Do You Floss?

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Is it good dental hygiene, or one of the longest scams in medical history? Flossing your teeth has been promoted by the government and dental organizations for decades, and suddenly it seems that no one knows why.

Last year, the Associated Press thought something was fishy and askedthe departments of Health and Human Services and Agriculture for evidence that zipping string between our teeth was a good idea. The later 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.

Just like that!

The federal government has been formally recommending flossing since 1979, first referencing it in the Surgeon General's Report for that year. The practice has been reinforced in the Dietary Guidelines the government issues every five years – up until this year.

The AP did its homework, examining 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 data were unequivocally brutal for floss fans. The evidence for flossing is "weak, very unreliable," of "very low" quality, and carries "a moderate to large potential for bias."

Even one 2011 study cited that did find flossing associated with a slight reduction in gum inflammation was undermined by reviewers who ranked the evidence as "very unreliable." A follow-through by a dental magazine stated that any benefit would be so minute it might not be noticed by users.

In their defense, the two leading professional groups — the American Dental Association and the American Academy of Periodontology — 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. But the AP notes that most of these studies used outdated methods or tested too few people.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.

It should come as no surprise that flossing is big business – or it was, until its effectiveness was debunked. The global market is predicted to reach almost $2 billion.