Objective: The aim of this study was to evaluate the antibacterial potential of NAC as an endodontic irrigant on the clinical isolates of the Enterococcus faecalis biofilm.Methods: NAC with a pH of 2.5 and 11 (NAC pH 2.5 and NAC pH 11, respectively) were exposed to clinical isolates of E. faecalis biofilms for 1 min. The NAC samples were compared to 2% chlorhexidine (CHX), which is commonly used as an irrigant in persistent infections. The antibacterial potential of these irrigants was evaluated by comparing the bacterial count of the E. faecalis colonies after they were exposed to the irrigants. Results:The NAC pH 2.5 test group showed a reduction in the E. faecalis colonies, but this reduction was not statistically significant when compared to the 2% CHX group results. The NAC pH 11 test group showed the greatest reduction in bacterial colonies, and this reduction was statistically significant when compared to the NAC pH 2.5 and 2% CHX groups' results. Conclusion:NAC pH 11 has antibacterial potential on the clinical isolates of E. faecalis biofilms.

Objective: The objective of this study was to evaluate the antimicrobial activity of mineral trioxide aggregate (MTA) and calcium hydroxide (Ca(OH)2)sealers on Enterococcus faecalis at various time points after the preparation of the sealer.Methods: Antimicrobial activity of MTA and Ca(OH)2 sealer on E. faecalis (ATCC 29212) was assessed by the direct contact test immediately, 1 day,and 7 days after the preparation of the sealer.Results: The antimicrobial effect of MTA sealer was greatest 1 and 7 days after the preparation of the sealer. The effect of Ca(OH)2 was greatest 1 dayafter the preparation of the sealer.Conclusion: MTA sealer showed constant antimicrobial activity on E. faecalis overtime. By contrast, Ca(OH)2 sealer showed decreasing antimicrobialactivity overtime, with the greatest antimicrobial activity being 1 day after the preparation of the sealer.

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Background: Chlorhexidine could have effect on shear bond strength of composite resin-dentin. Objective: The purpose of this study is to compare two methods of chlorhexidine application of shear bond strength degradation between composite resin and dentin. Methods: Thirty samples of dentin were taken from the crown of premolars and then divided into three groups (n = 10). Group 1 were applied bonding without chlorhexidine, group 2 were applied with liquid chlorhexidine and followed by bonding, group 3 were applied bonding which contains chlorhexidine. Each group was divided into two subgroups (n = 5): the group with and without 10% NaOCl immersion for one hour. Then, 4 samples in each subgroup were used to measure shear bond strength using Universal Testing Machine, and 1 sample was examined with Scanning Electron Microscope (SEM). Data were analyzed using SPSS 17 by Mann-Whitney and Kruskal Wallis test. Results: The highest mean shear bond strength without 10% NaOCl immersion was in group 1, while the highest mean with 10% NaOCl immersion was in group 3. Significant differences occurred between the groups 1 and 2, groups 2 and 3. Conclusion: Method of using bonding contains chlorhexidine can increase and inhibit degradation shear bond strength between composite resin and dentin.