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

techniques using a vinylpolysiloxane impression material (one-step double mix and two-step double mix) and different clinical situations on the accuracy of impressionmaterial.The accuracy of the impression material was indirectly assessed from stone casts obtained by pouring the impressions made of the Nissin dental model. The three clinical situations selected were a single crown preparation on maxillary right second premolar, three-unit FPD replacing missing maxillary right first molar and five-unit FPD replacing missing maxillary right first molar and first premolar. A total of 24 impressions were obtained for the master model and divided according to the clinical situations into three groups (S1, S2, and S3). Each group was further subdivided according to the impression technique into two subgroups (T1 and T2). Impressions were poured into a stone cast using type IV dental stone. The measurements were performed on the master cast by two methods: the Stereo-microscope and the Digital Imaging Analysis (DIA) to calibrate and verify the fidelity and the exactness of the measurements. While measurements of the produced stone casts were performed by the Digital Imaging Analysis (DIA). All data were collected, tabulated and statistically analyzed. Within the confines of this in vitro study, it can be concluded that the accuracy of the two impression techniques was within the acceptable clinical limit but the result showed higher statistically significant superiority for the one-step double mix impression technique

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