Flossing: Absence of Proof is Not Proof of Absence

Flossing: Never Like the Photo

Dentists and media have been telling us for generations that brushing and daily flossing are absolutely critical for preservation of teeth and gums into old age. A flurry of publicity in the last few days has people wondering if this is another instance of authorities blindly asserting healthy living ideals that are not only wrong, but might actually be harmful, as the USDA’s Food Pyramid and advice to eat low-fat, high-carb diets were.

Let the New York Times story, which was typical, explain:

For decades, the federal government — not to mention your dentist — has insisted that daily flossing is necessary to prevent cavities and gums so diseased that your teeth fall out. Turns out, all that flossing may be overrated.

The latest dietary guidelines for Americans, issued by the Departments of Agriculture and Health and Human Services, quietly dropped any mention of flossing without notice. This week, The Associated Press reported that officials had never researched the effectiveness of regular flossing, as required, before cajoling Americans to do it.

In a statement issued on Tuesday, the American Academy of Periodontology acknowledged that most of the current evidence fell short because researchers had not been able to include enough participants or “examine gum health over a significant amount of time.”

The revelation has caused a stir among guilt-ridden citizens who strive to floss daily but fall short of that lofty goal. Among experts, however, it has been something of an open secret that flossing has not been shown to prevent cavities or severe periodontal disease.

A review of 12 randomized controlled trials published in The Cochrane Database of Systematic Reviews in 2011 found only “very unreliable” evidence that flossing might reduce plaque after one and three months. Researchers could not find any studies on the effectiveness of flossing combined with brushing for cavity prevention.

“It is very surprising that you have two habits, flossing and toothbrushing without fluoride, which are widely believed to prevent cavities and tooth loss, and yet we don’t have the randomized clinical trials to show they are effective,” said Dr. Philippe Hujoel, a professor of oral health sciences at the University of Washington in Seattle.

But this is not unusual. Double-blind scientific studies are very expensive, and impractical for long-term effects on large populations. Because flossing is a procedure done by the study subjects themselves, there is no way of telling whether self-reported flossing is done correctly or at all, and lying about having faithfully flossed to your dentist is one of the most common white lies. “I always floss daily” is right up there with “I never think lustful thoughts about [sexually-attractive person who is not my spouse]!” in the book of self-serving fibs.

“Absence of Proof is Not Proof of Absence” — the lack of evidence of an assertion (“flossing helps prevent gum disease and preserves teeth”) is not evidence that the assertion is false. That would be the fallacy of Argument from Ignorance, often seen in the argument that there is no God because there is no evidence that He/She/It exists. If we have no evidence, we can’t determine anything about truth or falsehood. So all of these clickbait stories hinting everyone has been wasting their time flossing and authorities are full of it are simply wrong.

No studies are really needed because long experience of millions of dentists shows that regular brushing and flossing do tend to prevent gum disease and loss of teeth. While the evidence is not proof as the FDA might require it if it were a newly-proposed drug, my own personal results from periods of less and more dental hygiene efforts demonstrated that flossing helps. My gums improved and I had far fewer problems once I found two excellent time-saving devices for brushing and flossing.

First, electric toothbrushes with high-speed oscillating brush heads make brushing your teeth thoroughly yet gently easy and quick. These are marketed as ultrasonic, though that’s exaggerating bit. Here’s the one I use:

Philips Sonicare Diamond Clean Toothbrush

Flossing is notoriously tedious, with some types of floss shredding between teeth, cutting into fingers trying to hold it, and being almost impossible to get between back molars without stretching your mouth uncomfortably. There are several flossing helpers that ease this by holding a short segment of floss at the end of a long handle you can reach back with, but this is still time-consuming.

I found a great appliance which uses puffs of water or mouthwash instead of floss, and easily reaches back to flush the spaces between back molars:

Philips Sonicare Airfloss Ultra

This does a decent job of flushing out food particles, but is far more practical than the dental irrigators (Waterpiks) which spray far more water and take much more time to use. With the Airfloss, you place the head at the lower end of the junction between two teeth, push the button, and *puff* a tiny amount of high-speed liquid flushes out the crack. The consensus is that while this is not as good as thorough flossing, it is much better than the haphazard and occasional flossing most people do, and by making it easy to add to your routine, far more likely to become a regular habit. My dentist started complimenting me on my gum health shortly after I started using it regularly, and it continues to be excellent. One note: because of the high-tech nature of the machine, it doesn’t last as long as one might like — I went through a warranty replacement, but the company was good about sending me a new one when it stopped working. If you have to buy one every two years, it’s still a great deal better than gum surgery. You also need to practice to avoid spraying your surroundings, but it’s still far less messy than Waterpiks.

Jeb Kinnison

Writing About Life and Love

Flossing: Absence of Proof is Not Proof of Absence

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