One of the articles was stating that old root canals were a source of chronic infection in the body. The tooth has many smaller dentinal tubules, miles in total length, in addition to the main nerve canal. These might be a source of chronic infection after a root canal, that would go unnoticed by most, feeding toxins into the blood.
Apparently one common precondition of sinusitis (and cardiovascular and other diseases) is oral infection, which could include these very hidden micro-pockets of anaerobic bacteria deep in a tooth that had a root canal treatment.
If I had chronic sinusitis, given that I already have a bunch of root canals, I'd be looking to retreat them, with an aggressive sterilization, which can take a month between visits, perhaps with Calcium Hydroxide, as suggested on the site Root-Canal Treatment ... holistically... an "alternative alternative" viewpoint ! by Michael C. Goldman, DDS
The main impediment to such a retreatment would be the cost. Even for those of us covered by a dental plan, I doubt this would be covered. Root canal work on a tooth that is not currently in pain, especially a tooth that has already had a root canal, so has no functioning nerve, is not uncomfortable. One hardly needs the local anesthesia.
I don't know yet if there is any economical way to tell if ones root canals are causing ongoing infections.
Of course, if y'all sinusitis sufferers don't have any root canal work, then count your blessings, and my apologies for the useless ping.
Fortunately I have never had a root canal, but I'm off to check into your link re the balloon treatment for chronic sinusitis. Thanks a bunch.