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    ABSTRACT: To quantify the relationships between buffering properties and acid erosion and hence improve models of erosive potential of acidic drinks, a pH-stat was used to measure the rate of enamel dissolution in solutions of citric, malic and lactic acids, with pH 2.4-3.6 and with acid concentrations adjusted to give buffer capacities (β) of 2-40 (mmol·l(-1))·pH(-1) for each pH. The corresponding undissociated acid concentrations, [HA], and titratable acidity to pH 5.5 (TA5.5) were calculated. In relation to β, the dissolution rate and the strength of response to β varied with acid type (lactic > malic ≥ citric) and decreased as pH increased. The patterns of variation of the dissolution rate with TA5.5 were qualitatively similar to those for β, except that increasing pH above 2.8 had less effect on dissolution in citric and malic acids and none on dissolution in lactic acid. Variations of the dissolution rate with [HA] showed no systematic dependence on acid type but some dependence on pH. The results suggest that [HA], rather than buffering per se, is a major rate-controlling factor, probably owing to the importance of undissociated acid as a readily diffusible source of H(+) ions in maintaining near-surface dissolution within the softened layer of enamel. TA5.5 was more closely correlated with [HA] than was β, and seems to be the preferred practical measure of buffering. The relationship between [HA] and TA5.5 differs between mono- and polybasic acids, so a separate analysis of products according to predominant acid type could improve multivariate models of erosive potential. © 2013 S. Karger AG, Basel.
    Caries Research 09/2013; 47(6):601-611.
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    ABSTRACT: In this work a bioactive composite scaffold, comprised of bioactive-glass and gelatin, is introduced. Through direct foaming a sponge-like composite of a sol-gel derived bioactive-glass (70S30C; 70% SiO2, 30% CaO) and porcine gelatin was developed for use as a biodegradable scaffold for bone tissue engineering. The composite was developed to provide a suitable alternative to synthetic polymer based scaffolds, allowing directed regeneration of bone tissue. The fabricated scaffold was characterised through X-ray microtomography, scanning electron and light microscopy demonstrating a three dimensionally porous and interconnected structure, with an average pore size (170μm) suitable for successful cell proliferation and tissue ingrowth. Acellular bioactivity was assessed through apatite formation during submersion in simulated body fluid (SBF) whereby the rate and onset of apatite nucleation was found to be comparable to that of bioactive-glass. Modification of dehydrothermal treatment parameters induced varying degrees of crosslinking, allowing the degradation of the composite to be tailored to suit specific applications and establishing its potential for a wide range of applications. Use of genipin to supplement crosslinking by dehydrothermal treatment provided further means of modifying degradability. Biocompatibility of the composite was qualified through successful cultures of human dental pulp stem cells (HDPSCs) on samples of the composite scaffold. Osteogenic differentiation of HDPSCs and extracellular matrix deposition were confirmed through positive alkaline phosphatase staining and immunohistochemistry.
    Materials science & engineering. C, Materials for biological applications. 07/2013; 33(5):2669-78.
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    ABSTRACT: Background:An imperative to assess the economic impact of care at the end of life is emerging in response to national policy developments in a number of settings. Current focus on health benefits in economic evaluation may not appropriately capture benefits of interventions at the end of life. No instruments are available for measuring such benefits for economic evaluation of end-of-life care.Aim:To develop a descriptive system for a measure for use in economic evaluation of end-of-life care.Design:An initial phase of in-depth interviews was conducted to develop conceptual attributes for inclusion in a measure; a second phase of semi-structured repeat interviews with a subsample of informants was carried out to clarify and confirm the final set of attributes and to develop meaningful wording for a measure.Setting/participants:In total, 23 older people from three groups across the dying trajectory: older people (1) within the general population, (2) living in residential care and (3) receiving palliative care.Results:Interviews suggested that the important domains to include within this framework from the perspective of those approaching the end-of-life are choice/having a say in decision-making, love and affection/being with people who care, freedom from physical suffering, freedom from emotional suffering, dignity and self-respect, support, and preparation. A full descriptive system comprising seven questions, each representing one attribute, was developed.Conclusion:Economic evaluation should reflect the broader benefits of end-of-life care. Although the supportive care measure developed here requires validation and valuation, it provides a substantial step forward in appropriate economic evaluation of end-of-life care.
    Palliative Medicine 05/2013;
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    ABSTRACT: OBJECTIVES: Light cured materials are increasingly used in orthodontic clinical practice and concurrent with developments in materials have been developments in light curing unit technology. In recent years the irradiances of these units have increased. The aim of this study was to determine the safe exposure times to both direct and reflected light. METHODS: The weighted irradiance and safe exposure times of 11 dental curing lights (1 plasma arc, 2 halogen and 8 LED lights) were determined at 6 distances (2-60cm) from the light guide tip using a spectroradiometer. In addition, using the single most powerful light, the same two parameters were determined for reflected light. This was done at a distance of 10cm from the reflected light, but during simulated bonding of 8 different orthodontic brackets of three material types, namely stainless steel, ceramic and composite. RESULTS: The results indicate that the LED Fusion lamp had the highest weighted irradiance and the shortest safe exposure time. With this light the maximum safe exposure time without additional eye protection for the patient (at 10cm), the operator (at 30cm) and the assistant (at 60cm) ranged from 2.5min, 22.1min and 88.8min respectively. This indicates a relatively low short term risk during normal operation of dental curing lights. For reflected light at a distance of 10cm the risk was even lower, but was affected by the material and shape of the orthodontic bracket under test. SIGNIFICANCE: The short term risks associated with the use of dental curing lights, halogen, LED or plasma, appear to be low, particularly if as is the case adequate safety precautions are employed. The same is true for reflected light from orthodontic brackets during bonding. What is still unclear is the potential long term ocular effects of prolonged exposure to the blue light generated from dental curing lights.
    Dental materials: official publication of the Academy of Dental Materials 04/2013;
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    ABSTRACT: The aims were to investigate the effect of monoalkyl phosphates (MAPs) and fluoride on dissolution rate of native and saliva-coated hydroxyapatite (HA). Fluoride at 300 mg/l (as NaF) inhibited dissolution of native HA by 12%, while potassium and sodium dodecyl phosphates (PDP, SDP), at 0.1% or higher, inhibited dissolution by 26-34%. MAPs, but not fluoride, also showed persistence of action. MAPs at 0.5% and fluoride at 300 mg/l were then tested separately against HA pre-treated with human saliva for 2 or 18 h. Agents were applied with brushing to half the specimens, and without brushing to the other half. In control (water-treated) specimens, pre-treatment of HA with human saliva reduced dissolution rate on average by 41% (2 h) and 63% (18 h). Brushing did not have a statistically significant effect on dissolution rate of saliva-coated specimens. In brushed specimens, fluoride significantly increased the inhibition due to 2- or 18-hour saliva pre-treatment. It is hypothesised that brushing partially removes the salivary film and allows KOH-soluble calcium fluoride formation at the surfaces of HA particles. Inhibition was reduced by PDP in 2-hour/non-brushed specimens and in 18-hour/brushed specimens. PDP did not affect dissolution rates in the remaining groups and SDP did not affect dissolution rate in any group. Possible reasons for these variable results are discussed. The experiments show that pre-treatment with saliva can significantly modify results of tests on potential anti-erosive agents and it is recommended that saliva pre-treatment should be a routine part of testing such agents.
    Caries Research 04/2013; 47(5):355-363.
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    ABSTRACT: The aim of this work is to investigate the use of microtopographies in providing physical cues to modulate the cellular response of human mesenchymal stem cells on ceramics. Two microgrooved patterns (100 μm/50 μm, 10 μm/10 μm groove/pitch) were transcribed reversely onto alumina green ceramic tapes via an embossing technique followed by sintering. Characterization of the micropatterned alumina surfaces and their cellular response was carried out. Spread and polygonal cell morphologies were observed on the wider groove (50 μm/100 μm) surface. Cells seeded onto the narrow groove (10 μm/10 μm) surface aligned themselves alongside the grooves, resulting in more elongated cell morphology. More osteoid matrix nodules shown by osteopontin and osteocalcin biomarkers were detected on the larger grooved surfaces after cell culture of 21 days, indicating a greater level of osteogenicity. This study has shown that micropatterned wider groove (50 μm) topographies are more suitable surfaces for improving osseointegration of ceramic implants. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
    Journal of Biomedical Materials Research Part A 04/2013;
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    ABSTRACT: The potential for the use of well-defined nanopatterns to control stem cell behaviour on surfaces has been well documented on polymeric substrates. In terms of translation to orthopaedic applications, there is a need to develop nanopatterning techniques for clinically relevant surfaces, such as the load-bearing material titanium (Ti). In this work, a novel nanopatterning method for Ti surfaces is demonstrated, using anodisation in combination with PS-b-P4VP block copolymer templates. The block copolymer templates allows for fabrication of titania nanodot patterns with precisely controlled dimensions and positioning which means that this technique can be used as a lithography-like patterning method of bulk Ti surfaces on both flat 2D and complex shaped 3D surfaces. In vitro studies demonstrate that precise tuning of the height of titania nanodot patterns can modulate the osteogenic differentiation of mesenchymal stem cells. Cells on both the 8 nm and 15 nm patterned surfaces showed a trend towards a greater number of the large, super-mature osteogenic focal adhesions than on the control polished Ti surface, but the osteogenic effect was more pronounced on the 15 nm substrate. Cells on this surface had the longest adhesions of all and produced larger osteocalcin deposits. The results suggest that nanopatterning of Ti using the technique of anodisation through a block copolymer template could provide a novel way to enhance osteoinductivity on Ti surfaces.
    Advanced healthcare materials. 03/2013;
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    ABSTRACT: Traditionally, the academic content of many 3-year full-time postgraduate courses in orthodontics in the UK has been delivered using tutorial and lecture-based teaching. This is often teacher lead rather than learner centred. Even with the advent of teaching modules on the national virtual learning environment, although well liked by students, is still often teacher lead. An alternative on-line approach to learner-centred teaching is to use Wikis. Nine postgraduate students in the first term of their full-time 3-year specialist training programme at Bristol Dental School were divided into three groups and wrote a Wiki on three interrelated topics. This process was repeated in the second term using three different, but still interrelated topics. Following each, they were asked to give detailed feedback on their Wiki topic teaching. The results showed that students felt writing the Wikis was useful for team work, provided a more learner-centred approach, created a body of work in a live format that would be useful for revision and was a welcome variation on traditional teaching methods. The biggest problem encountered was the IT platform used to create the Wikis. The students also felt the Wikis should be assessed as a piece of group work rather than as separate individuals. Wiki topic teaching is a useful tool in the teaching of postgraduate orthodontics providing variation and a more learner-centred approach. Further exploration of the available IT platforms is required.
    European Journal Of Dental Education 02/2013; 17(1):e109-13.
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    ABSTRACT: Keratinocyte senescence acts as a barrier to tumour progression but appears to be lost in late pre-malignancy to yield GU-OSCC; a subset of OSCC possessing wild type p53 are genetically stable (GS-OSCC). In this study, fibroblasts from GU-OSCC were senescent relative to fibroblasts from GS-OSCC, epithelial dysplastic tissues and normal oral mucosa, as demonstrated by increased senescence associated ß-galactosidase (SA ß-Gal) activity and over-expression of p16(INK4A). Keratinocytes from GU-OSCC produced high levels of reactive oxygen species (ROS) and oxidative damage in normal fibroblasts resulted in an increase in the production of both TGF-ß1 and TGF-ß2. Treatment of normal fibroblasts with keratinocyte conditioned media (CM) from GU-OSCC, but not GS-OSCC or dysplastic keratinocytes with dysfunctional p53, induced fibroblast senescence. This phenomenon was inhibited by anti-oxidants and anti-TGF-β antibodies. TGF-β1-induced fibroblast activation, as shown by α-SMA positivity, preceded cellular senescence as demonstrated by the induction of p16INK4A expression and SA ß-Gal activity; ROS levels remained high throughout the experimental period and anti-oxidants inhibited the reaction. Senescent fibroblasts derived from GU-OSCC or normal fibroblasts treated with CM from GU-OSCC or H(2)O(2), but not non-senescent fibroblasts derived from GS-OSCC, induced invasion of non-tumorigenic keratinocytes in vitro. Epithelial invasion was promoted by fibroblast activation and amplified further by fibroblast senescence. The results demonstrate the functional diversity of cancer associated fibroblasts and show that malignant keratinocytes from GU-OSCC reinforce their malignant behaviour by inducing fibroblast activation and senescence through ROS and TGF-β-dependent mechanisms.
    Carcinogenesis 01/2013;
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    ABSTRACT: BACKGROUND: A recent review found little evidence for substantial effects of modifiable maternal exposures on offspring blood pressure (BP), but this may have been because almost all the studies reported on BP in early and mid-childhood. METHODS: This study uses data on 4723 mother-child pairs, collected as part of the Avon Longitudinal Study of Parents and Children, Bristol, England between 1991 and 1997; associations between three maternal variables (smoking during pregnancy, age at childbirth and prenatal diet) and offspring BP at approximately 15 years were assessed. Comparisons of maternal and paternal associations with offspring BP were carried out as a way of evaluating whether prenatal exposures exerted an influence through intrauterine effects. RESULTS: The selected maternal exposures were not associated with offspring BP, after minimal or full adjustment for potential confounders. Maternal and paternal associations with offspring BP for each exposure were found to be similar. CONCLUSIONS: The findings of this study suggest that associations between the selected maternal exposures and offspring BP do not emerge with age up to adolescence.
    Journal of epidemiology and community health 01/2013;
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