Supervisor : Ahmed Hassanein, Jihan Farouk. Includes Arabic Summary.Elsayed, Bassem Maged Ahmed,2023-12-282023-12-282023EG-CaMIUDNT Ths493 M.Sc. 2023https://iorep.miuegypt.edu.eg/handle/20.500.13071/204DISSERTATION NOTE-Degree type M.Sc.DISSERTATION NOTE-Name of granting institution Misr International University, Faculty of Oral and Dental MedicineIncludes bibliographic references.The accuracy of dental prosthesis fabrication can be influenced by different working die systems, including conventional, virtual, and 3D printed dies, which are utilized in various clinical situations. The success of single crowns relies heavily on achieving proper marginal and internal fit. Marginal fit refers to the gap size between the restoration's margin and the prepared tooth's finish line, while internal fit is assessed by evaluating the gap between the crown's fitting surface and the prepared tooth. Optimal marginal and internal fit are essential for ensuring the stability, durability, and periodontal health of single crowns. Although numerous studies have investigated the accuracy and reproducibility of three-dimensional printed (3D) models for diagnosis purposes, limited research has focused on assessing the marginal and internal fit of interim single crowns constructed using 3D printed dies in comparison to those fabricated on conventional and virtual dies. Therefore, the purpose of this study is to evaluate the marginal and internal fit of interim crowns fabricated using conventional, virtual, and 3D printed working dies. For this study, six physical impressions using PVS material were taken of a prepared maxillary right first molar to create conventional dies (group A). Additionally, six optical scans were performed using the Trios 3 intraoral scanner to fabricate virtual dies (group B), and 3D printed dies were generated as well (group C). The dies from the three groups were then scanned using a desktop scanner (3Shape E3) for the design and milling of interim crowns. Each crown was placed on its respective die for initial evaluation of the marginal fit. Subsequently, a triple scan protocol was employed to assess the marginal and internal fit of the crowns, which served as an indicator of the accuracy of the different die systems. This involved superimposing scans of the crown's fitting surface, the seated crown on its corresponding die, and a reference scan of the prepared typodont using Geomagic Control X software for comprehensive 3D digital evaluation. Statistical analysis was then conducted.127 pages : illustrations, photo ; 31 cmFixed prosthodontics