Background: Clinical evaluation of microbial reduction in laser-assisted endodontic treatment by diode laser 810 nm, an in vivo study.Methods: Forty teeth of single canals were treated in 40 patients in 2 groups. The laser group with 20 patients, control group with 20 patients. After access to the pulp chamber a kfile 10 was inserted into the canal to move in the pulp then canal was irrigated with 0.2 mL sterile saline solution. The canal was dried with 3 sterile paper points Iso 20. Each paper cone was left inside the canal after 30 seconds. These paper cones as first microbial samples were added to 200 BHI broth and sent to the microbiology laboratory. In the laser group, the canals were sterilized with 810 nm, 2W power, 200 mm fiber in continuous mode (CW), 2 mm/s radiation time, after 5 seconds of irradiation a 5 seconds rest, 4 times for each canal from apical to coronal with a circular movement. The second microbial samples were taken in both groups before obturation and sent to the microbiology laboratory.Results: The results show a reduction of 100% bacterial colonies by 810 nm diode laser with this new protocol.Conclusion: Diode laser, 810 nm, with this new protocol, 2 W, CW can kill all of the microbial colonies in laserassisted endodontic.

Statement of Problem: Commonly, calcium hydroxide is used as an intra-canal dressing for disinfection and accelerating the repair of periapical lesions.Purpose: The purpose of this study was to determine the effect of using calcium hydroxide as an intra-canal medicament on apical seal.Materials and Method: In this experimental study, total of 60 one-rooted extracted human central incisors were instrumented with step-back technique. K-FILE (No 35) was selected as master apical file and flaring was done up to  # 60. The teeth were randomly divided into two experimental each containing 20 teeth and two control groups each containing 10 teeth. In one experimental group, the root canals were filled with calcium hydroxide. After one week, the paste was removed using #35 Kfile and normal saline irrigation. The root canals of experimental and negative control groups were obturated with gutta percha and AH 26 sealer using lateral condensation technique. In the positive control group the root canals were not obturated. Dye penetration technique was used for evaluating the rate of longitudinal microleakage. Dye penetration was measured by a milimetric ruler under stereomicroscope. For statistical analysis, Mann-Whitney test was used.Results:The results showed that there was no significant difference in apical microleakage between experimental groups ( p< 0.05).Conclusion: Using calcium hydroxide as an intra-canal medicament has no negative effect on apical seal. Further leakage studies are suggested to confirm the results of the present study.