الفهرس 
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Abstract
Tooth sensitivity is one of the most common side effects of bleaching treatment which is directly related to the bleaching agent’s ability to spread fast after accessing the dental tissues and release free radicals that oxidize the organic components of the tooth structure, penetrating through dental tissues, and establishing direct contact with the pulp. The use of antioxidants has been widely debated as a way to speed up the elimination of any remaining oxygen in the tooth structure following the application of a bleaching gel, this means decreasing the damage caused by hydrogen peroxide on the pulp. Sodium ascorbate has been the most researched antioxidant in recent decades as it has a unique power to prevent oxidative damage to significant biological macromolecules. No clinical studies evaluating the impact of antioxidant application on tooth sensitivity after bleaching. Therefore, the aim of the present study was to investigate the effect of antioxidant (10% Sodium Ascorbate) on tooth sensitivity after two different bleaching techniques; power bleaching (32% hydrogen peroxide Light Whitening AC) and chemical bleaching (40% hydrogen peroxide Power Whitening YF) immediately after bleaching, 1 day, 1 week, 2 weeks and 1 month follow up periods. A total of ten patients of an age ranging between (18-25) years old were selected to participate in this study following detailed inclusion and exclusion criteria. Prior to the study, each patient received full mouth scaling and polishing and examined for sensitivity before the procedure. The study design included all anterior and premolar teeth of maxillary and mandibular arch of each participant which divided into four groups according to bleaching materials and/or antioxidant used. group A: maxillary right quadrant received power bleaching with antioxidant. group B: maxillary left quadrant received power bleaching without antioxidant. group C: mandibular right quadrant received chemical bleaching without antioxidant. group D: mandibular left quadrant received chemical bleaching with antioxidant. After isolation and application of gingival protector, the chemical bleaching gel was applied to the labial surface of mandibular anterior and premolar teeth and the power bleaching gel was applied to the labial surface of maxillary anterior and premolar teeth which was activated using LED source. The bleaching gels were left for 15 minutes then removed by high dental suction. Three sessions were performed then, the teeth were washed and dried. Then, A layer of 10% sodium ascorbate gel was applied to group A and group D for 15 minutes then, the surface was rinsed and dried. The tooth sensitivity was evaluated by using Numerical Rating Scale and Schiff Scale immediately after treatment, 1 day, 1 week, 2 weeks and 1 month follow up periods. Concerning the results of this study, it was noticed that using the antioxidant in group A after power bleaching in comparison to group B revealed a significance (p = 0.027* in NRS and p = 0.046* in SS) after one day from bleaching. In comparison between group A and group B according to NRS, using antioxidant after bleaching (group A) showed no sensitivity immediately after bleaching compared to two teeth (4%) with moderate pain without using antioxidant (group B). After one day, mild pain in two teeth (4%) was recorded in group A compared to mild pain in one tooth (2%) and moderate pain in six teeth (12%) in group B. After one week, no pain was recorded in group A compared to mild pain in three teeth (6%) in group B. Similar results were found using SS. According to the effect of the antioxidant on tooth sensitivity after chemical bleaching in group D in comparison to group C, it revealed a high significance (p = 0.001* in NRS and p < 0.001** in SS) after one day from bleaching. In comparison between group D and group C according to NRS, using antioxidant after bleaching (group D) recorded mild pain in one tooth (2%) immediately after bleaching compared to one tooth (2%) with mild pain and three teeth (6%) with moderate pain without using antioxidant (group C). After one day, mild pain in seven teeth (14%) and moderate pain in three teeth (6%) was recorded in group D compared to mild pain in ten teeth (20%), moderate pain in ten teeth (20%) and considerable pain in seven teeth (14%) in group C. After one-week, mild pain in one tooth (2%) was recorded in group D compared to mild pain in six teeth (12%) in group C. Similar results were found using SS. from the previous results, using antioxidant (Sodium Ascorbate) after bleaching was effective in reducing the intensity of tooth sensitivity at the different follow up periods especially after one day from bleaching.