I’m sure most of you have heard by now, as recently reported by the media, that the effectiveness of flossing is not, and has never been, proven by science.  We’ve been lied to by Big Floss people!  When I first read those media reports, I thought to myself, “Oh boy, here we go again, another irresponsible report about dentistry”.  The last example was a study that claimed an increased risk of developing brain tumors in relation to the number of bite wing dental x-rays taken.  Well, I took the time to read the actual study and it was complete nonsense, but it didn’t stop the media from reporting the nonsense.  But with that said, I didn’t want to assume that the flossing story was nonsense too, so I looked into it.

Cochrane Study “Flossing for the management of periodontal diseases and dental caries in adults”
This systemic review, which was mentioned in many of the media reports, does show that there is little scientific evidence to support the claim that flossing helps prevent periodontal disease or dental caries.  Well, there you go.  I guess this proves that flossing is a waste of time.  No it doesn’t, and here’s why.

A lack of evidence does not prove a positive claim (e.g. “flossing is ineffective”).  There are good reasons why the needed scientific evidence to “prove or disprove” that flossing is effective does not really exist.

1. There are significant ethical limitations.  Periodontal disease and dental caries, most often than not, develop over a number years.  There is a serious ethical problem with telling a control group to not floss for many years knowing that it would likely cause disease.  Studies can’t ethically do it.

2. Confirming that the study group is correctly flossing everyday over a long period of time is nearly impossible.  The only way to truly confirm patients are flossing everyday is to have dental professionals actually observe the study subjects flossing everyday (or do it for them).  As you can imagine, that would be super expensive, which is why studies essentially rely on self reporting.  But as every hygienist knows, the self reporting of our patients’ flossing habits is pretty much worthless.

3. The act of recommending daily flossing may be ineffective because people just won’t do it.  In this sense, it is not a claim of the actual physical effectiveness of flossing, but really a claim about human behavior.  Some studies come at it from this behavioral science perspective (not the ones mentioned in the Cochrane review).  When hygienists recommend flossing does it actually change patient behavior?  When physicians recommend exercise does it’s actually change patients behavior?  And so on.

The bottom line is this.  There is little scientific evidence to prove flossing is effective because obtaining that evidence is nearly impossible.  But on the other hand, there is plenty of anecdotal evidence from dental professionals that flossing is effective.  It’s not the best kind of evidence, but it’s all we’ve got.  My pediatric patients are always coming up with silly excuses for why they don’t or can’t floss.  This recent media report is just another one of those silly excuses.  Let’s keep it real.  People in the media, like most people, just don’t want to floss.

Links
– Cochrane Study “Flossing for the management of periodontal diseases and dental caries in adults”
– Snopes article: “Flossing Isn’t Backed by Science?”

Mark Frias, RDH