I used to believe that you had to brush your teeth to get the food particles out because if you didn't, when you slept, little bugs would get in your mouth to eat the food and in the process would eat your teeth causing cavities.
A childhood belief about general

others believed things like this
- I used to believe that if I didn't brush my teeth at night, ants would crawl into my mouth and eat my teeth.Anon
- I used to believe that eating burnt toast would make your teeth whiter and would brush your teeth for you.— Natasha
- I used to believe when i was about 4 (now 15) that dinosours died because they didn't brush their teeth— gullable
- I used to think that cockroaches would visit your house if you didn't brush your teeth.Anon
- I used to believe my dentist could give me a shot to straighten my teeth and prevent cavities.— sircigar
- I thought "Angel of the Moring", by Juice Newton said "just brush me teeth before you leave me"!!!Anon