Flossing: much ado about not much evidence

3 minute read

What happens when a standard medical practice is shown to have little evidence supporting its use?


What happens when a standard medical practice is shown to have little evidence supporting its use?

It’s unlikely you missed the recent reports claiming flossing can be abandoned with no detrimental effects to your teeth or gums. I admit that for a millisecond after hearing the news, a little part of my brain did a happy dance. Who likes flossing, right?

Apparently the US Department of Health and Human Services dropped the recommendation to floss last year on the basis there was no robust evidence in its favour. It’s the sort of “gotcha” story the lay press love – you can almost feel their glee – and in fact it was Associated Press that put in an FOI request about the evidence in the first place.

As we’ve heard, there wasn’t a lot. A 2012 Cochrane review found some evidence flossing can reduce the risk of gingivitis, insufficient evidence it helps or hinders in reducing plaque, and almost no evidence on its effect on dental caries.

While some dentists came forward disputing claims we can toss the floss, it was largely with anecdotal data. But it may turn out that flossing is useless – it wouldn’t be the first time a standard practice has later been proven ineffective.

Stenting for stable coronary artery disease was a multibillion-dollar industry before it was found to be no better than medical management. And what about arthroscopy for osteoarthritis of the knee, or vertebroplasty for osteoporotic fractures?

There are lots more, and we need to know about them. Such practices waste time and resources, and can even endanger patients. This is why we need initiatives such as Choosing Wisely’s call to identify practices that should no longer be offered.

I doubt this will be the case for flossing, however. As we know, absence of evidence doesn’t equate to evidence of absence. In other words, just because there’s no proof flossing is useful doesn’t mean it isn’t.

Or is it the case, as dentists may claim, that this is an instance where no evidence is needed?

A tongue-in-cheek BMJ article once made this point about parachuting. Called Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials, the authors found a dearth of trials.

In conclusion, they wrote, “everyone might benefit if the most radical protagonists of evidence-based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute”.


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