The problem with root canals (and this is not new information, it's just newly recognized by mainstream dentistry- and only there on the fringes) is that there is no way for the practitioner to truly sterilize where the root has been and basically an unnatural space is created which harbors intense infection in the fluid around the remaining bone....which is not a problem until this infection (which does not behave like normal infection...it's like infection on steroids) travels to other tissues in the body and causes all kind of holy hell.
This is something which has been researched intensely and documented by some very brilliant minds.
Read this (and really, read it...if you are thinking of getting a root canal, you should really take the time):
http://www.tldp.com/issue/157-8/157rootc.htm
It's far from the only thing out there to read, I just think he does an excellent job giving the basics and a bit of very interesting insight into the history of this large body of research (for instance, the practice of removing the tooth that was root canaled from the mouth of a person suffering chronic illness and embedding it under the skin of a rabbit...only to have the rabbit (in rapid fashion) develop the exact chronic illness being suffered by the patient....) There is a large body of very compelling evidence to back the idea that a root canal is actually an extremely bad idea for your long term health.
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