... still craved the flesh of human children, although it had been years beyond counting since she'd tasted one.
After the elders had caught her and removed her teeth, one by one, she hadn't been able to feed.
But not all of the elders felt comfortable sharing the tale of her specific horror with their children, and she was neutralized after all, so then what was the harm in keeping the story quiet and sparing those children nightmares ...
Enough forgot in time that she could show a new face — a face that was sweet and kind and giving. Who wanted old child's teeth, after all, and who would be upset about a child's glee on finding a surprise beneath a pillow on waking?
Well! She wanted old child's teeth, for as fate would have it, it was only those that could replace her own, and she tested and discarded (most often) or selected (very, very seldom) each tooth in her own empty mouth.
Most wouldn't fit, and those that did often didn't want to stay — but there were always a few each generation that were willing to grow in her maw.
Now there was one left, one to replace, and she could feast again.
The Tooth Fairy reached beneath the sleeping child's pillow and retrieved the lost tooth. She segmented it into the gap in her gum, twisting and pushing until she felt it take and root, felt it become hers instead of the girl's.
She looked at the mirror over the child's desk and smiled — her first full-toothed smile in eons. Her mouth was already watering at the proximity of the first bite, and the girl whimpered in her sleep as the Fairy drew back the bedcovers.