My parents told me that having too much candy, or particularly gum, would rot my teeth. I thought that it would instantly turn my teeth into the yellow rotten things I saw on posters at the dentist's office.
I still don't chew gum.
A childhood belief about chewing gum

others believed things like this
- i was told when i was young that if i swollowed gum my stomach would grow teeth to chew it— gammie
- I used to believe my dentist could give me a shot to straighten my teeth and prevent cavities.— sircigar
- 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