My reading tells me that root canals are effective well over 90% of the time. But you HAVE to have a crown put on the tooth after the root canal to finally seal it. Otherwise the root canal isn't really completed. Most root canal failures are due to the patient not going back for the crown, often for financial reasons after the root canal has already eaten into their budget. Infections are treated by removing the source...either the infected inner part of the tooth (via a root canal) or by pulling the whole tooth. Infections, anaerobic or aerobic, will then be cleared by the body in anyone who is not immune-compromised (diabetic, transplant patients), often even without antibiotics. If the root canal doesn't work, you can still have it pulled. But when the tooth is gone, it's gone.