الفهرس 
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Abstract
Introduction: Fluoride is needed for the normal development of bone and teeth; in high levels, it affects developing teeth and bone. Dental fluorosis (DF) is caused by ingestion of excess fluoride mainly through drinking water. The aim of this study: This study aims to investigate the effects of enamel abrasion and deproteinization on the shear bond strength of orthodonotic brackets to fluorosed enamel. Materials and methods: Metal brackets were bonded to the buccal surfaces of ninety fluorosed premolars and thirty normal premolars. Before bonding, the fluorosed premolars were divided randomly into three equal groups of 30 teeth each. The buccal surfaces of the teeth in group I were sandblasting by sandblasted by use of 50-µm aluminum oxide particles for 5 seconds at 40-Ib pressure with micro-etcher held at 10-mm distance. The buccal surface of group II utilized of deprotienization with sodium hypochlorite 5% for 1 minute. While the group III, there the buccal surface not subjected to surface treatment. The normal teeth, which represent group IV not subjected to surface treatment. Then the four groups etched with 37% phosphoric acid for 30 seconds. Therefore Transbond XT primer and adhesive were used. The application of adhesives systems was done according to the manufacturer’s instructions. After bonding, all teeth of four groups were used to assess the shear bond strength (SBS) using a universal testing machine and adhesive remnant index (ARI) using a stereomicroscope. Meanwhile, additional samples were investigated with scanning electron microscope (SEM) to show the types of etch pattern on fluorosed and normal enamel. The data were collected and statistically analyzed using IBM-SPSS software (version 25), Kruskal-wallis H test and Chi square test. Results: The SBS between the 4 groups were showed a statistically significant difference (p=0.002) a statistically significantly lower SBS in group II as compared to groups I and III. No significant difference exists between group IV and any of the other 3 groups. Also, no significant difference exists between group I and group III. A statistically significant difference in ARI between the 4 groups (p<0.0005). Conclusions: The shear bond strength of all experimental groups were within the range from 6 to 8 MPa. The sandblasting by using of 50-µm aluminum oxide particles for 5 seconds. Then, the enamel buccal surface conditioned using 37% phosphoric acid gel, resulting in no statistically significant differences when compared with fluorosed enamel without surface treatment. The utilization of 5% sodium hypochlorite for one minute as surface treatment on fluorosed enamel before etching, there were decrease in shear bond strength. And when compared with other three groups was significant difference.