Review of science dims gloss on dental floss
$2-billion flossing industry has not been able to conduct convincing studies that floss works
A review into the research around dental floss is drilling holes in the belief that dental floss is a basic tool needed to prevent cavities and gum disease.
The Associated Press review of several dental floss studies found shadowy proof for the long-held push to use floss — one of the most universal recommendations in public health circles.
So much so that the U.S. government's latest dietary guidelines quietly removed the recommendation.
Despite the lack of proof of efficacy the US federal government, dental organizations and manufacturers of floss have pushed the practice for decades.
Dentists hand out samples to their patients; the American Dental Association insists on its website that:
"Flossing is an essential part of taking care of your teeth and gums."
The US 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, which must be based on scientific evidence, by law.
Last year, the Associated Press asked the departments of Health and Human Services and Agriculture 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."
Wayne Aldredge, president of the periodontists' group, acknowledged the weak scientific evidence and the brief duration of many studies.
In many cases he said the effectiveness of floss is limited by human error — people do not use it correctly.
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."
Even companies with a big market share of the flossing business — by next year, the global market is predicted to reach almost $2 billion, with half in the United States, according to 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.
When flossing first gained acceptance, no proof was required of remedies.
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.
Damien Walmsley, a dentist and the scientific adviser to the British Dental Association, is among the skeptics.
"It's important to tell people to do the basics. Flossing is not part of the basics."