Recommendation: Floss once per day.
Every dentist has told me to floss, and it involves no risk, but I was still following the advice blindly (which I’ve found is a cardinal sin when it comes to health–question everything!) The part about cleaning out particles of food from between teeth makes perfect sense, so I don’t need evidence to back that up. On the other hand, I can’t help but wonder what people did before there was floss. Did they just lose teeth and contently suffer from gingivitis? Or were grass and splinters enough to get the job done? Or, do the sugar-loving bacteria in our mouth thrive on our modern diet? Whether the need to floss is recent or basic, I just want to know if it is as important as dentists say, and whether or not I must do it daily. Luckily I found evidence to support the recommendation. It even seems possible to get partial benefits from only flossing every other day, as discussed below…
Lower chances of death?
Published in 2011, research from a 17-year observational study of 5611 adults (52 to 105 yrs old) shed light on the importance of flossing independent of brushing. In other words, brushing alone is significantly riskier than brushing and flossing (even occasionally). Further, flossing and never brushing is healthier than doing neither. This establishes the reason to floss. Specifically, subjects who reported flossing daily enjoyed a 25% reduction in mortality risk over those who never flossed (adjusted for nightly brushing). Though this was just observation/correlation (not causality), it was also adjusted for “age at entry, smoking, alcohol, caffeine, active activities, other [lifestyle] activities, body mass index, high blood pressure, angina, heart attack, stroke, diabetes, rheumatoid arthritis, and cancer”.1 Health risk of not flossing was similar, in men, to that of not brushing (1.25 to 1.29) and was even higher in women (1.29 to 1.18).
Interestingly, use of mouthwash had no significant effect on risk of death. Caution: the phrases “mortality risk” and “risk of death” (terms used in these types of studies) can be misleading, as probability of death remains 100% in all subjects (and always will).
Improved gastric health
In 2012, research reported a link between daily and periodic flossing and gastric lesions. It was also the first study to report the association between gingival bleeding and gastric lesions. The study wanted to find evidence to support findings from Japan, China, Finland, and Turkey which reported links between dental health and gastric cancers. Among 131 subjects who underwent upper endoscopy procedures:
“The [odds ratio] for having gastric precancerous lesions was 2.89 [95% confidence interval (CI) = 1.09–7.64], comparing participants who did not floss regularly with those who did, after adjustment for age, sex, race, education attainment, body mass index, smoking status and H.pylori status. This pattern of association was similar when we considered frequency of flossing. Compared with flossing once per day or more, the ORs for gastric precursor lesions were 1.66 (95% CI = 0.41–6.78) and 3.40 (95% CI = 1.14–10.1) for individuals who flossed every few days or weeks and those who did not floss (P value for trend = 0.08), respectively.”2
In the discussion at the end of this study, it’s suggested that oral bacteria contribute to the development of various carcinomas as a result of inducing chronic inflammation. Therefore, it reasonably follows that proper dental hygiene can help reduce this risk. Even though it’s all observational data or conjecture, and I haven’t found any double-blind studies on it, flossing is so easy and cheap that there’s no reason not to do it.