Supervisor : Olfat ElSayed Hassanein, Asmaa Ali Mohamed Yassen, Inas Mohsen El-Zayat.Shawky, Aya Khaled Mohamed,2022-01-182022-03-272022-01-182022-03-272017.EG-CaMIUhttps://iorep.miuegypt.edu.eg/handle/20.500.13071/81DISSERTATION NOTE-Degree type M.Sc.DISSERTATION NOTE-Name of granting institution Misr International University, Faculty of Oral and Dental MedicineIncludes bibliographic references (p. 83-90)`Includes summary in Arabic.Dental aesthetics is considered an important concern that many patients seek for, aiming to reach an attractive smile. Tooth discoloration can be classified as the main etiological factor for esthetic problems in dental patients. It can be correctly evaluated and managed by detecting its type, location and intensity. There are two types of discoloration. Superficial extrinsic which is resulted from tea, coffee, smoking, wine and poor oral hygiene and it is considered the common type of dental staining. The second type is the intrinsic discoloration which is described as deep stains involving the inner dentin layer of the teeth and resulted from internal trauma , diseases , medications like tetracycline , over exposure to fluoride and aging .(1) Many techniques aid in improving tooth color such as whitening tooth pastes, professional cleaning and polishing by abrasive pastes, whitening strips and gels, enamel microabrasion by using abrasives and acids and bleaching techniques either internal or external. (2) Nowadays dental bleaching is one of the most dental procedures that can greatly overcome the problem of teeth discoloration. Generally, there are three different bleaching approaches including in office bleaching, at home bleaching and over the counter bleaching whitening products. Both in office and at home bleaching techniques are done under the dentist’s supervision in contrast to over the counter bleaching products. Each approach varies in concentrations of the bleaching agent and contact time of exposure. (3) Bleaching agents used in these bleaching approaches are hydrogen peroxide and carbamide peroxide which act as active ingredients. In office bleaching technique requires high concentration of hydrogen peroxide (25-35%) and short treatment time. On the other hand at home bleaching technique requires a low concentration of 10% carbamide peroxide which contains only 3% hydrogen peroxide and long treatment time. Despite, the great advancement in the field of dental bleaching, a lot of patients still suffer from heavy stained teeth that cannot be treated by applying the traditional high concentration bleaching agent even if it is combined with home bleaching. Hence, trials are being done to overcome this problem by enamel pretreatment using different acids or combined acids and abrasive particles as in the microabrasion technique. This technique aids to remove the porous surface enamel layer and any entrapped stains and increases the enamel surface energy that aids for more penetration of bleaching agents through these created micro pores. Enamel microabrasion can be done either by using acidic and abrasive agents such as (6% hydrocloric acid and silica or 37% phosphoric acid with pumice). It was claimed that this treatment is safe when combined with bleaching to achieve perfect smile appearance. Attaining and maintaining a lighter tooth color is the main goal of tooth bleaching, yet color regression usually happens after using hydrogen peroxide bleaching agent by time .(5) Thus, color change should be assessed immediately after bleaching and over an extended time period. Tooth color is a complex phenomenon that can’t be detected correctly by visual shade selection. Different color measuring devices are used for more accuracy such as spectrophotometer and colorimeter. Tooth is a biological unit in which other considerations rather than esthetics should be taken into consideration. Dental bleaching cannot be considered a successful technique when it leads to painful teeth. Sensitivity is one of the most common patients complain after vital tooth bleaching procedure. Hence, different desensitizing agents were added to some bleaching gels such as (fluoride and potassium nitrate) to overcome this problem. So that it was of value to evaluate the use of surface pretreatments as micro abrasion before bleaching on color change and teeth sensitivity.90 pages : illustrations ; 30 cmtextapplication/pdfengDentistry, Operativetext