The initial situation was that: RD has started non surgical re-endo of 36 which had been treated by resorcinol formaldehyde technique in the past. The dentist could negotiate all the canals but not the MB one because of the ledge in the middle third. He has obturated all available space and prepared the tooth for crown. Patient suffered from pain which was appear a week after the build up was done. RD decided to take out all the guttapercha and fiberpost and placed calcium hydroxide, then next visit Ledermix, finally left the tooth open and sent the patient to my office.