PS - root canals can be a source of toxicity.
http://www.integrativedentalmedicine.com/RCTtox.html
http://www.integrativedentalmedicine.com/RCTtoxstudies.html

There is apparently now a better way of doing them with different materials (sealants):
http://www.integrativedentalmedicine.com/ocalexic.html

However, I cannot vouch for how safe any rootcanal would be. But it looks like there are healthier alternatives.

Unfortunately toxins in the mouth aren't limited to the mouth. Amalgam, root canals, cavitations, metals/braces, incompatible dental materials etc can all affect the entire body. I guess it depends on a person's immunity, overall toxic load, sensitivies, and where their threshold is as to how much they can handle and for how long.