Objectives. The aim of this study was to determine whether irrigation with sodium hypochlorite, chlorhexidine, and ozone gas, alone or in combination, were effective againstEnterococcus faecalisandCandida albicans; these are microorganisms frequently isolated from teeth with periapical lesions resistant to endodontic treatment.Material and Methods. 220 single root teeth, recently extracted, were inoculated withCandida albicansandEnterococcus faecalis. The formulations tested were sodium hypochlorite at 1, 3, and 5% chlorhexidine at 0.2% and 2% and ozone gas applied for different periods of time. The combination of sodium hypochlorite at 5% and chlorhexidine at 2%, with gaseous ozone, were also assessed. For the most active treatments the mechanism of action was assessed through flow cytometry.Results. Sodium hypochlorite, chlorhexidine, and gaseous ozone alone were ineffective in completely eliminating the microorganisms. The association of chlorhexidine at 2% followed by ozone gas for 24 seconds promoted the complete elimination ofCandida albicansandEnterococcus faecalis. Flow cytometry shows that ozone and chlorhexidine act differently, which could explain its synergic activity.Conclusions. This new disinfection protocol, combining irrigation with chlorhexidine at 2% and ozone gas for 24 seconds, may be advantageous when treating infected root canals.

Objective: As clinical studies conducted to explore the safety and efficacy of new procedures are considered an important focus in endodontic research, the aim of this controlled clinical study was to compare a laser-assisted endodontic treatment using an erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser and radial firing tips (RFT) versus the conventional use of 3% sodium hypochlorite and interim calcium hydroxide paste, in teeth with chronic apical periodontitis. Methods: Forty-three single-rooted and premolar teeth were randomly assigned. In group 1, teeth were prepared and irrigated with 3% sodium hypochlorite and calcium hydroxide inter-appointment dressing was applied; in group 2 teeth were prepared with saline solution and irradiated with Er,Cr:YSGG laser using RFT2 (140 μs, 37.5 mJ, 20 Hz) and RFT3 (140 μs, 62.5 mJ, 20 Hz) at the first and second appointments, respectively, four times each, moving at 2 mm/sec ⁻¹ from apical to coronal. The primary outcome measure was change in apical bone density at 12 months, using the periapical index (PAI) for blind radiographic assessment. Results: Thirty teeth were examined and subjected to statistical analysis, 12 in the control group and 18 in the test group. There were two treatment failures in the control group that were not included for analysis; both groups exhibited statistically significant decreases in PAI scores. Conclusions: The present findings suggest that for single-rooted and premolar teeth, this laser-assisted protocol can achieve predictable endodontic outcomes, comparable to conventional strategies in 1 year of follow-up.

Aim: Bacteria levels of necrotic teeth are greatly reduced after endodontic treatment procedures but the presence of persisting microorganisms leads to continuous efforts to develop materials with antimicrobial properties. The purpose of the study was to determine the antimicrobial activity of polyethylenimine (PEI) against common bacteria and yeasts, regarding planktonic cells and biofilm, and to clarify its antimicrobial mechanism of action through flow cytometry. Materials and methods: The antibiofilm and antimicrobial effect of PEI was determined against Enterococcus faecalis, Staphylococcus aureus, Escherichia coli and Candida albicans strains using reference protocols. The effect of PEI was evaluated regarding adhesion, biofilm formation and biofilm disaggregation. In order to understand PEI cellular effects flow cytometric analysis was performed with different fluorescent markers. Results: It was verified that minimal inhibitory concentrations (MIC) values and minimal lethal concentrations (MLC) obtained for PEI were similar and ranged between 50 and 400 mg/l, proving the microbicidal and fungicidal activity of this compound. Antibiofilm activity was also proved for all the microorganisms. Severe lesion of the membrane and cell depolarization was demonstrated. Conclusion: Polyethylenimine showed antimicrobial and antibiofilm activity against microorganisms often associated with apical periodontitis. Clinical significance: Theoretically, prolonging the antibacterial effects of materials used in endodontics may be interesting to help prevent reinfection and possibly to affect residual bacteria that survived the treatment procedures. How to cite this article: Barros J, Dias A, Rodrigues MA, Pina-Vaz C, Lopes MA, Pina-Vaz I. Antibiofilm and Antimicrobial Activity of Polyethylenimine: An Interesting Compound for Endodontic Treatment. J Contemp Dent Pract 2015;16(6):427-432.