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Comment by asdff | Hacker News Reader

If you ever get treated at say a dental school, where they will have roving faculty each giving their own opinion to the dental student over your open mouth, you will learn there is so much subjectivity in dental practice. One point of contention is about when to do intervention. Some doctors want the procedure done because they believe the risk of not doing so is large. Others might say you've gotten by this far alright and maybe only intervene if things turn for the worse, better to keep your real tooth as long as you can. Some dentists might want to see a lot of x ray imagery and retakes until their ideal perspectives are captured, others weigh the risk of irradiation and favor taking as few as possible. Any restorative work is very much an art vs a science, some hands are genuinely more skilled and some might take a few redos to get a repair to not break in 2 days from the demands of your natural bite. They might even look at the x ray image of a past root canal from knowledgeable hands like we might the statue of David, showing it to other staff in amazement.

About the only thing that seems to be in agreement across the board is flossing and brushing your teeth.

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With modern X ray imaging devices I feel like the dangers of irradiation from dental imaging are probably quite low. If nuclear hormesis holds up, you may actually be better off getting the imaging done.

The problem is the same as the CT scan: as much as my health anxiety would love another set of CT scans to feel relieved about, even if they do find something potentially interesting it may be worse to act on it than to do nothing, while leaving other things that can't show up on imaging unnoticed, potentially diverting attention and giving you a false sense of security.

YouTuber and doctor Dr. Bernard "Chubbyemu" Hsu recently covered an upsetting example to demonstrate how doing additional routine scans wouldn't have helped and may have harmed in a specific sort of scenario that I'm sure many of us fear from time to time. It doesn't prove or even assert that such scans would be useless, only that they are far from a panacea and that it isn't settled science that we'd be better off with it.

https://youtu.be/YDYMMgyN4k0

And to me, I think that ties into how we're doing dentistry wrong: I think taking routine X rays for patients with healthy mouths, no history of issues and no symptoms is reckless. Maybe it is sometimes beneficial, but every single year as a requirement seems insane. Why not every 3? Are we really catching things early or are we drilling into teeth that are fine? I question it.

Of course, I'm just some chuckle fuck on the Internet with zero dentistry experience, but my knee-jerk is that something seems off here.

> as much as my health anxiety would love another set of CT scans to feel relieved about, even if they do find something potentially interesting it may be worse to act on it than to do nothing

I personally have a preference for having the maximum amount of information available to make a decision.

“Don’t get that “unnecessary” test, it might give you a result that might lead to treatment you don’t need” — hearing this blows my mind every time.

The treatment you don't need might be zero risk, but it might also have quite a bit of it. And some tests carry risks too: See how different countries have very different protocols. The US system, which is colonoscopy first, and where polypectomies will be done at the same time, can end up with bowel perforations when the polyp was not even cancer. So the diferente treatment protocol is not just about costs, but about balancing different risks.

The unnecessary test, leading to an unnecessary intervention, which gets you unnecessary long term issues is a real risk in many cases. It's not just a matter of doing a bonus blood test here or there.

To take it to the extreme:

If there were a risk free button that you could click to see a full breakdown of all illnesses no more how early stage, would you click the button?

It would include a report of cells that may eventually turn into cancer (or may not).

It would include things like polyps, and every other diagnosable condition.

Do you avoid pressing the button? Why?

I forget what this is called in medicine but someone linked about this on HN before. What I remember is this idea that there are so many things _that are wrong with all of us_, at any given time, that calling attention to and treating all of them would be more harmful than helpful. I think bodies being perfectly healthy is probably not how it works, it's more so that all the "bad" happening never rises to an emergent level.

I might avoid it because in reality the odds of it finding "something" are high, and the odds of that "something" being benign are high.

And then it's likely the options are 1) get a non-risk-free test, or 2) have constant anxiety about it (at least in my case)

Unnecessary medical treatments can have serious consequences. Even if you are absolutely certain you have a given condition, some treatments are very not worth it. More importantly, any given scan misses tons of important potential health issues. Not just the fact that CT scans don't show signs of MS vs MRIs, but neither of them will tell you about many cardiovascular conditions. So time spent treating made up issues from CT scans you don't need may be better spent doing other regular exams instead. Meanwhile, many aggressive cancers will be far too fast for any reasonable scan interval to catch in time. (And CT scans, to my understanding, can miss tumors early on, since it can't see as fine of detail as MRIs.)

But surely the mistake is doing the unnecessary treatment, not getting the information in the first place. In the above hypothetical where I could get an impossibly detailed full body scan result for free, I would absolutely do it.

I understand that in practice getting more information often leads to unnecessary treatment, so that in some cases the real world results are better if less investigation is done. But that's not inevitable; it depends on the choices made as a result of that information.

But how do you know the unnecessary treatment isn’t necessary? There is likely always something happening in your body that would suggest an unnecessary treatment. So if you start doing scans when you have no outward reason to, you’ll always find something that looks like it needs treatment.

There’s no perfect information in medicine.

The more scans you do, the more times you’ll make the wrong choice and unnecessarily treat something.

Well, first of all, if it were possible to do these scans on everyone, we would be able to better study what things that show up actually do benefit from treatment, and which are better to ignore.

Absent that, it would be a matter of judgment. Some people do get fairly extensive annual physical exams, so there is data out there. For each issue the scan found, it would be a matter of researching and making a judgment call on whether the risk/benefit weighs toward action. I would prefer to make those decisions with as much information as possible vs just remaining ignorant and hoping the things I don't know about are best left alone.

You don't seem to get it. There is no free lunch in medicine, because the human body and mind would have just discovered the free lunch during evolution and made it part of the bodies' natural healing process and daily routines.

This means all treatments have tradeoffs where you accept some damage to treat other damage and in the end you are mostly converting problems the human body can't deal with into problems the human body can fix on its own.

If you do an unnecessary treatment, you end up with a tradeoff with no benefits.

In the end everything has to follow a cost and benefit model

I think I disagree with your base premise. Evolution isn't magic, and its existence doesn't mean that the human organism is perfect. Even if the process of evolution itself were perfect, for one thing it has nothing to say about the health of the organism after child-rearing is complete, whereas we probably care quite a bit what happens to us at that point.

There's also no reason to believe that every treatment has trade-offs. Many do, but the claim that every treatment necessarily causes some damage in order to treat other damage is provably false. The most straightforward example I can think of is treating something like a vitamin deficiency. But there are plenty of more significant treatments that don't do any appreciable harm while providing significant benefit. Removing a precancerous skin legion, for example.

All that said, my previous comment was not advocating for unnecessary treatments. It was advocating for taking all available information into account when deciding on a treatment plan (or lack thereof). The fact that many treatments involve trade-offs does not seem to me to be a counter-argument.

Can I repeatedly press the button? Because then I'm pressing it, seeing what's up. Trying whatever low evidence/low risk method there is to "fix" it and then pressing it again.

Assuming there's no side effects to pressing the button of course.

Worth keeping in mind that no medical test has a false positive rate of zero, so whether a test is worth doing becomes a statistical question - and the accuracy of some of those tests is different depending on whether a doctor first screened you to be likely to have a certain condition.

If you were to do something like run every cancer test possible then _eventually_ you'll find one that says you have cancer, but it's not a valuable result because statistically one of them was eventually going to say that. I don't think most doctors are doing significant statistical analysis to determine what tests to give you, but the general concept that you don't simply run every test you can for fun is very sound, screening beforehand can rule out a significant amount of false positives while hopefully not significantly increasing the chance that something is missed.

As somewhat more real example, rapid strep throat tests overall rarely give an inaccurate positive result, meaning that if the test shows a positive result you can be pretty confident you have strep throat and need antibiotics. However the false positive rate of rapid strep throat tests is extremely dependent on the patient first being screened for symptoms of strep throat - there are lots of asymptomatic strep throat carriers who have no symptoms but do have the bacteria, they don't need treatment but do give a positive result on the test. Thus if you were to give a rapid strep throat test to an entire school to try and eliminate all cases of strep throat then you'd find that ~10% to ~20% of the school gets a positive result. In that situation at least the tests are cheap and you could potentially resolve the situation over a number of weeks, but not every test is so simple.

Having the maximum amount of information assumes you know which information is useful and relevant. That isn’t always clear in medicine.

Treatments you don’t need can be worse than no treatment.

Assuming you're not a specialized doctor, you're in no position to interpret that information. The person doing the interpreting usually has incentives that are perfectly misaligned with yours. And even assuming no malice, medical professionals tend to overestimate the benefit and underestimate the risk of the procedures they specialize in. One would hope that doctors would be required to be great statisticians, but alas..

> Assuming you're not a specialized doctor, you're in no position to interpret that information.

Why?

That's like saying no one other than a mechanic should be allowed to look under the hood.

Given your preference you really should avoid that test. Science barely understands the human body, despite all the overconfidence and pretense. We do not have “maximum” information about our bodies in any meaningful sense; only half-knowledge that often backfires spectacularly. That is why there is so much subjectivity in doctors’ opinions and such.

The ADA no longer recommends routine x-rays - they should only be taken when there is something specific that needs to be investigated.

TIL. That's good to know, makes me feel a bit better. I'm sure my dentist will want an Xray anyway next time I come in.

Hmm, googling it, it seems like a cross country flight is equal to 40 dental xrays. had no idea it was that low.

There is a reason why Los Algodones has 1000 dentists for a city with population of 5000. It is called Molar City.

Off topic: The idea of a City of Dentists seems like a Grim Fandango [0] kinda thing. Bonus points if somehow "cotton" (algodon) can be worked into the afterlife themes.

[0] https://en.wikipedia.org/wiki/Grim_Fandango

> If nuclear hormesis holds up

TIL of that theory: https://en.wikipedia.org/wiki/Radiation_hormesis

It's fiercely debated but as time goes on it seems like it is at least partially true. I'm guessing that some effects of radiation really do map better to LNT whereas others map better to radiation hormesis; why and when is a mystery, I think. Maybe some folks more vested in this topic have an idea.

The most fascinating example of hormesis I can think of is that after the atomic bombing of Hiroshima, some people who would've received a relatively small dose of radiation seemed to have a slightly lower cancer risk than people who wouldn't have received any additional radiation.

https://pmc.ncbi.nlm.nih.gov/articles/PMC6937943/

I'm sure there is plenty of debate about these studies and their methodology, but I have some suspicions. There seems to have been a lot of handwaving and intentional omission to explain away or ignore why LNT didn't seem to match reality. Radiation hormesis may be an illusion itself, but as it stands it appears LNT is unable to explain experimental evidence sufficiently. We're clearly missing something, and there is a lot of potential conflict of interest, especially given the obvious incentives for the energy sector...

But also, I just read Wikipedia and watch YouTube causally, so hell if I know.

> after the atomic bombing of Hiroshima, some people who would've received a relatively small dose of radiation seemed to have a slightly lower cancer risk than people who wouldn't have received any additional radiation.

What if this is survivorship bias selecting for some common trait that correlates with better radiation tolerance and lower cancer risk (like age).

IIRC, it's based on the distance from the blast radius. The confounding thing about it is the fact that there is apparently a range of distance from the explosion where people have lower incidence of cancer than people who were even further way.

That seems hard to explain.

Death typically hits your heart first.

I am not sure what you mean to say with this but reading back through this thread I'm not sure if what is implied here has come through very well. The idea is that well outside the range of where people died from being evaporated, there was a much larger range of people who were exposed to a lot of ionizing radiation from various sources like black rain. But, then, there's a range where people exposed to relatively low doses but higher than background radiation seem to have lower cancer incidence than average. So there is a distance where it is higher than average, then further away from that, it becomes lower than average, before finally going back to average.

This doesn't necessarily imply that radiation hormesis is the only possible explanation, but the easy hand-waves are all basically out. Something weird is happening here and it seems to repeat in different circumstances, too. There is not much to go on other than confounding results and proposed mechanisms as far as I can tell.

Last I checked, actual evidence that flossing is helpful seems pretty limited.

" In light of the results of this comprehensive literature search and critical analysis, it is concluded that a routine instruction to use floss is not supported by scientific evidence."

https://pubmed.ncbi.nlm.nih.gov/19138178/

I regularly get food particles out of my molars using floss that brushing wouldn't have been able to, so for me it works.

https://pubmed.ncbi.nlm.nih.gov/35451656/

Conclusions: Interproximal gingival inflammation may be significantly reduced by toothbrushing alone, the effect being significantly enhanced when toothbrushing is combined with dental floss.

I have always been an infrequent flosser, but deep down I've hoped for something like this to reach mainstream scientific consensus for a while so I no longer beat myself over it. Fingers crossed this is not a skewed study

At my dentist’s recommendation I’ve been using Proxabrush every day. It is very important not to force it, and my teeth are very tight so I had to get the smaller ones (I even have trouble flossing between some) but I had some early decay between some teeth and these seem really good with trapped material before regular electric brushing.

There are two tricks to mostly avoid flossing. Before you brush your teeth, use a interdental brush in the gaps between your teeth. Depending upon the shape of your mouth and tooth placement, there might be one or two gaps that you cannot reach. Next, brush your teeth. Finally, one or twice a week, after you brush your teeth, floss the gaps that your interdental brush cannot reach. Why after brushing? So your flossing won't smell bad. That is one of the biggest complaints about flossing when people are surveyed.

Water flosser.

Came to post this. These things are frigging amazing and like $20. Absolutely everyone should have one. Really you can floss and brush and it still gets stuff. I wish they existed when I was younger! Buy one! Thank me later!

On the 'dentists don't really know what they're doing' front, my kid's orthodontist ($$$$) describes himself as a "fencing contractor". Conversely, I got the water flosser tip from an Indonesian dentist who I hired opportunistically on holiday for a clean; he turned up in flip-flops but decanted to bare feet during operating and gave the most sage advice I've ever had in 40+ years of dentists: BUY A WATER FLOSSER. Terimakasih, Doktor!

>I wish they existed when I was younger!

Me too, had to wait until the 1960's.

The marketing push was really effective, even on black & white TV.

The originals were so powerful that it would rarely leave anything more than floss would leave behind.

I can only imagine the water jet on new units over the decades got so much weaker maybe because somebody did some accidental eye damage or something.

What I like to do once a week is to use it with hot water, not too hot but about like hot coffee or tea which I do not drink.

I believe there are many types of germs that are highly adapted to thrive at your normal body temperature, and do not survive at temperatures too many degrees away from that.

This seems really good for the gums too not just between the teeth, and the modern offerings basically massage the gums when you pound them with the water jet, the old units would have been too painful for that.

Also on a deep minor toothache just getting started, which feels like it is way down between the root & bone, I have sprayed the tooth directly long enough to heat up the whole tooth which seems to work

I told my dentist how much I liked my water flosser, and he immediately said "that's fine but it's not very effective, you still need to use regular floss too".

Meanwhile my dentist said I should be using a water flosser instead of regular flossing.

I use both, and I can say that I definitely get more out from between my teeth with the water flosser. These days string floss is just for when I have something big stuck tightly that I know the water flosser won't be able to shift.

> actual evidence that flossing is helpful seems pretty limited

If I don't floss my breath smells terrible because of bacteria and bacteria causes tooth decay. I'm pretty certain I'm not special.

It depends on the bacteria living in your mouth.

Some people get lucky, and even with low brushing, won't get cavities.

50+, terrible at brushing and oral hygene in general. Actually lived in the jungle for years, almost like a caveman. 25+ years without a single dentist visit. Was in Thailand last spring, went to a dentistry shop in the mall as a walk-in, paid about 45 dollars for a deep cleaning and panoramic x-ray. Other than some startlingly crunky plaque in the rinse and spit cycles, zero cavities, zero need for intervention. It all comes down to the microbiome. I blame the complete lack of 'antiseptic' mouthwash and other interventions that skew the microbial populations, combined with just plain good luck.

I refuse to use antibiotic soaps either. I reserve the tools of sterility for the space in front of my laminar flow hood and the like when preparing live cultures for cheeses and brews. I lived where fluoridated water was a practice during my early years when my teeth had formed - as that's actually when the flouride has the most impact...once the teeth are built, there's little effect from consuming flouride on the enamel.

Later in late grade-school I lived in a place where fluoridated water had not happened, and so the school was doing a routine annual flouride mouth rinse-and-spit routine in the class. Was a 'conscientious objector' causing some chagrin for the teachers, they would pass out the little cup of chemical brew and start the timer, while i just stared at the paper cup and got threatened with having to write "I will ...." sentences as punishment. Even that didn't really have any impact on my actions. Adding another hashmark by my name on the blackboard as a tally of pages of meaningless repetitive sentences which I would never actually do or turn in. That had zero leverage against my test scores or passing any subject. So what if I couldn't go out to recess to sweat on a bare dirt playground with zero swings or other appeal. Fine by me.

But, by 3rd grade I already had my own two-stage steromicroscope and was acutely aware of the need for balanced microbiomes in all of life, learning about soil and aquatic microbiomes from my grandfather. So, very much not the normal kid.

All that aside, my gums could use more care, so I'm trying to be more diligent and brush daily with salt, baking soda and the tiniest bit of fennel and mint oil. Its showing some improvement.

You can still lose your teeth to receding jaw bones (aka gum recession).

It's not the gums that are receding. It's the fucking bone on which the regenerative soft tissue grows on.

I love this story, but science was invented so we didn’t have to stick to anecdotes. For myself, I’ll take my chances with the “recommended treatment”.

Do you realize that “recommended treatment” is actually anecdote itself and not a science?

Pretty much our overall health depends on various internal and external factors, that includes immunity and external environment, including food we are using, so you have to use your own brains and scientifical methods to figure out what works INDIVIDUALLY for you and “recommended treatment” at this point is nothing else than a belief in religion, because you actually do not understand what it is at this point, as you have not done your research.

>>>but science was invented

Please do not be this condescending "new age moron" teaching others what is science and making cringe to others like me, that hears it. It seems, that YC is plagued with this type of attitude, while actual science starts with curiosity and methods applied and not some belief in religion of Science. It also is a scourge of modern times, that so many professionals, that are doing science result in faking it with hopes of making it eventually, which itself is a complete failure of science as it is very simply a methodology - based on observations and collected knowledge and not a Bible of instructions, that give their holders religious title of Scientist.

I've said this before but not specifically about dentistry.

If all recommended treatments have been tried with no success, the real solution will have to be something that is not recommended.

With all other things held constant, in such a case the non-recommended approach would have best been the first and only treatment deployed.

What is "deep cleaning" compared to regular, twice a year dental cleaning?

it's what happens when there hasn't been regular 'twice a year' cleaning since before the dental hygenist was born. We had a laugh about that, she asked how long it had been since my last cleaning, and when i told her she laughed and said 'So, longer than I've been alive." So, it took about twice as long as the 'twice a year' variety.

Is this because people don’t floss properly? Or is it a study of people who floss properly?

Flossing is not merely essential to dislodging recalcitrant food particles, but also gives great stimulation to the gums themselves, and none of that effort is a waste, IMHO.

It is not sugar that causes dental caries, but bacteria. Flossing that old food out from between teeth is guaranteed to cut down bacteria growth!

Furthermore, my new and wonderful dentist and his hygienists wholeheartedly recommend and encourage the practice.

So perhaps you can excuse me for ignoring a singular “research study”.

It was a systematic review, not a “singular ‘research study’”. A newer 2019 Cochrane review[0] found about the same:

> The evidence was limited in applicability and was incomplete. The included studies only presented data on gingivitis, plaque, and adverse events; most did not measure or report other important outcomes such as periodontitis or interproximal caries. … Additional use of floss or interdental brushes compared to toothbrushing alone may reduce gingivitis or plaque, or both, and interdental brushes may be more effective than floss. The evidence is low to very low‐certainty, and the effect sizes observed may not be clinically important.

[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC6953268/

I am highly skeptical. In my younger years, I brushed regularly but did not floss at all. After dealing with a surprising number of cavities over a short period of time, I decided to just start flossing, morning and night.

Not only does flossing remove quite a bit of, er... stuff... that toothbrushing does not seem to get, I have not had a single new cavity in 25 years. The only issues I've had were old fillings falling out, including one that cracked my tooth which required a crown. Not a lot of work considering the time span.

Obviously one person is not "data" but seeing as I am that one person, I'm going to keep flossing.

May be age also plays a role. May be you started flossing around the same time your teeth became harder on its own...

I'd take it with a grain of salt at least in terms of personal experience.

It's kind of like how science-based lifting is spreading among the bodybuilding community. Is it useful? Absolutely. The issue with it as general advice is that most people don't know how to properly utilize it by missing basic concepts like applying appropriate intensity with solid form.

I don't have to floss in a perfect scenario, but maybe my technique is wrong. Even if I floss after brushing, I'll still find food lodged in between tight spaces. In this case I just floss because then I can at least remove that doubt.

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