eli5: Why do your teeth feel so gross when you first wake up even though the last thing you did before sleeping was brush your teeth?

Question

I assume it has something to do with the bacteria in your mouth thriving and replicating from the warm, moist, undisturbed environment…. But you’re not eating at night to help form plaque so I don’t get it.

In: 1710

Answer 1

It’s because you didn’t actually remove all the bacteria in your mouth during your last brushing. I’m not insulting your brushing habits, it’s just not realistic to expect that you removed 100% of the bacteria every single time you brush. Also, remember that bacteria and other pathogens are airborne. This means even if you did succeed in removing every single last bacterium when you brushed, your first breath contaminates your mouth all over again. Essentially we are playing catchup at all times, trying to keep the inevitable invasion of bacteria at bay as best as we can.