Yes, root canals are can be very tricky and it is questionable whether they are useful at all. Many people suffer complications from this procedure.
Many dentists are now prescribing Pau 'd Arco to their patients who are allergic or sensistive to antibiotics. It works as a wide-spectrum antibiotic, but with no side-effects, sometimes as fast as a few hours. Take 4 capsules three times per day and, once the infection has subsided, 2 caps three times daily for at least 2 weeks. For low immunity it can be taken ongoing. If you haven't cleaned out the colon lately, this would be a good time, to make sure no waste is backing up into the mouth (from the colon).