The Associated Press recently published an article called “Medical benefits of dental floss unproven”. A similar one from the New York Times followed: “Feeling Guilty About Not Flossing? Maybe There’s No Need.” The BBC continued the trend with “Should you floss or not? Study says benefits unproven”. Vox chimed in with a characteristic “The AP asked the government for proof that flossing works. The answer: ¯\_(ツ)_/¯”. News.com.au rounded out the set with “Flossing is a complete waste of time: investigation”.
In a world where climate-change-deniers, anti-vaxxers, and young-earth-creationists serve as elected representatives, clearly overwhelming scientific evidence is insufficient when the message is inconvenient. This is not assisted by scientific journalism being, on the most part, bad (see Huffington Post’s “A Glass Of Red Wine Is Equivalent To An Hour At The Gym”).
The reason for bad science reporting is economic: newspapers want readers, and more people click on “wine = gym” than anything printed in Nature. I hope you are skeptical of the gym wine equality. If not, ask what the consequences would be if you swapped wine with the gym? These stories are an incredibly dangerous form of bad science. They’re not an argument against flossing, but against doing so badly. They’re not an argument against flossing, but an argument against doing it poorly.
If you read the articles you might notice that the studies cited are in fact studies of studies. You would be right in concluding that there is relatively little evidence for the benefit of flossing in particular. But is that really the message you take away from these headlines? I, personally, read them as “Hey! Person who is statistically likely to be relatively undisciplined in oral hygiene! Relax 🙂 Your dentist is talking crap. Click here to have your laziness validated!”
You may feel broadly the same. The real problem in the data, by way of insufficient and poorly controlled studies, is very different to the cognitive dissonance these articles inspire. Here is a quick refresher on tooth decay. You are mostly bacteria (though not 10:1). Some of those bacteria live in your mouth, where you also put food and grind the food into small pieces. Lots of food either contains sugar, or can be converted to sugar. If this food stays in your mouth, the bacteria digest it and produce acid. This breaks your teeth. This hurts. So you don’t want food and bacteria to stay on your teeth.
I am not a dentist but teeth + acid = bad times for you. Don’t soak your mouth in acid. Don’t leave sugar or starch in your mouth for bacteria to eat. Rinsing with clean (fluoridated) water is great. Brushing your teeth helps some more. And when there are bits of food in between your teeth, you probably need something more than water and the toothbrush. Vice-President of the American Academy of Periodontology, Wayne Aldredge, uses floss. One of the authors of anti-floss papers, Fridus Van Der Weijden, uses toothpicks.
So you don’t have to floss, but you do have to clean your mouth out. Properly. Professor Joerg Eberhard, speaking with Honi, says “interdental cleaning is even more important than using a toothbrush”.
But back to the story that broke. Here are some quotes from the studies that were cited: “Flossing plus tooth brushing showed a statistically significant benefit compared to tooth brushing [alone] in reducing gingivitis”.
“Professional flossing performed on school days for 1.7 years on predominantly primary teeth in children was associated with a 40 per cent caries risk reduction.”
“The dental professional should determine, on an individual patient basis, whether high-quality flossing is an achievable goal.”
“There is some evidence from twelve studies that flossing in addition to tooth brushing reduces gingivitis compared to tooth brushing alone.”
In short, those clickbait headlines should actually read “Flossing Works But You’re A Bit Shit At It”. With a lede like that, the article is probably not going to get many readers, but that’s science.