Supervisor : Adel Ezzat Khairy, Ola Mohamed Ibrahim Fahmy, Dina Mohamed Salah El DineAbouelfotouh, Ingy Farag Ismail,2022-01-182022-03-272022-01-182022-03-27EG-CaMIUhttps://iorep.miuegypt.edu.eg/handle/20.500.13071/92DISSERTATION NOTE-Degree type M.Sc.DISSERTATION NOTE-Name of granting institution Misr International University, Faculty of Oral and Dental MedicineIncludes bibliographic references (p. 61-66)Cosmetic dentistry is becoming one of the main concerns for most of the patients. Whiter teeth are believed to be associated with health or beauty.(1) Patients are demanding a ‘perfect smile’. Tooth discoloration has different etiologies; can be internal or external or combined. Intrinsic tooth discoloration can be due to remnants of pulp tissue trapped inside the pulp chamber, or due to internal bleeding of the pulp vessels due to trauma or systemic drug intake, while extrinsic stains results mainly from dietary factors and smoking. (2) Food containing stains as red wine, coffee and tea may cause development of stains, also carotene containing food as oranges and carrots and tobacco use either chewing or smoking will cause extrinsic stains.(3) Tooth discoloration could be treated by different treatment approaches starting from the least invasive method as whitening tooth paste, professional cleaning (scaling and polishing) to remove surface stains, internal bleaching of non vital teeth, external bleaching of vital teeth, micro abrasion of enamel with abrasives and acids, macro abrasives, crowns and veneers, which are the most aggressive method. (4, 5) Bleaching is one of the least aggressive modality that gained popularity. Mechanism of bleaching with hydrogen peroxide works by the breakdown of hydrogen peroxide (H2O2) molecules into hydroxyl free radicals. These free radicals attack the organic molecules in teeth and break the carbon double bonds into single bonds which ends up with teeth more lighter in color.(6) Although tooth whitening has been accepted as one of the least aggressive methods for treatment of tooth discoloration, tooth bleaching can be done either in office or at home or a combined method between inoffice and at-home bleaching. Some authors suggested that, (7,8,9) at-home bleaching is more cost effective, commonly used and provides better color stability. In-office technique was said to give better results and Introduction 2 owing to its short application time made it more requested by the patients.(10) In an attempt to overcome the drawbacks of in-office bleaching technique and the long exposure time of at-home technique, the combined bleaching technique which immerged. This technique is supposed to give better and more durable results in whitening teeth.(11,12) Also, it gives less exposure time to bleaching materials decreasing the susceptibility to hypersensitivity as side effect with the in-office bleaching technique.(13,14) However going “too far” with the bleaching process can result in some adverse effects as tooth sensitivity and gingival inflammation. Thus, the efficiency in terms of color change, color stability and safety in terms of tooth sensitivity had to be studied. Therefore, a randomized controlled clinical trial was done to assess which technique gives better results with minimal side effects.68 pages : illustrations ; 30 cmtextapplication/pdfengDentistry, Operativetext