Rubber dam isolation, tooth disinfection，acess to the pulp of the chamber, microbiological sample with two sterile paper points, then mechanical preparation with NITIMTWO to 25#06, and cleaned with 5 ml of 2.5% NaClO between each endodontic file. At the end of the procedure, root canals were ultrasonic irrigated with 2.5% NaClO, 17% EDTA for 1 min followed by irrigation with 0.9% normal saline to remove the smear layer, then take the sample again, drying the canal and fill the canal with a commercial calcium hydroxide-based paste. After 2 weeks, the canals were filled with AH-Plus sealer and Gutta-percha by vertical condensation. The teeth were take crown restoration. Follow up at 3, 6, 12 and 24 months.

Rubber dam isolation，tooth disinfection，acess to the pulp of the chamber, microbiological sample with two sterile paper points, then mechanical preparation with NITIMTWO to 25#06, and cleaned with 5 ml of 2.5% NaClO between each endodontic file. At the end of the procedure, root canals were ultrasonic irrigated with 2.5% NaClO for 1 min, then 17%EDTA for 1 min followed by irrigation with 0.9% normal saline to remove the smear layer, drying the canal, aPDT, then take the sample again. then dried the canals and filled the canals with AH-Plus sealer and Gutta-percha by vertical condensation. The teeth were take crown restoration. Follow up at 3, 6, 12 and 24 months.

tooth was isolated using a rubber dam in order to avoid the outside microbe

Quantification the total bacteria

patient subjected sensation and doctor remark the symptoms after clinical examination

take X ray, measure the lesion and compare to post-treatment