Fluoridated Mouthwash

What It Does: A mouthwash containing fluoride, a mineral naturally found in water and soil, coats the teeth with a protective film that strengthens tooth enamel, making it more resistant to decay.

Best For: The cavity-prone, those who don’t have fluoridated water, or those who drink bottled or filtered water (see The Importance of Fluoride).

Pro: Fluoride is the only mouthwash ingredient that has been proven to prevent cavities.

Con: Fluoride doesn’t protect against gum disease. “Unfortunately, antibacterial ingredients are not compatible with fluoride,” says John Featherstone, Ph.D., a professor of preventive and restorative dental science at the University of California, San Francisco, “so it’s difficult to have an all-in-one mouthwash.”

Brands: ACT, Colgate Phos-Flur.

Tip: Fluoride has to remain on your teeth to work, so swish for a full minute and don’t drink anything immediately afterward.

Prescription-Only Mouthwash

What It Does: Fights germs that cause gingivitis. Clinical trials have shown that chlorhexidine, the active ingredient in prescription mouthwashes, has much stronger antibacterial properties than the ingredients in over-the-counter brands.

Best For: Those with gingivitis or more advanced gum disease, known as periodontitis.

Pro: These mouthwashes are the only ones approved for treating gum disease by the U.S. Food and Drug Administration.

Cons: Chlorhexidine can stain teeth a dingy brown. Mouthwashes containing chlorhexidine are prescription-only to ensure that a dentist monitors the staining. Most contain alcohol.

Brands: Peridex.

Tip: Ask your dentist about using a spray instead of a rinse. A 2004 study in the Journal of Clinical Periodontology found that using a chlorhexidine spray, rather than a mouthwash, reduced staining.