I'm sure anything is possible, but it certainly would be rare. I would think the autoimmune process would be more likely in your case since most AI diseases are 'triggered' by either an infection, virus, illness and even trauma/surgery...anything that causes a major immune response. Oral surgery could definitely be a trigger.

I understand not wanting to go the steroid route (I regret my years of steroids and the now permanent damage to my body), but if the course he prescribed is short (5-10 days in a taper), then it might be worth it just to see if the your symptoms improve. If they do, then you would at least know which direction to look for the cause (things with inflammation). You don't have to continue the steroids after you see they help...at this point just focus on hunting down the source of the inflammation.