Supervisor : Abeer Abdulhakim Elgendy, Ahmed Hussein Abuelezz. Includes Arabic Summary.Serageldin, Yomna Adel Wagih Fahmy,2023-12-282023-12-282023EG-CaMIUDNT Ths499 M.Sc. 2023https://iorep.miuegypt.edu.eg/handle/20.500.13071/207DISSERTATION NOTE-Degree type M.Sc.DISSERTATION NOTE-Name of granting institution Misr International University, Faculty of Oral and Dental MedicineIncludes bibliographic references.Root canal retreatment is a non-surgical endodontic procedure that includes the removal of root canal filling material from the root canal. After the removal of root canal filling, the canals are cleaned and shaped again, and reobturated. It is considered the first alternative option when primary endodontic treatment does not achieve the desired healing outcome. Conventional root canal retreatment techniques do not completely remove root canal filling material from the root canal walls. A certain amount of debris remains attached to the root canal surface even after using various methods to retrieve the root canal filling. Those areas of the root canal system remain inaccessible to the different effects of irrigation and disinfection approaches. The heat generated along the external root surface is another main drawback of the retreatment procedure. To improve the efficacy of root canal filling removal, many types of reciprocating retreatment files and ultrasonic retreatment tips have been developed. These files and tips vary in the motion through which they remove the root canal filling, which in turn affects the amount of remaining root canal filling, the amount of heat released on the external root surface, and the time during which the root canal filling is removed. So, the study aimed to compare the efficiency of vibration motion to reciprocation motion in retreatment and investigated which motion produced more heat on the external root surface. Forty-eight maxillary first permanent molars were selected. Access, cleaning and shaping, and obturation using bioceramic sealer were performed in all distobuccal canals. The technique of obturation used was the lateral compaction technique. The teeth were randomly divided into two main groups (n=24) according to the technique of removal of root canal filling material; Group A: vibration motion and Group B: reciprocation motion. The canals were evaluated for the percentage of remaining root canal filling using a stereomicroscope. The amount of heat released on the external root surface was measured using a thermocouple. The time of removal of root canal filling was calculated using a stopwatch.157 pages : illustrations, photo ; 29 cm + 1 CD-ROM (4 3/4 in.)Endodontics