The answer is YES. When you fall asleep without brushing your teeth, bacteria in your mouth feed on the food particles left on your teeth. It takes about 24 hours for bacteria that build around your teeth to mature. That bacteria then produce acidic waste which eats at your enamel and causes cavities to form over time. The plaque left behind on your teeth also calcifies over time and becomes impossible to remove without a visit to the dentist. Your teeth are especially vulnerable to cavity-causing agents and gum disease when we sleep because antibacterial saliva production slows. Thus, brushing your teeth before bed and when you wake up is highly recommended.
It’s important to note that gum, mouth freshener, and mints will make your mouth feel fresher, but will not remove the plaque that brushing and flossing remove. So find two minutes between checking Facebook and chasing Pokemon to brush and floss your teeth before you go to bed and when you wake up, for healthier teeth and fewer visits to the dentist.