Ulrich Baumgarten / Getty
You've never noticed your friend's breath being rank or anything (except for that one time after eating a tuna and onion sandwich), but on a group trip in a shared hotel room, she jumped into bed without brushing her teeth. You asked what gives and she was all, "sometimes I do, and sometimes I don't." Then she added, "most of the time I'm too sleepy to." You're not judging, exactly, but you were raised to brush every morning and night.
Sometimes you skip out on flossing, but you're confident that brushing before bed keeps cavities and other bacterial scaries away. Your friend, however, tells you her teeth are flawless, and that dental hygiene is a capitalist plot, so now you're wondering if you've wasted hours of your life (a recommended two minutes a night) brushing your teeth before bed.
Unsurprisingly, our mouths are pretty gross. All warm and sticky, the oral cavity is the perfect environment for all sorts of bacteria to grow. "The most common preventable disease is dental caries [dental cavity], which is caused by the bacteria Streptococcus mutans," says Alex Shalman, cosmetic dentist and clinical instructor at NYU College of Dentistry. "While we all have the S. mutans bacteria in our mouth...it thrives mostly in an acidic environment."
As we stuff our faces with carbs, coffee, and straight up sugar, our mouths become progressively more acidic, which feeds bacteria like S. mutans and other bacteria that form plaque. The only way to keep these bacteria from staging a military coup in our mouths is to 'disrupt' them by brushing our teeth. The American Dental Association (ADA) recommends that you brush your teeth at least twice within a 24-hour period, so that these little suckers can't settle in and cause major damage. "Brushing our teeth has a two-fold benefit," says Shalman. First, regular brushing breaks up the dental plaque and bacteria already hanging around on our teeth, and it removes food which contributes to the acidic environment. So when we brush, we're essentially slowing down tooth decay.
The Worst That Can Happen:
Shalman says that the worst case scenario of not brushing our teeth enough—again, in the morning and consistently at night—is having rampant decay. "Decay can then lead to painful infections which need extensive dental work, and ultimately the loss of teeth." Another side effect of not brushing? Periodontitis, a.k.a. gum disease. And it can slide downhill from there. "If the bacteria that causes periodontal disease provokes our immune system to attack it, the collateral damage of this immune response can ultimately cause bone loss and tooth loss, as well as systemic effects to our internal organs," Shalman warns. He goes on to say that our immune system sends out a crazy response to the offending bacteria, and destroys bone and anything else in its path. There's also evidence that poor oral hygiene can contribute to heart disease. Yikes.
What Will Probably Happen:
If your friend is truly averse to slithering off the couch to brush before bed, only brushing once a day probably won't yield a deteriorated jaw bone and missing teeth. What will happen, however, is plaque buildup which increases risk of cavities and gum disease. Here's why night-time brushing is especially important: "At night the saliva flow is reduced tremendously and saliva is a natural lubricant. It flushes things away from the teeth," says Mazen Natour, professor of periodontology and implant dentistry at the NYU College of Dentistry. "By having saliva at a reduced flow at night, things tend to stick easier and faster." Natour adds that if you're only brushing in the daytime, you've got a lot of hours and meals between brushing for plaque to build up on your teeth. "As a personal opinion, if you really want to choose to brush once a day, I would say [brush] at night."
What You Should Tell Your Friend:
Tell your friend that they should really consider brushing before bed. And tell yourself, since you're so smug, that you should consider brushing your teeth in the morning, after lunch and before bed. "Brushing once a day is better than not brushing at all, but it's not ideal because we do not eat only once," Natour says. "Every time we eat, we feed the bacteria and help it proliferate and... that leads to cavities and periodontal disease." A recent study found that Korean adults who are encouraged to brush three times a day for at least three minutes had lower incidences of periodontal disease than Americans and Australians who are taught to brush twice a day. So yeah before you judge, you and your homie might both benefit from a little extra brushing.
Correction: A previous version of this article states that Mazen Natour is director of implant surgery at NYU College of Dentistry. He is director of the implant honors program at NYU College of Dentistry, as well as a professor of periodontology and implant dentistry.
Read This Next: Braces Can Actually Be Bad For Your Teeth