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Based the fact that Londero 2022 seems to have reasonably sound methodology (in terms of blinding, randomization, preregistration etc), and seemingly addresses one of the key critiques of most of the studies in the 2019 Cochrane review (studies on gums that are otherwise pretty healthy) by looking at rates of Gingival Index >= 2 ("moderate inflammation: redness, edema, and glazing, or bleeding on probing", which does seem a desirable state to avoid), I'm starting to be talked round to resolving yes. I'll consider doing so next week, to give no-holders some time to talk me down in the meantime.

Does flossing with a water flosser count?

@a2bb I had in mind dental floss.

Ok, we have plenty of time to research it before 2187.

Currently thinking that I wouldn't resolve to yes until, for example:

Cochrane study or similar has something like medium-confidence that flossing reduces something like periodontitis or cavities that seemly clearly unhealthy.

Welcome people's thoughts.

@CalebW

I wouldn't have bet and locked away as much mana if I didn't expect a relatively prompt resolution, but maybe that's on me. Regardless though, I do think @JayBaxter answers your market question as you originally wrote it.

@snazzlePop

Fair enough - I did try to manage expectations with a 'preliminary' and 2187 resolution date.

I think I'd be happy to resolve based on Jay's study if someone can point me to evidence that reductions of the gingival index of the levels found Jay's study have non-trivial health benefits. Conversely, given that Cochrane circa 2019 hadn't found any studies sufficient to give them medium confidence, I'd also be open-minded to the possibility to hearing out any case that the Jay study might not be 'gold standard'.

@snazzlePop Happy to float you or maybe provide some exit liquidity if you're feeling stuck in the market.

@CalebW my read of Jay's study (I only read the abstract because the full text is paywalled) if translated into a sentence or two, would be: "swelling, redness, and bleeding of the gums was significantly reduced by flossing, even when everyone involved including the control group got personalized teeth cleaning advice and regular plaque removal".

A gingival index of 2, which is where the subjects started, involves moderate redness, swelling, and bleeding on probing. I would consider "my bits are less red and swollen, and less prone to bleeding when touched" to be a non-trivial health benefit for any bit outside of my mouth, and although as I mentioned in an earlier comment I have not always been equally concerned about gum swelling and bleeding, this was an inconsistency on my part, not like, reasonable medical advice.

@equinoxhq The study's downloadable at researchgate: https://www.researchgate.net/publication/360119884_Efficacy_of_dental_floss_in_the_management_of_gingival_health_a_randomized_controlled_clinical_trial

@CalebW thanks for that. I see my understanding from my reading of the abstract needed some nuancing - the flossing subjects seem to have started with a GI of 2 in 37% of sites, and that was reduced to 16% after 30 days, while the toothbrushes only group started at 41% gi =2, and reduced that to 23% of sites after 30 days. The overall gingival index went from 1.4 to 1.1 for flossers, and went up from 1.4 to 1.8 for those who only brushed. If I'm reading it right.

Still, it does seem to show an effect. And the Cochrane review also showed most studies they looked at showed positive effects from flossing, it's just their confidence in those results was not high.

Personally, if I was asking myself "does intervention X work" and running a Manifold question about it, and after some looking the best answer I could find was "studies seem to point to yes, but for various reasons that vary by study the confidence in that answer should not be high" then I would resolve it to either yes or N/A, but not no. If the study results came to conflicting conclusions, I might be more prone to resolve no, but still might resolve N/A, as to me a clear "no" result needs grounds to say "there is evidence this does not work", rather than "no studies have been done" or "results of studies were mixed or sketchy". The question you seem to be trying to answer is "is there hard evidence that allows us to be confident flossing works at a populstion level". You did make that clear in your preliminary resolution criteria, which everyone should have read before betting, so, fine, but it's not the impression one would get from the question title. It reminded me of this SlateStarCodex essay about headlines that say "there is no evidence for x", which can mean either "we don't know whether x is true or false, so null hypothesis" or "we know x is false". Specifically what came to mind was Scott's discussion of the claim that there is no evidence parachutes work, because a proper study where some people jumping out of planes are in the "no parachute" control group, has not been done.

https://www.astralcodexten.com/p/the-phrase-no-evidence-is-a-red-flag

There's plenty of evidence parachutes work, without a randomized controlled trial, and in a somewhat similar way it's easy for anyone to get evidence that flossing works for themselves, so some participants in a market like this may feel you're not being reasonable if you resolve No on the basis of weak scientific studies. I think it's pretty fair play if you follow your own clearly stated resolution criteria and resolve No on parachu... flossing working if you make a good faith effort to find studies that meet the level you set out in your resolution criteria, and none exist. But, going "this study satisfies me that flossing works, but making gums bleed less is trivial so I'm going to resolve no" seems sketchy, so you'd need to clarify why Jay's study doesn't meet you bar if it doesn't, and also, cost-benefit analysis seems very open to gaming to get a particular result, so if you're open to clarification of what would be worth it to you from a benefit perspective up front and what would not, that would likely be helpful.

@equinoxhq yeah, to be clear, no is definitely not on the table at the moment based on what I'm aware of, given the weak positive evidence and lack of definitive null evidence

@CalebW ah, good. "No if it doesn't" could have meant "yes if a high quality study says yes, no if a high quality study says no, undefined otherwise" or it could have meant "yes if a high quality study says yes, otherwise no". I was leaning toward the latter interpretation of how you would resolve until I read this comment.

I mean, having once done a quick self experiment (2 weeks no flossing, see what difference it makes)... yes?

Having flossed inconsistently for years and observed that every time I went to the dentist my gums bled an unpleasant amount and it was painful, but now that I floss consistently my gums bleed 0 or very little and while it's not exactly a pleasant experience to have someone stick tools in your mouth, it's better... same conclusion.

Also having noted how much gunk I can remove by flossing after doing my honest best to clean my teeth thoroughly, leaving that gunk in place seems like a horrible idea that will not end well, so, same answer.

So if a headline result from an RCT was that there was no benefit to flossing, my prior would be that the headline was misleading, they screwed something up, or they were defining "benefit" in a narrow way that excluded the benefits I've seen.

It’s not going to cure your tooth decay, but flossing does clear some amount of plaque and smelly food particles. So it has been common practice to encourage flossing for gingivitis prevention; dentists agree it probably helps clean what brushing alone logically doesn’t. Sure, most flossing-benefit studies have been unreliable or biased, but there’s also little or no empirical evidence against flossing. There are probably better alternatives, but I can’t think of any potential hygiene measure not worth one minute of your time.

First hit on Google for floss RCT for me shows that it significantly improves gingival inflammation https://pubmed.ncbi.nlm.nih.gov/35451656/

@CalebW

I think this satisfies your 'Yes' criteria.

In addition, here's some further evidence indicative of flossing having benefits (albeit not a RCT): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7375740/

It does make your breath less bad though