News stories earlier this week have challenged the conventional wisdom dispensed by dentists for decades: that flossing your teeth regularly helps prevent tooth decay and gum disease.
A widely-cited Associated Press article by Jeff Donn headlined, "Medical Benefits of Flossing Unproven" notes that "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...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.
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Flossing has been proven to clean between the teeth, resulting in a cleaner mouth. Whether that in turn translates into fewer cavities is another matter. After reviewing published peer-reviewed studies, dentist (and co-host of the science-themed Prism Podcast) Grant Ritchey acknowledged in an interview with Seeker that "there isn't a lot of robust research that convincingly demonstrates the efficacy of flossing in the prevention of either dental caries (cavities) or periodontal (gum) disease."
So the evidence shows that flossing doesn't work?
Not so fast, Ritchey says: "That's not the same as claiming that it has been demonstrated that flossing doesn't work. When you thin slice the systematic review on flossing and dental caries, it actually does show that when done correctly -- five times per week by a dental professional -- dental decay was reduced by 40 percent. So in my opinion, the gist of the article should be 'Flossing poorly has no effect on dental caries or periodontal disease.'"
So saying that "flossing doesn't work" is like saying that dieting doesn't help people lose weight: It can -- but only if you do it right. It is true that most people don't floss correctly, but floss is a dental hygiene tool, and like any tool it can be used correctly, incorrectly, or not at all. If you're like most people and don't floss correctly, then flossing won't reduce tooth decay; if you're like most people and don't stick to a healthy diet, then you won't lose weight.
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Though the story is being cast in some circles as exposing a carefully guarded international conspiracy by Big Dental, the research has been known and available for years. Even though flossing is not as effective at reducing tooth decay as many have been led to believe, it's hardly alone. The efficacy of other medical advice, products, and procedures have been questioned, including mammograms, common cold medicines, Tylenol pain relievers, many antidepressants, and so on. And every few months a new study is published casting doubt on the safety and/or effectiveness of widely used herbal supplements including St. John's Wort, echinacia, and glucosamine. In fact a staple of many households across the country -- the daily multivitamin -- is widely regarded by doctors and nutritionists as unnecessary and a waste of money.
Athletic coaches invariably encourage students and athletes to warm up or stretch before exercise or practice, though there's no evidence it does any good: It hasn't been scientifically shown to reduce injury, prevent sore muscles or improve performance. The advice to wait 30 minutes to swim after eating, heard at swimming pools across the country, is just an old wives tale as well. These kinds of cautions and folk wisdom, commonly advised -- though less often followed -- become routine in our lives despite lacking clear statistical evidence of their benefits.
As for dental floss Dr. Ritchey advises, "If you want to prevent tooth decay, you should focus on reducing your sugar intake, use a fluoridated toothpaste, and perhaps a fluoride mouth rinse. I think it's fair to say that the literature doesn't support flossing in the prevention of gum disease and cavities specifically, but I still believe it should be done." Donn, the AP journalist whose reporting recently questioned the value of flossing, agrees: He still flosses his teeth.
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