I don't remember, but when I was very very young I would be so terrified that my mother said that the hygienist once suggested it. My mother thought that was a horrible thing to say.
You know how a lot of cartoons and even live action-shows show dentists as being evil and sadistic and treatment is more like a brutal punishment for not taking better care of your teeth. Maybe that was part of the fear. Of course, it's completely different if it's an educational program where the Aesop is that you shouldn't be afraid, that having a horrible toothache is much worse than getting it treated, and that the "dentist is your friend". That last one is nonsense, though. The dentist is not really my friend any more than a bank teller or the hair dresser, unless I actually know know them well enough and consider them a friend. They're not really my friends nor my enemies.