It is advised to brush your teeth at least twice a day, but when? Just before bed is a gimme because you’re about to lie mostly still for 6+ hours. Best to not leave food particles to fester.
What’s the best time for an earlier brushing? After breakfast? After lunch? After work/school?
Plus, what’s up with TV and movies having breakfast scenes where they get up and head right out the door? Did they already brush and now they’re going to leave food to fester all day? Eww.
As someone else said: food softens the enamel and makes your teeth more vulnerable so brushing right after breakfast may cause way more damage. I always brush my teeth before breakfast and almost never have any problems with my teeth. I know that my friends who frequently need treatment for their teeth brush them after breakfast.
But that’s of course anecdotal evidence that doesn’t say much, and I’m no dentist, so I may be wrong.