Antimicrobial, antibiofilm and cytotoxic activity of silver nanoparticles and farnesol solutions for root canals desinfection.

Abstract

Silver (Ag) is known for its antimicrobial effects therefore it has being used in the treatment of burns, wounds and eye infections. With the advances in nanotechnology, some nanomaterials have been developed, such as silver nanoparticles (AgNPs) which has been used as therapeutic agent to prevent bacterial colonization of medical devices such as catheters and orthopedic prostheses and it have recently been evaluated in the Dentistry field. Farnesol is a sesquiterpene alcohol naturally found in propolis and in essential oils of citrus fruits and has been reported to have antitumor activity, as well as antimicrobial and antibiofilm effects, either by preventing biofilm formation or by attacking biofilms already established. The aim of this study is to evaluate the antimicrobial and antibiofilm activity besides cytotoxic properties of AgNPs and farnesol solutions used in final root canal irrigation. Initially the antimicrobial activity of the AgNPs (5-10 nm) and farnesol solutions will be evaluated at different concentrations against C. albicans and E. faecalis by determining the minimal inhibitory concentration (MIC) and minimal microbicidal concentration (MMC). To evaluate antibiofilm efficacy, bovine dentin blocks will be divided into three groups: GI- treated with AgNPs, GII- treated with farnesol and GIII- untreated. After the treatment of the dentin blocks with NPsAg for 24 hours, the samples will be inoculated with E. faecalis and incubated for additional 24 hours at 37°C under microaerophilic conditions. The analysis will be performed by confocal laser microscopy and by CFU mL-1 counts. Cytotoxicity will be assessed in mPDL cell culture. MTT and Comet assays will be performed in order to assess cell viability and genotoxicity after the cells being in contact with different AgNPs and farnesol concentrations at different periods. To evaluate disinfection effectiveness of the AgNPs and farnesol solutions into root canal system (RSC), the concentration obtained from MMC, which must show no cytotoxicity effects, will be used as irrigating solution at the final stage of root canal instrumentation in human teeth infected by E. faecalis. The specimens will be divided into five experimental groups: G1- 2.5% NaOCl + EDTA + saline, G2- 2.5% NaOCl + EDTA + saline + AgNPs, G3- 2.5% NaOCl + EDTA + saline + farnesol, G4- saline + AgNPs, G5- saline + farnesol and two control groups (G6- without irrigation and G7- sterile culture medium). After microbiological samples, serial decimal dilutions and seeding, the number of CFU mL-1 will be determined. Data will be statistically analyzed using ANOVA and Tukey tests with 5% of significance level.