Currently the advances in the field of 3D printing are causing a revolution in the (bio-)medical field. With applications ranging from patient-specific anatomical models for surgical preparation to prosthetic limbs and even scaffolds for tissue engineering, the possibilities seem endless. Today, the most widely used method is FDM printing. However, there is still a limited range of biodegradable and biocompatible materials available. Moreover, printed implants like for instance cardiovascular stents require higher resolution than is possible to reach with FDM. High resolution is crucial to avoid e.g. bacterial growth and aid to mechanical strength of the implant. For this reason, it would be interesting to consider stereolithography as alternative to FDM for applications in the (bio-) medical field. Stereolithography uses photopolymerizable resins to make high resolution prints. Because the amount of commercially available resins is limited and hardly biocompatible, here we investigate the possibility of using acrylates and vinylesters in an effort to expand the existing arsenal of biocompatible resins. Mechanical properties are tailorable by varying the crosslink density and by varying the spacer length. To facilitate rapid production of high-resolution prints we use masked SLA (mSLA) as an alternative to conventional SLA. mSLA cures an entire layer at a time and therefore uses less time to complete a print than conventional SLA. Additionally, with mSLA it takes the same time to make 10 prints as it would to make only one. Several formulations were prepared and tested for printability and mechanical strength.
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PURPOSE: Limited information is available on the effect of Immediate Dentin Sealing (IDS) on the fracture strength of indirect partial posterior restorations. This study evaluated the effect of IDS on the fracture strength and failure types of two indirect restorative materials.MATERIALS AND METHODS: Standard MOD inlay preparations were made on sound molars (N=40, n=10 per group) and randomly divided into four groups to receive the inlay materials with and without the application of IDS: Group L-IDS-: Li2Si2O5 (Lithium disilicate, IPS e.max) without IDS; Group L-IDS+: Li2Si2O5 with IDS; Group MR-IDS-: Multiphase resin composite (MR, Lava Ultimate) without IDS; MR-IDS+: MR with IDS. Inlays made of L were etched with 5% hydrofluoric acid, and MR inlays were silica coated. After silanization, they were cemented using adhesive resin cement (Variolink Esthetic DC). The specimens were thermo-mechanically aged (1.2×106 cycles, 1.7Hz, 8000 cycles, 5-55°C) and then subjected to load to failure (1 mm/min). Failure types and locations of debondings were classified. Data were statistically analyzed using ANOVA, Mann Whitney U-test and Chi-square tests (α=0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0), values were calculated.RESULTS: After aging conditions, no apparent changes were observed in marginal integrity but occlusal wear facets were more common with MR than with L (p<0.001). Material type and the application of IDS significantly affected the results (p=0.013). While group L-IDS- showed the lowest mean fracture strength (1358±506N) among all groups (p<0.05), application of IDS significantly increased the results significantly (L-IDS+: 2035±403N) (p=0.006). MR groups with and without IDS, did not show significant difference (MR-IDS-: 1861±423, MR-IDS+: 1702±596 N) (p=0.498). When materials without IDS are compared, L showed significantly lower results than that of MR (p=0.035). With the application of IDS, no significant difference was noted between L and MR materials (p=0.160). Weibull distribution presented the highest shape (0) for L-IDS+ (5.66) compared to those of other groups (3.01-4.76). Neither the material type (p=0.830), nor the application of IDS (p=0.54) affected the severity of the failure types. In 95% of the cases, the IDS layer left adhered on the tooth surface after fracture tests. In groups where no IDS was used, resin cement remained on the tooth surface in 44% of the cases (p=0.001). No significant differences were observed between the materials with respect to cement remnants or IDS after fracture (p=0.880). The incidence of repairable failure types (83%) was more common with L than with MR (75%) material (p>0.05).CONCLUSION: Immediate dentin sealing improves adhesion, and thereby the fracture strength of inlays made of lithium disilicate but not that multiphase resin composite.
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AIM: To compare the shear bond strength (SBS) after aging of two dual-curing composite resin cements to multiphase composite resin (experiment) and glass-ceramics (control).METHODS: Seventy computer-aided design/computer-aided manufacturing (CAD/CAM) blocks were prepared: 24 multiphase composite resin blocks (Lava Ultimate; experiment), and 12 control blocks (groups 5 and 6: 6 IPS e.max CAD, 6 IPS Empress CAD). Surface treatments of the experiment groups were: 1) Al2O3 airborne particle abrasion; 2) bur-roughening; 3) silica-coated aluminum oxide particle abrasion; and 4) hydrofluoric (HF) acid etching. Per study group, Variolink II (a) and RelyX Ultimate (b) were used as cements. Per treatment group, four cement cylinders were adhered to the conditioned blocks (n = 12). After thermocyclic aging (10.000x, 5°C to 55°C), notch-edge shear testing was applied. Modes of failure were examined. A P value of 0.05 was considered significant.RESULTS: Groups 1a (18.68 ± 3.81) and 3a (17.09 ± 3.40) performed equally to 6a (20.61 ± 4.10). Group 5a (14.39 ± 2.80) did not significantly differ from groups 1a, 3a, and 4a (15.21 ± 4.29). Group 2a (11.61 ± 3.39) showed the lowest bond strength. For the RelyX Ultimate specimens, mean bond strengths were: 1b (18.12 ± 2.84) > 4b (15.57 ± 2.31) > 2b (12.34 ± 1.72) = 3b (11.54 ± 2.45) = 6b (12.31 ± 1.87) > 5b (0.78 ± 0.89). Failure mode analysis showed a significant association between bond strength values and modes of failure (chi-square).CONCLUSION: The SBS of the composite cements to the multiphase composite resin that was treated by Al2O3 or silica-coated aluminum oxide particle abrasion is comparable to the bond of the control groups.
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In the high-tech mechatronics world, aluminum and steel are well known materials, while carbon fiber is often neglected. In the RAAK project 'Composites in Mechatronics', the use of carbon fiber composites in mechatronics is investigated.
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OBJECTIVES: To evaluate the clinical performance of partial glass-ceramic (IPS e.max Press) posterior restorations.MATERIALS AND METHODS: A total of 765 restorations in 158 patients were placed between 2008 and 2018 and evaluated in a prospective study during regular dental care visits between 2015 and 2018. The restorations were luted with a conventional photo-polymerized resin composite (HFO) in conjunction with an Immediate Dentin Sealing procedure (IDS). Intra-oral photographs and radiographs were made and evaluated using USPHS criteria.RESULTS: The mean observation time was 53.3 months (range 3-113 months). Three absolute failures occurred (tooth fractures, n = 2; apical re-infection, n = 1) all leading to the loss of the restored tooth. Repairable and salvageable failures occurred in 9 teeth (endodontic complications, n = 7; secondary caries, n = 1; debonding, n = 1). The survival and success rates according to Kaplan-Meier after 5 years cumulated to 99.6% and 98.6%, respectively. Location (premolar/molar and mandibula/maxilla), pre-restorative endodontic status (vital/devitalised) and extension of the indirect ceramic restoration (number of sides and cusps involved) did not significantly affect the cumulative success rate (log rank test, p > 0.05). The condition of the vast majority of the restorations remained unaffected for 5 years.CONCLUSIONS: Partial glass-ceramic posterior restorations (pressed lithium disilicate (IPS e.max press, Ivoclar Vivadent) luted by means of a conventional photo-polymerized resin composite in conjunction with the use of an IDS procedure have an excellent medium-term prognosis.CLINICAL RELEVANCE: Partial glass-ceramic posterior restorations can be considered as a highly reliable treatment option. Location and extension of the restoration and pre-restorative endodontic status do not affect success rate.
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According to the critics of conventional sustainability models, particularly within the business context, it is questionable whether the objective of balancing the social, economic and environmental triad is feasible, and whether human equality and prosperity (as well as population growth) can be achieved with the present rate of natural degradation (Rees 2009). The current scale of human economic activity on Earth is already excessive; finding itself in a state of unsustainable ‘overshoot’ where consumption and dissipation of energy and material resources exceed the regenerative and assimilative capacity of supportive ecosystems (Rees 2012). Conceptualizing the current ‘politics of unsustainability’, reflected in mainstream sustainability debates, Blühdorn (2011) explores the paradox of wanting to ‘sustain the unsustainable, noting that the socio-cultural norms underpinning unsustainability support denial of the gravity of our planetary crises. This denial concerns anything from the imminence of mass extinctions to climate change. As Foster (2014) has phrased it: ‘There was a brief window of opportunity when the sustainability agenda might, at least in principle, have averted it’. That agenda, however, has failed. Not might fail, nor even is likely to fail – but has already failed. Yet, instead of acknowledging this failure and moving on from the realization of the catastrophe to the required radical measures, the optimists of sustainable development and ecological modernization continue to celebrate the purported ‘balance' between people, profit and planet. This is an Accepted Manuscript of a book chapter published by Routledge/CRC Press in "A Future Beyond Growth: Towards a Steady State Economy" on 4/14/16 ,available online: https://doi.org/10.4324/9781315667515 LinkedIn: https://www.linkedin.com/in/helenkopnina/
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Sustainable consumption is interlinked with sustainable production. This chapter will introduce the closed-loop production, the circular economy, the steady state economy, and Cradle to Cradle (C2C) models of production. It will reflect on the key blockages to a meaningful sustainable production and how these could be overcome, particularly in the context of business education. The case study of the course for bachelor’s students within International Business Management Studies (IBMS) program at three Universities of Applied Science (vocational schools), and at Leiden University College in The Netherlands will be discussed. Student teams from these schools were given the assignment to make a business plan for a selected sponsor company in order to advise them how to make a transition from a linear to circular economy model. These case studies will illustrate the opportunities as well as potential pitfalls of the closed loop production models. The results of case studies’ analysis show that there was a mismatch between expectations of the sponsor companies and those of students on the one hand and a mismatch between theory and practice on the other hand. The former mismatch is explained by the fact that the sponsor companies have experienced a number of practical constraints when confronted with the need for the radical overhaul of established practices within the entire supply chain and students have rarely considered the financial viability of the "ideal scenarios" of linear-circular transitions. The latter mismatch applies to what students had learned about macro-economic theory and the application through micro-economic scenarios in small companies. https://www.springer.com/gp/book/9783319656076 LinkedIn: https://www.linkedin.com/in/helenkopnina/
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This chapter will introduce the circular economy (CE) and Cradle to Cradle (C2C) models of sustainable production. It will reflect on the key blockages to a meaningful sustainable production and how these could be overcome, particularly in the context of business education. The case study of the course for bachelor’s students within International Business Management Studies (IBMS), and at University College in The Netherlands will be discussed. These case studies will illustrate the opportunities as well as potential pitfalls of the closed loop production models. The results of case studies’ analysis show that there was a mismatch between expectations of the sponsor companies and those of students on the one hand and a mismatch between theory and practice on the other hand. Helpful directions for future research and teaching practice are outlined. https://www.springer.com/gp/book/9783319713113#aboutBook https://www.linkedin.com/in/helenkopnina/
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With a market demand for low cost, easy to produce, flexible and portable applications in healthcare, energy, biomedical or electronics markets, large research programs are initiated to develop new technologies to provide this demand with new innovative ideas. One of these fast developing technologies is organic printed electronics. As the term printed electronics implies, functional materials are printed via, e.g. inkjet, flexo or gravure printing techniques, on to a substrate material. Applications are, among others, organic light emitting diodes (OLED), sensors and Lab-on-a-chip devices. For all these applications, in some way, the interaction of fluids with the substrate is of great importance. The most used substrate materials for these low-cost devices are (coated) paper or plastic. Plastic substrates have a relatively low surface energy which frequently leads to poor wetting and/or poor adhesion of the fluids on the substrates during printing and/ or post-processing. Plasma technology has had a long history in treating materials in order to improve wetting or promote adhesion. The µPlasma patterning tool described in this thesis combines a digital inkjet printing platform with an atmospheric dielectric barrier discharge plasma tool. Thus enabling selective and local plasma treatment, at atmospheric pressure, of substrates without the use of any masking materials. In this thesis, we show that dependent on the gas composition the substrate surface can either be functionalized, thus increasing its surface energy, or material can be deposited on the surface, lowering its surface energy. Through XPS and ATR-FTIR analysis of the treated (polymer) substrate surfaces, chemical modification of the surface structure was confirmed. The chemical modification and wetting properties of the treated substrates remained present for at least one month after storage. Localized changes in wettability through µPlasma patterning were obtained with a resolution of 300µm. Next to the control of wettability of an ink on a substrate in printed electronics is the interaction of ink droplets with themselves of importance. In printing applications, coalescence of droplets is standard practice as consecutive droplets are printed onto, or close to each other. Understanding the behaviour of these droplets upon coalescence is therefore important, especially when the ink droplets are of different composition and/or volume. For droplets of equal volume, it was found that dye transport across the coalescence bridge could be fully described by diffusion only. This is as expected, as due to the droplet symmetry on either side of the bridge, the convective flows towards the bridge are of equal size but opposite in direction. For droplets of unequal volume, the symmetry across the bridge is no longer present. Experimental analysis of these merging droplets show that in the early stages of coalescence a convective flow from the small to large droplet is present. Also, a smaller convective flow of shorter duration from the large into the small droplet was identified. The origin of this flow might be due to the presence of vortices along the interface of the bridge, due to the strong transverse flow to open the bridge. To conclude, three potential applications were showcased. In the first application we used µPlasma patterning to create hydrophilic patterns on hydrophobic dodecyl-trichlorosilane (DTS) covered glass. Capillaries for a Lab-on-a-chip device were successfully created by placing two µPlasma patterned glass slides on top of each other separated by scotch tape. In the second application we showcased the production of a RFID tag via inkjet printing. Functional RFID-tags on paper were created via inkjet printing of silver nanoparticle ink connected to an integrated circuit. The optimal operating frequency of the produced tags is in the range of 860-865 MHz, making them usable for the European market, although the small working range of 1 m needs further improvement. Lastly, we showed the production of a chemresistor based gas sensor. In house synthesised polyemeraldine salt (PANi) was coated by hand on top of inkjet printed silver electrodes. The sensor proved to be equally sensitive to ethanol and water vapour, reducing its selectivity in detecting changes in gas composition.
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Introduction: Given the complexity of teaching clinical reasoning to (future) healthcare professionals, the utilization of serious games has become popular for supporting clinical reasoning education. This scoping review outlines games designed to support teaching clinical reasoning in health professions education, with a specific emphasis on their alignment with the 8-step clinical reasoning cycle and the reflective practice framework, fundamental for effective learning. Methods: A scoping review using systematic searches across seven databases (PubMed, CINAHL, ERIC, PsycINFO, Scopus, Web of Science, and Embase) was conducted. Game characteristics, technical requirements, and incorporation of clinical reasoning cycle steps were analyzed. Additional game information was obtained from the authors. Results: Nineteen unique games emerged, primarily simulation and escape room genres. Most games incorporated the following clinical reasoning steps: patient consideration (step 1), cue collection (step 2), intervention (step 6), and outcome evaluation (step 7). Processing information (step 3) and understanding the patient’s problem (step 4) were less prevalent, while goal setting (step 5) and reflection (step 8) were least integrated. Conclusion: All serious games reviewed show potential for improving clinical reasoning skills, but thoughtful alignment with learning objectives and contextual factors is vital. While this study aids health professions educators in understanding how games may support teaching of clinical reasoning, further research is needed to optimize their effective use in education. Notably, most games lack explicit incorporation of all clinical reasoning cycle steps, especially reflection, limiting its role in reflective practice. Hence, we recommend prioritizing a systematic clinical reasoning model with explicit reflective steps when using serious games for teaching clinical reasoning.
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