Effect of endodontic irrigants on biofilm matrix polysaccharides

Aim To specifically investigate the effect of endodontic irrigants at their clinical concentration on matrix polysaccharides of cultured biofilms. Methodology Saccharolytic effects of 3% H2O2, 2% chlorhexidine ( CHX), 17% EDTA, 5% NaOCl and 0.9% saline ( control) were tested using agarose ( a 1- 3 and beta 1- 4 glycosidic bonds) blocks ( n = 3) in a weight assay. The irrigants were also applied to threespecies biofilms ( Streptococcus mutans UAB 159, Streptococcus oralis OMZ 607 and Actinomyces oris OMZ 745) grown anaerobically on hydroxyapatite discs ( n = 6). Glycoconjugates in the matrix and total bacterial cell volumes were determined using combined Concanavalin A-/Syto 59-staining and confocal laserscanning microscopy. Volumes of each scanned area triplicates/sample) were calculated using Imaris software. Data were compared between groups using one-way ANOVA/Tukey HSD, alpha = 0.05. Results The weight assay revealed that NaOCl was the only irrigant under investigation capable of dissolving the agarose blocks. NaOCl eradicated stainable matrix and bacteria in cultured biofilms after 1 min of exposure ( P < 0.05 compared to all groups, volumes in means +/- standard deviation, 10 (-3) mm(3) per 0.6 mm(2) disc; NaOCl matrix: 0.10 +/- 0.08, bacteria: 0.03 +/- 0.06; saline control matrix: 4.01 +/- 1.14, bacteria: 11.56 +/- 3.02). EDTA also appeared to have some effect on the biofilm matrix ( EDTA matrix: 1.90 +/- 0.33, bacteria: 9.26 +/- 2.21), whilst H2O2 and CHX merely reduced bacterial cell volumes. Conclusion Sodium hypochlorite can break glycosidic bonds. It dissolves glycoconjugates in the biofilm matrix. It also lyses bacterial cells.