Why is it important to brush your teeth in the night?

So you remove the plaque bacteria before you sleep. During sleep salivary flow is less and the bacteria just stays in one place. Saliva is a double edged sword: We need it to break down our food and keep bacteria flowing rather than stagnant, but at the same time saliva is filled with plaque bacteria. However, it is still better to have saliva flowing rather than stagnant.