Nanoscopic dynamic mechanical analysis of resin-infiltrated dentine, under in vitro chewing and bruxism events

The aim of this study was to evaluate the induced changes in mechanical behavior and bonding capability of resin–infiltrated dentine interfaces, after application of mechanical stimuli. Dentine surfaces were subjected to partial demineralization through 37% phosphoric acid etching followed by the application of an etch-and-rinse dentine adhesive, Single Bond (3M/ESPE). Bonded interfaces were stored in simulated body fluid during 24 h, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling (I), 24 h cycled in sine (II) or square (III) waves, sustained loading held for 24 h (IV) or sustained loading held for 72 h (V). Microtensile bond strength (MTBS) was assessed for the different groups. Debonded dentine surfaces were studied by field emission scanning electron microscopy (FESEM). At the resin–dentine interface, both the hybrid layer (HL) and the bottom of the hybrid layer (BHL), and both peritubular and intertubular were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform the nano-Dynamic Mechanical analysis and to estimate the complex and storage modulus. Dye assisted Confocal Microscopy Evaluation was used to assess sealing ability. Load cycling increased the percentage of adhesive failures in all groups. Specimens load cycled in held 24 h attained the highest complex and storage moduli at HL and BHL. The storage modulus was maximum in specimens load cycled in held 24 h at peritubular dentine, and the lowest values were attained at intertubular dentine. The storage modulus increased in all mechanical tests, at peritubular dentine. An absence of micropermeability and nanoleakage after loading in sine and square waveforms were encountered. Porosity of the resin–dentine interface was observed when specimens were load cycled in held 72 h. Areas of combined sealing and permeability were discovered at the interface of specimens load cycled in held 24 h. Crack-bridging images appeared in samples load cycled with sine waveform, after FESEM examination.This work was supported by grants MINECO/FEDER MAT2014-52036-P and FIS2013-41821-R

Independent ferroelectric contributions and rare-earth-induced polarization reversal in multiferroic TbMn2O5

Three independent contributions to the magnetically induced spontaneous polarization of multiferroic TbMn2O5 are uniquely separated by optical second harmonic generation and an analysis in terms of Landau theory. Two of them are related to the magnetic Mn3+/4+ order and are independent of applied fields of up to 7 T. The third contribution is related to the long-range antiferromagnetic Tb3+ order. It shows a drastic decrease upon the application of a magnetic field and mediates the change of sign of the spontaneous electric polarization in TbMn2O5. The close relationship between the rare-earth long-range order and the non-linear optical properties points to isotropic Tb-Tb exchange and oxygen spin polarization as mechanism for this rare-earth induced ferroelectricity.Comment: 8 pages, 5 figure

Landau Theory of Domain Wall Magnetoelectricity

We calculate the exact analytical solution to the domain wall properties in a multiferroic system with two order parameters that are coupled bi-quadratically. This is then adapted to the case of a magnetoelectric multiferroic material such as BiFeO3, with a view to examine critically whether the domain walls can account for the enhancement of magnetization reported for thin films fo this material, in view of the correlation between increasing magnetization and increasing volume fraction of domain walls as films become thinner. The present analysis can be generalized to describe a class of magnetoelectric devices based upon domain walls rather than bulk properties.Comment: 9 pages, 4 figure

Climate Impact Screening and Reporting: A Venture Capital Perspective

According to the International Energy Agency’s (IEA) Net-Zero Scenario, about one-third of the emissions reductions needed by 2050 depend on technologies that are currently in development. Additionally, climate adaptation finance faces an even larger investment gap. The Climate Venture Capital community must demonstrate tangible climate impact to truly earn its reputation. However, accurately and reliably screening, evaluating, and monitoring climate impact is challenging, with many metrics and methods still needing to be ascertained, clarified, and standardized. With the support of Princeville Capital, CCSI offers insights into unresolved issues: Attribution and baselining Paris-aligned thresholds for prioritization Indirect impact and tailored KPIs Adaptation investment thesis and scorecard

Ions-modified nanoparticles affect functional remineralization and energy dissipation through the resin-dentin interface

The aim of this study was to evaluate changes in the mechanical and chemical behavior, and bonding ability at dentin interfaces infiltrated with polymeric nanoparticles (NPs) prior to resin application. Dentin surfaces were treated with 37% phosphoric acid followed by application of an ethanol suspension of NPs, Zn-NPs or Ca-NPs followed by the application of an adhesive, Single Bond (SB). Bonded interfaces were stored for 24 h, submitted to microtensile bond strength test, and evaluated by scanning electron microscopy. After 24 h and 21 d of storage, the whole resin-dentin interface adhesive was evaluated using a Nano-DMA. Complex modulus, storage modulus and tan delta (δ) were assessed. AFM imaging and Raman analysis were performed. Bond strength was not affected by NPs infiltration. After 21 d of storage, tan δ generally decreased at Zn-NPs/resin-dentin interface, and augmented when Ca-NPs or non-doped NPs were used. When both Zn-NPs and Ca-NPs were employed, the storage modulus and complex modulus decreased, though both moduli increased at the adhesive and at peritubular dentin after Zn-NPs infiltration. The phosphate and the carbonate peaks, and carbonate substitution, augmented more at interfaces promoted with Ca-NPs than with Zn-NPs after 21 d of storage, but crystallinity did not differ at created interfaces with both ions-doped NPs. Crosslinking of collagen and the secondary structure of collagen improved with Zn-NPs resin-dentin infiltration. Ca-NPs-resin dentin infiltration produced a favorable dissipation of energy with minimal stress concentration trough the crystalline remineralized resin-dentin interface, causing minor damage at this structure.This work was supported by the Ministry of Economy and Competitiveness (MINECO) [Project MAT2014-52036-P]

Efficacy and micro-characterization of pathophysiological events on caries-affected dentin treated with glass-ionomer cements

The aim of this study was to evaluate if mechanical cycling influences bioactivity and bond strength at the glass-ionomer cement-dentin interface, after load cycling. Microtensile bond strength (MTBS) was assessed with Ketac-Bond (conventional glass ionomer/GIC) or Vitrebond Plus (resin-modified/RMGIC), in sound dentin or in cariesaffected dentin (CAD). Debonded dentin surfaces were studied by field emission scanning electron microscopy (FESEM), and remineralization was evaluated through nanohardness (Hi) and Young’s modulus (Ei), Raman spectroscopy, and Masson's trichrome staining technique. Load cycling did not affect MTBS, except when Ketac- Bond was applied on sound dentin, which attained 100% pretesting failures. Minerals precipitated in porous platforms. GIC promoted total occlusion of tubules, and RMGIC originated empty or partial occluded tubules. In sound dentin, load cycling produced an increase of the relative presence of crystalline minerals after using Ketac-Bond (Phosphate peak, from 18.04 up to 81.29 cm-1 at hybrid layer, and from 19.28 up to 108.48 cm-1 at the bottom of the hybrid layer; Carbonate peak, from 8.06 up to 15.43 cm-1 at the hybrid layer, and from 7.22 up to 19.07 cm-1 at the bottom of the hybrid layer). Vitrebond Plus, in sound dentin, attained opposite outcomes. In CAD treated with Ketac- Bond, the highest Hi (1.11 GPa) and Ei (32.91 GPa) values were obtained at the hybrid layer after load cycling. This GIC showed increased and immature mineral components (an average of 25.82 up to 30.55 cm-1), higher frequencies of crosslinking (considering the pyridinium ring at hybrid layer, from 4.1 up to 6.86 cm-1; at bottom of the hybrid layer, from 7.55 up to 8.58 cm-1) and worst collagen quality (considering the ratio amide I/AGEs-pentosidine at the hybrid layer, from 0.89 up to 0.69 cm-1; at the bottom of the hybrid layer, from 1.39 up to 1.29 cm-1) after load cycling, at the interface of the CAD samples. Both Hi and Ei of CAD treated with RMGIC were not affected 4 after load cycling, though phosphates, carbonates and crystallinity increased. The organic components showed a dissimilar crosslinking and an improvement of the nature of collagen. Trichrome staining showed lower signs of demineralization or exposed proteins after mechanical loading, though Vitrebond Plus exhibited a slight increment in red intensity at the interface. The null hypothesis to be tested is that bond strength, chemical bonding and mechanical performance of the tested ionomer-based cements would not be influenced by the application of load cycling on restorations of sound and caries-affected dentin substrates.Project MAT2014-52036-P supported by the Ministery of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER)

Dexamethasone-doped nanoparticles improve mineralization, crystallinity and collagen structure of human dentin

zation. This study aims to evaluate bonding ability and both mechanical and chemical behavior of demineralized dentin infiltrated with polymeric nanoparticles doped with dexamethasone (Dex-NPs). Methods: Dentin conditioned surfaces were infiltrated with NPs, Dex-NPs or Dex-Zn-NPs. Bonded interfaces were also created and stored for 24 h or 21d, and then submitted to microtensile bond strength testing. Dentin remineralization was analyzed by Nanohardness, Young’s modulus and Raman analysis. Results: At 21d of storage, dentin treated with undoped-NPs attained the lowest nanohardness and Young’s modulus. Dex-NPs and Zn-Dex-NPs increased dentin nanohardness and Young’s modulus after 21d Raman analysis showed high remineralization, crystallinity, crosslinking and better structure of collagen when functionalized Dex-NPs were present at the dentin interface. Conclusions: Infiltration of dentin with Dex-NPs promoted functional remineralization as proved by nanomechanical and morpho-chemical evaluation tests. Dexamethasone in dentin facilitated crystallographic maturity, crystallinity and improved maturity and secondary structure of dentin collagen. Clinical significance: Using dexamethasone-functionalized NPs before resin infiltration is a clear option to obtain dentin remineralization, as these NPs produce the reinforcement of the dentin structure, which will lead to the improvement of the longevity of resin restorationsGrant PID2020-114694RB-I00 funded by MCIN/AEI 10.13039/501100011033Funding for open access charge: Universidad de Granada / CBUA

Ultra-structure characterization of self-etching treated cementum surfaces

Objectives: to evaluate the effect of different conditioning treatments on surface roughness and topography of dental cementum. Study Design: Extracted human canines were used for the present study. The mesial surface from the cervical third of the roots were ground flat with wet 600-grit silicon carbide paper. They were polished (up to 1/4 µm diamond paste) and treated as follows: 1) No treatment, 2) 35% H3PO4 during 15 s, 3) Clearfil SE Bond primer (SEB), 4) One-Up Bond F (OUB). The adhesive systems were applied following manufacturer?s instructions. SEB primer and OUB were removed from surfaces by washing and ultrasonic agitation with ascending ethanol solutions. Digital images of treated surfaces (5x5 and 15x15 µm) were obtained by means of an atomic force microscope (AFM) analysis. The average surface roughness (Ra nanometers) of the scanned areas was assessed. Data were analyzed by ANOVA and SNK multiple comparisons tests (p<0.05). Results: phosphoric acid treatment produced the highest mean roughness value, at all scan sizes. At 5x5 µm AFM images, for self-etch adhesive systems no differences in roughness were detected. At 15x15 µm, when One-Up Bond F was employed the lowest value was obtained. Conclusions: When phosphoric acid treatment was applied, cementum surface roughness increased and a strong demineralization with exposed collagen fibers could be observed

Improved sealing and remineralization at the resin-dentin interface after phosphoric acid etching and load cycling

Introduction. The purpose of this study was to investigate the micro-morphology of the resin-dentin inter-diffusion zone using two different single-bottle self-etching dentin adhesives with and without previous acid-etching, after in vitro mechanical loading stimuli. Materials and Methods. Extracted human third molars were sectioned to obtain dentin surfaces. Two different single-bottle self-etching dentin adhesives, Futurabond U (FUT) and Experimental (EXP) both from VOCO, were applied following the manufacturer's instructions or after 37% phosphoric acid application. Resin-dentin interfaces were analyzed with dye assisted confocal microscopy evaluation (CLSM), including the calcium-chelation technique, xylenol orange (CLSM-XO). Results. The confocal microscopy revealed that resin-dentin interfaces of unloaded specimens were deficiently resin-hybridized, in general. These samples showed a rodhamine B-labeled hybrid complex and adhesive layer completely affected by fluorescein penetration (nanoleakage) through the porous resin-dentin interface, but thicker after phosphoric acid-etching. Load cycling promoted an improved sealing of the resin-dentin interface at dentin, a decrease of the hybrid complex porosity, and an increment of dentin mineralization. Load cycled specimens treated with the xylenol orange technique produced a clearly outlined fluorescence due to a consistent Ca-mineral deposits within the bonding interface and inside the dentinal tubules, especially when the experimental adhesive was applied.This work was supported by grants MINECO/FEDER MAT2011-24551, MAT2014-52036-P, and CEI-Biotic UGR