I wish I could tell you more but not very knowlegable in this area. I had a saliva duct stone when I was about 7years of age that Dr. removed in his office. Again I had one when I was about age-35 but hate to admit it, I removed it myself.
It seems to me I've read that Sjrogren's does cause saliva-duct stones. In fact I believe I read this in Mary Shomon's book "Living Well With Autoimmune Disease", which I highly recommend. She details how that Sjrogren's is also an autoimmune disease were antibodies attack mucous membranes, causing severe dry mouth, eyes, etc... I know I have never had it, so don't know what my duct stones were from. I do know it caused me pain under my tongue and in my throat because saliva builds up and has no where to go. Eating was sometimes painful.
I hope you get the answers you need soon!