Brushing your teeth before you go to sleep at night helps protect against plaque buildup, tooth decay, and gum disease. If you are particularly susceptible to cavities and gum disease, dentists recommend that you brush immediately after dinner, then again right before bedtime. Should we brush at night? While it's optimal to brush your teeth both in the morning when you wake up and at night before you go to bed, brushing at night is actually more important. ... However, saliva production decreases at night, allowing plaque to form and bacteria to attack your tooth enamel.