Flossing Day

What the day is

Flossing Day is observed on November 27, and is kept on the day after Thanksgiving, which is a joke about the meal immediately preceding it.

Origin and background

The practice is older than most people assume. Levi Spear Parmly, a dentist working in New Orleans, was recommending waxed silk thread between the teeth in the early nineteenth century. Commercial dental floss followed in the 1880s, and mass production through the twentieth century made it standard advice everywhere.

In 2016 that advice ran into an unexpected problem. A news agency asked the federal government to produce the evidence supporting the flossing recommendation carried in the national dietary guidelines. The recommendation was quietly dropped from the guidelines, and officials acknowledged that the supporting evidence had never been properly assessed.

The reporting that followed was widely misread. Reviews of the trials did find the evidence weak, but weak in a particular sense: the studies were small, short, and unable to verify whether participants flossed correctly, or at all. That is an absence of good evidence rather than evidence of absence, and the two are easy to confuse. Dental associations kept the recommendation, reasoning that plaque between teeth has to be removed somehow and that nothing else reaches it.

The more useful finding in the same body of research concerns technique and tools. Interdental brushes perform at least as well as floss in several reviews, and better for people with larger gaps between their teeth. Poor technique accomplishes very little, which may account for some of the weak trial results in the first place.

How to take part

• Floss once, properly: curve the thread against the side of each tooth rather than snapping it straight down between them.
• Try interdental brushes, which many people use more consistently because they are easier to handle.
• Do it at whatever time of day you will actually repeat. Consistency beats timing.
• Ask a dentist or hygienist to watch your technique once. It takes two minutes and usually changes something.
• Do not treat the 2016 story as permission to stop. It did not say what the headlines said it said.