Call nowDirections

Flossing and the Death of Expertise

In the summer of 2016, a dental health story briefly dominated the headlines. What was the scoop? According to the Associated Press, the longstanding recommendation of the American Dental Association that patients floss regularly was not based on “strong evidence.” That is to say, some scientists had done research, and then other scientists had deemed that research to be of low value.

Why then, you might ask, would the ADA make such a recommendation? And what was it about the recommendation that made the Associated Press consider it to be worthless? It turns out that the ADA’s recommendation on interdental cleaning, which dates back to 1908, was based partly on something that our society increasingly devalues: expert opinion.

The ADA responded to the news story with an appeal to authority: “As doctors of oral health, dentists are in the best position to advise their patients on oral hygiene practices because they know their patient’s oral health status and health history.” The ADA added that flossing is beneficial because it removes plaque, which contains harmful bacteria that cause tooth decay and gum disease.

To be clear, research has been done on the benefits of flossing, and the ADA considers that this research does have value. And as the ADA points out, it can be challenging to do research on flossing, since people tend to lie to their dentists about their flossing habits.

Moreover, expert opinion is unanimous. In the U.S., the American Academy of Periodontology issued a statement on the efficacy of flossing to prevent gum disease. Here in Toronto, the Ontario Dental Association weighed in on the “great floss debate” by devoting the next issue of Your Oral Health magazine to flossing. The editor, Dr. Deborah Saunders, stated: “My colleagues and I were quite concerned and immediately went to great lengths to reassure our patients of the facts—flossing is an integral part of everyone’s individual oral health-care routine.”

The media, however, was not convinced by the response of the experts. News outlets began publishing sensationalist stories exhorting people to “drop the floss.” The more responsible news outlets pointed out that the ADA was standing by its recommendation, but this was buried beneath attending-grabbing headlines claiming that flossing is unnecessary.

The stakes are high. Tooth decay is a major public health issue. According to the U.S. Center for Disease Control and Prevention, it is the most common chronic disease among children aged 6 to 11 and among adolescents aged 14 to 17. Among adults, tooth decay is the second most common disease, after the common cold.

In his 2017 book The Death of Expertise, Tom Nichols argues that, in developed nations, laypeople are increasingly rejecting the advice of experts, turning their backs on centuries of accumulated knowledge. Nichols attributes this tendency to a culture in which all opinions are held to be equal, even those that are factually wrong. It is a historical trend, he warns, that can have dire consequences for public health and even for democracy.

Tooth decay is already one of the most common diseases, despite being preventable. Given the increasing devaluation of expertise, it might just become more common.