1,721,160 research outputs found
Predicting bone remodelling around root-form dental implants
No full textDental implants are a common treatment for the partially or fully edentulous patient. Increasing patient demands have driven implant development, most recently to patient-specific root-analogue implants that resemble the patient’s natural root-form. Laser sintering technology has increased the range of candidate implant materials, including metals, ceramics and polymers [1].Screw-form dental implants result in an average of 0.5mm crestal bone loss over 5 years. Bone loss and subsequent gingival recession impairs the functional and aesthetic outcomes of implant therapy. Crestal bone loss may be caused by stress shielding, and finite element (FE) analysis can be used to predict the remodelling stimulus in orthopaedic applications by comparing the strain energy density (SED) in intact and implanted models. The aim of this study was to compare the remodelling stimulus generated by root-form implants using three differing stiffness materials.A model of a mandibular canine and local osseous structures was produced from patient CT data. Intact and implanted model variants were generated and solved using Ti-6Al-4V (E=110GPa), zirconia (E=200GPa) and PEEK (E=4GPa) implant materials. Linear-elastic material properties were applied to the implant, enamel, dentin and cortical/cancellous bone. A hyperelastic material model was applied for the periodontal ligament in the intact case. The model was loaded with a typical bite-force of 200N at 12°. The SED change was interrogated in the elements surrounding the implant.The mean change in cortical SED from the intact to the implanted models was -84.1%, -86.7% and -40.5% for the titanium, zirconia and PEEK respectively. In the intact model, the peak cortical stimulus was focused around the crestio-labial region. The titanium and zirconia models showed low stimulus at the labial crest, whilst the PEEK model exhibited relatively uniform stimulus over the labial cortical surface (Figure).This study highlights the influence of implant material upon initial bone remodelling stimulus. The model indicated that high stiffness root-form implants create crestal load bypass by encouraging apical load transfer, like screw-form implants. This suggests that high stiffness implants may have a propensity for adverse cortical bone remodelling in a region of aesthetic and functional importance, which more flexible or compliant implants would avoid
Dataset supporting the University of Southampton Doctoral Thesis "The Design, Development and Characterisation of a Novel Intervertebral Disc Prosthesis"
No full textDataset supporting the University of Southampton Doctoral Thesis "The design, development and characterisation of a novel intervertebral disc prosthesis" by M. Godfrey.
COMSOL_data_Chapter_3 is the data extracted from a COMSOL model showing the contact stress between NP and vertebral endplate (refer to figure 3.22 in thesis). Read the data in Excel.
Spine_spectral_data_Chapter_4 contains the spectral data in the fibre optic experiment. Read the .dat files using notepad or alternative. Increasing file numbers increment axial displacement. Refer to figures 4.5 to 4.8 in the thesis.
Pin-Porcine_Chapter_5 contains the force-displacement data for the pin-penetration experiments. Use Excel or Bluehill to read the data. Variables are labelled in the data files. Each file relates to each vertebra sample and repeats are all included within each file.
3Hz_Hysteresis_Chapter_6 is force-displacement data for hysteresis measurement. Refer to figure 6.14 in the thesis. Read the data using excel.
Bolometer_Results_Chapter_6 contains thermal images (jpegs) from the bolometer experiment. Read the time-domain data using notepad or equivalent. Vertical temp data is in the spatial domain. Refer to figure 6.11 in the thesis.
Fatigue DIC Data_Chapter_6 is binned into 500-image segments (numbering relates to the images). The data is split into the long and short tests. Refer to figures 6.5 and 6.6 in the thesis.
The files labelled '2kN_XX_Eyy_Line_through_band' is the data used to produce figure 6.18 in the thesis. Read this data with Excel.
Data used for the first two appendices is also provided. A1 is gravimetric data from the injection moulding and B2 is force-displacement data from the mesh tensile testing. Read with Excel.
Note: files labelled 'PS' refers to the biomimetic implant and 'M6' refers to the commercial implant by Orthofix.
Related publications:
M. Godfrey, “Spinal implant,” UK Patent 2302888.9, 28/February/2023
M. Godfrey, S. Jantzen, A. Dickinson, C. Holmes, A. Taylor, and M. Browne,
“Spatially distributed circumferential strain measurement in an artificial
annulus fibrosus using fibre bragg gratings,” British Society for Strain
Measurement 16th International Conference on Advances in Experimental Mechanics,
2022.
Related projects/Funders:
EPSRC DTP 2018-19 (grant number EP/R513325/1)
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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