Supervisor : Nihal Sabet, Mohamed Mokhtar Nagi.Abd El Wahab, Maram Hossam El-Din,2022-01-182022-03-272022-01-182022-03-272019.EG-CaMIUThs285https://iorep.miuegypt.edu.eg/handle/20.500.13071/93DISSERTATION NOTE-Degree type M.Sc.DISSERTATION NOTE-Name of granting institution Misr International University, Faculty of Oral and Dental MedicineIncludes bibliographic references (pages 75-89)Patients typically need a root canal treatment when there is inflammation or infection in the root canals. Root canal treatment is an oftenstraightforward procedure to relieve pulpal pain and render the tooth function and asymptomatic. During root canal treatment, an endodontist carefully removes the pulp inside the tooth, cleans, disinfects and shapes the root canals, and obturate to seal the space. A three-dimensional obturation of the system of the root canal through the whole length of the canal is one important goal under which successful root canal therapy can be achieved. Many obturation techniques have been introduced to obtain a threedimensional filling of the root canal system and increase the quality of the apical seal, although root canal treatment has high success rate when conducted appropriately, failures could happen that are usually accompanied by badly treated canals. Unfortunately, failure of endodontic treatment is mainly caused by intraradicular infection. This endodontic infection should be treated by removal of the filling material and retreatment procedure There are many techniques that have been proved to be effective in the removal of the materials that fill the root canal from root canal system, such as the usage of endodontic hand files, Gates Glidden burs,Nickel Titanium rotary devices, laser, ultrasonic devices ,heated device, as well as the usage of assistant solvents. Traditionally, the usage of hand files in the elimination of gutta percha in the presence or absence of solvent can be a boring, time consuming procedure particularly if the root filling material is perfectly compressed Recently, a novel rotary nickel titanium system which were tailored for retreatment processes have been included to endodontics field. The 1 Introduction protaper universal retreatment (PTUR) system is one of these systems, Protaper Universal retreatment files which was designed to be used in sequence to remove filling material with Rotation motion. None of the retreatment instruments examined the reciprocation motion on retreatment procedure, hence in this study Wave one and wave one gold were used as a retreatment instrument. Recently, using of Cone-beam computed tomography (CBCT) in endodontics became a common technique .It showed a great competence in comparison with other traditional radiographic techniques in many cases such as the assessment of the root canal system and resorptive lesions. In addition it helps in the diagnosis of apical periodontitis, and in designing a plan for treatment of endodontic surgery. Although a great deal of useful information can be obtained from Cone Beam Computed Tomography, we must also consider that Cone Beam Computed Tomography is a radiographic technique with an exposure dose that is significantly greater than intraoral radiography. To avoid overuse or abuse of Cone Beam Computed Tomography, several guidelines have been published Therefore, this work was accomplished to examine the efficacy of Wave One and Wave One Gold in retreatment procedure94 pages : illustrations, photo ; 30 cmtextapplication/pdfenEndodonticstext