[Studies on design for resin veneered crowns. 1. Adhesive resin luting agents reinforcement effect].
Resin veneered crowns show several drawbacks which affect the veneering resin: peeling, fracture, falling and also discoloration by leakages from the metal-resin border. The purpose of the present study is to find out a principle of resin veneered crown design allowing the solution of the above-mentioned problems. As a preliminary step, the influence of luting cements on the relative rigidity of veneered crowns and metal frameworks was examined by measuring the strain to static and impact charges on several portions of crowns. The investigation led to the following results: 1. The magnitude of the strain to a static charge increased with the number of shocks but beyond 100 shocks, no variation could be observed. 2. The magnitude of the strain to a static charge was proportional to the weight of the charge. 3. The strain of crowns and metal frameworks set with PanaviaEX had a magnitude smaller than the strain of those set with Fitchecker. 4. The strain to an impact charge had a magnitude 1-4 times larger than the strain to a static charge. 5. The adhesive resin luting agent reinforcement effect could be clearly confirmed.
Adhesive 4-META/MMA-TBB Opaque Resin with Poly(methyl methacrylate)-coated Titanium Dioxide
An adhesive opaque resin for veneering on cast metal was developed with 4-methacryloxyethyl trimellitate anhydride and poly (methyl methacrylate)-coated titanium dioxide prepared by aqueous phase polymerization. The opaque resin was a modified 4-META/MMA-TBB resin. The powder consisted of 20% of the encapsulated material and 80% PMMA instead of pure PMMA powder. This resin hides the metal color when the thickness of the resin is as thin as 50 μm. The opaque resin bonded strongly to both cobalt-chromium alloy and visible-light-cured veneering resin. This self-curing opaque resin is applicable not only for bonding veneering resin to an alloy surface but also for bonding fixed partial dentures to enamel surfaces.
Phase characterisation of simulated high burn-up UO2 fuel
Abstract To determine the lattice constant variation with burn-up and the oxidation behaviour at high temperatures, simulated UO2-spent fuels with burn-ups up to 200 GWd tM−1 were prepared by cold pressing and sintering and characterised by X-ray diffraction analysis and thermogravimetry. The fcc-lattice parameter of the sintered samples determined at room temperature, showed a continuous decrease with the simulated burn-up. During oxidation the conversion of the simulated fuels to the (U,FP)4O9 and (U,FP)3O8-type phases was strongly delayed when the simulated burn-up exceeded 80 GWd tM−1. Also, at high burn-ups (>100 GWd tM−1), large fractions of the (U,FP)4O9-type phase remained untransformed to (U,FP)3O8 after prolonged exposure to air at 950–1000°C. This suggests a marked widening of the (U,FP)4O9-phase field when the amount of substituted uranium atoms exceeds values of about 8%.