Ex vivo evaluation of the effects of several root canal preparation techniques and irrigation regimens on a mixed microbial infection.
OBJECTIVE
To assess the ex vivo effectiveness of the alternated use of 1% NaOCl and 15% citric acid in association with two instrumentation techniques for the disinfection of root canals infected with Enterococcus faecalis and Candida albicans.


METHODS
Eighty human mandibular premolars with straight, oval root canals standardized to 15 mm in length were infected with a mixed culture of E. faecalis and C. albicans for 28 days. Five other teeth were used as controls and were neither contaminated nor instrumented. Specimens were divided into two groups (n = 40), according to whether the canal preparation technique used manual (K-type) or rotary (Protaper Universal) instruments. These groups were further divided into four subgroups (n = 10) according to the irrigation solution used: saline, 1% NaOCl, 1% NaOCl with alternated use of 15% citric acid and 5.25% NaOCl. Root canals were prepared with a crown-down technique until a size 50 K-file or with rotary preparation until an F5 instrument. Microbiological sampling was performed before (S1) and after (S2) the chemomechanical preparation, using sterile paper points. The specimens were split, and 0.02 g of dentine chips was collected from the root thirds to verify the presence of microorganisms in root canal walls.


RESULTS
Saline and 1% NaOCl were less effective in reducing microorganisms compared with 1% NaOCl with alternated use of 15% citric acid or 5.25% NaOCl alone (P < 0.05). Both manual and rotary preparations significantly reduced microorganisms regardless of the irrigation solution used (P < 0.05). However, there was no significant difference between the canal preparation techniques (P > 0.05).


CONCLUSIONS
Irrigation with 5.25% NaOCl and 1% NaOCl alternated with 15% citric acid reduced microorganisms in infected root canals significantly more than saline and 1% NaOCl.
Department of Restorative Dentistry, Dental School, University of São Paulo, São Paulo, Brazil. vcnakamura@usp.br
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Nakamura
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Cai
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Candeiro
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Ferrari
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Caldeira
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Gavini
D001641:Bicuspid / Q000382:microbiology; D002176:Candida albicans / Q000187:drug effects*; D019343:Citric Acid / Q000627:therapeutic use; D003786:Dental Pulp Cavity / Q000382:microbiology*; D003804:Dentin / Q000382:microbiology; D004203:Disinfection / Q000379:methods; D013293:Enterococcus faecalis / Q000187:drug effects*; D004867:Equipment Design; D006801:Humans; D012388:Root Canal Irrigants / Q000627:therapeutic use*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D012965:Sodium Chloride; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D019227:Tooth Apex / Q000382:microbiology
D012388:Root Canal Irrigants; D019343:Citric Acid; D012965:Sodium Chloride; D012973:Sodium Hypochlorite