doing it wrong
What the Flossing Evidence Actually Says
In 2016 reporters asked for the evidence behind the flossing recommendation. It couldn't be produced, and flossing quietly left the US guidelines.
Three separate people, in three separate threads, arriving at the same unsettling place:
I’ve heard with flossing there’s not much evidence it does any good. It’s more like “it doesn’t do any harm so may as well floss”. r/LifeProTips
I recently read that there is actually no scientific evidence that flossing is of benefit. That doesn’t mean that it doesn’t just that no one has evidence that it does. r/LifeProTips
Isn’t there no evidence that flossing improves your dental health? r/LifeProTips
They’re not making it up, and the second one has the important half of the sentence.
What actually happened
The US government had recommended flossing since 1979. Under US law, federal dietary guidelines have to be backed by scientific evidence.
On 7 January 2016 a new edition of those guidelines came out, and the flossing recommendation had quietly been dropped. No announcement. No explanation.
Reporters at the Associated Press then asked the health and agriculture departments to produce the evidence behind the recommendation that had just vanished. In a letter back, the government acknowledged that the effectiveness of flossing had never been researched as the law required.
The AP went on to examine 25 studies comparing brushing alone against brushing plus flossing. The evidence came back rated weak, very unreliable, of very low quality, and carrying a moderate to large risk of bias.
That’s the story. Notice what it isn’t: nobody ran a study, found flossing useless, and pulled the recommendation. It came out on procedure — the paperwork couldn’t support the claim it was making.
Why the proof is missing
To prove flossing prevents cavities and tooth loss, you’d need to take a large group of people, randomly assign half of them to never clean between their teeth, and follow both groups for ten or twenty years.
No ethics committee approves that study. So it hasn’t been run, and it won’t be.
What exists instead are short trials, and short trials can only measure things that change quickly. Gum inflammation changes in weeks. Cavities and bone loss take years. So the studies measure the fast thing and stay silent on the slow one — and the silence gets read as a negative result.
There’s a second problem nobody mentions: most trials rely on people flossing properly at home, unsupervised. Most people don’t. A study where half the treatment group is doing it wrong finds a smaller effect, and that’s a measurement failure, not a biology finding.
What the evidence does support
Split the claim in two and it gets much clearer.
“Flossing prevents cavities.” Not proved. May well be true. Nobody has the trial.
“Cleaning between teeth reduces plaque, bleeding and gum inflammation.” This one the short trials do show, fairly consistently. And it matters, because gum disease starts at exactly the surfaces a brush cannot physically reach — the flat sides where two teeth touch.
So the honest version isn’t flossing does nothing. It’s the strong claim is unproven and the modest claim is supported — which is a much less interesting headline, which is why nobody ran with it.
The reply that ended one thread
Someone tired of the argument put it better than the studies do:
Why are you looking for evidence, I mean what could it hurt u can’t be that lazy to put your toothbrush on the other hand??? It won’t kill u to try at least no proof needed because your not wasting time, or hurting urself r/LifeProTips
Blunt, but it identifies the real asymmetry. The cost of flossing when it turns out not to matter is a few minutes a week. The cost of not flossing when it does matter is measured in teeth.
What to actually do about it
Use whatever you’ll actually use. String floss, picks, interdental brushes, a water flosser. In studies of real people, the tool that gets used beats the tool that scores best in a lab and sits in a drawer.
Interdental brushes beat floss where they fit. For anyone with visible gaps, they clean the surface more thoroughly and take less coordination.
Judge it by bleeding. Healthy gums don’t bleed. If yours do when you clean between them, that’s the thing to fix — and if that stops after a couple of weeks, you’ve just run the experiment on yourself.
The short version
The flossing evidence is genuinely weak. That’s a fact about the studies, not about your teeth.
Some things are hard to prove because they’re false. Others are hard to prove because proving them would mean deliberately wrecking somebody’s mouth for a decade.
Questions people actually ask
Is there any proof that flossing works?
For preventing cavities, no strong proof. For reducing gum inflammation and bleeding, yes — that's the claim the trials actually support.
Why did flossing get dropped from the US guidelines?
It disappeared from the January 2016 edition with no explanation. When reporters asked for the evidence behind it, the government acknowledged the effectiveness had never been researched as the law required. It came out on procedure, not on a finding that it doesn't work.
Should I stop flossing then?
No. Absence of proof isn't proof of absence, and the reason the proof is missing is that the study nobody will run would mean telling people to neglect their teeth for years.