Don't rinse with water straight after toothbrushing | Hacker News Reader

Don't rinse with water straight after toothbrushing

nhs.uk

37 pointspierlu74 comments

From "Potential fluoride toxicity from oral medicaments" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651468/):

"The beneficial role of fluoride for the maintenance of good oral health has been known for many decades and strongly evidenced by scientific research. However, it must be emphasized that tooth decay (dental caries) is not caused by fluoride deficiency and fluoride supplementation will never reverse the active or gross carious lesions. Since the level of safety of fluoride is low, products that contain a high level of fluoride should be stored and used according to the recommendation and should be monitored by a qualified dental professional especially in children and pregnant women. In children, the swallowing reflex is not very well developed and the fluoride containing dental products are flavored hence increasing the possibility of a child to consume an excessive dose of fluoride."

Maybe swallowing fluoride is not such a good idea?f

(Also, can someone compare toxicity levels of lead versus fluoride?)

Most toothpaste has about 1000 ppm of fluoride (0.1%), which isn't a "high level" - in fact, it means that one blob of it on a toothbrush has about the same fluoride content as a large glass of fluoridated water.

"High level" in this case comes in with fluoride rinses or specialty toothpaste, which can have 5000+ or 10000+ ppm of flouride.

So I'm supposed to leave the toothpaste in my mouth? For how long?

EDIT: I'd also like to point out that I have been rinsing my mouth after brushing for the last 40 years, never used mouthwash, and never had a cavity.

You can spit but don't add water. That should get rid of most of it.

Have you ever brushed your teeth?? (Just joking)

I think we all use excessive amount of toothpaste. That makes us get a mouth full of foam, that subsequently forces us to rinse instead of just spit.

Great marketing by Colgate. They just show the toothpaste covering the entire length of the brush and we all follow along.

I just got a very short brush.

Right but the question is for how long? Surely you're not supposed to never put water in your mouth again, so how long should you wait? 1 minute? 10 minutes? An hour?

30 minutes according to some dentists I know.

I used to rinse my mouth with water, now I just spit the toothpaste.

I haven't asked but this may be recommended only if you're not using an abrasive toothpaste which could damage your teeth enamel.

Depends what you're optimizing for. If you never eat or drink anything again, your teeth will stay healthy until you die...?

I've heard dentists recommend brushing after every meal. Which really doesn't seem realistic for people who snack or regularly drink coffee / tea.

I'm not sure if this is correct but when I was in college I noticed a couple guys who just spit and didn't rinse at all. Like, ever. They just brush, spit out some toothpaste, and then move on to the next step of their routine.

At the time it seemed kinda freaky to me since I always rinse the toothpaste out when I finish brushing, but maybe they were doing it right... I can't get over the feeling over toothpaste stuck in my mouth, though. Perhaps it's one of those things that's hard to change once you establish a pattern in childhood.

If it kills the bacteria on your mouth that’s got to hurt your gut too.

Brushing is mainly supposed to mechanically take the bacteria off of your teeth, like washing your hands, not kill them chemically. The fluoride exists to help keep enamel intact.

It's not about killing bacteria, its about leaving fluoride ions in a slightly basic or at least nonacidic environment for long enough to convert hydroxyapatite to fluorohydroxyapatite. This chemical reaction takes time, but considerably strengthens your teeth against corrosion and prevents cavities.

Hah. This is perfectly normal for me. I have never done the rinsing after toothbrushing thing. There's definitely something about childhood patterns though. The slight taste of toothpaste in my mouth makes me feel clean and refreshed. I brush my teeth several times a day, usually just before I go somewhere.

So you just walk away from the sink and let a poisonous substance sit in your mouth while you slowly but surely swallow it all?

I never thought about it that way, but I guess so. Sometimes I even have a sip of water if it is too toothpasty.

“Don't rinse your mouth immediately after brushing, as it'll wash away the concentrated fluoride in the remaining toothpaste”

Sorry but that’s unacceptable to me. Come up with a better way for me to clean my teeth or I’ll keep rinsing immediately.

I do actually do this with fluoride and alcohol free mouthwash though. That’s easier to not rinse for 30 minutes.

Well, the free advice and the rationale behind it has been given. Now you can do what you want with it. They're your teeth, after all.

You may have higher levels of calcium in your saliva than normal. I know someone who has poor dental hygiene practices and never had a cavity, partly due to excess calcium. Instead of cavities, he has problems with calcium deposits accumulating in his plaque.

My point is, you may simply be an outlier rather a meaningful counter example.

Also from the article: "It's best to floss before brushing your teeth."

Why? I would have thought it makes more sense to brush, then floss, then wash at the end so the fluoride stays longer

I'm guessing the toothpaste is able to penetrate the gaps that were filled by debris.

I suspect it doesn't really make a difference, there may have been one mediocre study which showed a couple percent improvement, or more than likely one opinion simply gained more traction than the other.

Both orders have downsides - if you floss first, you risk forcing detritus back between your teeth while brushing.

If you brush first, you risk leaving some of the gunk from between your teeth on the surfaces - although perhaps now it will be bound loosely enough to be washed off with water.

Either way you're probably getting rid of most of the organic material anyway.

The idea is that stuff dislodged by the flossing gets brushed away and spit out when you brush. If you floss after brushing, it is more likely the floss debris will remain on your teeth. You’ve just moved it from between to a side.

That was the argument I found when I recently looked into this. It makes sense if all you’re doing is brushing and flossing. If there are further steps in your routine that would take care of the flossing leftovers, I expect the order does not matter.

I always thought that flossing mostly moves the dirt from between your tooth to another side. So I always brush after flossing.

(I also never thought about fluoride so of course I rinse after brushing and I will continue to do so because otherwise it would be very uncomfortable)

As far as I know a function of flossing is to disrupt bacteria in places that your brush can't reach.

Presumably another is to dislodge food stuck there.

I can imagine that floss + rinse would accomplish both well enough, especially if it's twice a day (but surely most people brush one a day)

I use a toothpaste for sensitive teeth due to some recessions (due to hard brushing, don't push so hard kids!) The dentist and manufacturer of the toothpaste both recommend you don't rinse post-brush to ensure the numbing agent stays on your teeth.

I can very much recommend an electric toothbrush against brushing too hard. Depending on the model it lets you know when you push too hard. It has helped me a lot.

Also, according to my dentist the receded gums don't grow back which is quite scary.

Oh, but you can grow it back through a gun graft, and I had it done successfully. Healthy gum tissue is removed from the roof of the mouth and uses to build the gum back up where it has receded.

And it is an extremely invasive and painful procedure that should be avoided at all costs if you can. And if you don’t change your habits, you’ll have to have it multiple times.

Note that the rationale is that it washes out most of the lingering fluoride, which is presumably more of a concern in the UK where the water isn't fluorinated.

In the US, drinking water supplemented with fluoride for this very reason, so feel free to rinse out your dislodged food scraps after brushing and ignore this advice from the NHS.

Water in the UK is also supplemented with flouride. I think the point is that toothpaste contains more.

Only about 10% of it, according to Wikipedia. https://en.wikipedia.org/wiki/Fluoridation_by_country (75% of those with community water systems in the U.S., for reference.)

10% of water in UK, not 10% of toothpaste.

Sure. Of course toothpaste has flouride. There's nowhere that's untrue, I assume. But the person I responded to made a claim about water flouridation in the UK which was mostly false.

There are actually fluoride-free "natural" toothpastes that have unfortunately been growing more common. As one might expect, they are of dubious effectiveness.

Do you have more information on this? I thought that fluoride was toxic and thus shouldn't be swallowed. Are the quantities too small to harm you yet sufficient to prevent the formation of caries?

It is a small amount. It helps, but is not enough to completely prevent cavities. You still need to brush your teeth like normal.

It's significant enough to prevent some tooth decay, but insignificant when it comes to toxicity.

Water fluoridation rates are well under dangerous levels - about 0.7 mg/L for artificially fluoridated water, vs 2+ mg/L long-term to actually cause any problems. Even that small amount helps with reducing tooth decay, as was shown in the US in studies starting in the 50s comparing areas with naturally fluoridated water with areas without it.

Unless of course you drink filtered water.

Carbon filters are fine.

In some areas there is too much of fluoride naturally and it must be removed, not added.

Geographical areas associated with groundwater having over 1.5 mg/L of naturally occurring fluoride, which is above recommended levels https://en.wikipedia.org/wiki/Water_fluoridation#/media/File...

In the United States, recommended fluoride levels in drinking water are 0.7ppm, whereas toothpaste is 1000ppm - 1500ppm.

So even with fluoridated water you want to avoid rinsing.

Fluoridation is by no means universal in the US—around 69.2% of public water in 2006, according to Wikipedia[1]. In some areas, resistance is strong and cuts across diverse political orientations. Portland's 2012 attempt to fluoridate, for example, drew opposition on the basis of libertarianism, environmentalism and science skepticism.

[1] https://en.wikipedia.org/wiki/Water_fluoridation_in_the_Unit...

Interesting advice. Also interesting that it used inches rather than metric. Is that common?

That's why my dentist recommends a fluoride mouthwash after brushing.

My routine:

1. Floss 2. Waterpik (water + mouthwash) 3. Electric brush, no rinsing

waterpik should do the job of flossing already, you can probably skip step 1, at least according to this study:

https://www.ncbi.nlm.nih.gov/pubmed/24282867

This advice ought to be printed on every tube of toothpaste.

>Don't rinse your mouth immediately after brushing, as it'll wash away the concentrated fluoride in the remaining toothpaste.

That is the point.

It's weird that we don't know what teeth were like before fluoride was invented. The knowledge isn't directly accessible to everyday people. Sure, we know some examples, but what about the averages? Was everyone's teeth just completely screwed, all the time? How could evolution work that way? We need our teeth to eat.

It's further complicated by the invention of processed sugar, which ruins teeth. Before that, presumably it wasn't quite as bad to live without fluoride. But again, the knowledge seems kind of hard to find.

Anecdotally, I lucked out by not listening to a dentist when they said one of my teeth had to come out. Still have it six years later, and it's fine. Apparently it was a rather intense toothache that eventually went away.

Considering that "back then" (e.g. 2000 years ago) people didn't consume sugar, soft drinks, and their food was mostly natural and sparse (no 3 meals and 2 snacks), plus the fact that people didn't live to 100yo, I would assume that tooth decay was less of a problem.

Interesting article for about 12,000 years ago: https://eu.usatoday.com/story/news/nation/2014/01/06/tooth-d...

The comparison to London 200 years ago is astonishing, sugar is bad for us a hundred different ways!

> Was everyone's teeth just completely screwed, all the time? How could evolution work that way? We need our teeth to eat.

Grains have sugar in them that cause tooth decay. You can blame agriculture, mostly.

We do know how bad teeth were a century ago. There's even evidence that humans several thousands of years ago didn't have as many cavities as we do today because of their diet.

I'm not in a position to give you advice, but be very careful with your teeth. A tootache can lead to an infection that if not treaded may kill you.

> It's weird that we don't know what teeth were like before fluoride was invented.

We have teeth from fossils that are a few thousand years old all the way to over a million years old.

https://www.npr.org/templates/story/story.php?storyId=129562...

https://www.smithsonianmag.com/science-nature/oldest-human-f...

https://www.nationalgeographic.com/news/2018/01/oldest-human...

> Was everyone's teeth just completely screwed, all the time?

Well, often, yes. See, for example, the history of pre-modern dentures, which were common for people in only their 30s and 40s (George Washington's teeth all fell out before he even reached 30!).

> How could evolution work that way?

Two reasons:

First, if you've had children, you're surplus material. Most people throughout history who have had children have done so by the age of 30 or 40, and so after that, their teeth just don't matter, evolution-wise.

Second, humans evolved in an environment with very limited access to sugar and acidic foods. Sugar and acidic foods are the main cause of cavities, and have been common since the invention of civilization and extremely common since the advent of mass industrialization.

> Still have it six years later, and it's fine.

It's probably not fine. It's entirely possible to have teeth that are apparently pain-free right up until they literally snap in half from deep cavities.

If a dentist recommends a treatment, I always get a blind second opinion. I've had many alleged cavities, which allegedly needed filling, go undetected and untreated by the next dentist. 5-10 years later, I'm convinced the dentists who claimed I needed fillings were so eager to make money they jumped the gun.

I think wild animals in nature have pretty much perfect teeth - they don't eat sugar. Same with people in remote parts of Africa (whenever I see a photograph from national geographic, everyone seems to have perfect teeth).

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