After I started using a water pik, my dentist switched from recommending I return every 4 months, to every 6 months, without me telling the dentist that I was using the water pik.

I observe a clear difference in my gums, which appears to be due to the water pik, but I don't know whether it affects cavities.

[ Question ]

Should I floss?

by willbradshaw 2 min read24th Dec 201910 comments

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[Content note: This post seems to have ended up somewhere between a very long question and a very uncertain post, so I'm not sure where it belongs.]

I don't floss, and have never managed to maintain any interdental cleaning habit for more than a few weeks. Apart from enduring the standard admonitions from the dentist every six months or so, this has not yet caused me any issues. However, I'm starting to feel I should either start flossing (or using some alternative method) or decide not to, rather than just feeling vaguely guilty about it. So here I am to seek advice.

The main reason I'm not sure what I should do here is that when it comes to flossing, we seem to be in the unusual situation where the preponderance of evidence runs squarely against the very strongly stated position of basically every dentist and dental association in the world.

The dental profession seems to be unanimous in its belief that everyone should absolutely floss, and its stated reasons for believing this make intuitive sense: the bacteria that damage your teeth and gums don't care where they grow, and if you don't clean in between your teeth they'll happily accumulate there and cause progressive damage over time. Also flossing is cheap and easy and, like, teeth are really important y'all, don't take the risk.

The trouble is, the empirical support for this position just isn't there. There doesn't actually seem to be much evidence that flossing improves, well, anything really. The biggest recent story on this is this AP broadside from 2016, which claims that there is little evidence for any benefits from flossing, and what evidence there is is weak and low-quality; you can find links to the most-relevant recent studies there. But there seem to have been concerns about the evidence base for flossing going back decades, which dentists have ignored because the impact of flossing seems so obvious to them.

Last time I looked into this a few years ago I found a great post from some dental association being like "okay we admit we're really confused about the results coming out of these studies, but seriously we dentists can all tell the difference between people who floss and those who don't and the mouths of those who do look much better". I can't find it now, which makes me sad, because 100% of the rest of the response to these evidentiary concerns is dreadful. "[W]hile the effectiveness of flossing isn’t proven, it’s also not disproven, at least not yet". "We know there’s a possibility that it works, so we feel comfortable telling people to go ahead and do it". And so on. I know reversed stupidity is not intelligence, but it's hard for me not to take responses like these, often from very highly-placed dentists, as evidence that the pro-flossing position is very flimsy.

One point made in that post I can't find (which is also referenced here and here, is that there is some evidence for (fairly small) benefits from regular professional flossing, but much less for either regular amateur flossing or irregular professional flossing. This might resolve some of the confusion: really good flossing might have benefits (though I'm guessing smaller ones than dentists seem to think), but only if it's done well, and people are bad at it. But since we have yet to reach a post-scarcity society where everyone has their own professional robot dental hygienist, this seems to be a point for the anti-flossing side.

Finally, I think it's worth pointing out that flossing is certainly not cost-free: it's unpleasant for lots of people, requires substantial time investment to learn the technique, and imposes a significant aggregate time cost when aggregated over your life. Alternatives that are easier to use, like interdental brushes or easy-picks, are much more expensive. And that's excluding the effort required to emplace a lasting habit. Despite the universal and loud exhortations of dentists everywhere, a lot of people (one-third of Americans, two-thirds of Brits) don't floss, which seems to belie the claim that the costs of flossing are trivial.

All of this may suggest that I'm coming down hard on the anti-flossing side. Certainly my best guess is that the benefits of flossing are substantially smaller than dentists seem to think, and that the loud claims about it being essential to basic dental hygiene are overblown. But it does make me pretty uneasy to set myself so strongly against the beliefs of what seems to be a large majority of direct subject experts in this domain, and despite what I said in the previous paragraph the cost of not flossing if they're right does seem higher than the cost of flossing if they're wrong. More generally this seems like a good case study in making decisions in the face of uncertainty: probably people who already have a flossing habit should keep it, but what about people who have never flossed, or those like me who have repeatedly tried and failed to build a lasting habit? I'm interested in hearing the community's views on this.

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8 Answers

From A Network Meta-analysis of Interproximal Oral Hygiene Methods in the Reduction of Clinical Indices of Inflammation:

The present BNMA enabled us to quantitatively evaluate OH aids and provide a global ranking of their efficacy. Among 10 IOH aids, interdental brushes and water-jets ranked high among the aids for reducing gingival bleeding. Unsupervised flossing did not yield substantial reductions in gingival inflammation. The present findings are aligned with the recommendations set forth following a consensus meeting during the 11th European Workshop in Periodontology3 that forced the periodontal community to rethink the recommendation for flossing across groups and levels of periodontal health. The present work corroborates the recommendations derived from the workshop proceedings, which state that flossing cannot be generally recommended for managing gingivitis except for sites where the interdental space is too limited to allow the passage of an interdental brush without trauma. In fact, our meta-analysis did not limit the selection to interproximal hygiene aids to interdental brushes and floss but also suggested that water-jet devices and potentially toothpicks, when used under intensive oral hygiene instruction, may be beneficial homecare aids in the management of gingivitis. Given the prevalence of gingivitis, providing the general public with efficacious alternatives to flossing would likely have significant public health impact.

Flossing has received the most attention among IOH aids and is highly recommended by dentists and dental associations alike due to its conceptually superior capability of removing plaque for interdental areas.50 Therefore, a word of caution regarding the interpretation of findings from the present study is important. The present NMA does not refute the efficacy of flossing for removing interproximal plaque around teeth. The challenge of performing a technically-demanding OH habit51 such as flossing may help explain it’s relatively poor ranking against other IOH aids. When performed effectively, flossing is likely an efficacious approach against gingival inflammation and potentially dental caries.52 For example, one study confirmed that daily (weekdays) professional flossing can prevent the incidence of caries in schoolchildren by 40%.52 Nevertheless, trials assessing the efficacy of self-administered flossing and dental caries have largely failed to show any effect.53 These findings support the hypothesis that flossing is indeed efficacious, but its effective application is elusive. Our results support that dental floss is not the quintessential IOH method. Persons that are effectively using floss should not be instructed to discontinue their OH habits. Importantly, as suggested by our findings, other OH adjuncts actually have an increased likelihood of being effective in reducing gingival inflammation, such as interdental brushes, waterjet devices and dental toothpicks with the appropriate OH instruction.

I personally use a water-jet (Waterpik) and it works well for me in terms of both hedonics and dental health results. (I googled for "waterpik meta analysis" and this paper was the first result that came up.)

Suggestion: floss half your mouth and see if the dentist can tell the difference.

I did this with both a water pik and floss (apparently I never wrote that up) and my hygienist definitely didn't notice.

One thing they did notice, and has some experimental backing, was oral probiotics.

I went from rarely flossing, to flossing every night, when I started trying to set an example for my eldest child. When my new baby was born, I neglected flossing for several weeks, since doing things with a new baby is hard. I promptly experienced unpleasant gum problems that I doubt are coincidental, and have put in more effort towards flossing on a daily basis.

I stopped flossing over 20 years ago to no noticable detriment. My hygienists are unable to tell that I don't floss, other than that I admit it. I do use an electric toothbrush with interdental bristles, though.

Going without technique might simply damage the gums sufficiently to outweigh the benefits and more.

Proper flossing that will not damage the gum is relatively easy to learn.

I would guess that most aren't even trying to learn how to floss......

This may muddy the evidence

Dentists recommend: Mouth wash (my dentist friend told me "it's good") Using toothpaste.

I've looked into the literature 5+ years ago. Looks like both of those pieces of advice aren't based on any evidence (definitely not solid, but I recall no evidence rather)

Flossing and brushing co-occur. So it's less easy to collect at least anecdotal evidence.

Well, there’s a doubtful benefit, but the cost of flossing is very low: less than $10 a year in flossing supplies. The time cost is negligible because you can combine flossing with other activities you’d be spending time on anyway, like reading or watching videos. YMMV, but I don’t find it unpleasant—mildly satisfying in fact.Also, be aware that if you find it unpleasant, that may change as you get used to it. So the cost benefit calculation winds up positive for most people, although maybe not for you if you find it very unpleasant and that doesn’t go away after some time.

First, when I don't floss, my gums bleed when the hygienist starts working on my mouth. Indeed, if I don't floss for 10 days or so, my gums bleed when I start flossing again. There is absolutely no question that it's noticeable when I don't floss. Given that, I have to conclude that on some level flossing is "toughening" my gums. I view that as a good thing.

Second, I floss after I have brushed my teeth. But after I've brushed my teeth, and before I floss, I rinse. So I expect my mouth to be somewhat clear of food bits. But then, when I rinse again after I've flossed, I see more leftover food bits coming out of my mouth. So I have to conclude that on some level flossing is improving my oral hygiene.

Third, I have read several times -- most recently in the 23 December NY Times article, "Tackling Inflammation to Fight Age-related Ailments -- that periodontal disease can be a source of chronic inflammation, which in turn is thought to be bad. Routine dental cleanings are recommended, and I put flossing smack square in there (see reason #2). From this perspective flossing is a simple expected value proposition. The potential benefits of flossing far outweigh anything that can possibly be gained from not flossing.

In the same way that making my bed is a great way to start the day, for me flossing is a great way to end it. After I've flossed I feel as though I've dotted the last "i" and crossed the last "t" in a day well-lived.