Application of laser scanning microscopy for the analysis of oral biofi lm dissolution by different endodontic irrigants

Background: Multi-specie biofi lms are highly resistant to antimicrobials due to cellular interactions found in them. The purpose of this study was to evaluate, by confocal laser scanning microscopy, the biofi lm dissolution effectiveness of different irrigant solutions on biofi lms developed on infected dentin in situ. Materials and Methods: A total of 120 bovine dentin specimens infected intraorally (30/group) were treated by the following solutions: 2% of chlorhexidine digluconate, 1%, 2.5% and 5.25% of sodium hypochlorite (NaOCl). The solutions were utilized for 5, 15 and 30 min with 2 experimental volumes 500 μL and 1 mL. All the samples were stained using an acridine orange and the biofi lm thickness before (control group) and after the experiments were evaluated, utilizing a confocal microscope at ×40. The Mann-Whitney U and the nom-parametric Kruskal-Wallis Dunns tests were utilized to determine the infl uence of the volume and to perform the comparisons among the groups respectively. The signifi cance level was set at P < 0.05. Results: Statistical differences were not found among the control and the 2% chlorhexidine digluconate groups at any experimental period (P > 0.05). The biofi lm dissolution treated with 1% NaOCl was directly proportional to the exposure time (P < 0.05). The higher values of biofi lm dissolution were found in 2.5% and 5.25% NaOCl groups (P > 0.05). Conclusion: The higher exposure times and concentrations of NaOCl were not suffi cient to dissolve 100% of the biofi lm. However, all NaOCl solutions were more effective than 2% chlorhexidine digluconate to dissolve organic matter.