Hemodynamic performance of Edwards Intuity valve in a compliant aortic root model.

Numerous designs of bioprosthetic valves exist. The sutureless surgical valve is a newer design concept which combines elements of the transcatheter valve technology with surgical valves. This design aims at shorter and easier implantation. It was the aim of this study to perform hemodynamic and kinematic measurements for this type of valves to serve as a baseline for following studies which investigate the effect of the aortic root on the valve performance. To this end, the Edwards Intuity aortic valve was investigated in a new in vitro flow loop mimicking the left heart. The valve was implanted in a transparent, compliant aortic root model, and the valve kinematics was investigated using a high speed camera together with synchronized hemodynamic measurements of pressures and flows. The valve closure was asynchronous (one by one leaflet), and the valve started to close before the deceleration of the fluid. The aortic root model showed a dilation of the sinuses which was different to the ascending aorta, and the annulus was found to move towards the left ventricle during diastole and towards the aorta during systole.

[People's interest in health information]. / Nutzung von Gesundheitsinformationen.

Well-informed citizens and patients regard health policy innovations as a key element when it comes to reforms in the health service--both in health economics and with regard to prevention issues. We evaluated the data provided by the 2003 Telephone Health Survey (GSTel03) to examine demographic and social distinctions in the use of different information sources. At the same time we examined whether there are any population-related differences in people's interest in health information depending on their levels of health awareness, attitudes to prevention and related modes of behaviour. The data generated by the survey show that there is considerable interest in health-related topics. Only 2% of the people questioned used no information sources for this purpose. In addition to more traditional media (books, newspapers, information from pharmacies), information provided by health insurance companies and via the Internet is becoming increasingly important. With the exception of the Internet, all other sources of information are used more frequently by women than by men, and demand for most of the information media increases with age. The frequency of information use and the number of different media used increase from the lower to the upper strata of society. As far as selected variables of health-related behaviour are concerned (smoking, sport, alcohol), the results show a link between a more positive attitude to health and a greater interest in information.

Keto-enol/enolate equilibria in the N-acetylamino-p-methylacetophenone system. Effect of a beta-nitrogen substituent.

The cis-enol of N-acetylamino-p-methylacetophenone was generated flash photolytically and its rates of ketonization in aqueous HClO(4) and NaOH solutions as well as in HCO(2)H, CH(3)CO(2)H, H(2)PO(4)(-), (CH(2)OH)(3)CNH(3)(+), and NH(4)(+) buffers were measured. Rates of enolization of N-acetylamino-p-methylacetophenone to the cis-enol were also measured by hydrogen exchange of its methylene protons, and combination of the enolization and ketonization data gave the keto-enol equilibrium constant pK(E) = 5.33, the acidity constant of the enol ionizing as an oxygen acid pQ(a)(E)= 9.12, and the acidity constant of the ketone ionizing as a carbon acid pQ(a)(K)= 14.45. Comparison of these results with corresponding values for p-methylacetophenone itself shows that the N-acetylamino substituent raises all three of these equilibrium constants: K(E) by 3 orders of magnitude, Q(a)(E) by 1 order of magnitude, and Q(a)(K)by 4 orders of magnitude. This substituent also retards the rate of H+ catalyzed enol ketonization by 4 orders of magnitude. The origins of these substituent effects are discussed.

Spectroscopy and reactivity of Kekulé hydrocarbons with very small singlet-triplet gaps.

Two Kekulé hydrocarbons, 2,2-dimethyl-2H-benzo[cd]fluoranthene (1) and its benzannellated analogue 2,2-dimethyl-2H-dibenzo[cd,k]fluoranthene (2), were generated photochemically from two different photoprecursors each and investigated spectroscopically in cryogenic matrices by UV-vis, fluorescence, and EPR and in solution using ns flash photolysis and chemical trapping experiments. Hydrocarbon 1 is a ground-state singlet species, whereas compound 2 has a triplet ground state, the first such neutral Kekulé hydrocarbon. This difference, which is supported by density functional calculations, has profound influence on the spectroscopy and reactivity of the two compounds. Using the results of the spectroscopic measurements, trapping experiments, and density functional calculations, the singlet-triplet gap for 1 is estimated to be 2.3-2.8 kcal mol(-1), with the singlet the ground state, and 0.8-1.3 kcal mol(-1) for 2, in favor of the triplet.

[The influence of different polishing systems on dental veneering materials]. / Der Einfluss verschiedener Poliersysteme auf zahnärztliche Verblendmaterialien.

Experimental studies were conducted to investigate the efficacy of seven polishing systems (Dia Finish, Kohinoor, Dia Glace, Kenda, Shofu, UNOR, Opal) when used on seven ceramic materials (Empress, Vitadur Alpha, Celay, Cerec, Vita Titanium Porcelain, TiBond, Duceratin), in some cases also on resins (Visiogem, Spectrasit, composite, resin teeth), and on natural enamel. The surface quality of 100 specimens was examined with an optical profilometer and a scanning electron microscope and subsequently evaluated. Polishing the ceramic materials with Kohinoor or Dia Finish resulted in a very high surface polish.. Of the resins, Spectrasit yielded a very high polish when Dia Finish, Dia Glace or Opal were used. Using the tested polishing systems, surface polish results can be obtained intraorally on ceramic restorations that are at least equivalent to glaze-fired ceramic surfaces, if not better. This means that an additional glaze firing is no longer required when ceramic restorations have been modified by grinding. The Dia Finish, Dia Glace, and Kohinoor polishing systems are particularly recommended for finishing and polishing cemented ceramic or resin inlays. The results are similarly favorable when polishing the natural dental enamel, so an excellent homogenous transition from enamel to dual cement and ceramic restoration can be achieved during the final polishing step for cemented restorations.

The speed limit for protein folding measured by triplet-triplet energy transfer.

A direct measure of intramolecular chain diffusion is obtained by the determination of triplet-triplet energy-transfer rates between a donor and an acceptor chromophore attached at defined points on a polypeptide chain. Single exponential kinetics of contact formation are observed on the nanosecond time scale for polypeptides in which donor and acceptor are linked by repeating units of glycine and serine residues. The rates depend on the number of peptide bonds (N) separating donor and acceptor and show a maximum for the shortest peptides (N = 3) with a time constant (tau = 1/k) of 20 ns. This sets an upper limit for the speed of formation of the first side-chain contacts during protein folding.

Modern alternatives to amalgam: cementable restorations and inlays.

There are still no replacement materials on the market that are equal to amalgam. However, alternatives of differing qualities are available and, for the most part, clinically proven. This article attempts to make a scientific and clinical comparison of these alternatives with respect to esthetics, biocompatibility, chemical durability, and treatment cost. The evaluation suggests that cementable restorations, in particular electroformed inlays and onlays, are superior to bonded ceramic inlays.

[The modification of the metal ceramic bond by blended gold coating]. / Beeinflussung des metallkeramischen Haftverbundes durch Blendgoldbeschichtung.

The esthetic appearance of porcelain-fused-to-metal restorations is often compromised in areas in which the ceramic veneer has to be kept very thin. In order to overcome this esthetic problem, bonding gold products are offered by dental manufactures which act as an alloy seal, thereby improving the natural color appearance of the ceramic veneer. In addition, the bond strength between ceramic materials and alloys is said to be maintained or in some cases even increased. The present study investigated the effect of various types of bonding gold layers on strength of the bond between ceramic materials and numerous dental alloys as a function of the type of alloy used, using thermocycling over a period of two months with a total of 85,000 temperature changes. The analysis of the results obtained shows that, contrary to manufacturers' claims, only two of the eight bonding gold products can be recommended, and only for three of the twelve alloys tested, as far as the alleged added adhesion is concerned. Only very few combinations of alloys and bonding gold products did not adversely affect adhesion at all or only insignificantly.

[Mandibular hybrid dentures with 4 implants. An in-vitro stress analysis]. / Unterkiefer-Hybridprothesen mit vier implantaten. Eine In-vitro-Spannungsanalyse.

Four two-component implants (Bonefit) inserted in a mandibular model were fitted with various overdentures and then subjected to tension analysis using wire strain gauges. The implants were positioned between the mandibular foramina of the model; data were obtained for mesial, distal, lingual and buccal compressive and tensile loads of 50 N on duplicates of the prosthodontic base at the level of the first molar, using a measuring wire gauge. The greatest forces were registered for the secondary-splint telescope crown prosthesis; these forces were up to three times as high as the corresponding axial load. In the case of bar attachments, it is not so much the strain on the implant when the prosthesis is loaded that tends to cause problems, but rather the original process of screwing down the overdenture on insertion. During this process, the implants are subjected to forces so high that the use of a torque indicator is deemed to be indispensable as a clinical consequence of this finding. For similar considerations, a conditionally removable bar construction should not be removed during follow-up examinations. Magnetically retained dentures, by contrast, barely exert any tensile forces on the implants.

[The effect of the aeration status on the corrosion behavior of Ni-Cr alloys]. / Einfluss der Belüftungssituation auf das Korrosionsverhalten von Ni-Cr-Legierungen.

Using in vitro tests, the influence of aeration cells that develop in narrow crevices of dental restorations, on the corrosion behaviour of two Ni-Cr alloys (Wiron 88 and Rexillium III) was investigated. The results revealed a 1.6-fold higher ion release in the deaerated part of the electrolyte compared with the aerated one, whereas the ion release was 18-fold higher with Rexillium III. The total analyzed substance loss was 11.1 (S.D. 5.7) and 181.9 (S.D. 48.0) micrograms/cm2, respectively.

[Mercury vapors from premeasured amalgam capsules]. / Quecksilberdämpfe aus vordosierten Amalgamkapseln.

12 dental amalgam capsules were tested for mercury leakage during trituration, storage, and disposal. The pertinent measurements were taken using two different measuring systems, both of which were based on the principle of optical absorption. While the results were excellent for half of the encapsulated products, some were deficient with respect to impermeability or safe handling. Five products cannot be recommended for regular use in the dental office. Overall, dental amalgam capsules of the latest product generations release lower mercury vapors; however, there are always exceptions, which is why periodical checks are recommended to protect the dentist and his or her team from avoidable exposure to mercury vapors.

[New procedures for resin-metal bonds. A comparative in-vitro study]. / Neue Verfahren für den Kunststoff-Metall-Verbund. Eine vergleichende In-vitro-Studie.

Since 1984 it has been possible to create a chemical bond between dental alloys and composite resins resembling the metallo-ceramic bond. Modern systems based on silanization (Rocatec, Silicoater MD, and Spectralink), in connection with the specific resins used in these systems (VisioGem, Dentacolor, and SR-Isosit-N), were tested for their bond strength to 9 common dental alloys (of 7 different types) with regard to shear strength, the topography of the fracture surfaces, and metallographic microstructure transformations. No major structural transformations were observed for any of the systems tested. A notable degree of interdependence was seen in the Silicoater MD system whose bond strength to non-precious alloys (among others) was the lowest in the test. The Rocatec system, on the other hand, showed a superior bond to all types of alloys, especially to pure titanium.