Tongues are kind of like freakishly strong yet unattractive pets that live in our mouths: You forget to take care of them until they start to smell, then they really start to smell, and you find yourself saddled with an eye-popping medical bill.
The point of that gross analogy was to introduce the concept of tongue scraping, which, like most beauty/health trends, is newish but not new at all to other parts of the world. The Romans did it. Eighteenth- and 19th-century Europeans did it. And practitioners of Ayurveda, from 5,000 BCE to present day, do it every morning.
Not to give you a complex or anything, but right this minute, your tongue's probably coated in white stuff laden with bacteria that could cause health issues ranging from bad breath to oral disease. (Want a fun, light read? Reference this scientific article and this one.) The good news is that, with a tongue scraper, you can manually remove the gunk and turn your covered-in a-film-of-nastiness muscular hydrostat into a healthy, pink, Gisele-at-the-2013-Met-Gala one.
Now, you technically don't have to go out and buy a special tool, but toothbrushes aren't designed to conform to the squishy-sponginess of the human tongue and might not clean as effectively as scrapers. But what's $7—the price of this easy-to-clean stainless steel model—when you're preventing cavities and tooth decay and that sour coffee-with-dairy aftertaste?
The only downside here is nature: When you, um, stick something that far back into your mouth (where the bacteria live), your gag reflex is bound to kick in. Just remember to relax, exhale, and do not go there, do not go there, do not—too late.
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