Aim: This study was done to evaluate and compare antimicrobial effect of 2% chlorhexidine (CHX) and N-Acetyl cysteine (NAC) irrigating solutions against two different bacterium species.

Materials & Methods: This study was conducted on 60 newly extracted non carious permanent maxillary incisors teeth of both genders. Biomechanical preparation was done up to size 40 K- file. Well prepared microbial suspensions of mixed culture of the studied bacterium were inserted into root canals. It was further incubated for 48 hours. All 60 samples were segregated into 3 groups. Group I (Chlorhexidine), group II (N-Acetylcysteine NAC). The third group was kept as control group (sterile distilled water). The antimicrobial effect in each group was observed, documented and compared.

Results: Statistical analysis was completed using statistical software Statistical Package for the Social Sciences version 21. S. S. mutans bacterial colony count was highest in group III and lowest in group II. Specifically it was 6.54±0.67 in group I, 3.76±0.34 in group II, 11.34± 2.21 in group III. E. faecalis count was found maximum in group III and minimum in group II. Efficiently it was 5.34± 0.43 in group I, 4.65± 0.89 in group II, 12.32± 2.54 in group III (Table 3). The difference was significant (P< 0.05).

Conclusion: N-Acetylcysteine showed to be exceptionally efficient against colonies of E. faecalis and S. mutans. Hence N-Acetylcysteine can be used as an alternative root canal irrigant. Here in this study the authors have studied efficiency of two irrigating solutions wherein N-Acetylcysteine found to be more efficient in lowering bacterial count. N-Acetylcysteine may possibly be proved as promising innovation in endodontic.