Well I haven't seen one used by a dentist either. I can imagine they may have at one time and at least some may still use them in a lab.
I found mine collecting dust at a local camera shop and the old man said he actually got it from a dentist who was the original owner.
I've seen a few photos of this lens, but not any with the the guide sticker still on it. So posting some here for posterity and for the pleasure of the lens fetishists
cheers