As you can see I have this 3D mark model and I am interested in a way to complete (close it) on the Z axis .(add a smoothed chin and top part).
This can be using any known tool or transformation from anything like meshlab, 3ds max, blender etc.
Thanks a lot!
There's not much detail in your question about either your modeling skill / experience, nor in fact any sense of what you've tried so far, making this question pretty much the definition of vague... so any answer at this point will be of severely limited utility.
I see some serious edge artifacts which make me think this is either scan data or photogrammetry, and has not been retopologised at all, and so will be quite hard to work with.
I would retopologise to get decent edge & poly flow, as well as a more workable polycount, and then use typical multi resolution sculpting tools to add in the details you wish.
If you're only worried about "filling in" the void for the purposes of a 3D print, meshlab has a set of tools both for filling holes and voids which should be adequate for this task; Netfabb also has an autorepair functions which similarly fill voids and holes for 3D printing.
