I had a completely unnecessary root canal on the same tooth, left side, in 2005. The same year I developed health issues for the first time in my entire life, Never so much as cold or sniffle prior. Not suggesting it was the cause - more the final impediment.
I begged against having it done, but dentist insisted it was necessary. Asked him what he was putting in there during the last session of the procedure and he gave me the most glib response - rattled off some crap he knew I wouldn't understand. Clearly annoyed with me by that point.
What I have always wondered is just what is in there. Do you know if Amalgam is still used? I know you're not in the US, but what material is currently used in AU?
V sent to me some pretty scary info on the assault to one's health imposed by root canals. I'd consider getting it pulled but would hate to have a big gap there. Ho hum...