Evaluation of the Effect of Enterococcus faecalis Biofilm on the 2% Chlorhexidine Substantivity: An In Vitro Study

• We correlated 2% chlorhexidine substantivity and antimicrobial residual effect on human dentin.
• High-performance liquid chromatography was used to quantify chlorhexidine.
• Confocal laser scanning microscopy was used to check bacterial viability.
• The experimental periods were 48 hours, 7 days, and 30 days.
• Chlorhexidine remained on dentin for 7 days, inhibiting bacterial regrowth.
• The presence of E. faecalis biofilm did not affect 2% chlorhexidine maintenance.

IntroductionThe aim of this study was to correlate the bacterial viability and the presence of 2% chlorhexidine (CHX) solution on dentin by means of confocal laser scanning microscopy and high-performance liquid chromatography for 48 hours, 7 days, and 30 days.MethodsOne hundred twenty-three extracted human teeth were used. Samples were divided into 4 groups according to the solution (CHX or saline) and the presence of Enterococus faecalis biofilm. Samples were kept in contact with 5 mL of the solution for 5 minutes. Each group was divided into 3 subgroups according to the evaluation period (n = 10). Statistical analysis was performed by using the Kruskal-Wallis test, the Mann-Whitney U test (P < .05), and the Spearman rank correlation coefficient (P < .01).ResultsThere was a negative correlation between the percentage of live cells and the amount of remaining CHX (P = .000). CHX significantly reduced the percentage of viable cells compared with saline after 48 hours (P = .007). Differences were maintained in the 7-day evaluation period (P = .001). After 30 days, the CHX group presented an increase of viable cells, thereby becoming similar to saline (P = .623). Simultaneously, the remaining CHX was significantly reduced in the 30-day specimens (P = .000).ConclusionsThe results of this study indicate that 2% CHX solution was detected for 48 hours and 7 days with a low percentage of viable cells. The presence of microorganisms on human dentin did not affect 2% CHX maintenance.