The first time I encountered somebody who brushed their teeth before breakfast, I was baffled too. But then I learned something...
There are people who have bad morning breath, and there are those who don't. Those who have it, tend to sleep with an open mouth, the others with their mouth closed. I started sleeping with an open mouth during my teens, and thus I began to have bad morning breath, and it tastes awful too. So, of course I brush my teeth now before breakfast.
Wonder if everybody realized this connection 😂
