The information on the internet is accurate concerning legacy root canals using now outdated sealers which over time will leak leading to infection of an area without adequate blood flow to be controlled by the immune system. The infection releases toxins that are responsible for the general health problems we read so much about here at curezone. If you have a 20 year old root canal it will likely fail at some point.
Your dentist has confirmed yours is not infected by xray so maybe you should look elsewhere for the source of your health concerns.
Attached is a link showing the new modern practice of doing a root canal. It takes some degree of discernment between well meaning fanatics on curezone and a medical establishment we know usually does more harm than good. The truth always lies somewhere in between.
I served in the US Air Force in the 70's as a dental technician fighting the war on tooth decay. I've seen it all, still suffer post traumatic stress from my stateside assignment in Austin, Texas. LOL
Lady Bird Johnson was even treated at our clinic.