The effects of antimicrobials on endodontic biofilm bacteria.
BACKGROUND
In the present study, confocal microscopy, a miniflow cell system, and image analysis were combined to test in situ the effect of antimicrobials and alkali on biofilms of Enterococcus faecalis, Lactobacillus paracasei, Streptococcus anginosus, and Streptococcus gordonii isolated from root canals with persistent infections.


METHODS
Biofilms formed for 24 hours were exposed for 5 minutes to alkali (pH = 12), chlorhexidine digluconate (2.5%), EDTA (50 mmol/L), and sodium hypochlorite (1%). The biofilms were then characterized by using fluorescent markers targeting cell membrane integrity (LIVE/DEAD) and metabolic activity (5-cyano-2,3-ditolyl tetrazolium chloride and fluorescein diacetate). In addition, the biofilm architecture and the extent to which coating of the substrate surface with collagen influenced the resistance pattern to the chemicals were also analyzed.


RESULTS
NaOCl (1%) affected the membrane integrity of all organisms and removed most biofilm cells. Exposure to EDTA (50 mmol/L) affected the membrane integrity in all organisms but failed to remove more than a few cells in biofilms of E. faecalis, L. paracasei, and S. anginosus. Chlorhexidine (2.5%) had a mild effect on the membrane integrity of E. faecalis and removed only 50% of its biofilm cells The effects were substratum-dependent, and most organisms displayed increased resistance to the antimicrobials on collagen-coated surfaces.


CONCLUSIONS
The biofilm system developed here was sensitive and differences in cell membrane integrity and removal of biofilm cells after exposure to antimicrobials commonly used in endodontics was discernible.
Chávez de Paz
Luis E
LE
Department of Oral Biology, Faculty of Odontology, Malmö University, Malmö, Sweden. luis.chavez.de.paz@od.mah.se
Bergenholtz
Gunnar
G
Svensäter
Gunnel
G
D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002462:Cell Membrane / Q000187:drug effects; D002710:Chlorhexidine / Q000494:pharmacology; D003094:Collagen; D015169:Colony Count, Microbial; D003786:Dental Pulp Cavity / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D004492:Edetic Acid / Q000494:pharmacology; D013293:Enterococcus faecalis / Q000187:drug effects / Q000502:physiology; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D012388:Root Canal Irrigants / Q000494:pharmacology*; D012973:Sodium Hypochlorite / Q000494:pharmacology; D013291:Streptococcus / Q000187:drug effects / Q000502:physiology; D013379:Substrate Specificity
D000891:Anti-Infective Agents, Local; D005456:Fluorescent Dyes; D012388:Root Canal Irrigants; D003094:Collagen; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D002710:Chlorhexidine