I am asking the Teeming Millions to help avert a domestic crisis.
My wife tells me I should brush my teeth in cold water. She says there are too many minerals and nasty things which come out of the average hot water system.
I was brought up believing one should brush one’s teeth in hot water, as you’d wash your dishes and clothes.
So, which is the better temperature for your overall health and oral hygiene?
Cold water, if only because hot water softens the plastic toothbrush bristles, so you won’t get as thorough a cleaning job.
It won’t matter in any measureable way; you use so little (what… maybe a few mls?) that it won’t stay at whatever temperature it starts at anyways. You’ll have several orders of magnitude more effect simply by drinking a cup of coffee or pop (sugars, acids, high heat). Not sure about the stiff bristles thing - it’s really easy to tear up your gums with even a soft brush by scrubbing away like you’re trying to get rust off your faucets; it doesn’t take much to brush plaque away (you can wipe a lot off with a napkin).
Your wife’s concerns about hot tap water are common but wrong; this has been discussed here before -
… OK how the f*ck did that happen? - first time I’ve screwed up and submitted before I was done… bah, here’s the whole thing over again:
It won’t matter in any measureable way; you use so little (what… maybe a few mls?) that it won’t stay at whatever temperature it starts at anyways. You’ll have several orders of magnitude more effect simply by drinking a cup of coffee or pop (sugars, acids, high heat). Not sure about the stiff bristles thing - it’s really easy to tear up your gums with even a soft brush by scrubbing away like you’re trying to get rust off your faucets; it doesn’t take much to brush plaque away (you can wipe a lot off with a napkin).
Your wife’s concerns about hot tap water are common but wrong; this has been discussed here before - if anything the hot water will have fewer disolved minerals than the cold.
Warm water. You’ll brush longer, and when you brush longer, you can brush correctly, instead of grinding in a rush.
I was told to use cold water, hot water will soften your teeth…you want nice hard strong teeth, not soft rubbery teeth.
Riiiight. I had noticed that my teeth go soft and rubbery after drinking hot coffee, it all makes sense now.
Why? 
I brush with cold water (because I don’t particularly like the sensation of warm water in my mouth) and actually spend longer brushing than my girlfriend, who uses lukewarm water because her teeth are sensitive to the cold. I also have sensitive teeth, but it doesn’t stop me eating ice-cream either. After a few moments the water warms in your mouth and gets mixed with the toothpaste, so after the initial shock you can brush as long as you like.
I find cold water more refreshing, I think the only danger with warm water is if it’s been standing in the pipe for a long time, which allows things like legionaires disease to flourish. If you haven’t used your water system for a period of months (say in a holiday home) it’s worth running the water cold to flush the pipes of stagnant water.
As for HOT water, I’m not sure that if the water was hot enough to actually kill all known bacteria you’d be able to put it in your mouth without scalding yourself. By the same token, you might as well brush with Domestos.
Why do people believe this? By passing through a hot water tank, some deposits in the water will actually collect inside the tank, which means that hot water will actually have fewer ‘nasty things’/minerals than cold water.
As for the hot/cold vote, since brushing is a bit rough on the gums by nature, that sensitive tissue is best treated with cold water. Gums are put through a bit of a test as the teeth are brushed, so cold water would be best for them to keep inflamation to a minimum.
Who uses water?
I brush and spit without water. Of course that might be because I don’t have indoor plumbing…
Never mind warm or cold, do you leave the tap running water, full on, the whole time you have your brush in your mouth scrubbing?
Or do you turn it off and then back on when it’s time to rinse and spit?
If you leave the tap running; do you ever think about how much water is being wasted? Water that has been treated and cleaned and piped into your home at some cost of energy to someone.
All over the world people lack access to clean water, and we send who knows how much of it right back down the drain, twice a day for most people, just so we can groove on the sound of the water running whilst we brush.
Anyone else ever thought of this?
(sorry for the hijack but the OP made me think of this again…)
You can’t draw any conclusions unless you know more about the plumbing of the building.
Cold water is most likely to be coming straight from the mains. Hot, on the otherhand, could have spent the last 24 hours sitting anywhere; maybe the hot water tank, maybe some other tank. As this is not drinking water you’ve no guarantees at all about its quality.
The hot water in my last place came from Victorian era lead-lined water tank, prior to heating. The cold came direct from the mains. Guess which I used to brush my teeth with?
Besides. Brushing with hot water is ickie and probably gives you cooties.
No. Yes - for the reasons given.
Yes.
I have thought of this, but for some reason I can’t explain, the water seems to taste better when the tap’s running. Just a psychological thing.
As for the cost of treating and piping it etc, it’s my water, I pay for it (it’s metered), so I’ll do what I want with it. Everyone should spoil themselves every once in a while. 
Well, I do use hot water because I want to soften the bristles - I can’t find soft-bristled toothbrushes easily, and I tend to use too much pressure. I don’t see why softer bristles won’t do as thorough a cleaning job; I’ve read over and over that it is better to use soft than medium bristles, but every store only seems to carry medium. Medium bristles coupled with too much pressure (I can’t make myself do it more lightly, I’ve tried) equals bleeding gums. When your gums bleed because you’ve shredded them, you’re less likely to brush.
Anyway, I solved the whole bristle problem by going to a Sonicare®, but I still use the hot water to rinse - it does a better/quicker job of removing excess toothpaste. And feels better on my sensitive teeth. Cold water hurts!
I think the problem here is the ‘should’ word. If you’re getting hung up on it re brushing your teeth, I hate to think how you get through other major decision-making processes. What do you like to do? If it isn’t hurting anyone else, you may do it.
I don’t think the temp of the water matters. If you have old yucky pipes, the hot or cold water would be equally gross, I think.
The only thing I think matters is that you DO brush your teeth. Your wife should be grateful for that fact. My ex husband (one of the reasons he’s an ex) had to be freakin’ REMINDED to brush his teeth everyday. Why would someone have to be reminded of a basic hygienic ritual??? But that’s another thread.
OH…and another hijack along these same lines. Are you supposed to rinse with water after you brush?? I do…all those particles and plaque that just got brushed off need to be rinsed out, right? Some people I know just brush and spit. Yuck!! But then again, if the toothpaste has fluoride in it, shouldn’t the fluoride not be rinsed away? This has always been a conundrum for me.
Sigh.
Who would have thunk that brushing one’s teeth could bring up all these questions?
bumping the thread…I wanna know what you guys do! Spit and rinse, or just spit?
SuperLorie, I’d hate to think that there are people out there who don’t know enough to rinse the toothpaste out of their mouth after they brush.
I’d just as soon leave shampoo in my hair.
Well, I don’t think I’m wasting water since I brush my teeth while I’m in the shower every morning when I get up and every night when I go to bed. I usually take a pretty hot shower. Rinse, spit, brush, rinse, spit, brush again, rinse, spit, done.
I’m 41 and have never had a cavity and still have all of my teeth…