When Should Evidence – Or Rather Lack Thereof – be Ignored?

When the European Federation of Periodontology (EFP) was about to publish their 2014 workshop proceedings, eyebrows were raised in particular after reports of a press conference emerged. I remember that “Flossing may be a waste of time” (as there was no evidence for the prevention of interdental gingivitis found after thorough literature search), but can’t find the respective newspaper article anymore. As Professor Iain Chapple outlined, if there is space in between teeth, interdental brushes would do better as an adjunct to toothbrushing.

We need to be careful how we transmit that message to the public because that is not to say that floss doesn’t have some role to play. But the only role it appears to play is where we have no gaps between the teeth and we have a healthy situation and in that situation it may not be possible to use these other  devices. And where that happens then floss is something that we would suggest is worth using even though we actually don’t have any evidence that doesn’t mean it doesn’t work we don’t just have the studies to prove that it doesn’t work in that healthy situation.

It is worth listening to Chapple’s thoughtful comments on dental floss in its entirety.

A couple of days ago, the Associated Press has repeated the statement (“Flossing is a waste of time”) even adding, it might be harmful.

Last year, the Associated Press asked the Departments of Health and Human Services and Agriculture for their evidence [about dental floss] and followed up with written requests under the Freedom of Information Act.

A total of 25 studies were assessed by the AP which mostly compared toothbrushing with toothbrushing in combination with dental floss. They concluded (as previously the European group) that evidence for flossing was “weak, very unreliable,” of “very low” quality” and carries “a moderate to large potential for bias.”

In the AP article, further claims are made.

Floss can occasionally cause harm. Careless flossing can damage gums, teeth and dental work. Though frequency is unclear, floss can dislodge bad bacteria that invade the bloodstream and cause dangerous infections, especially in people with weak immunity, according to the medical literature.

Well, it seems so as if the old adage “Floss or die” is right now being replaced by “Floss and die.”

While these messages went viral and were even repeated in the mass media, the EFP has so far been silent on the revived issue while the American Academy of Periodontology (AAP) published, on their webpage, a statement in favor of flossing.

As its President, Dr. Wayne Aldrege, correctly states, “Flossing is an effective and useful way to remove the plaque, especially in between the teeth or under the gum line-places where a toothbrush cannot reach.”

But how should one judge the lack of evidence in this case? It may surprise some EBM advocates but most of dentists’ daily work actually lacks sound evidence. Nevertheless, it has shown to be effective. I have posted here on this blog years ago a stunning short video showing a monkey mom teaching her offspring how to use tourists’ hair for kind of flossing teeth. When mother Nature recommends, isn’t that the ultimate proof of evidence? Poorly conducted dental studies with high risk of bias should be repeated properly. If a systematic review of high-quality randomized controlled studies yields a strong effect, it has the potential to end a story once and forever. If it turned out that only low quality studies were available with high risk of bias, this would indicate an area for new research. I would expect a new definitive, long-term, multi-center trial which would have the potential to answer an important question: whether some patients or subjects are to be advised to floss.

12 August 2016 @ 1:35 pm.

Last modified August 19, 2016.



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