The rubber dam was placed on the tooth and the area was disinfected with chlorhexidine/ethanol (0.5 % / 70 %). Size 15 reamers were inserted into both canals to the length previously measured from the preoperative radiograph and a working length radiograph was taken. The working length radiograph showed joining of the two canals before apex. Both canals were prepared using flexoreamers and NiTiflex K-files in continuous rotation and with balanced force technique to size 50 / 20 mm. Hedstroem files were used in addition to help in cleaning and shaping the middle and coronal portions of the canal system. The canals were constantly irrigated with 0.5 % sodium hypochorite. At the end of the preparation the canals were irrigated with 17 % neutral EDTA and dried with nr. 45 paper points.

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