Floss Before Brushing | Hacker News Reader

Floss Before Brushing

alearningaday.blog

52 pointsimasl4287 comments

I'm surprised that this isn't self-evident. Flossing dislodges stuff from between your teeth. Brushing beforehand means you don't have an opportunity to remove that stuff.

Why don't you have the opportunity? Flossing removes the stuff.

Not completely. It might end up on the floss but it might also end up on your teeth or gums.

How does brushing remove it then? I'm guessing it's still in between your teeth.

And just rinsing removes it.

I have talked about this flossing topic surprisingly often and it's one of the reasons I believe the majority of people are idiots with zero critical thinking. Especially in regards to health. No one seems to read inlets or understand them. It's awful.

There's the argument that flossing afterwards would drag some fluoride/nHAP to the space between your teeth which wouldn't be reachable by the toothbrush.

So I floss during brushing. One pass with the toothbrush, floss, second pass with toothbrush, rinse.

I've also seen some tiktoks with people coating the floss with toothpaste so it reaches in between the teeth.

My dentist says the opposite, since toothbrush bristles don't get between the teeth. According to her, brushing after flossing just pushes all the dislodged stuff back between the teeth.

In my opinion, it doesn't really matter which you do first, as long as you rinse well after each step. I brush first - get most of it with the brush and rinse, then get the rest of it with the floss and rinse.

Surfactants in toothpaste should prevent anything sticking while brushing.

1. Rinse with water.

2. Brush without toothpaste.

3. Floss

4. Brush with toothpaste.

General awareness of if what you’re doing is successfully getting stuff out of your teeth beats following a guiding principle and trusting it’s automatically working.

Well, the benefit here is the application of fluoride, which isn't something most people are actively thinking about maximizing.

My logic was that brushing deposits fluoride onto the teeth, and that I want that there.

Flossing feels not that different from following up toothbrushing by rinsing (bad): it's removing a bunch of the amazing good stuff the toothpaste is designed to deposit.

On the subject of dental health: Bill Burr, the comedian, worked as a dental assistant when he was younger. He gave a piece of advice on his podcast that I wish I had heard when I was young: if a dentist tells you that you have a cavity, get a second opinion.

Once that outer layer of enamel is breached, it will never be as resilient again.

This is how I've always done it and I was blown away when I found out people do it backwards. It makes no logical sense.

Why not? Brushing and swishing removes most of the particles, and then you floss to reach the tight spaces.

Because when you floss you create more particles

Doesn't rinsing your mouth out with water solve this?

Nowadays the advice is not to rinse so you don't rinse away the fluroide from the toothpaste.

I can’t imagine not rinsing after brushing, with your mouth full of toothpaste

It so happens that this is what I was doing, which is good. However, for years I was brushing after eating my breakfast because I assumed it was the better way as then you aren't going about your day with your breakfast on your teeth. But when I looked into it I found that for a variety of reasons it is apparently better to brush before breakfast. So it was an important lesson in not assuming the "obvious" (to you) way is the best.

I'm curious what these reasons are

(My second thought after typing that was "I suppose I could just ask an LLM though")

There are 'best to brush' timelines around eating/drinking. Usually you want to either:

- Brush no less than 15m before eating

- Do not brush until 45m+ after eating

I don't fully understand the science, as I'm not a dentist, but it's something related to the way that things stick to/are absorbed by enamel and dentin.

I believe water is the exception here, you can drink water and then immediately brush. You should not brush and then immediately drink water though. You want the toothpaste to stick around and form a barrier.

Supposedly, after eating the pH in the mouth drops and becomes more acidic, which softens the enamel, so brushing will do more harm than good. That's my understanding.

So long as you leave a gap of 45 minutes, you're still better off cleaning After breakfast as far as I understand.

While we're on the subject, if you brush after meals, you're doing it wrong.

Brush first thing in the morning (before your first meal/drink, other than water), and last thing at night (well after your last meal).

Plaque acid is at its lowest, so this approach results in the least damage to enamel from brushing. (Amongst other reasons.)

For a similar reason, only have a thorough brush in the morning, and a mild brush in the evening.

I thought the ideal order was brush, floss, mouthwash.

Using mouthwash every time is not ideal because most mouthwashes disrupt your oral microbiome which will result in undesired side-effects like teeth staining etc.

I've heard this before, yet my mouth remains... unaffected.

What does an "oral microbiome" even mean? I understand what it means in the literal sense, but would a person's mouth be dysfunctional if it were hypothetically devoid of microbes? Is there an accepted healthy oral microbiome composition?

You can get oral probiotics, like lactibiane buccodental. These healthy bacteria compete with harmful bacteria that causes cavities and gum disease.

You're saying we can make good toothpaste but we can't make good mouthwash?

Citation required.

No, mouthwash after brushing removes the fluoride that the toothpaste has just deposited. Similarly, avoid rinsing after brushing.

There's not really a 'good' time to use mouthwash. Maybe an hour or more after a meal, if you're in a rush - but no sooner than that, as the tooth enamel will still be softened by the food.

Even with flouride mouthwash? You're saying the paste/gel is physically more capable of depositing flouride or something?

For whatever reason, (in the US) mouthwash contains far less fluoride than toothpaste.

So, mouthwash before toothpaste. Or do as I do, and use mouthwash intermittently when in the bathroom, to boost the time there is fresh fluoride inhibiting bacteria on my teeth and gums.

Most importantly, don't rinse after either - same idea.

For anyone who's curious, Reach TotalCare Floss is the best:

   * Very shred-resistant
   * Grippy, even when wet, so you don't have to turn your fingertips purple
   * Thin enough to fit most teeth, but supposed to have some sort of textured surface to work better

I find that regular old Reach waxed works just as well, and has two benefits over Totalcare: it's more comfortable and it's cheaper — dirt cheap for floss, really.

For me at least, traditional floss shreds and breaks. The finger-tips aspect is a deal breaker for me. Floss is such a minor expense at the end of the day, it doesn't make sense to worry about the price -- that said, the non-slippery-when-wet aspect means you can use less of Totalcare, evening out the price differential somewhat.

I also rinse after flossing before brushing. Then I rinse again after brushing.

I also rinse throughout the day whenever I can. It's not a routine for me as much as a habit along with generally always having plenty of water to keep things moving and clean.

Rinsing after brushing removes the fluoride of toothpaste.

Even fluorided mouthwash is about 100x less fluoride than toothpaste.

Rinsing at other times is good, though.

I'm pretty sure if I don't rinse I will have a mouth full of foam and crap I just brushed off.

Might sound like an ad but I don’t care:

I cannot recommend enough Jordan Expand floss. There are probably other brands that have these but that’s just the one I know.

The amount of shit this floss scrapes out is like an order of magnitude more than regular floss. Going back to plain floss feels like you’re not even flossing, it just glides over without really doing anything.

What about rinsing your toothbrush as you brush? Is there a min number of times you should do so? Just can I just wash it out when i am done?

Did they teach it the other way around somewhere? Here (Germany) I've been told floss before brush for as long as I can remember...

When I get my teeth cleaned at the dentist, flossing is the last thing done. So I assume people internalize that

So a stupid question, but does teeth cleaning do something more than removing the stone (calculus)? My dentist removes that with a spike during a checkup and isn't doing any upsells so I've never in my life had a separate cleaning appointment.

My dentists have always done a floss, polish, and fluoride treatment (in addition to the tooth scraping) as part of my cleanings.

Yeah, scrape away any built up plaque, polish, floss, check for cavities, x-rays every other visit (once a year).

Cavities & x-rays is a check-up though, covered by my health insurance. Cleaning would be a separate session out of pocket

I don't know what to tell you. Every 6 months I go to the dentist. They do all those things. They bill my insurance. I pay whatever is left over.

Yes yes, I got it :) Was just curious about the different approaches.

Every checkup includes a cleaning so they're usually used interchangeably (at least everywhere I've lived in the US).

Dentists don't usually do any of the cleaning, that's the job of the dental hygienists.

Worth pointing out the evidence for flossing at all is pretty darn poor.

Yeah, but have you ever smelled a little bit of meat that has been stuck between your teeth for a while?

IMO, it varies by person. I rarely have inter-tooth cavities, so I seldom floss.

Is there empirical evidence that this order is more effective?

The article cites a study saying that it is.

https://pubmed.ncbi.nlm.nih.gov/29741239/

(a study linked in the article)

The essay links to this study, so yes:

https://pubmed.ncbi.nlm.nih.gov/29741239/

I was a bit confused about why it would matter, but then realized I brush, then floss, then use a fluoride rinse, which isn't really addressed by the study. If you didn't use a rinse or a fluoride floss, presumably the toothpaste from brushing would be more likely to get into the areas between your teeth after flossing.

If you use a fluoride rinse or fluoride floss I'm not sure it would matter much, or brushing first might even be better, because it would remove material to make flossing more effective. Maybe?

Again, "fluoridated" is not equal. In concentrations:

Drinking water << mouthwash << toothpaste (assuming all are "fluoridated").

How do people here feel about water flossers?

I got one recently. Felt like my teeth have never really been clean before.

From my convo with the dentist (N=1): flossing is better. But anything is better than not doing anything.

Incredible for post-popcorn, and for $10 nowadays a no brainer. I still find floss does a better job at scraping the sides of the tooth vs water flossers for dislodging.

The most important thing is to find something that you'll use regularly. If you find water flossing easier to do daily than manual flossing, that's more important than which is better at cleaning your teeth.

I guess this goes for water pickers use too

I mean, it's advice from someone on the internet, are there any studies to back it up?

Edit: I missed the study linked at the bottom.

I floss after brushing, just because brushing removes a lot of particles. If I floss before, there is just so much more flossing I need to do to get everything out. I learned another thing recently, to use a proper brushing technique, I think it's the modified Bass technique. I also make sure to let the bristles go underneath the gum line.

Well, TFA linked to https://pubmed.ncbi.nlm.nih.gov/29741239/

I stubbornly floss every day and every yearly checkup my dentist tells me it does not help and recommends me to stop doing it.

Maybe your dentist just needs more business? Im half kidding but i once had a dentist that told me I had 4 cavities that needed to be fixed, but when I to a 2nd dentist, she spotted zero cavities

Some dentists are way too aggressive about fillings. My dentist keeps a watch on smaller cavities and if they aren't progressing terribly they hold off.

I have had the exact same experience. Always worth it to get a second opinion before any dental work.

That's absolutely happening. https://jacobin.com/2025/07/private-equity-dental-care-healt...

IIRC there were studies saying that flossing isn't as great as people suppose it is.

My completely uneducated guess is that it's marginally useful for people with good teeth (shape, spacing) because debris doesn't accumulate as easily, and brushes are effective.

For my case (crooked teeth, very narrow gaps) it's a great helper to get out the debris, morsels of food etc. that the brush can't get out.

I shared this with HN on many occasions. My wife has crowded teeth, doesn't floss, barely touches her waterpik, doesn't use any proper brushing technique. She probably had a couple of fillings done since I met her 20 years ago. In the meantime I have cavities almost every year, one root canal and a dental implant on a previosly failed root canal. I flossed since university and use mouth rinses and electric toothbrushes and so on. Except for genetics, there are a few differences in our habits throughout the years. I would always brush in the evenings but I was neglecting mornings (somehow I internalized something that a teacher once said that brushing in the morning is silly because you haven't eaten anything). I also drink way too much coffee which is acidic, she doesn't drink any. And lastly, I would at times avoid dentist appointments for years, which probably didn't help.

Edit: I forgot to mention, when I was younger, I used to snore and breathe through my mouth a lot. I think this has also negatively affected my teeth.

Oh, genetics trump everything.

You started out good with what seemed like an easy comparison, she doesn't floss, you do, she still has better teeth. But then you go on to show all the other differences, especially not always brushing twice a day, different diet, avoiding dentist, and its hard to understand the point of your post.

My wife and I have an almost identical routine and diet, we use the same brand electric brushes, always twice a day, and usually have coffee together. However, she's not had many dental problems, but I've had to go to the dentist tons this year. Oh, incidentally I also knocked my front teeth out in a cycling accident.

You're right, I lost the plot. I still think it's mostly genetics, just because her hygiene and frequency of dentist visits are comparable to mine. I wish I was keeping record though, because little things can add up. I obviously placed low priority on morning brushing but on the other hand she never flosses, and here we're discussing the minute details of flossing technique.

I read an article a few years ago about what brushing actually does for your teeth and why it works. The premise was that brushing applies fluoride and removes the bacterial film that eventually turns into plaque - and that about 2 minutes of brushing a day would be sufficient if we were perfect at brushing. Doing it twice a day ensures that you get good coverage. It also went into the best brushing technique etc.

Since reading that I've not stressed about missing the odd brush here and there. I've also been more conscious how I brush. I stopped flossing because my gums seem quite sensitive to it and it doesn't have great evidence of effectiveness. I use a inter-denture pick/brush occasionally when needed. This all seems to have improved things for my teeth considerably, my dentist now saying they're really clean - and ironically stopped suggesting I floss more.

I wasn't joking in my previous post about the cycling accident that destroyed my front teeth, except that it happened 20 years ago. This year the crowns I had fitted failed so I've had those removed and implants installed. It's been very painful, I left replacing them probably 10 years longer than I should have. Yesterday I got a temporary bridge on the implants, which I can't use for biting. Still 2-3 months away from having the permanent new crowns fitted.

I've recently realized how much technique matters, I was advised to use the modified bass technique (and also an inter-dental brush around the implant). My aggressive brushing used to cause my gums to recede, even with expensive soft toothbrushes, but I think it's improving since adopting the new technique. Sorry to hear about your painful experience. I do a lot of cycling and my greatest fear is falling and hurting my teeth. Actually, my implant is a result of me not taking out a molar that had a root canal a decade ago and was getting inflamed a lot. Should've extracted it much earlier, because the recurring inflammation ate away the bone. I was lucky they had enough bone to work with, needed to wait half a year for it to heal and grow after extraction (there is still a visible depression in the gumline). I do floss, but one minor annoyance is that it catches on these ridges where my filling are, I even managed to break a piece once, so I'm a bit more hesitant about scraping with the floss.

This is plausible. My dentist says I should use toothpicks, but they are not useful for me as they don't really fit between my teeth. I do the most problematic of my tooth with an "extra small" pick now, and I can usually get those four gaps done before the pick breaks.

Well based on the amount of shit I dig out even if I floss after, and it’s effect on my breath, ima keep doing it.

Yes, that's exactly my reasoning. Even if it doesn't help for anything, it just feels satisfying and more clean. Kind of like picking your nails.

Some people do over floss and it can cause permanent gum damage. I assume that is a tiny fraction though.

there are studies that show that flossing with the wrong technique doesn't do much. and it's meh on cavity prevention. what it does do is prevent gingival inflammation, which can be good for gum health, especially if you're prone to getting food caught in there.

If you floss too hard or aggressively then that can be bad for your teeth/gums. If you floss only rarely causing your gums to bleed when you do and you don't wash or brush away the dried blood, that can also be bad. But I don't believe that any dentist in good faith would advise not to floss, if done properly.

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