The patient was referred to me for root canal treatment of upper left sixth tooth with active fistula.  
  RVG picture – untreated mesial canals.  
  View of tooth’s chamber before repeated root canal treatment.  
  The RVG picture taken after treatment of 4 root canals.  
  An intraoral picture taken 7 days after beginning of the treatment. The fistula spontaneously backed up after proper root canal treatment.