The flossing debate and what to make of it
LEIPZIG, Germany: Last week, a story by the Associated Press (AP) claiming that the benefits of flossing have never been properly researched went viral. The resulting extensive media reports have taken one message from this: flossing is overrated. Is it really that simple though? This article attempts to summarise recent reporting on the topic and reactions by the dental community around the globe.
“There’s no solid evidence that flossing actually works”—this statement by his son’s orthodontist gave US reporter Jeff Donn the impetus that started the entire debate. Investigating this issue further, the AP national writer found out that since 1979 the US federal government has recommended flossing, first in a surgeon general’s report and later in the Dietary Guidelines for Americans issued every five years. “A combined approach of reducing the amount of time sugars and starches are in the mouth, drinking fluoridated water, and brushing and flossing teeth, is the most effective way to reduce dental caries,” the 2010 guidelines state.
Because these national recommendations must be based on scientific evidence under the law, Donn asked the US departments of Health and Human Services and Agriculture for their evidence under the Freedom of Information Act. In their response to the AP, the government acknowledged that the effectiveness of flossing had never been sufficiently researched. The flossing recommendations were consequently excluded from the 2015–2020 dietary guidelines. However, the same applies to the advice to drink fluoridated water and brush one’s teeth, which were both removed from the latest guidelines—yet nobody has concluded from this that toothbrushing is a negligible part of oral hygiene.
To be objective, existing research about the effects of flossing is weak, of low quality or has a moderate to large potential for bias (having been conducted mainly on behalf of companies that manufacture floss), several review studies have found. As one of the many dental professionals commenting on this fact, Dr Wayne Aldredge, President of the American Academy of Periodontology, acknowledged the weak scientific evidence and the brief duration of many studies. However, he still urged his patients to continue to floss in order to help avoid periodontal disease. “It’s like building a house and not painting two sides of it,” he explained in an interview. “Ultimately those two sides are going to rot away quicker.”
Just like Aldredge, dentists and dental associations around the globe have issued statements—for the most part vigorously defending flossing as an effective way to help remove plaque and food build-up between the teeth and thereby lower the risk of developing gingivitis, periodontitis and tooth decay. For example, the American Dental Association (ADA) stated that “a lack of strong evidence doesn’t equate to a lack of effectiveness”. Moreover, the ADA stressed that the Department of Health and Human Services reaffirmed the importance of flossing in a statement to the ADA on 4 August, stating that “professional cleaning, tooth brushing, and cleaning between teeth (flossing and the use of other tools such as interdental brushes) have been shown to disrupt and remove plaque”.
The German Dental Association stated that flossing remains an important means of cleaning interdental spaces, especially the narrow spaces of the anterior teeth. According to the organisation, current studies have neither demonstrated nor disproved the effectiveness of flossing. Nevertheless, patients should not conclude that less thorough dental care is advised.
Dr Øyvind Asmyhr, head of the Norwegian Dental Association, acknowledged in his statement: “There is much we do in medicine and dentistry that is not evidence-based, but that does not mean it does not work. All sense and clinical experience suggests that daily brushing combined with flossing helps to reduce the amount of biofilm (bacteria coating) on all tooth surfaces, which prevents the development of caries, gum problems and bad breath.” Moreover, Asmyhr remarked that until research conducted over longer periods proves the contrary, the dental association will continue to recommend flossing and sees no reason for people to change their oral health routine.
Commenting on the debate as well, the British Society of Periodontology emphasised that the evidence supports the use of small interdental brushes for cleaning between the teeth, where there is space to do so, in preference to flossing. In addition, the organisation referred to the official recommendation to patients agreed on during the 11th European Workshop in Periodontology on the prevention of periodontal disease in 2015: “Daily cleaning between your teeth using special interdental brushes is essential for treating and preventing gum disease. Floss is of little value unless the spaces between your teeth are too tight for the interdental brushes to fit without hurting or causing harm.”
Taking all these opinions into account, what is it that patients and dentists can take away from the current discussion? Regardless of deficient study designs, inconclusive results or media sensationalism that picked up on only a tiny part of the underlying facts, there are at least two statements regarding flossing that can be acknowledged universally: First, flossing can cause harm if performed incorrectly. For example, careless flossing can damage the gingivae, teeth and dental work. Moreover, there is evidence that floss can dislodge bacteria that may invade the bloodstream and cause dangerous infections, which is especially of concern in people with a weak immune system. Second, common sense suggests that common oral problems such as caries and inflammation in the interdental spaces can be avoided solely by removing debris between the teeth, which makes flossing beneficial for one’s oral health regardless.
Maybe the entire debate is best summarised with the words of Dr Tim Iafolla from the US National Institutes of Health, who said that, if the highest standards of science were applied in keeping with the flossing reviews of the past decade, then it would be appropriate to drop the flossing guidelines. However, he continued: “It’s low risk, low cost. We know there’s a possibility that it works, so we feel comfortable telling people to go ahead and do it.”