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UBC Theses and Dissertations

A comparison of crown marginal fit fabricated using digital and conventional methods Ng, Jonathan


Purpose. The aim of this study was to determine and compare the marginal fit of crowns fabricated using digital and conventional methods. Materials and Methods. A maxillary right second bicuspid, set in a typodont (Frasaco, Greenville, N.C., USA), was prepared for a ceramic crown. The maxillary typodont was then digitized, using a 3Shape D700 lab scanner (3Shape Inc., New Jersey, N.Y., USA) and the digital file was used to mill a replica of the maxillary arch out of a monolithic block of yttria-stabilized zirconia, to serve as master model. Digital impressions of the prepared maxillary right second bicuspid were recorded using a 3M LAVA C.O.S. scanning unit. Scan files were exported as .STL files and e-mailed to the dental lab. Files were inputed (Core3dcentres®; Las Vagas, Nevada, USA) into a digital design workflow for digital articulation, digital wax-up, and design of the final crown. Fifteen crowns were produced by 5-axis milling IPS e.max® CAD (Ivoclar Vivadent, Liechtenstein) lithium disilicate glass-ceramic blocks. An additional fifteen IPS e.max® Press (Ivoclar Vivadent, Liechtenstein) lithium disilicate glass-ceramic crowns were produced using a conventional impression and laboratory fabrication methods. The original zirconia die was removed from the zirconia master model for evaluation of crown margins. Circumferential marginal gap measurements were taken at eight measurement locations: mesial, distal, buccal, palatal, and associated line angles. The marginal gap measurements were made to determine the vertical component of marginal gap, according to the definition of marginal fit. Results. A total of 240 images (2 groups, 15 crowns per group, 8 sites per crown) were recorded and measured. The overall mean vertical gap measurement for the digitally made crowns was (48 +/- 25) μm, which was significantly smaller than that for the conventionally made ones (74 +/- 47) μm. Conclusion. The fully digital fabrication methodology provides a better fitting crown margin than the conventional methodology.

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