I used to believe there was something seriously wrong with me because I would have nightmares that all my teeth were falling out. After discussing this with several friends over the years, I know this is a common nightmare of anyone who grinds their teeth while they are sleeping.
A childhood belief about sleeping

others believed things like this
- 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 believe that eating burnt toast would make your teeth whiter and would brush your teeth for you.— Natasha
- 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
- Until I was about 8 I believed that your back teeth keep growing in until you have a full circle of teeth.Anon
- When I was very young, I assumed that false teeth were taken from dead people's teethAnon
- when I was a kid. I used to believe hens had teeth.— lév michot