What you just told me about your past experience would be perfect for this story.
Here is what I had an idea of doing, try just focusing on the kid, forcing himself brush his teeth before bed. That would be your narrative. He cuts corners and doesn't floss. Instead of the the TF just extracting the teeth, it is eating the gunk left behind between the teeth, that's where the best parts are. Your final "gotcha" sentence could be something along the lines of not flossing
Every person that's read it assumed he extracted it... I call him the Tooth Fairy because it's better than "The Dentist". I do rather like the idea of devouring them, however, and I could work that into some sort of back story.