We Fact-Checked the Viral Mouthwash Advice That’s Floating Around TikTok

Social media can be an incredible resource, but taking unchecked health advice from a stranger on one of the apps isn’t always the best approach to well-being. Anna Peterson, a London-based dental professional, recently went viral on TikTok for explaining that using mouthwash after brushing promotes tooth decay. So before you throw out your mouthwash or rearrange your brushing routine, we decided to explore her claim.

In the video, viewers are told that rinsing with a fluoride-containing mouthwash effectively washes away the fluoride-containing toothpaste you just used. Mouthwash, Peterson explains, contains a significantly lower percentage of fluoride than toothpaste, and it’s not enough to protect the teeth. This practice, then, can lead to tooth decay, she says in her video. This sounds plausible, but both Lawrence Fung, DDS, a dentist in Los Angeles, and Mona Riaz, a registered dental assistant and researcher at the University of Michigan School of Dentistry, disagree with this take.

While you definitely shouldn’t rinse with water for this reason—doing so rinses fluoride out of the mouth, effectively sabotaging efforts to protect your teeth—when it comes to mouthwash, the situation is a bit more nuanced, Riaz explains. “There’s not enough evidence to support that the amount of fluoride rinsed away with a mouthwash has really any detrimental effects on the tooth,” she says.

In fact, Riaz says rinsing with a fluoridated mouthwash right after brushing would likely cause you to break even—or even come out ahead—in terms of the fluoride exposure your teeth will get. She says, in most cases, toothpaste is significantly diluted by saliva, which means its fluoride concentration is diminished. And most people don’t brush for the full two minutes recommended, either, which also means they’re not necessarily getting the high levels of fluoride from brushing that the TikTok video suggests.

Supplementing with fluoride-containing mouthwash, then, may actually be helpful. Yes, it’s lower in fluoride than toothpaste, but you’re using a larger quantity of it, it’s a simpler product (meaning it has fewer ingredients to compete with the fluoride), and it’s not getting diluted in the same way, says Riaz. “You can actually end up getting more fluoride from mouthwash than you do from toothpaste,” she says. So if you’re someone who doesn’t necessarily adequately brush, or who rinses your mouth with water after brushing (stop this, though!), Riaz would actually recommend using a fluoride-containing mouthwash after.

If you do adequately brush and don’t rinse, it may be better to use fluoridated mouthwash at a different point in the day, e.g., after eating a meal, refreshing your breath before a meeting, etc. This is recommended, by Riaz and the American Dental Association, because it increases your daily fluoride exposure—you get it when you brush and when you later rinse, too. And as the original TikTok video says, brushing after you eat can erode teeth. For this reason, Riaz agrees that fluoridated mouthwash is a better option than brushing after meals for people who deal with erosion.

Riaz’s recommendations regarding mouthwash also depend on the patient’s risk profile. If someone comes to her with new cavities and tells her that they’re using mouthwash after brushing, she might tell them to try holding off until another point in the day to ensure they’re increasing their overall fluoride exposure. If a patient is rinsing with mouthwash right after brushing and doesn’t have new cavities, she wouldn’t adjust their routine—because it’s working.

However, all of this changes if you’re dealing with a mouthwash that doesn’t contain fluoride, and Riaz points out that many do not. If you’re using a non-fluoridated rinse, you should avoid using it directly after brushing, full-stop, and instead utilize it at other points in the day—at least two hours after brushing—as recommended above.

Ultimately, though, both Riaz and Dr. Fung support the use of fluoride-containing mouthwash in most patients. Dr. Fung notes that it’s better able to get into the nooks crannies of your teeth than toothpaste, while Riaz reiterates that most people don’t do a great job of brushing adequately, and so mouthwash use can help increase their exposure to protection. “It is a very rare case for me to not recommend fluoride to an adult,” says Riaz.

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