الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
One of the most common important global oral health problems in the world today is dental caries. Strategies to prevent dental caries could be achieved by two ways, either by reducing the attacking forces or by enhancing the host resistance. Decreasing the attacking forces, could be achieved by removal of dental plaque or by decreasing the number of pathogenic microorganisms in saliva. On the other hand to enhance the host resistance, there are different ways like reducing enamel’s solubility in acids and covering the enamel surface by a barrier such as fluoride varnish. (Rugg-Gunn, 2013)
Fluoride varnishes have been widely used in many countries for decades. The action of fluoride in fluoride varnish makes it useful in caries prevention and caries arrest. Moreover, fluoride varnish is also used to treat dentinal hypersensitivity. Various researchers have attempted to increase the antibacterial effect of dental materials by incorporation of bactericidal agents such as nanosilver particles. The addition of nanosilver particles to fluoride varnish has been stated to have a very good protective effect against oral streptococci. (Goa et al, 2018)
This in-vitro study was conducted to compare between antimicrobial effect of fluoride Varnish containing nanosilver particles with different concentrations (432 μg/mL -216 μg/mL -108 μg/mL) and conventional fluoride Varnish on Oral Streptococci.
The strains of streptococcus mutans and streptococcus salivarius was isolated on Mitis Salivarius Bactrian agar plates after incubation for 24 hours at 37 C. After identification of the isolated strains, Mueller–Hinton agar were prepared and divided into groups for materials application. Each plate of Mueller–Hinton agar was digged in the middle for making a hole for materials application. The three concentrations of nanosilver fluoride varnish and the conventional fluoride varnish was labled at the back of each Mueller–Hinton plate by a marker. Each plate containing Streptococcus mutans culture received 50 μL of nanosilver fluoride varnish (432 μg/mL-216 μg/mL -108 μg/mL) and the conventional fluoride varnish respectively by the aid of the micropipette device.This step was repeated for the plates containing Streptococcus salivarius culture. Then the plates was incubated at 37°C for 24 hours anaerobically in the incubator. (kumar et al, 2010)
The antibacterial property of materials were assessed, which appeared from the circular zones of bacterial inhibition around each material. The diameter of these zones of bacterial inhibition were measured in millimeters using ruler (from the edge of the zone from one end to the next edge).
Statistical analysis was performed using (ANOVA) test, followed by Tukey’s post hoc test for comparison between groups.The level of significance was set at P < 0.05.
The results showed that there was statistically significant difference in the mean inhibition zones diameters between conventional fluoride varnish Fluor Protector and all three concentrations of nanosilver fluoride varnish (432 μg/mL -216 μg/mL -108 μg/mL) against both Streptococcus mutans and Streptococcus salvarius. Regarding streptococcus mutans there was a direct correlation between the inhibition zones diameter and the concentrations of nanosilver particles in the nanosilver fluoride varnish. Thus the antibacterial effect of nanosilver fluoride varnish against streptococcus mutans organisms gradually increases with the increase of the nanosilver particles concentration. On the other hand concerning.