When I was young I saw an episode of some kids TV show where a granny's false teeth were stolen by a 'hand' (think 'Thing' from the Addamm's Family...). Somehow I got it into my head that a hand was going to come and take all my teeth out when I was asleep. I still remember trying to get to sleep that night, but keep my mouth tightly closed at the same time...
A childhood belief about monsters

others believed things like this
- When I was very young, I assumed that false teeth were taken from dead people's teethAnon
- 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
- Until I was about 8 I believed that your back teeth keep growing in until you have a full circle of teeth.Anon
- Until I was around 8 or 9 years old, I thought dentists took your teeth out and replaced them with new teeth.— Verapamilo
- I used to think that my right hand wasn't my right hand anymore if I turned around.— Mike