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 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 wire service looked at what it described as "the most rigorous research conducted over the past decade." That included 25 studies, according to the report.
Take it away, AP:
The findings? The evidence for flossing is "weak, very unreliable," of "very low" quality, and carries "a moderate to large potential for bias."
The AP also examined studies cited by professional groups and found that they were flawed — they involved too few test subjects, or they didn't last long enough, or the focused on the wrong thing.
Flossing is supposed to help prevent plaque build-up, which can be bad news for teeth and gums. (You probably already know this.)
In a statement, the American Academy of Periodontology acknowledged there was a problem with research on the matter, stating that "much of the current evidence does not utilize a large sample size or examine gum health over a significant amount of time."
The organization still encouraged patients to keep up the practice, though.
"Additionally, many of the existing studies do not measure true markers of periodontal health such as inflammation or clinical attachment loss," the statement continued. "In the absence of quality research, patients should continue to include flossing as a part of their daily oral hygiene habit."
The American Dental Association called "interdental cleaners" like floss "an essential part of taking care of your teeth and gums."
"To maintain good oral health, the American Dental Association recommends brushing for two minutes, twice a day with a fluoride toothpaste, cleaning between teeth once a day with an interdental cleaner and regular dental visits advised by your dentist," the ADA said in the statement, released Tuesday.
In an interview, Wayne Aldredge, president of the periodontists’ group, said that many dental patients aren't flossing correctly, instead moving the floss in what the wire service called a "sawing motion." Aldredge said he encourages patients to floss, even with the shaky evidence.
"It’s like building a house and not painting two sides of it," he told AP. "Ultimately those two sides are going to rot away quicker."
In case this helps, here's a video on proper flossing technique, posted by the ADA: