Recently, bleaching treatment is requested not only for discolored teeth but also for healthy white teeth for esthetic reasons. Bleaching treatment is a minimal interventional treatment having the same concept as dental treatment without drilling. fore bleaching, and then LaserWhite10™ which includes carbamide peroxide was applied to all the teeth and activated with a semiconductor laser for bleaching. After bleaching. The color of the enamel surface of the specimens was measured and surface conditions were inspected by SEM. The bleaching procedure was done once (Group I), twice (Group II), and thrice (Group III). All measurements were compared among the three groups, and all SEM observations were inspected and the following results were obtained. 1. There were significant differences in color between pre-and post-treatment of teeth in Group I. The average color difference (ΔE) between the two was ΔE1=2.32±0.28. There were no obvious changes of enamel surfaces inspected by SEM. 2. The average color difference between the two was ΔE2=3.33±0.38 in Group II. The enelel surfaces were a little rough by SEM observation. 3. The average color difference between the two was ΔE3=3.53±0.41 in Group III. Enamel prism structures were found by SEM observation. A better bleaching effect was obtained with more times of bleaching, but the enamel surfaces became rougher. Therefore, the most effective bleaching procedure is once. The problem with carbamide peroxide that the bleaching effect became weak by increasing the number of bleaching times is improved. For clinical aspects, the bleaching procedureshould be performed no more than twice due to the surface condition of enamel, color alteration, and treatment time.
