No more, no less.
One is not enough.
Three is too much.
Four is right out.
if you brush for 2 minutes but don't get enough passes over each square mm of surface area, you have done a bad job of brushing
instead of watching the clock, imagine each of those surface areas and make sure you hit them
plus gums, tongue, roof of mouth, etc.
No more, no less.
One is not enough.
Three is too much.
Four is right out.