Recently the Department of Agriculture and Health and Human Services quietly removed the recommendation for flossing from their dietary recommendations. This has lead to an onslaught of tantalizing stories claiming that we have all been lied to. Just look at these headlines:
Feeling Guilty About Not Flossing? Maybe There’s No Need The New York Times
A Big Problem With Flossing CBC News
Is Flossing Bulls**t? Vice.com
Or this doozy (we will get back to this one later)
As usual, the reality is not as exciting as the headlines make it seem. Let’s see if we can unwind the confusion a little bit. It is much easier to write a short story with black and white statements based on fuzzy logic than it is to discuss nuance and proper evaluation of evidence. So bear with me, this will take a few minutes.
Quality of Evidence For Flossing
I am a proponent of evidence informed dentistry and medicine. Let’s just get that out here and acknowledge my biases. Never-the-less, much of what we do in dentistry is based on poor quality research. To most dentists this is old news! In my circles of dental nerdom this topic has been discussed many times, and while there are major efforts to improve the quality of our evidence and how we evaluate it, I wouldn’t hold out hope for any breakthrough new research any time soon.
The Cochrane Organziation publishes large scale reviews of literature and this is their final conclusion regarding the evidence surrounding flossing:
There is some evidence from twelve studies that flossing in addition to toothbrushing reduces gingivitis compared to toothbrushing alone. There is weak, very unreliable evidence from 10 studies that flossing plus toothbrushing may be associated with a small reduction in plaque at 1 and 3 months. No studies reported the effectiveness of flossing plus toothbrushing for preventing dental caries.
If you are anything like I was when I first read this 4 or 5 years ago there are probably questions swirling around in your head. How can we recommend something with so little evidence? Have I been fooling myself all these years? Does this mean I can fall asleep watching TV with less guilt? This doesn’t look good does it.
Before we decide to throw out the floss with the bathwater let’s look at why we lack good studies. Most diseases we are trying to prevent with flossing take years or decades to develop. This means that we need really, really long studies, and in those studies we need people who commit to not flossing. For a study like this to work we need a very large population of people, committed and well funded research facilities, and a university ethics committee willing to sign off on asking thousands of people to skip something generally agreed upon to have significant health benefits and minimal side effects. Also, it seems the government and private research funds would rather spend the money required to do this on more pressing challenges like curing cancer. As much as I love teeth I can’t say I blame them.
Sadly, it is true. There is not a lot of evidence to support the health benefits of flossing , but hang with me here.
The Great Appeal to Ignorance Error
If you read all the headlines the argument seems to go like this: “Flossing is useless because it hasn’t proven to be beneficial.”. This is called an Appeal To Ignorance and is an error in Logic where one asserts that something is true because it hasn’t been proven to be false, or something is false because it hasn’t been proven to be true.
Remember that headline mentioned earlier that read “Flossing:Dental cleaning habit offers few medical benefits, review says”. This is a perfect example of this logical error and is ABSOLUTELY THE WRONG CONCLUSION. The reality is much less boring: We need more research. I guess the headline “We need more evidence to prove that flossing is beneficial” just doesn’t make as good of a story……….
Now, before I go too crazy with this idea, let’s be clear that this is dangerous ground in the world of evidence based medicine/dentistry. There is a lot of crazy stuff sold to the public on the grounds of “you can’t prove it doesn’t work” In order to stand behind a treatment recommendation in the absence of good evidence we have to have some other rationale or circumstantial evidence (see below)
The Circumstantial Evidence
We have established that based on direct scientific studies alone we can’t necessarily make a statement that flossing is beneficial, but also can’t claim that it is useless. How are we left to make this decision then? Sometimes there are things we do in medicine and life that, while not proven directly, have a strong basis in biology and we should deduce
there is a benefit until proven otherwise.
Think of it this way; we don’t have well designed studies that prove parachutes are necessary to survive jumping out of an airplane, but who wants to volunteer to be in the control group that jumps out of a plane without one?
In dentistry we have a pretty good idea that bacteria plays a role in the progression of periodontal disease (along with genetics, and a host of other things like tobacco use). At the risk of oversimplifying it, our best models go something like this:
Bacteria around your gums >> inflammation due to immune response >> inflammation and Immune response disrupts natural bone renewal >> This disruption causes a slow break down of the bone support for teeth >> eventual tooth loss due to Periodontal disease
There is also the model for cavities (which we have much better evidence for by the way)
Bacteria + sugars >> Acid produced by the bacteria >> Acid eats a hole in your tooth (cavity) >> eventual tooth loss due to cavities
Common to both of these scenarios are bacteria. It is reasonable to conclude that controlling and reducing the bacteria around our teeth will help to reduce the end disease. This is an example of a Biologic Rationale for treatment, and biologic rationale is the first step in evaluating a therapeutic claim. Despite our lack of hard evidence for therapeutic benefit, what research available has uncovered nothing to contradict this notion of a Biologic rationale for controlling bacteria. The kicker to this whole debate is that there are minimal to no known side effects from flossing properly (unless you do it too aggressively). It’s almost all upside.
Flossing has been around for a long time, and I doubt the recommendations from dentists and dental organizations will change any time soon. I for one would love to see better studies, but unless something more definitive comes along I wouldn’t suggest giving up flossing just yet.
I stand behind the recommendation for flossing, just as every dental organization does. It has minimal side effects, there is good biologic plausibility for a benefit and based on decades of observation it appears to have a benefit. Remember, the Surgeon General and the Department of Agriculture and Health and Human Services didn’t actually say to stop flossing they just raised the bar of what they require for their recommendations. I support such measures because it keeps many dubious medical claims out of our policies. The therapies without strong evidence must make a claim for benefits in other ways. I hope I have done this for flossing here.
-Dr David Wetherington is a private practice general dentist in Arvada, CO. We are accepting new patients, so if you have the need, please call us at 303-463-8570
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