Olympic gold-medal swimmer Ryan Lochte’s stunning smile had me looking closer at what I thought at first looked like braces on his teeth.

Ryan Lochte poses with his dental braces bearing the U.S. flag and his gold medal after winning the men's 400m individual medley swimming event at the London 2012 Olympic Games on July 28, 2012 in London. (Fabrice Coffrini/AFP/Getty Images)

Grills (or, if you’re hip enough, grillz) are purely decorative coverings for one or more teeth; made popular by hip-hop and rap music artists in the late 1980s and early 1990s. They are usually made of gold or another precious metal, and they’re often decorated (like Lochte’s) with jewels. You can order them online or buy them on eBay; apparently some jewelers and tattoo parlors offer them, too, though I couldn’t find listings for any in the greater D.C. area.

The American Dental Association offers a bit of guidance regarding grills; basically, the ADA says, they’re okay if they’re made of safe materials, they fit properly, you don’t wear them constantly and you keep them clean. The ADA Web site recommends talking with a dentist before getting a grill.

ADA spokesman Matthew Messina says, “If Ryan Lochte wants to wear grills on the podium as a personal statement, that’s great. The challenge is how long you wear it and what’s it made of.” Beyond that, Messina says, “The thing with grills is to keep them clean.”

Celebrities who can afford grills that are made of precious metals and “fit real well” are ahead of the game; cheaper grills may contain nickel, to which gum tissue may have an allergic reaction. (Messina adds that some cheap grills may contain lead, which you definitely don’t want in your mouth.)

Because they snap onto your teeth, grills that are poorly fitted can also irritate the gums; they also allow for bacteria to gather between the metal and your teeth and gums, which can cause gum disease and cavities. Grills worn constantly also can actually move your teeth, “like a bad retainer,” Messina says.

Still, it’s easy enough to prevent grill-related problems. Messina recommends wearing them sparingly, cleaning them thoroughly between wearings, and flossing and brushing your teeth before and after wearing them.

It’s worth noting that proper fitting of grills requires taking an impression of your teeth — which in most states is considered practicing dentistry, Messina says; in most jurisdictions, he says, non-dentists who do so are “working outside the law.”