Failed root canal has developed a little pocket at the root. I think that's what was actually infected a year ago when I had a similar problem - exasperated by a wisdom tooth that came loose from that plus grinding/TMJ... I'm pretty sure that's what's infected again given the location of the swelling. But it's beginning to go down now and definitely less painful than it was. I'm going to post (probably tomorrow) about some of the things I've been doing to treat it. (We go to a low-income type of dentist which requires 2 weeks to get in for an appointment, by which point, I'll either be better or in the hospital! Not to mention the fact that I'm supposed to be traveling then.)