What Happens In Your Mouth When You Go To Sleep?

You brush your teeth, go to bed feeling clean and fresh, and then before you know it you wake up with a strong feeling that something horrible happened in your mouth overnight to get it to this unconscionable state.

There is plenty​ that can occur in your mouth overnight, and you may not even know it.

Saliva Flow Slows Down

First of all, if you’ve ever drooled on your pillow you know that you don’t swallow saliva quite as often while you sleep. Saliva is what flushes the mouth out during the day, keeping bacteria from stagnating and causing problems. Bacteria are naturally-occurring in the mouth, so the saliva is really the warrior on the frontlines protecting your teeth.

When you sleep saliva gets swallowed a little less frequently (due to relaxed muscles in your mouth) and bacteria are bound to build up. This is amplified if you don’t brush your teeth before bed and allow the bacteria from your food from that day to sit unbothered on your pearly whites.

Additionally, consider this: your mouth is essentially a hothouse for bacteria, which is their favorite environment. A hot, moist atmosphere is what allows them to flourish and expand their reign. (source)

In a word, a substantial contributor to morning breath is simply bacteria​.


Teeth grinding (medically known as bruxism) in your sleep is another common issue that can lead to oral health problems. Grinding your teeth or clenching your jaw at night can lead to headaches, sore jaws, even cracked or loose teeth. If you wake up with any of these sensations, mouth guards are a common solution that will protect your teeth from themselves. (source)

The mouth is a wild and wonderful place, a world that has its own systems and processes for self-care and preservation. While you sleep, your mouth is vulnerable to the things you don’t realize take place. By brushing your teeth before bed and using mouthwash, you might not be evading the morning breath that follows, but you’re absolutely giving your teeth the tools they need to fight bacteria while you slumber.