I've heard that rinsing with water after teeth brushing lowers or negates the benefits that fluoride provides to our teeth, but I've also heard everything in between; from there's no problem with it, to rinse with as little water as possible, to mix water with toothpaste and rinse with it.
Example from http://www.theguardian.com/lifeandstyle/2011/feb/08/how-to-brush-your-teeth:
So, should you rinse your mouth out with water when you have finished brushing or leave some toothpaste in your mouth? "For children, I would say wash out, because if they still have adult teeth that have yet to come through, they may end up with too much fluoride in their body, which can damage their teeth. For adults, it's good to leave a film, but in moderation – you don't want a mouthful of toothpaste. I have a semi-rinse: I put a tiny bit of water in my mouth to brush away the toothpaste on my tongue."
and from http://lifehacker.com/5978107/dont-rinse-your-mouth-out-after-brushing-your-teeth:
I know this this is not common practice, but it is actually quite important! Fluoride, one of the active ingredients in toothpaste, doesn't spend much time in contact when your teeth when you are brushing. Thus, it is crucial to let it work after you have already brushed your teeth. According to dentist Dr. Phil Stemmer, from The Fresh Breath Centre in London, "Rinsing washes away the protective flouride coating left by the toothpaste, which would otherwise add hours of protection." If you are thirsty drink a glass of water before brushing your teeth!
In contrast, this article quotes http://www.oralanswers.com/rinse-after-brushing:
Previous studies have indicated that rinsing the mouth with a beaker of water after toothbrushing may compromise the caries reducing effect of fluoride toothpaste. It is concluded that post-brushing rinsing with water, under the conditions of this study, does not significantly affect the caries reducing effect of a fluoride toothpaste.
I think the reason that there is some disagreement on this subject is because not rinsing after brushing appears to be only beneficial if you are at a high risk of getting cavities.
And as two commenters said below, not rinsing feels kind of counter intuitive, but seems to be the way to go. Is it?
Assuming normal and healthy teeth, what's actually better? Which one carries the most benefits? Should we rinse with water or not? Are there studies about this? Is there a consensus yet?