For what it may be worth to you: I have two root canals on back-most teeth, done in 2002 and 2009. They have never bothered me, BUT: I ingest a Bowel Tolerance dose of ascorbic acid every day [and have for the past 20 years], i.e. I believe all of that supplemental ascorbic acid has solved any toxicity issue(s) that root canals are strongly suspected to cause.
If you are interested, Infa, in learning more about Bowel Tolerance dosing with ascorbic acid, this article written by Dr. Robert Cathcart, M.D., will instruct: http://vitamincfoundation.org/www.orthomed.com/titrate.htm
If you have any questions, comments, and/or concerns about ascorbate/vitamin C therapy, please feel free to post them here and/or contact me privately.
Best wishes, Infa,