It may be common practice, but rinsing your mouth after brushing your teeth is not a good idea. Redditor giubaloo explains why:
I know this isn’t common practice, but it’s actually quite important. Fluoride, one of the active ingredients in toothpaste, doesn’t spend much time in contact with your teeth when you brush. That’s why it’s critical to leave it on after you’ve brushed your teeth. According to dentist Dr. Phil Stemmer of The Fresh Breath Centre in London, “rinsing removes the protective layer of fluoride that toothpaste leaves behind, which would otherwise add hours of protection.” If you’re thirsty, drink a glass of water before brushing your teeth.
This is fairly common advice from dentists. I’ve heard mine say it, and a quick Google search will turn up lots of recommendations that say the same thing. An article in The Guardian also delves into the subject. It’s not a good idea for children who don’t yet have adult teeth. Adults, however, could do with a little leftover, but without stuffing their mouths with toothpaste, of course. Those who don’t want to rinse their mouths, however, can buy a fluoride rinse and use it afterwards instead of water.
