الفهرس 
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Abstract
The aim of the present study was to prepare and characterize silver nanoparticles AgNPs paste, compare the antimicrobial effect of different concentrations of silver nanoparticles AgNPs paste used as intra canal medication and calcium hydroxide Ca(OH)2 against Fusobacterium and Candida after 3 different times of application 3, 7, and 14 days, and clinical application of most effective concentration of AgNPs and Ca(OH)2 on selected patients with necrotic pulp and their outcome on clinical success. The microorganisms were isolated from necrotic pulp tissues taken from twenty patients with necrotic pulps of anterior teeth with no periapical lesion and were identified by culturing in agar plates and PCR. The microbial suspension was prepared from the two most predominant types of microorganisms resulted from samples identification; Fusobacterium and Candida. The microbial suspensions of the two selected microorganisms were standardized to 0.5 McFarland. Antimicrobial evaluation was done using agar diffusion method. Twenty patients with necrotic pulp tissues were divided into 2 groups according to the type of medicament used, ten patients for each group. The medicaments used were Ca(OH)2 paste and 0.03 mg/ml AgNPs. Two microbiological samples were taken using H-file, one after access cavity preparation and the second after removal of intra canal medication which was inserted for one week after mechanical preparation. Mechanical preparation was completed using REVO-S rotary system. Irrigation was done using saline. Obturation was done using Revo-S gutta percha points. Resin sealer was used. Microbiological samples were incubated at 37 ̊ C for one day aerobically and for 5 days anaerobically. The colonies were identified by Culture characterstics, Microscopic examination, Biochemical reactions, and Polymerase chain reaction (PCR). Follow up were done for all patients after one month and three months by clinical and radiographic evaluation.Colony forming units CFUs were counted and data were analyzed. Results showed that Fusobacterium was the most prevelant microorganisms found in the samples of necrotic pulps. Candida was the second most isolated, followed by Lactobacillus, Enterococcus, Peptostreptococcus, Actinomyces, Prevotella, Porphyromon, Difteroid. For Candida: After three days, Ca(OH)2 group had a statistically significantly high mean inhibition zone values, but there was no statistically significant difference between 0.03 mg/ml AgNPs group and 0.003 mg/ml AgNPs group. For Fusobacterium: After three selected time periods, 0.03 mg/ml AgNPs group had the statistically significantly high mean inhibition zone values among other groups. There was a statistically significant decrease in CFUs between before and after treatment with Ca(OH)2 group and 0.03 mg/ml AgNPs group with 17.95 % and 42.86 % percentage reduction respectively. But in AgNPs group, there was no statistically significant decrease in number of CFUs for Candida between before and after treatment. AgNPs paste showed good antibacterial effect and less antifungal effect. Under the conditions of the present study, the following was concluded. The microbiota of necrotic pulp was poly microbial infection with the prevalent of Fusobacterium and Candida. AgNPs paste seems to be a valuable option in the battle against maximum amount of bacteria. It seems that the concentration of the material had a great influence on its antimicrobial effect.