When U.S. federal government issued its latest dietary guidelines this year, the flossing recommendation had been removed, without notice. As Associated Press reports, the government acknowledged the effectiveness of flossing had never been researched, as required.
Dental organisations and manufacturers of floss have pushed the practice for decades. The federal government has recommended flossing since 1979.
However, the guidelines must be based on scientific evidence, under the law. So, last year, the Associated Press news agency asked the U.S. 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 carefully researched
, as required.
Conducted over the past decade 25 studies 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." A commentary in a dental magazine stated that any benefit would be so minute it might not be noticed by users.
Also, most of these studies used outdated methods or tested few people.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.
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.
Besides, 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.
Count dentist Damien Walmsley, scientific adviser to the British Dental Association, said to AP: "It's important to tell people to do the basics. Flossing is not part of the basics."