الفهرس 
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Abstract
Objectives : This study was intended to investigate the effect of different in-office bleaching techniques on enamel micro-hardness and surface roughness. Materials and Methods: In this experimental study, three different bleaching agents (one light-activated and two chemical-activated) were used. Sixty sound human permanent maxillary central incisors were selected. Samples were fixed in cylinder plastic mold (2 cm width and 2 cm height) fabricated with using self-polymerized acrylic resin. Teeth were divided into two groups according to the test conducted on, micro-hardness test group (n=30) and surface roughness test group (n=30). Each group was further divided into three subgroups (n=10) according to the bleaching material used. All specimens were tested before and after bleaching application. Data for each test was tabulated and statistically analyzed. Results: Regarding the result of enamel micro-hardness, there was statistical significant reduction in the mean values of all tested groups after bleaching (p≤ 0.001), with highest mean value recorded for the Zoom followed by Dash and lowest for the Boost group. Regarding the result of surface roughness, there was no statistical significant difference between mean values of all groups after bleaching (P=0.76). Conclusion : All tested in-office bleaching systems were significantly decreased the enamel micro-hardness with insignificant change in enamel surface roughness.