> Brushing at night is the most important. Saliva naturally fights the growth of bacteria on your teeth. Your mouth dries out at night and reduces your mouth's ability to do this. Ideally, you would keep your teeth clean at all times but that's of course not realistic. A while back I read many websites and opinions about this very question. The main consensus seemed to be that people brush in the morning because it makes them feel good to start their day with a clean mouth (not because it's the best time to do it).