tell me if this is clear. you have the head in one geometry (aka one transform node) and every tooth in a single separated geometry.

you have done the blend shape for the head modifiyng the vertex of the head geometry(in c omponent mode) and translating the tooth in the right position (object mode translation).
blend shape works with the different relative position of the component (vertex, edge, etc etc) and not with the differences in the transform node (position, scale, rotation).

and that is at the base of your problem. try to do the blendshape moving all the vertex of the tooth and not the toothObject