Swimming a few laps in the pool is great exercise, but this fitness routine could be eroding your enamel. Chlorine -- which gets in your mouth while you're swimming more often than you realize -- has a low pH balance, which can cause dental abrasion, eventually leaving your teeth brittle, sensitive and prone to decay. Smile saver: "Opt for salt-water swimming whenever possible," says Irwin Smigel, DDS, a celebrity cosmetic dentist in New York City and president of the American Society of Dental Aesthetics. "Salt water is actually good for your teeth and has a natural antibacterial and healing effect on your mouth." Don't have a salt-water option? Chew on this as soon as you step out of the pool: Supersmile Professional Whitening Gum ($4), which has ingredients to stabilize the pH balance of your mouth, counteracting the acidity that leads to erosion.