Methods: In order to form the biofilms, we inoculated a Brain Heart Infusion broth with Streptococcus gordonii ATCC10558 and P.g before perfusing it, in anaerobiosis, for 7 days via a closed circuit containing 2 Modified Robbins Devices (MRD-LPMR-12E) (Tyler Research-Canada) assembled in parallel. Biofilms grew on hydroxyapatite discs bonded on the bottom of the MRD plugs and were then treated for 30min with CHX on the first MRD and with CHX plus low intensity DC (1,5mA or 10mA) on the second one. The bactericidal effect against biofilms was evaluated after culture by comparing the mean proportion of P.g killed at T=10min.
Results: In the first series of biofilm treatments (CHX +/- 1,5 mA DC), the mean proportion of P.g killed was respectively 81,06% (+/- 8,55) for the biofilms undergoing CHX only and 79,08% (+/- 9,96) when they were treated as well with 1,5mA DC. The difference was not statistically significant (p>0,05).
In the second series (CHX +/- 10mA DC), we found a proportion of P.g killed of 84,9% (+/-2,76) with CHX and 98,93% (+/- 0,55) when CHX was used in addition with the DC. Here, the difference was significant (p<0,05). Conclusion: These results show that CHX 0,2% is efficient against P.g when the latter is located within a biofilm as is the case in subgingival plaque. Moreover, we also report an electrical enhancement of chlorhexidine 0,2% efficacy against Porphyromonas gingivalis biofilms when used in conjunction with 10 mA currents. The improvement discribed here is called the BIOELECTRIC effect.