Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Orthodontics

Digital models are becoming the standard orthodontic record in many dental practices around the world. They have gained popularity in orthodontics due to their advantages over plaster in storing, retrieving, sharing of information, diagnosis and treatment planning cases. This is due to feasibility of the virtual environment which shortens the time required for each procedure. Digital models have been made from alginate impressions as well as with intra-oral scanners to prove their reliability and accuracy. Therefore, the main objective of this study was to relate dental measurements on 3-D models obtained through intraoral scanning and extra-oral scanning modalities and evaluate their diagnostic accuracy to the reference standard plaster replica in a sample of Egyptian population. Twenty-four adult male and female subjects of the Egyptian population were randomly selected for this study. Intra-oral scanning, extra-oral scanning of the plaster models obtained via alginate impression, extra-oral scanning of the plaster models obtained via rubber base impression, extra-oral scanning of the rubber base impression and extra-oral scanning of the alginate impression were done for all subjects. Linear dental measurements included intermolar width, interpremolar width, intercanine width, mesiodistal width of 1st permanent molar, 1st premolar, canine and central incisor and arch width. All data were collected, tabulated and subjected to statistical analysis. The results showed small differences between the plaster and digital models. The small differences could be appropriate for clinical use for the majority of parameters. Intra-observer reliability analysis for 14 out of the 16 measurements showed that all variables exhibited good to excellent reliability. The most accurate digitization technique was the 3Shape laboratory scanner of the cast of the alginate impression

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