arcgis desktop - Trying to use Tkinter to open dialog box in ArcMap

The following script works great from the command line but crashes from the pythonaddin:

import Tkinter

import tkFileDialog
root = Tkinter.Tk()
root.withdraw()
pathtest = tkFileDialog.askopenfilename()

print pathtest

pathtest = pythonaddins.OpenDialog('Open Item', True) does not work for me because it suppresses filetypes that I need to see (pdf).

I know this is a duplicate question but I just joined the site and could not comment on other posts.