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Biomedical subjects

B N Edwards

Publications and source records attributed to B N Edwards.

6 recordsLinked to original sources
PubMed2003

A sub-50meV spectrometer and energy filter for use in combination with 200kV monochromated (S)TEMs.

A high-energy resolution post-column spectrometer for the purpose of electron energy loss spectroscopy (EELS) and energy-filtered TEM in combination with a monochromated (S)TEM is presented. The prism aberrations were corrected up to fourth order using multipole elements improving the electron optical energy resolution and increasing the acceptance of the spectrometer for a combination of object area and collection angles. Electronics supplying the prism, drift tube, high-tension reference and critical lenses have been newly designed such that, in combination with the new electron optics, a sub-50 meV energy resolution has been realized, a 10-fold improvement over past post-column spectrometer designs. The first system has been installed on a 200 kV monochromated TEM at the Delft University of Technology. Total system energy resolution of sub-100 meV has been demonstrated. For a 1s exposure the resolution degraded to 110 meV as a result of noise. No further degradation in energy resolution was measured for exposures up to 1 min at 120 kV. Spectral resolution measurements, performed on the pi* peak of the BN K-edge, demonstrated a 350 meV (FWHM) peak width at 200 kV. This measure is predominantly determined by the natural line width of the BN K-edge.

Journal Article↗
PubMed1995

Comparative analysis of bone stresses and strains in the Intoss dental implant with and without a flexible internal post.

The clinical success of any dental implant is dependent upon the maintenance of good-quality bone supporting it. Previous studies have shown high values of strain around the neck of an implant under lateral loading. These high values may lead to fatigue damage and resorption in lower strength cancellous bone. In this study, the finite element method has been used to study the bone strain distribution around the following implants: (a) an Intoss dental implant, referred to as the 'standard' implant; (b) a comparative Branemark implant and (c) a modified Intoss implant with a central flexible post, referred to as the 'modified' implant. Three different bone distributions have been investigated under axial and lateral loading: (a) implant surrounded by cortical bone; (b) implant tip supported by cortical bone with a thin layer of cancellous bone along the length and top of the implant; (c) implant tip and top supported by cortical bone with a thin layer of cancellous bone along the remaining length. For the standard implant, similar maximum equivalent strain values were predicted for the bone surrounding a comparable length Branemark-type implant. Modification of the standard implant design to include a flexible central post resulted in a decrease in the maximum von Mises stresses and equivalent strains in the cancellous bone. It is postulated that this will reduce the likelihood of bone fatigue failure and subsequent resorption in this bone. Thus the proposed design change is predicted to be highly beneficial in terms of bone load transfer.

Bone Resorption↗
PubMed1992

Analysis of surface cleanliness of three commercial dental implants.

Six routinely packaged commercially pure titanium dental implants (three commercial brands) were analysed using secondary ion mass spectrometry to examine the outermost surface layer. The aim of the analysis was to compare the surface purity (99.95%) of the implants with the substrate metal, common to all three brands. The use of a low primary ion current density provided a nominal protection limit of 0.01% or 100 p.p.m. All the implants examined had extremely pure surfaces. However, only one brand of implant had an ultraclean oxide surface in relation to the substrate.

Dental Implants↗
PubMed1987

Contributory factors and etiology of sciatic nerve palsy in total hip arthroplasty.

Twenty-three peroneal and sciatic nerve palsies occurred in 21 patients following hip arthroplasty. Apparent risk factors included revision operations, being female, and significant lengthening of the extremity. The amount of lengthening was correlated with the development of either a peroneal palsy or sciatic nerve palsy. In cases of peroneal palsy the average lengthening was 2.7 cm (1.9 cm-3.7 cm) in comparison with 4.4 cm (4.0 cm-5.1 cm) for sciatic nerve palsies. Seven of these nerve palsies occurred among 614 consecutive patients treated at one institution during the period 1983-1985. This corresponded to an overall incidence of 1.1%. Electromyography demonstrated that peroneal stretch palsies originated primarily at the level of the neck of the fibula with some diffuse but lesser involvement along the proximal course of the peroneal division of the sciatic nerve.

Adult↗