Influence of Smear Layer on the Antimicrobial Activity of a Sodium Hypochlorite/Etidronic Acid Irrigating Solution in Infected Dentin.
BACKGROUND
The aim of this study was to evaluate the influence of the smear layer on the antimicrobial activity of a 2.5% sodium hypochlorite (NaOCl)/9% etidronic acid (HEBP) irrigating solution against bacteria growing inside dentin tubules.


METHODS
Dentin tubules were infected with Enterococcus faecalis by centrifugation. After 5 days of incubation, the smear layer had formed in half of the samples, which were then treated with 2.5% NaOCl either alone or combined with 9% HEBP for 3 minutes. The percentage of dead cells in infected dentinal tubules was measured using confocal laser scanning microscopy and the live/dead technique. The smear layer on the surface of the root canal wall was also observed by scanning electron microscopy. Results of the percentage of dead cells were compared using parametric tests after subjecting data to the normalized Anscombe transformation. The level of significance was P < .05.


RESULTS
In the absence of the smear layer, 2.5% NaOCl alone and combined with 9% HEBP showed high antimicrobial activity without significant differences between the 2. The smear layer reduced the antimicrobial activity of 2.5% NaOCl significantly, whereas the solution with HEBP was not affected. No dentin tubules free of the smear layer were obtained in the 2.5% NaOCl group. In the case of 2.5% NaOCl/9% HEBP, 95.40% ± 3.63% of dentin tubules were cleaned.


CONCLUSIONS
The presence of the smear layer reduced the antimicrobial activity of 2.5% NaOCl. The combination of 2.5% NaOCl/9% HEBP exerted antimicrobial activity that was not reduced by the smear layer.
Department of Microbiology, School of Dentistry, University of Granada, Granada, Spain.
Ana
A
Morago
Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil.
Ronald
R
Ordinola-Zapata
Department of Stomatology, School of Dentistry, University of Granada, Granada, Spain.
Carmen María
CM
Ferrer-Luque
Department of Stomatology, School of Dentistry, University of Granada, Granada, Spain.
Pilar
P
Baca
Department of Stomatology, School of Dentistry, University of Granada, Granada, Spain.
Matilde
M
Ruiz-Linares
Department of Microbiology, School of Dentistry, University of Granada, Granada, Spain. Electronic address: mtarias@ugr.es.
María Teresa
MT
Arias-Moliz
D000890:Anti-Infective Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development; D001641:Bicuspid / Q000382:microbiology; D003731:Dental Caries / Q000382:microbiology*; D003786:Dental Pulp Cavity / Q000382:microbiology; D003804:Dentin / Q000187:drug effects / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development; D012968:Etidronic Acid / Q000494:pharmacology*; D006801:Humans; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D012388:Root Canal Irrigants / Q000494:pharmacology*; D016369:Smear Layer / Q000382:microbiology*; D012973:Sodium Hypochlorite / Q000494:pharmacology*
D000890:Anti-Infective Agents; D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite; D012968:Etidronic Acid
Antimicrobial activity; etidronic acid; infected dentin; root canal irrigants; smear layer; sodium hypochlorite