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 far as I know, getting cavities is a lot about genetics. I floss and brush after dinner and breakfast and don’t overthink it and I’ve been fine for many decades now.
Getting cavities is a lot about the prevelance of sugar and highly-refined carbs. Some people are more susceptible than others due to differences in saliva, but the typical western diet is horrible for your teeth.