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SURFACE DISINFECTION OF BOVINE DENTIN SAMPLES INFECTED WITH ESCHERICHIA COLI FOR THE ASSESSMENT OF ENDODONTIC IRRIGANTS

Alexandr Semenov

Abstract

The assessment of antiseptic solutionsпїЅ efficacy for root canal irrigation in terms of dentinal tubules disinfection is a challenging task. The samples used for this purpose should be standardized according to bacterial counts and the depth of their penetration inside dentinal tubules. However, the samples could be contaminated with bacteria from the surface of dentin during the sample acquisition. The treatment of dentin surface with antiseptic solutions will allow to avoid this contamination and thus to assess only the presence of bacteria inside dentinal tubules. Aim: to compare the antimicrobial activities of 3% sodium hypochlorite and 3% hydrogen peroxide solutions as surface antiseptics for the preparation of dentin samples used for the evaluation of endodontic irrigants. Materials and methods cylinders prepared from bovine teeth were autoclaved and contaminated with E. coli suspension. The samples were divided into 5 groups according to the antiseptic and the time of exposure: Group I (3% H2O2, 5 minutes), Group II (3% H2O2, 20 minutes), Group III (3% NaOCl, 1 minutes), Group IV (3% NaOCl, 5 minutes), Group V, control (sterile saline). After the samples were treated with antiseptic solutions, the surface disinfection was assessed with 2 methods: 1) canals were irrigated with sterile saline, which was collected and incubated with Brain Heart Infusion broth; 2) dentine shavings were obtained by scratching the surface with sterile round burs, the shavings were plated in culture media and incubated for 24 hours and 7 days microbial growth was assessed. In order to assess the bacterial penetration inside dentinal tubules the samples of root dentin were obtained during the enlargement of root canals with sterile round burs. Twenty mg of dentine shavings of each sample were obtained, dispersed in sterile Brain Heart Infusion broth followed by the preparation of 5 serial dilutions, plated in culture media and incubated for 7 days at 37 degrees C; microbial growth was assessed after 24 hours and 7 days. Results the antiseptic treatment accomplished in groups II (3% H2O2, 20 min) and IV (3% NaOCl, 5 min) allowed for the surface disinfection of dentin samples. However, the exposure of dentin samples to 3% NaOCl solution for 5 minutes caused the decrease of bacterial counts inside dentinal tubules which is not acceptable for the preparation of experimental samples. Conclusion The treatment of dentine samples with 3% H2O2 for 20 minutes provides surface disinfection without the decrease of bacterial counts inside dentinal tubules.

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DOI resolver: doi.org/10.5593/sgem2017h/63/s25.046

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