الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The most common side effect of orthodontic treatment is white spot lesions, which are defined as clinically detectable manifestations of subsurface enamel demineralization, representing the first stage of caries formation. Nearly 50% of patients after 12 months of treatment present with white spot lesions, due to many factors as difficult oral hygiene and the addition of orthodontic appliances in the mouth creates a rapid increase in bacterial flora, predominantly Streptococcus mutans and Lactobacillus. Together, these factors create an environment that favors the demineralization of enamel. Orthodontic brackets are fixed attachments that are in direct contact with the surface of the tooth enamel and, due to several factors such as their intricate design, the duration of the treatment, and the dental hygiene of the patient, a greater accumulation of biofilm occurs, increasing the levels of acidogenic bacteria, most notably Streptococcus mutans and Lactobacillus. These bacteria are able to lower the pH of the biofilm in orthodontic patients to a greater degree than in patients without orthodontics. Therefore, the progression of caries is faster. Limited information is available on which orthodontic brackets are most susceptible to adhesion of cariogenic Streptococcus mutans and Lactobacillus which are the main responsible for dental caries. The current study was conducted to investigate antimicrobial effect of nanosilver coated stainless steel brackets in prevention of enamel demineralization in orthodontic patients. This study was carried out on thirty-two females’ patients attending the Orthodontic clinic at the Faculty of Dentistry, Tanta University, scheduled to have maxillary and mandibular first premolars extracted as a part of orthodontic treatment. The age ranging from 13-16 years. They were divided into 2 equal groups. group I (experimental group) n = 16 patients in which 64 nanosilver coated stainless steel brackets were bonded in the upper and lower first premolars and group II (control group) n = 16 patients in which conventional uncoated stainless steel brackets were bonded in the upper and lower first premolars in this group. the silver nanoparticles were synthesized and characterized before and after coating with several techniques for safety and human welfare. According to debonding schedule time of the study, one and two months, the patients were recalled to debonded the brackets and extract the corresponding premolars for each study period. The plaque adhered around the brackets was transferred in a sterile test tube with 2 ml phosphate buffer saline for the antiadhesion bacterial analysis. The extracted teeth were cleaned and prepared for evaluation under scanning electron microscope that study enamel ultrastructure and energy dispersive x-ray analysis that evaluate the mineral content of the teeth. Comparison between two groups was performed using unpaired student t-test and Paired t-test with level of significance was set to be 0.05. There was a significant difference between the two groups throughout the study periods, and energy dispersive x-ray microscopy and scanning electron microscopy images revealed that nanosilver coated brackets have a significantly better result in the prevention of enamel demineralization around orthodontic brackets.