An in vitro evaluation of the antimicrobial efficacy of irrigants on biofilms of root canal isolates.
OBJECTIVE
The bactericidal effect of four antimicrobial agents was investigated against single-species biofilms derived from a range of root canal isolates.


METHODS
Single-species biofilms of Prevotella intermedia, Peptostreptococcus micros, Streptococcus intermedius, Fusobacterium nucleatum and Enterococcus faecalis were generated on membrane filter discs and subjected to 15 min or 1 h incubation with 5 p.p.m. colloidal silver, 2.25% sodium hypochlorite (NaOCl), 0.2% chlorhexidine, 10% iodine or phosphate buffered saline (PBS) as a control. The antimicrobial activity of the agents was neutralized and the bacterial cells were harvested from the discs by vortexing, serially diluted in reduced transport fluid, plated on fastidious anaerobe agar containing 5% horse blood, incubated anaerobically and colony-forming units calculated.


RESULTS
Iodine and NaOCl were more effective than chlorhexidine except against P. micros and P. intermedia where they were all 100% effective. Iodine and NaOCl elicited a 100% kill after 1 h incubation for all strains used. However, after 15 min, they showed differing bactericidal effects depending on the strain. None of the agents were effective against F. nucleatum after 15 min but NaOCl, iodine and chlorhexidine were all effective after 1 h. Colloidal silver was generally ineffective.


CONCLUSIONS
The effectiveness of a particular agent was dependent on the nature of the organism in the biofilm and on the contact time. NaOCl was generally the most effective agent tested, followed by iodine. However the clinical efficacy of these agents must be considered in light of the complex root canal anatomy and polymicrobial nature of root canal infections.
Spratt
D A
DA
Department of Conservative Dentistry, Eastman Dental Institute for Oral Health Care Sciences, University College London, University of London, London, UK. d.spratt@eastman.ucl.ac.uk
Pratten
J
J
Wilson
M
M
Gulabivala
K
K
D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001431:Bacteriological Techniques; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002021:Buffers; D002710:Chlorhexidine / Q000494:pharmacology; D015169:Colony Count, Microbial; D003786:Dental Pulp Cavity / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000187:drug effects; D016967:Fusobacterium nucleatum / Q000187:drug effects; D006801:Humans; D007455:Iodine / Q000494:pharmacology; D010462:Peptostreptococcus / Q000187:drug effects; D018713:Prevotella intermedia / Q000187:drug effects; D012388:Root Canal Irrigants / Q000494:pharmacology*; D012834:Silver / Q000494:pharmacology; D012965:Sodium Chloride; D012973:Sodium Hypochlorite / Q000494:pharmacology; D013291:Streptococcus / Q000187:drug effects; D013997:Time Factors
D000891:Anti-Infective Agents, Local; D002021:Buffers; D012388:Root Canal Irrigants; D012834:Silver; D012965:Sodium Chloride; D007455:Iodine; D012973:Sodium Hypochlorite; D002710:Chlorhexidine