I, personally, would have it that every tooth in that mouth comes from a separate dead person. Those things should be scattered around towns, the wilderness, everywhere. They're constructed by the local people, who have some... odd... views regarding what happens after death. They believe that dead spirits seek to regain the feelings and senses they experienced in life, and that a free dead spirit will attempt to possess anyone it can. In order to prevent this, they set up those wooden statues. Whenever someone dies, they add a single tooth from that person's mouth to one of those statues. If there aren't any spare, they build a new one.
They believe that the spirits are, during the daytime, banished by the light of the sun, unless they can hide in something. They spirits of the dead are drawn to the wooden statue their tooth is in, preventing them from possessing anyone else, but are bound by the wooden frame, so they cannot move. They get to experience some sensations however, the wind on their bodies, the smells, and so forth, so at least they get some pleasure from it. They just stand there, watching. But sometimes, for reasons no-one seems fully able to explain, they just move. No-one ever sees them do this, of course. Vandals or pranksters are a fairly common explanation. But, other times, they seem to end up in places that it should simply not be possible for one of those wooden bodies to be transported. And other times, the positioning of the limbs or the arrangement of the paint seems to have changed. The places they are found in are also somewhat unusual. Looking into someone's window, for instance, or waiting near a busy restaurant.
This is becoming more and more common.