To floss or not to floss

To floss or not to floss : That is the question!

What happened?

I have a patient who is very aware and well informed. I found out that she had stopped flossing. She reported that she has read news reports in blogs and news network websites, based on the latest evidence, that floss is a waste of time and it does not really work. She quoted from the likes of New York Times, the Guardian, the Daily Mail; which she looked up online and showed me on her phone during the appointment. She was right, there were reports and these reports quoted high quality research. I informed her that I will get back to her in next appointment, once I read and understand the research behind it. I also informed that personally, it was hard to believe this news but I would look into the evidence as an unbiased layman, to understand the issue from her point-of-view, and educate myself as well.

How can it be explained? What is the evidence?

I looked into the news reports. The links to the reports can be found in the references. I followed the links to the research articles that they provided, and read those articles. These were based on 2 systematic reviews, one was in the Cochrane Database of Systematic Reviews, the other was published in the Journal of Clinical Periodontology.

The news reports quoted the exact words and implied their meaning to what it means to them. The conclusion of the review said: “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.” So let us explore what “weak, very unreliable evidence” is defined as? Cochrane reviews use GRADE approach (Grades of Recommendation, Assessment, Development, and Evaluation), which is a way that investigates the quality and quantity of the evidence. “Weak” comes from the GRADE approach, which says that the quality of the studies, collectively, based on the objective assessments do not allow us to make a strong recommendation. It goes from high, moderate, weak and very weak recommendation. Then, “very unreliable” comes collectively from GRADE approach and Cochrane RoB (Cochrane Risk of Bias) tool. It talks about the quantitative analysis, taking into account, the statistical and clinical significance of the outcomes. The reviews mostly looked into the plaque and gingival indices (plaque is tartar on the tooth which is a biofilm of bugs and plaque index is a number given to the amount of plaque present on a tooth. Gingival index is breakdown of gums assessed with redness present and bleeding when you tease the gums) as outcome measures, and how numerically they were affected by using floss, and how clinically significant that could be.

Evidence of absence is not the absence of evidence and the actual inference here is that we do have evidence, though low-quality, and it does show that there is beneficial effect of using floss against plaque. I went through all the other systematic reviews on the subject, to find out mixed results. The quality of the reviews also varies, and it is imperative to have high quality reviews in oral health care. In the next appointment with the patient, when we spoke about the issue, I was able to convince her about the importance of flossing and explained her in laymen terms what they exactly mean.

What did the event mean for me? What have I learned?

It is an age of information revolution. We have a lot of information available at a single click of the mouse, or tap of a finger. Our patients read what is out there and ask questions. Sometimes, the language of the research literature is misinterpreted and ideas are wrongly reported by the news reports or even by the patients as well. We should be able to understand not only how to make sense of the literature ourselves but have the patience to explain it in simple terms to the patients.. I encourage my colleagues as well to stay abreast and updated on what is out there in the news about dentistry and how well it is supported by research evidence.


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