“I don’t need to floss” is a sentence my dentist never used to hear – not until recently, when the latest Dietary Guidelines for Americans stopped recommending it. Now, lots of his patients are telling him they’ve stopped. Despite the NHS advising daily flossing – and almost all dentists being fans of interdental cleaning – an investigation by Associated Press found “little proof that flossing works”.
But how can it not be good for you? Between our teeth are interdental sites coated in dental plaque. Plaque is a layer of bacteria mixed with organic matter that coats teeth and causes gum inflammation (gingivitis) and tooth decay. Early warning signs include bleeding gums. Toothbrushes get rid of plaque from other surfaces, but are not so good between teeth. Surely floss can reach the parts that brushes can’t?
The solution
The lack of good research emerged in a 2011 systematic review by the Cochrane Oral Health Group. Its summary of results from 12 studies found only weak evidence that flossing (plus brushing) reduces bleeding from gums, and none for plaque reduction. But good studies are hard to do. The quality of flossing varies. One study showed that professional flossing five times a week can reduce tooth decay – a result not seen in any studies of self-flossing – so it’s clearly a skill. Experts advise moving the floss, held in a C shape, away from the gum in an up-and-down motion.
However, the Cochrane paper actually said that, although the research was poor, the benefits of flossing probably outweighed any risks. Bleeding gums is a risk factor in developing chronic gum disease than can destroy the bone underneath. Professor Damien Walmsley, a scientific adviser for the British Dental Association, says that brushing teeth twice a day with a fluoride toothpaste and only occasionally eating sugar treats after meals is the best way to prevent tooth decay. He believes flossing is of little value and that small interdental brushes are better at cleaning the gaps between teeth.
No one, however, is arguing that flossing isn’t useful for dislodging unsightly food stuck between teeth. My own dentist, Richard Travers, thinks we can drop the daily enslavement and reduce flossing to twice a week, increasing if our gums start bleeding. His gut feeling, from what he sees, is that both flossing and interdental brushes are useful. And, in a recent feature in the British Dental Journal, senior dentists including Phil Ower, the president of the British Society of Periodontology, announced that they still floss their own teeth.
Having had to swallow American jibes about “British teeth” for all these years, my little chest swelled with dental pride on Tuesday when I learned that the Americans don’t know absolutely everything about teeth – and dental patients in particular. For dental floss has now officially been declared dead in the US.
Well, I say dead. A great many American dentists still want it kept on a respirator just in case it shows a flicker of life – like when there’s a piece of Cajun chicken lodged between the most distant molars, or you need to make a video of your child’s tooth being pulled out by a homemade space rocket.
The fact is, the British dental profession gave floss a quiet burial years ago after sneaking it out the back and finishing it off humanely with a lump-hammer. Yes, in the UK we realised ages ago that – and if you still religiously floss daily, look away now – flossing simply doesn’t work as a health measure (or a fetish).
Related: Everyone recommends flossing – but there’s hardly any proof it works
Let me say that again. FLOSS DOES NOT WORK. Not at all. There’s not a shred of evidence that it does any good whatsoever. I mean, it seemed a good idea at the time – 1882 to be precise – but modern evidence would demonstrate that it doesn’t improve gum health one jot (to use the scientific term).
The British Society of Periodontology, the organisation that specialises in gum health, has known about the black heart of floss for years and currently recommends the use of single-tufted interdental brushes for effective cleaning between the teeth. The American Dental Association and the American Academy of Periodontology however, are largely ignoring the fact that their government’s latest Dietary Guidelines for Americans has quietly dropped its recommendations for flossing because under the law, the guidelines must be based on scientific evidence.
The enthusiasm with which American dental professionals promote flossing despite the evidence, has raised the notion of a conspiracy with floss manufacturers. I don’t believe for a second that American dentists are in cahoots with floss makers, but why do they cling to the notion that floss is a good idea and keep recommending it? Perhaps because, like flossing, it’s a habit and after over a century of promoting the use of floss, it must be extremely difficult to backtrack and say: “Houston, we may have a problem.”
The Brits never had that dilemma. As a nation we were never great flossers anyway and now we know that our patients had an uncanny and instinctively accurate inkling that the lacklustre recommendations of their dentists and hygienists were best ignored.
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I can see why Americans like to promote floss. As a dentist I can appreciate that if flossing is done “properly”, the technique is precise, even elegant. If you have a regular flosser in the chair, you know the patient cares about their teeth, having dedicated a fair chunk of their day to a particularly tedious and often unpleasant task.
But even with the best technique, the evidence doesn’t support flossing as an adjunct to brushing. Most patients, even if they bother to get the minty-waxed out the box, are exceptionally heavy-handed and macerate their gums like they’ve been chewing on bare vacuum cleaner flex. Even in controlled studies, after instruction, the patients taking part couldn’t floss properly. I know of no dentist who flosses. Not one. And of the colleagues who don’t walk away bored witless when I have broached the subject of flossing, most admit that when they tried it, it was really difficult to do effectively, even with their assumed level of dexterity.
Nowadays in the UK, we (I hope, how I hope) all recommend single-tufted interdental brushes as an adjunct to regular brushing. The studies prove beyond doubt that they significantly reduce plaque deposits, decreasing gum inflammation and reducing the risk of gum disease and bone loss. They either have a conventional toothbrush handle or look a bit like a toilet brush on a stick, though it’s best not to think about lavatories while you are using them. The only time I reluctantly suggest floss is when a patient has an area so crowded, floss is the only way of getting between the teeth. And even then I cross my fingers.
Floss is dead. Long live the single-tufted interdental brush.
It’s one of the most universal recommendations in all of public health: floss daily to prevent gum disease and cavities.
Except there’s little proof that flossing works.
Still, the US federal government, dental organizations and manufacturers of floss have pushed the practice for decades. Dentists provide samples to their patients; the American Dental Association insists on its website: “Flossing is an essential part of taking care of your teeth and gums.”
Related: Everything you ever wanted to know about teeth (but were afraid to ask the dentist)
The federal government has recommended flossing since 1979, first in a surgeon general’s report and later in the Dietary Guidelines for Americans issued every five years. The guidelines must be based on scientific evidence, under the law.
Last year, the Associated Press asked the health and agriculture departments for their evidence, and followed up with written requests under the Freedom of Information Act.
When the federal government issued its latest dietary guidelines this year, the flossing recommendation had been removed, without notice. In a letter to the AP, the government acknowledged the effectiveness of flossing had never been researched, as required.
The AP looked at the most rigorous research conducted over the past decade, focusing on 25 studies that generally compared the use of a toothbrush with the combination of toothbrushes and floss. The findings? The evidence for flossing is “weak, very unreliable”, of “very low” quality, and carries “a moderate to large potential for bias”.
“The majority of available studies fail to demonstrate that flossing is generally effective in plaque removal,” said one review conducted last year. Another 2015 review cites “inconsistent/weak evidence” for flossing and a “lack of efficacy”.
One study review in 2011 did credit floss with a slight reduction in gum inflammation – which can sometimes develop over time into full-fledged gum disease. However, the reviewers ranked the evidence as “very unreliable”. A commentary in a dental magazine stated that any benefit would be so minute it might not be noticed by users.
The two leading professional groups – the American Dental Association and the American Academy of Periodontology, for specialists in gum disease and implants – cited other studies as proof of their claims that flossing prevents buildup of gunk known as plaque, early gum inflammation called gingivitis, and tooth decay. However, most of these studies used outdated methods or tested few people. Some lasted only two weeks, far too brief for a cavity or dental disease to develop. One tested 25 people after only a single use of floss. Such research, like the reviewed studies, focused on warning signs like bleeding and inflammation, barely dealing with gum disease or cavities.
Wayne Aldredge, president of the periodontists’ group, acknowledged the weak scientific evidence and the brief duration of many studies. In an interview at his private practice in New Jersey, he said that the impact of floss might be clearer if researchers focused on patients at the highest risk of gum disease, such as diabetics and smokers.
Still, he urges his patients to floss to help avoid gum disease. “It’s like building a house and not painting two sides of it,” he said. “Ultimately, those two sides are going to rot away quicker.”
Wayne Aldredge, president of the American Academy of Periodontology, holds a piece of dental floss. Photograph: Julio Cortez/AP
Aldredge also said many people use floss incorrectly, moving it in a sawing motion instead of up and down the sides of the teeth. Pressed about the origins of his organization’s endorsement of flossing, he said it may simply have “taken the ADA’s lead”.
When the ADA was asked for proof of its claim that flossing helps prevent early gum disease and cavities, the group cited the 2011 review and a 2008 two-week study that measured bacteria and did not even consider gum disease.
In a later statement to the AP, the ADA said flossing “removes plaque” and “is proven to help remove” debris from between teeth. A video on its website proclaims that flossing “helps prevent gum disease”. When pressed, Matthew J Messina, a practicing dentist and spokesman for the dental association, acknowledged weak evidence, but he blamed research participants who didn’t floss correctly.
Even companies with a big market share of the flossing business – by next year, the global market is predicted to reach almost $ 2bn, with half in the United States, according to the publisher MarketSizeInfo.com – struggled to provide convincing evidence of their claims that floss reduces plaque or gingivitis. Yet the industry has paid for most studies and sometimes designed and conducted the research.
Procter & Gamble, which claims that its floss fights plaque and gingivitis, pointed to a two-week study, which was discounted as irrelevant in the 2011 research review.
Johnson & Johnson spokesman Marc Boston said floss helped remove plaque. When the AP sent him a list of contradicting studies, he declined to comment.
The floss-making companies partner with the ADA through its Seal of Acceptance program. The ADA promotes the seal to companies as something that “directly affects the purchase decisions of consumers”; each manufacturer is charged $ 14,500 for the evaluation. If it approves the product, the ADA then charges an additional annual fee of $ 3,500.
The ADA says it rigorously evaluates products and makes no profit from the program. However, floss companies themselves are allowed to design the studies.
“The funding can come from companies – no problem at all,” said Marcelo WB Araujo, a dentist and vice-president of the ADA’s Science Institute, who joined the organization after serving as an executive for Johnson & Johnson. “The design can start from the company.”
When flossing first gained acceptance, no proof was required of remedies. The dentist Levi Spear Parmly is credited with inventing floss in the early 19th century. By the time the first floss patent was issued, in 1874, the applicant noted that dentists were widely recommending its use.
The ADA has been promoting floss universally since 1908. “They just looked into what they did every day in their clinical practice and what they would recommend for patients,” said Araujo.
Count Damien Walmsley, a dentist and scientific adviser to the British Dental Association, among the skeptics. “It’s important to tell people to do the basics. Flossing is not part of the basics.”
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Floss can occasionally cause harm. Careless flossing can damage gums, teeth and dental work. Though frequency is unclear, floss can dislodge bad bacteria that invade the bloodstream and cause dangerous infections, especially in people with weak immunity, according to the medical literature.
National Institutes of Health dentist Tim Iafolla acknowledged that if the highest standards of science were applied in keeping with the flossing reviews of the past decade, “then it would be appropriate to drop the floss guidelines”.
Regardless, he added, Americans should still floss.
“It’s low risk, low cost,” he said. “We know there’s a possibility that it works, so we feel comfortable telling people to go ahead and do it.”
