, or commute to work while Renewal strips break up stains from coffee, tea, wine, and cigarettes. But unlike the original Whitestrips, Renewal also targets buildup below the enamel, removing up to 20 years of discolorations, according to the company. The secret is in Renewal’s peroxide gel formula: It’s the same enamel-safe ingredient used by dentists to bleach away stains. After just ten days, or one box of Renewal strips, Crest promises you’ll have a visibly whiter and more youthful smile—and if you don’t, they’ll refund your money. So go ahead, pick up some strips and smile, at least till another gray hair grows in. —Erika Villani