Is there a specific trend as to when the swelling comes and goes? Although probably pretty rare, it may be a blocked salivary gland of some sort up there which will swell when you're about to eat and subside when done eating. These tend to occur more often in the lower lip area. Its called a mucocele.
But you may want to follow up with an oral surgeon if the dentist can't seem to be able to treat/diagnose the problem.
That's possible. If its a sinus infection, a course of antibiotics should fix the problem. May want to ask your primary physician for a check and see
Thanks ! The only trend that I can determine is that it occurs later at night often when I am asleep, although one episode happened at 10:30 am. One other coincident item is that most times that it has happened I've noticed that my left nasal passage is blocked (same side as the gum swelling)... could this be related to some kind of sinus problem?