Good dental hygiene is important. So is not scaring the crap out of kids!
Earlier this year, a photo appeared online of a Doraemon plush toy that had been filled with teeth in order to teach children how to brush properly. The result was an unintentionally frightening teaching tool.
However, that mishmash is no anomaly. As DannyChoo points out, the above product's tagline is, "The teeth are inside this smiling head so that the kids don't need to be scared while listening to how to brush their teeth." Um...
If anything, what seems to make these puppets so unsettling is that their cartoony aesthetic clashes with the realistic human teeth. The cute outward appearance is so children won't be scared, but the addition of teeth ultimately makes the whole effect worse than, say, a much more abstract set of gums and teeth.