saliva is essentially continually buffering the pH in your mouth. The gut can buffer itself a lot easier because it's inside. But when you're right in front of the outside world and your mouth is open for six, seven, eight hours at night, and saliva flow rate drops off anyway at night, even if your mouth is closed, a saliva gland shut down if you're in deep sleep, that's part of the restorative process.

And again, saliva isn't really needed. Your tongue is not moving if you're in REM sleep. There's not much washing and cleaning going on. Think of a spin washer, a clothes washer with the impeller, and it's not going to clean the dirt and do what it's supposed to do if it's not spinning and moving and if there isn't enough water in there.

Essentially what it does is it allows the bad bugs to proliferate and do more damage. It also drops the pH in the mouth so that you're demineralizing quicker than you are remineralizing. Again, you need a optimal pH for that fixing, that equilibrium to work.