Effect of eugenol exposure time and post-removal delay on the bond strength of a self-etching adhesive to dentin.

OBJECTIVES: This study evaluated the effects of the exposure time of eugenol-based provisional restorative material and the time elapsed between the provisional material removal and the adhesive procedure on the bond strength of the composite to dentin. MATERIALS AND METHODS: Human third molars were sectioned into two halves that were enclosed in resin cylinders. The cavities were prepared over the buccal/lingual faces with diamond burs. Zinc oxide and eugenol (ZOE) provisional material was inserted into cavities and left for 24 hours, 7 days or 14 days. The cavities not restored with ZOE were used as controls. After ZOE removal or over fresh dentin (control), self-etching Adper SE Plus was applied immediately, after a 7- or 14-day delay. The cavity was restored with non-eugenol provisional material during this delay period. Cylinders of resin cement were built-up over the hybridized dentin. A shear load was applied to the cylinders at a crosshead speed of 0.5 mm/minute until failure. The data were statistically analyzed using two-way ANOVA and Tukey's tests (α=0.05). RESULTS: Using IRM as a provisional restoration for 24 hours followed by its removal and immediate adhesive application resulted in the lowest values of shear bond strength. There was no significant difference between the other experimental conditions. CONCLUSIONS: The use of IRM for 24 hours adversely affected the shear bond strength of a self-etching adhesive to dentin. The recovery of the proper bond strength occurred one week after IRM removal.

Covariance and sensitivity data generation at ORNL.

Covariance data are required to assess uncertainties in design parameters in several nuclear applications. The error estimation of calculated quantities relies on the nuclear data uncertainty information available in the basic nuclear data libraries, such as the US Evaluated Nuclear Data Library, ENDF/B. The uncertainty files in the ENDF/B library are obtained from the analysis of experimental data and are stored as variance and covariance data. In this paper we address the generation of covariance data in the resonance region done with the computer code SAMMY. SAMMY is used in the evaluation of the experimental data in the resolved and unresolved resonance energy regions. The data fitting of cross sections is based on the generalised least-squares formalism (Bayesian theory) together with the resonance formalism described by R-matrix theory. Two approaches are used in SAMMY for the generation of resonance parameter covariance data. In the evaluation process SAMMY generates a set of resonance parameters that fit the data, and, it provides the resonance parameter covariances. For resonance parameter evaluations where there are no resonance parameter covariance data available, the alternative is to use an approach called the 'retroactive' resonance parameter covariance generation. In this paper, we describe the application of the retroactive covariance generation approach for the gadolinium isotopes.

Evaluation of silicon neutron resonance parameters in the thermal to 1800 keV energy range.

Because silicon is a major constituent of concrete and soil, neutron and gamma ray information on silicon is important for reactor shielding and criticality safety calculations. Therefore, much effort was put into the ENDF/B-VI evaluation for the three stable isotopes of silicon. The neutron capture cross section of natural silicon was recently measured at the Oak Ridge Electron Linear Accelerator (ORELA) in the energy range 1-700 keV. Using the ENDF/B-VI evaluation for initial values, a new evaluation of the resonance parameters was performed by adding the results of the ORELA capture measurements to the experimental database. The computer code SAMMY was used for the analysis of the experimental data; the new version of SAMMY allows accurate calculations of the self-shielding and multiple scattering effects in the capture measurements. The accuracy of the radiative capture widths of the resonances was improved by this analysis. Accurate values of the s-, p- and d-wave neutron strength functions were also obtained. Although the resonance capture component of the present evaluation is 2-3 times smaller than that in ENDF/B-VI, the total capture cross section is much larger, at least for energies >250 keV, because the direct capture component contributes values of the same order of magnitude as the resonance component. The direct component was not taken into account in the ENDF/B-VI evaluation and was calculated for the first time in the present evaluation.

Neutron cross section measurements at ORELA for improved nuclear data and their application.

To support the Nuclear Criticality Safety Program, the Oak Ridge Electron Linear Accelerator (ORELA) has been used to measure the total and capture neutron cross sections of several nuclides in the energy range from 100 eV to -600 keV. Concerns about the use of existing cross section data in nuclear criticality calculations have been a prime motivator for the new cross-section measurements. Our new capture cross sections of aluminium, silicon, chlorine, fluorine and potassium in the energy range from 100 eV to 600 keV are substantially different from the cross sections in evaluated nuclear data files of ENDF/B-VI and JENDL-3.2.

Bilateral traumatic renal artery thrombosis with survival after hemodialysis and renal transplantation.

A case of bilateral thrombosis of the renal arteries following blunt trauma is presented. The patient was a 12-year-old boy who was treated by chronic hemodialysis and subsequently renal transplantation. A review of the literature reveals only 8 such cases reported previously. The condition is unusual and requires early diagnosis because the success of renal vascularization is entirely dependent upon prompt timing of the operation.