Evaluation of the Susceptibility of Multispecies Biofilms in Dentinal Tubules to Disinfecting Solutions

• The effect of the source of biofilm bacteria on their susceptibility in dentinal tubules to disinfecting solutions is evaluated.
• Mature mono- and multispecies biofilms in dentinal tubules are more resistant to disinfectants than corresponding young biofilms.
• The susceptibility of the monospecies Enterococcus faecalis dentin biofilm showed strain-related differences, whereas the multispecies biofilms from different donors showed similar susceptibility.

IntroductionThe present study evaluated the effect of the source of biofilm bacteria on their susceptibility in dentinal tubules to disinfecting solutions using an infected dentin model.MethodsInfected dentin blocks were prepared. Enterococcus faecalis strains VP3-181 and Gel 31 were introduced into dentinal tubules by centrifugation to form monospecies biofilms, whereas 3 specimens of pooled plaque bacteria collected from different donors were used to grow multispecies biofilms in dentin. After 1 and 3 weeks of incubation, the samples were subjected to sterile water, 2% chlorhexidine (CHX), and 2% sodium hypochlorite (NaOCl). After the 3-minute exposure, the proportions of killed bacteria in dentin canals were assessed by viability staining and confocal laser scanning microscopy.ResultsThe proportion of killed bacteria in mature (3 weeks) mono- and multispecies biofilms was lower than in young biofilms (1 week) after treatment (P < .05). E. faecalis Gel 31 biofilms and multispecies biofilms were more resistant than VP3-181 biofilms. No differences in the susceptibilities to the disinfecting agents of the 3 multispecies biofilms were detected; 2% NaOCl was more effective against multispecies biofilms in dentin than 2% CHX (P < .05), whereas no significant difference was detected between 2% CHX and 2% NaOCl against the E. faecalis strains.ConclusionsMature mono- and multispecies biofilms in dentinal tubules are more resistant to disinfectants than corresponding young biofilms. The susceptibility of the monospecies E. faecalis dentin biofilm showed strain-related differences, whereas the multispecies biofilms from different donors showed similar susceptibility.