May L.G.,Sao Paulo State University |
Kelly J.R.,University of Connecticut Health Center |
Bottino M.A.,Sao Paulo State University |
Hill T.,Ivoclar Vivadent Inc.
Objective: To determine the influence of cement thickness and ceramic/cement bonding on stresses and failure of CAD/CAM crowns, using both multi-physics finite element analysis and monotonic testing. Methods: Axially symmetric FEA models were created for stress analysis of a stylized monolithic crown having resin cement thicknesses from 50 to 500 μm under occlusal loading. Ceramic-cement interface was modeled as bonded or not-bonded (cement-dentin as bonded). Cement polymerization shrinkage was simulated as a thermal contraction. Loads necessary to reach stresses for radial cracking from the intaglio surface were calculated by FEA. Experimentally, feldspathic CAD/CAM crowns based on the FEA model were machined having different occlusal cementation spaces, etched and cemented to dentin analogs. Non-bonding of etched ceramic was achieved using a thin layer of poly(dimethylsiloxane). Crowns were loaded to failure at 5 N/s, with radial cracks detected acoustically. Results: Failure loads depended on the bonding condition and the cement thickness for both FEA and physical testing. Average fracture loads for bonded crowns were: 673.5 N at 50 μm cement and 300.6 N at 500 μm. FEA stresses due to polymerization shrinkage increased with the cement thickness overwhelming the protective effect of bonding, as was also seen experimentally. At 50 μm cement thickness, bonded crowns withstood at least twice the load before failure than non-bonded crowns. Significance: Occlusal "fit" can have structural implications for CAD/CAM crowns; pre-cementation spaces around 50-100 μm being recommended from this study. Bonding benefits were lost at thickness approaching 450-500 μm due to polymerization shrinkage stresses. © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. Source
Ivoclar Vivadent Inc. | Date: 2015-02-04
Dental impression materials and adhesives. A system for making dental impressions primarily comprised of dental impression trays, colloid impression materials, syringes and different syringe tips, fingertip extenders, and an illustrated technical user manual sold therewith.
Ivoclar Vivadent Inc. | Date: 2014-06-12
Zirconia dental ceramics exhibiting opalescence and having a grain size in the range of 10 nm to 300 nm, a density of at least 99.5% of theoretical density, a visible light transmittance at or higher than 45% at 560 nm, and a strength of at least 800 MPa.
Ivoclar Vivadent Inc. | Date: 2011-07-12
A nonmagnetic alloy is provided based on a palladium-cobalt binary system with the addition of gold, has a coefficient of thermal expansion (CTE) of about 13.8 to about 15 and may include one or more of the following additive metals: aluminum, boron, chromium, gallium, lithium, rhenium, ruthenium, silicon, tantalum, titanium, and tungsten.
Ivoclar Vivadent Inc. | Date: 2013-10-08
Methods and systems are disclosed for automatically generating a customized digital design of a dental restoration. The customized digital designs are generated using a set of design parameters that are specific to the dental lab ordering the restoration. As such, the resulting dental restorations require less modification by the lab and accommodate the preferences of the ordering lab.