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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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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This article will discuss philosophical debates on economic growth and environmental sustainability, the role of management responsibility, and the risk of subversion to business as usual. This discussion will be framed using the concepts of Cradle to Cradle (C2C) and Circular Economy about sustainable production. The case study illustrating the danger of subversion of these progressive models discussed here is based on the assignments submitted by Masters students as part of a course related to sustainable production and consumption at Leiden University. The evaluation of the supposedly best practice cases placed on the website of the Ellen MacArthur Foundation or those awarded Cradle to Cradle certificate has led some students to conclude that these cases illustrated green-washing. Larger implications of identified cases of green-washing for the field of sustainable business and ecological management are discussed. “This is a post-peer-review, pre-copyedit version of an article published in 'Philosophy of Management'. The final authenticated version is available online at: https://doi.org/10.1007/s40926-019-00108-x LinkedIn: https://www.linkedin.com/in/helenkopnina/
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This proposal is directed at the creation of sustainable embedding and preservation methods for biomaterials, in particular those incorporating structural colours (SCs). SCs use the interaction of light with highly ordered, nanostructured materials to generate colour. SCs are intense, angle dependent, can be polarized, non-fading and non-toxic; all characteristics with advantages over pigments. SCs can be created from bacteria, are widely found in nature and offers a route to the creation of high-performance biobased materials: i.e. ‘green’ replacements for dyes. However, naturally derived structural coloured biomaterials, particularly bacteria, require preservation or embedding – an essential step in developing durable products. The current embedding agent is an epoxy resin which is not a sustainable reagent. Indeed, there is a wider need for thermoset matrix materials and other polymers that are more environmentally friendly yet with good performance and cost. In this proposal we will develop such matrix materials using bacterial SCs as a test case and the primary application.
