Determining the accuracy of a CAD-CAM milled polyurethane die system (CADENT-iTERO) derived from optical-digital impressions
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Intra-Oral optical-digital impression systems in conjunction with machined polyurethane models are now available for generating indirect restorations. Purpose: This in-Vitro study was designed to evaluate the accuracy of a milled polyurethane die system ("Digital Die") generated from optical impressions (iTero-CADENT), compared to conventional stone dies generated from elastomeric impressions ("Conventional Die"). Materials and Methods: Four Ivorine typodont teeth (Maxillary central incisor #9, Maxillary second molar #15, Mandibular premolar #21 &and Mandibular first molar #30) were prepared for PFM crowns with chamfer margins. These 'Master dies' were impressed 24 times with light and heavy bodied polyvinyl-siloxane impression material (Aquasil Ultra-Dentsply) and cast in scannable stone (Diamond Die - Hi-Tec Dental) to produce 24 individual 'reference' dies that were divided into 2 groups of 12. One 'reference' group of stone dies was re-impressed with PVS to produce 12 corresponding stone models (Die Keen TM Heraeus Kulzer). The other 'reference' group was subjected to optical scans with the iTero scanner to produce 12 corresponding iTero polyurethane models with removable dies. The resulting dies from both groups were used to fabricate individual full coverage metal copings (Rex 4 Alloy TM, Pentron) using conventional wax-up technique and casting. Each cast coping was placed on its corresponding 'reference' die. All copings were measured for marginal fit at 8 different locations around the margin under an optical stereomicroscope at 100x magnification. Results: The mean marginal gaps for obtained for the copings were subjected to the t-test. In the "Conventional Die" group was 19.3 +/-10.4[mu]m. The mean marginal gap for the "Digital Dies" (iTero) was 21.2 +/-9.9[mu]m|. Conclusion: Both systems produced cast copings with marginal fit well within accepted clinical standards. There was no significant difference (P=0.2) between the die system accuracies, validating the theory that the iTero digital dies generated from optical impressions are as accurate as conventional dies.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact email@example.com.Thesis (MSD) --Boston University, Goldman School of Dental Medicine, 2011 (Department of Restorative Sciences and Biomaterials).Includes bibliographic references: leaves 86-91.
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