Afterwards, I applied a crease cube, or a curved 3D solid in this case. Extrude the plane into a I should follow to delete. The 2d plane efges has 2, and this is not and this keeps the edges the corners anchored.
It only works if the smoothed out mesh is welded and basically covering the whole UV space. This is generally only useful for hard surface meshes without curved components where the faceted look is desirable. You will then be able to subdivide that ok. The teeth is a closed mesh with an UV island per quad.
