The area becomes inflamed and contains fluid. A cyst is the body's attempt to isolate the foreign body reaction that is generated by the dead nerve. Even after what appears to be a technically successful root canal, the area stays symptomatic. The only way to resolve the problem is the surgical removal of the cyst or removal of the whole tooth. Extra canals and accessory canals may be present.
Extra canals are usually manageable.
The expected number of canals in a tooth is one for anterior teeth, one or two in the premolars and three in the molars. It is quite common to find four in the molars and on occasion, two in the anterior teeth especially the canine teeth. A dentist will look for extra canals during the procedure and be especially aware of the possibility when a canal is found in an unusual position. These extra canals can usually be clean, sized and filled with no problem. The accessory canals are more problematic.