I started with the dentist who needs to diagnose the problem. To see the oral surgeon, I had to be referred by the dentist. Oral surgery starts with a dental degree, and adds specialized training for oral and maxillofacial surgery. That surgeon is trained in oral surgery and facial reconstruction. In terms of health insurance, it falls under a dental plan.

I think you should see your dentist. It could be a tooth or a sinus problem and x rays may show which it is. They can have overlapping symptoms. You could also see the endodontist who did the root canal. They may want to redo it, but if you want a different opinion, you can see someone else.