Did you brush your teeth? Brush them thoroughly, otherwise they will decay. Do not only brush your teeth, but also your tongue as well. Talking about brushing teeth, I'll tell you a secret, don't use too much toothpaste. Each time just use a little bit, the amount about as big as the head of a chopstick, like a garden pea should be enough. If you use too much toothpaste, your teeth will turn black. There are some children who brush their teeth very often, and their teeth are still black.
Brush your teeth three times a day (after meals or sweets); and when you brush your teeth, brush them up up, down down, and around. Brush your tongue as well, so you won't have bad breath.