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Effect of chlorhexidine hexametaphosphate nanoparticles on properties of a glass ionomer cement of high-viscosity


The use of nanotechnology in the health sciences has increased significantly in recent years and is of great importance in dentistry. In this study will be evaluated the influence of incorporating chlorhexidine hexametaphosphate nanoparticles (HMP-CLX) on physico-chemical, mechanical and antibacterial properties of a glass ionomer cement (GIC) of high viscosity. After the synthesis and characterization of nanoparticles, they will be added to the GIC in concentrations of 1%, 2% and 5%. The GIC without added nanoparticles will be used as control group. In the first part of the study we will analyze the ability to release chlorhexidine and fluoride release and recharge. For each test, specimens (n = 10 per group) measuring 6 mm in diameter and 3 mm in height will be maintained in 1 mL of artificial saliva at 37 °C for 1 h, 24 h, 7, 15 and 30 days. The CLX concentration in saliva will be measured by ultraviolet spectrophotometry at 255 nm, and the dosage of fluoride by specific electrode. On the 30th day, the specimens will receive a topical fluoride application and the release will be measured after 1 h, 24 h, 7, 15 and 30 days to evaluate the recharge of fluoride capacity . In the second part of the study, we wil analize microbiological and biochemical composition, as well as the metabolic activity of the biomass and biofilm formed on the specimens of GIC containing the same concentrations of nanoparticles CLX - HMP (n = 10 per group and type of analysis ). Polymicrobial biofilms grow on each specimen, which will be suspended in 2.0 ml of McBain medium with saliva diluted in glycerol (106 cfu/ml). Incubation is performed under anaerobic conditions at 37 °C for 72 hours. Then total microorganisms, total aciduric bacteria, mutans streptococci and lactobacilli are quantified. The metabolic activity will be evaluated by XTT, biomass by crystal violet staining and biochemical analysis by checking the production of proteins, carbohydrates and lactic acid. Finally, we will evaluate the adhesion of the material to sound and caries affected dentine using microshear test. 80 human third molars, which are divided into two groups (n = 40) in accordance with the condition of the substrate (sound dentine and caries affected dentine), and then each of these groups will be divided into four sub groups(n = 10) in accordance with the concentration of nanoparticles CLX - HMP added to the GIC (0%, 1%, 2% and 5%). On dentine surface of each tooth,two specimens of 1 mm diameter and 1 mm in height will be made. Microshear test will be performed 24 hours after preparation in one of the specimens and after six months of storage, on the other specimen. Then we will evaluate fracture patterns. According to the data distribution and homogeneity of variances, the most appropriate tests for each set of data will be applied. The significance level is 5%. (AU)

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