Disabled Linked Duplicate?

I just found out about linked duplicates today so I apologize if the answer is pretty simple but… I have 2 files open right now, and in one file (the one that I’m actually modeling in) I’m needing to do a linked duplicate on a tooth, however when I go into edit mode nothing happens as shown in the gif below:
http://i.imgur.com/o8teEgD.gif
However in another file, linked duplicate is working as excepted/should as seen in this gif:

Is it possible I might have some how disabled changes from being able to be made? I’ve made sure to check the “Linked” property but nothing happens.

EDIT:

Ok so I found out its from having a modifier on the object… Is there a way to still doing linked duplication with modifiers being active on them?

Linked duplication means the object share object data, object data being mesh in this case. Changes to the mesh won’t be realtime when objects have modifiers on them, have to change modes.

Add your object to a group, add group instance, then all your group instancies have the same modifiers and behaviour like your second gif.