an in-vivo study comparing antimicrobial activity of chlorhexidine 0.2% to sodium hypochlorite 0.5% as canal irrigant.

statement of problem: bacterial agents are the primary cause of pulpoperiapical diseases. therefore, an irrigating solution with proper antibacterial ability should be used to eliminate the bacterial agents during canal instrumentation. purpose: the aim of present study was to compare the antibacterial effect of 0.2% chlorhexidine to 0.5% sodium hypochlorite as canal irrigating solutions. materials and methods: in this study 20 single canal teeth with necrotic pulps were selected by vitality tests and divided in two groups each one consists of ten. each canal irrigated with 12 ml of 0.2% chlorhexidine in the first group and 0.5% sodium hypochlorite in the second one. each canal was instrumented by 6 k- type files by step back procedure (two minutes for each file). after canal instrumentation, sterile cotton pellet was placed on the pulp chamber and the canals were filled temporarily by cavit. samples were selected by two strile paper points both before the canal instrumentation (after accessing the canal) and 48 hours later. samples were cultured on mitis salivarius agar and anaerobic blood agar and then, the colony counts were reported in terms of cfu/ml. results: elimination percent mean of streptococcus mutans and anaerobics with 0.2% chlorhexidine were 99.9 and 99.02 respectively and for 0.5% hypochlorite were 99.7, and 92.7 respectively. conclusion: there was no significant difference between these two irrigating solutions by non parameteric mann-whitney test.