Hybrid Layer Research Articles

The roles of 10-methacryloyloxydecyl dihydrogen phosphate and its calcium salt in preserving the adhesive–dentin hybrid layer

Objectives10-Methacryloyloxydecyl dihydrogen phosphate (MDP) has been regarded as the most effective dentin-bonding monomer for more than 20 years. Although the dentin-bonding promoting effect of MDP has been well demonstrated, the mechanisms by which it benefits the stably of collagen within the adhesive–dentin hybrid layer are not currently fully understood. The objective of this study was to investigate the roles of MDP and its calcium salt in preserving the adhesive–dentin hybrid layer. MethodsMDP-conditioned collagen was investigated by Fourier-transform infrared spectroscopy, Ultraviolet–visible spectroscopy, and molecular docking. The structural changes to the dentin surface upon acid-etching and MDP-conditioning were observed by SEM. X-ray diffraction and nuclear magnetic resonance were used to investigate the chemical interactions between MDP and HAp. The collagen-protecting effects of MDP and its Ca salt were investigated using in-situ zymography, rhMMP-9 colorimetric assay, hydroxyproline assay, and molecular docking. ResultsMDP forms a stable collagen-phosphate complex through hydrogen bonding with the collagen in dentin. Furthermore, it generates MDP-Ca salts that are deposited on the dentin collagen scaffold, protecting it from degradation. Moreover, both free MDP and the MDP-Ca salt inhibit matrix metallopeptidase and exogenous proteases, with the inhibitory effect of the calcium salt being significantly stronger than that of the free form. SignificanceMDP-based adhesives preserve the collagen within the hybrid layer by simultaneously improving collagen’s resistance to exogenous enzymes and inhibiting MMP activity, both of which contribute to the longevity of dentin–resin bonding.

Conjugate Natural Convection of a Hybrid Nanofluid in a Cavity Filled with Porous and Non-Newtonian Layers: The Impact of the Power Law Index

This study deals with the effect of the power law index on the convective heat transfer of hybrid nanofluids in a square cavity divided into three layers. The effect of a solid fluid layer is also given attention. A two-dimensional system of partial differential equations is discretized by using the generalized finite element method (FEM). A FEM having cubic polynomials (P3) is employed to approximate the temperature and velocity components, whereas the pressure is approached using quadratic finite element functions. The discretized set of equations have been solved using Newton’s method. The numerical code which is used in this study has been validated by comparing with experimental findings. Mathematical simulations are performed for different sets of parameters, including the Rayleigh number (between 103 and 106), the power law index (between 0.6 to 1.8), Darcy number (between 10−6 to 10−2), undulation (between 1 and 5) and the thermal conductivity ratio (between 0.1 and 10). The results infer that a remarkable penetration of streamlines is figured out towards the porous hybrid layer as the power law index is increased. The average Nu increases with increasing Ra, and the maximum value is noted at Ra=106. There is no much alteration observed for isotherms at the solid layer by increasing Da. The average Nu decreases by increasing the undulations. The rate of heat transfer is enhanced at the heated boundary and solid fluid interface of the cavity by raising the ratio of thermal conductivity.

An innovative clustering technique to generate hybrid modeling of cooling coils for energy analysis: A case study for control performance in HVAC systems

Despite past studies, no comprehensive models or empirical correlations cover all aspects of performances of cooling coils under different flow regimes (laminar, transition, and turbulent). Moreover, the cooling coil is characterized by a highly nonlinear dynamic subject to multiple inputs, coupling between the latent and sensible heat transfer modes, uncertain disturbances, and strong dependence of the overall heat transfer coefficient on the flow type, all causing significant challenges when it comes to modeling. Therefore, a hybrid layer structure model was adopted in this study to overcome these challenges. The new approach used two different optimization methods, Neural Networks' Weights and Takagi-Sugeno (TS) fuzzy, and the hybrid layers tuned by the Gauss-Newton algorithm (GNA). The proposed model covered three types of fluid flow to represent the dynamic behavior of the water-side and air-side heat transfer coefficients, each of which was divided into seven clusters and had its unique TS consequence. This study also administered meaningful fitness tests in the responses of the eleven independent variables that serve as its inputs. Furthermore, its application shows the control performance saving more than 44% of HVAC system energy. Based on the results, it was concluded that the proposed model is suitable for estimating energy and cost savings for electric power and water flow rate efficiency. In addition, the response of all types of output flow can be evaluated when changing eleven independent variables that are manipulated by three different controllers.

Chemical and morphological characterization of self-etch primers incorporated with nanochitosan

This in vitro study evaluated experimental self-etch primers incorporated with different concentrations of nanochitosan gel (NC gel) and their action on the coronal and radicular dentin surface of bovine incisor teeth and the primer influence on the adhesive interface. Sections of 3 × 3 mm of coronal and root bovine dentin were flattened, and the smear layer was formed and standardized with 400 and 600-grit sandpaper. Root and coronal fragments (n=5) were treated with different primers: Clearfil™ SE Primer, Primer 1 – without NC gel, Primer 2–5% NC gel, Primer 3–10% NC gel, and Primer 4–15% NC gel. Primers were actively applied and left on the surface for 20 s. Images were acquired before treatment and immediately after primer application by confocal 3D laser scanning microscopy (x2160) to assess the degree of surface modification and dentinal tubule alteration. For adhesive interface analysis, dentin specimens (n=5) were treated with the evaluated primers, followed by the bond agent from Clearfil™ SE adhesive system, and restored with composite resin. Morphological analysis of the dentin surface and adhesive interface was performed using scanning electron microscopy (SEM) and chemical characterization using Fourier-transform infrared spectroscopy (FTIR). In coronal dentin, Clearfil™ SE Primer exposed fewer tubules than the experimental primers (p<0.05), and the percentage of open tubules was similar for all groups in root dentin (p>0.05). Primer 2 and Primer 3 showed higher values of perimeter and area for root dentin compared to the other groups (p<0.05), while Primer 1 was similar to Clearfil™ SE Primer (p>0.05). The incorporation of NC gel affected the behavior of the experimental primers. The addition of 10% of NC gel promoted a thicker and continuous hybrid layer with no gaps; however, higher concentrations of nanochitosan gel impaired the formation of a regular hybrid layer which is not favorable for an acceptable adhesion to the dentin substrate.

Hybrid coatings for orthopaedic implants formed by physical vapour deposition and microarc oxidation

This study is focused on the preparation of new hybrid layers intended for surface modification of Ti-6Al-4V alloys for potential orthopaedic and dental applications. Combination of the technology of physical vapour deposition (PVD) and subsequent micro-arc oxidation (MAO) was utilized for the deposition of Ti and ZrTi to form hybrid oxide layers. The oxide layers were prepared using an alkaline electrolyte with glycerol as an additive under micro-arc discharge conditions with different Si content on their surfaces. The hybrid ZrTi coatings with a Zr/Si structure achieved the best tribological properties described by a low friction coefficient of 0.3 and high abrasion resistance. There was also an increase in corrosion potential and polarization resistance of hybrid ZrTi coatings. Although the proliferation of human bone marrow mesenchymal stem cells was slower on these hydrophilic Ti and ZrTi coatings than both on uncoated Ti-6Al-4V and the reference tissue culture polystyrene dishes, both types of hybrid coating promoted greater osteogenic differentiation of these cells, indicated by approx. twice as high activity of alkaline phosphatase. The hybrid oxide layers newly developed in this study – especially the layers with Zr – are therefore promising for coating metallic bone implants.

Super-stretchable polymer-AgPdCu superlattice electrodes for high-performance wearable electronics

Highly-stretchable and semi-transparent polytetrafluoroethylene (PTFE)/AgPdCu (APC)-PTFE-based superlattice electrodes were realized by alternately sputtering very thin APC-PTFE hybrid layers on a polyurethane (PU) substrate at room temperature. The electrical and mechanical properties of the superlattice electrodes were optimized by controlling the PTFE thickness and the number of layers of the stacked superlattice. The optimal PTFE/APC-PTFE/PTFE/APC-PTFE/PTFE superlattice electrode showed a sheet resistance of 8.5 Ohm/square and maintained a high conductivity, even at a strain of 100%. The outstanding mechanical stretchability of the superlattice electrode is attributed to the 3-dimensional conductive APC network structure in the PTFE polymer matrix . In addition, the external strain applied to the superlattice electrode led to a change in the optical transmittance that could be used for optical switching in stretchable electronics. The superlattice electrodes can be utilized to fabricate stretchable electroluminescent devices, stretchable thin film heaters, and wearable temperature sensors . This successful demonstration of stretchable devices that include highly stretchable superlattice electrodes demonstrated the feasibility of this manufacturing strategy for use in next-generation stretchable and wearable electronics . • Fabrication of highly conductive and stretchable metal-polymer 3D nanocomposites by continuous co-sputtering of polymer and metal target. • The number of stacked layers and thickness of the polymer and polymer-metal hybrid films were controlled to form an alternating superlattice structure. • The optimized electrode showed a sheet resistance of 8.5 Ohm/square, an average transmittance of 34.0% for visible light, and stretchability that reversibly maintained a high conductivity at up to 100% strain. • The optimized electrode was applied as stretchable thin-film heater, electroluminescent device, and wearable temperature sensor.

Enhancement of Corrosion Resistance Properties of Electrodeposited Ni/nano-TiC Composite Layers.

This paper presents novel results on the effects of the dispersion of titanium carbide nanoparticles (50 nm mean diameter) into a nickel-plating electrolyte on the corrosion behavior of the nanocomposite layers obtained. The Ni/nano-TiC layers are compared with pure nickel layers obtained at the same electrodeposition parameters with 60 mA·cm−2 current density and 10 min deposition time. The comparative corrosion performances are investigated using a three-electrode electrochemical cell in a solution (mixed boric acid with lithium hydroxide), which simulates the primary water circuit of pressurized water reactors (PWRs). Open circuit potential measurement and electrochemical impedance spectroscopy were employed as the electrochemical methods, using an electrochemical workstation connected to an electrochemical cell, as well as a PC with software to drive the experimental work. The results clearly revealed enhanced corrosion properties for the Ni/nano-TiC hybrid layers as compared to the pure Ni layers. The significantly improved corrosion behavior can be attributed to the TiC nanoparticles embedded into the Ni matrix, which have the effect of insulating centers at the composite layer/corrosive solution interface.

On-chip integrated process-programmable sub-10 nm thick molecular devices switching between photomultiplication and memristive behaviour

Molecular devices constructed by sub-10 nm thick molecular layers are promising candidates for a new generation of integratable nanoelectronic applications. Here, we report integrated molecular devices based on ultrathin copper phthalocyanine/fullerene hybrid layers with microtubular soft-contacts, which exhibit process-programmable functionality switching between photomultiplication and memristive behaviour. The local electric field at the interface between the polymer bottom electrode and the enclosed molecular channels modulates the ionic-electronic charge interaction and hence determines the transition of the device function. When ions are not driven into the molecular channels at a low interface electric field, photogenerated holes are trapped as electronic space charges, resulting in photomultiplication with a high external quantum efficiency. Once mobile ions are polarized and accumulated as ionic space charges in the molecular channels at a high interface electric field, the molecular devices show ferroelectric-like memristive switching with remarkable resistive ON/OFF and rectification ratios.

Influence of Er:YAG laser irradiation settings on dentin-adhesive interfacial ultramorphology and dentin bond strength.

This study evaluated the effects of Erbium-doped yttrium aluminium garnet (Er:YAG) laser settings and dentin bonding agents on ultramorphological characteristics of resin-laser-irradiated dentin interfaces and dentin bond strength (BS) of these adhesive systems. Additionally, dentin depth affected by Er:YAG laser irradiations was measured. The experiments were performed on occlusal dentin surfaces of third molars that were flattened with 600-grit SiC sandpaper. Treated-dentin with laser settings (250 mJ/4 Hz and 160 mJ/10Hz) were the experimental groups, while SiC abraded dentin was the control. These three dentin treatments and three adhesives (two self-etchings and one etch-&-rinse adhesive) formed nine groups for the ultramorphology of laser-ablated dentin-adhesives interfacial analysis, using a transmission electron microscope (TEM). For BS (n=8), the same nine groups were tested with addition of the two evaluation times (24 h after sample preparation or 1 year). The depths of Er:YAG laser effects into the dentin were measured using a TEM (n=10). Ablated-dentin depth and BS data were analyzed by one- and three-way ANOVA, respectively, and Tukey's test (α=0.05). Hybrid layer formation was only observed for controls, while for laser-treated dentin, adhesives were bonded to dentin with resin tags formation. Laser settings reduced the BS for all adhesives at 24 h, while at 1 year, etch-&-rinse adhesive presented the highest BS, regardless treatment (control or laser settings). Dentin depth affected by laser settings was similar. The laser irradiation altered the bonding mechanism of the adhesives to dentin and reduced the BS for self-etching adhesives. Etch-&-rinse adhesive yielded the highest BS at 1 year. Laser settings similarly affected the dentin in depth. HIGHLIGHTS: Er:YAG laser irradiation settings produced similar effects on depth and bond strength to dentin. The etch-&-rinse adhesive yielded the highest dentin bond strength regardless of the type of dentin treatment at 1 year.

Mesoporous silica/epoxy coated cotton fabric for durable oil-water separation

A simple, durable, superior UV-shielded, self-cleanable, hydrophobic/superoleophile cotton fabric was developed using SBA-15 mesoporous silica and epoxy coating (SE). The cotton fabric surfaces after coating with SE showed the highest water contact angle value of 146° and lowest surface free energy of 13.9 mN/m. As a filtration membrane, the developed SE/cotton delivered 95.8% oil–water separation efficiency with a notable flux value of 6800 L/m2h against diesel–water mixture. The presence of an epoxy and silica hybrid layer on the surfaces of cotton fabric induced self-cleaning behavior and notable durability against UV light (UPF-29), pH resistance, washing fastness, and mechanical abrasion. Hence, the present coating developed using mesoporous silica and epoxy can be applied to different types of textile substrates to construct durable low-cost membranes.

Influence of roughening and EDTA application on shear bond strength to sclerotic dentin: in vitro study

This study evaluated two different adhesive systems (Adper Single Bond 2 – SB2; Palfique Bond – PALF) to bovine sclerotic dentin with and without dentin pretreatments. For this purpose, 200 incisors were randomly distributed into eight groups (n = 25), according to the pretreatment (none; diamond bur roughening – BUR; EDTA application – EDTA; and BUR + EDTA) and adhesive system (SB2 and PALF). A flat dentin area was obtained through wet polishing with 200, 320, 400, and 600-grit SiC paper after the teeth were embedded in chemically activated resin, with the exposed dentin surfaces parallel to the horizontal plane. Each dentin surface received two or three cylinders of flowable resin (Opalis Flow; FGM). The resin cylinders were made directly on the sclerotic dentin surface after each specific micro shear bond strength test (μSBS) treatment. The results were recorded, and the failure patterns were classified through stereomicroscopy. Parallelly, 16 bovine teeth were selected and treated according to each group, sectioned in a precision cutting machine, and analyzed using scanning electron microscopy. Results were analyzed by two-way ANOVA and Tukey’s test (α = 0.05). There were statistically significant differences among the μSBS values (p < 0.05). Groups with pretreatment showed values significantly higher (p < 0.05). Cohesive failure was prevalent within the adhesives. PALF produced thinner hybrid layers when compared to SB2, but diamond bur roughening was capable of enhancing its thickness. In conclusion, the pretreatments of sclerotic dentin evaluated in this study resulted in better μSBS results in both tested adhesives systems.

Gas-solid photo-catalytic reduction of CO2 to CO on calcined sulfonated cobalt phthalocyanine/ZnO/reduced graphene oxide under simulated sunlight

Preventing climate change and achieving carbon neutralization depend on strengthening the carbon cycle in industry and limiting carbon emissions to ambient air. Our aim is to reduce CO2 to valuable CO by gas-solid photo-catalytic reduction under sunlight. We prepared catalysts by one-step synthesis with graphene oxide (GO) and ZnO, surface modified with a monolayer of sulfonated cobalt phthalocyanine (CoPcS), which were calcined to obtain photocatalyst samples containing Co(II), ZnO and reduced graphene oxide (rGO). Results of TEM, SEM-EDS, XRD, XPS, PL and ESR revealed that the photocatalyst samples possessed a hybrid layer microstructure, heterojunction, and excellent electron-hole pair separation. Evaluation of the photocatalytic reduction reactivity showed that CO selectivity reached 96.2–99.0% and top CO yield was 26.15 µmol.g−1.h−1.

Engineering of corrosion product-polymer hybrid layers for enhanced CO2 corrosion protection of carbon steel part two: Computational investigation and surface characterisation

Carbon dioxide internal corrosion of carbon steel pipelines remains a major issue that is typically mitigated via the addition of corrosion inhibitors. In specific operational environments, a protective natural corrosion product layer known as iron carbonate (FeCO 3 ) can evolve on internal pipeline walls, providing comparable corrosion inhibitionefficiency to that achieved from surfactants. However, in some instances, incomplete corrosion product coverage can initiate localised corrosion. In our previous work, we demonstrated the ability of Poly (allylamine hydrochloride) (PAH) to act synergistically with FeCO 3 when the corrosion product exhibits partial coverage of ×65 carbon steel surfaces in an aqueous CO 2 corrosion environment. In this work, we employ density functional theory (DFT) to show that PAH is able to coordinate with both FeCO 3 and the bare carbon steel surface, producing a FeCO 3 -PAH hybrid structure. The surface and chemical properties of a naturally formed FeCO 3 and the FeCO 3 -PAH hybrid layers are characterised employing scanning electron microscopy (SEM) coupled with focused ionic beam (FIB), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). • The PAH molecules adsorb onto the carbon steel surface and corrosion product (FeCO 3 ) via chemisorption and physisorption. • The PAH molecules interact with FeCO 3 through coordination and hydrogen bonding producing a hybrid layer. • The PAH centres of interaction with film-free carbon steel and FeCO 3 film are protonated and neutral amine groups. • The crystal structure and layer thickness of FeCO 3 and FeCO 3 -PAH hybrid layers are characterised and compared.

Collagen Cross-Linking Lignin Improves the Bonding Performance of Etch-and-Rinse Adhesives to Dentin.

To evaluate the biomodification ability of lignin used as pre-treatment in human dentin before the application of an etch-and-rinse adhesive. Experimental hydroethanolic solutions with different cross-linking agents were used: 6.5% proanthocyanidins (PAC, from grape-seed extract); 2% cardanol (CARD, from cashew-nut shell liquid); lignin (LIG, from eucalyptus) at 1, 2 or 4% concentrations. The negative control (NC) was ethanol 50 v%. Extracted molars were prepared, and dentin microtensile bond strength (μTBS) was evaluated after 24 h water storage or 10,000 thermocycling aging. Further specimens were processed for SEM nanoleakage, micropermeability confocal microscopy evaluation and in situ degree of conversion (DC) through micro-Raman spectroscopy. Demineralized dentin sticks were submitted to a three-point bending test to evaluate the elastic modulus (E) before and after 1 min biomodification using the tested solutions. Moreover, it was also evaluated the mass changes and hydroxyproline (HYP) release after 4-weeks of water storage. Vibrational collagen crosslinking identification was evaluated through micro-Raman spectroscopy. The results were analyzed by analysis of variance (ANOVA) and Tukey’s test (α = 0.05). A significant reduction in μTBS was observed in groups NC (p < 0.001) and CARD (p = 0.026). LIG-4% showed no significant reduction in μTBS after aging (p = 0.022). Nanoleakage micrographs showed hybrid layer protection with all agents, but reduced micropermeability was attained only with lignin. Polymerization was negatively affected in the presence of all tested cross-linking agents, except LIG-1%. Lignin and cardanol increased the dentin E values, but only lignin reduced the mass loss in dentin specimens. Effective collagen crosslinking (1117 cm−1 and 1235 cm−1) was detected for all agents. HYP release was significantly lower with LIG-1% than NC (p < 0.001). Lignin was able to perform collagen cross-linking and prevent the degradation of unprotected dentin collagen, thereby improving the bonding performance of the composite restorations performed in this study.

A high-performance, single-electrode and stretchable piezo-triboelectric hybrid patch for omnidirectional biomechanical energy harvesting and motion monitoring

Triboelectric nanogenerators (TENGs) have recently drawn much attention in the field of biomechanical energy harvesting and motion monitoring. However, the electrode stretchability and contact-separation model induced complicated packed structure remain a problem that heavily affects output performance during various human movements and requires to be urgently addressed. Here, a single-electrode piezo-triboelectric hybrid nanogenerator (SEP-TENG) integrated with stretchable liquid-metal metal electrodes is reported, which simultaneously achieves outstanding energy harvesting performance and skin-comfort human motion monitoring. A polarized piezoelectric BaTiO3/silicon rubber (SR) composites film is served as the effective negative tribomaterial, benefiting from the improved dielectric constant and piezoelectric charge transfer, the optimized SEP-TENG generates a high peak power density of 5.7 W/m2 while contacted with human skin. Besides, owing to the ultralow Young's modulus of the SR encapsulation layer and tribo-piezoelectric hybrid layer, the homogeneous integrated multilayer composite serves no break till a 745% elongation, promoting that the SEP-TENG could effectively harvest biomechanical energy and realize stable power supplying for wearable electronics even under large deformation state. Furthermore, the SEP-TENG could comfortably attach to the finger joints and collect bending energy. This work provides a novel design methodology for a single-electrode TENG to realize omnidirectional biomechanical energy harvesting and motion monitoring.

Textile functionalization by combination of twin polymerization and polyalkoxysiloxane‐based sol–gel chemistry

AbstractThe surface modification of textile fibers by coating with nanostructured organic–inorganic hybrid materials is presented. The hydrophobic, solvent resistant and mechanically robust coatings were produced by combining the twin monomer 2,2′‐spirobi[benzo‐4H‐1,3,2‐dioxasiline] (TM) and polyalkoxysiloxanes (silica precursor polymers) in a catalyzed polymerization process. For the application in textile finishing, both aqueous emulsions and ethanolic solutions of mixtures were developed. The precisely adjusted ratio of TM and polyalkoxysiloxanes enabled controlling of the organic and inorganic portions in the hybrid layer. The polymerization process can be advantageously combined with the ring‐opening polymerization of hexamethylcyclotrisiloxane (HMCTS). The resulting ethanolic twin prepolymer solutions and the polyethoxysiloxane emulsions were easy to handle and thus represent a novel and attractive binder for PET surfaces. The coated fabrics were analyzed by means of scanning electron microscopy and X‐ray photoelectron spectroscopy showing hybrid material formation as a homogeneous, sealed surface layer. Improved hydrophobicity as well as resistance to mechanical stress was proven by water droplet‐ and Martindale tests.

A multi-functional dentine bonding system combining a phosphate monomer with eugenyl methacrylate

ObjectiveThe tooth-resin composite interface is frequently associated with failure because of microbial contamination, hydrolytic and collagenolytic degradation. Thus, designing a dentine bonding system (DBS) with an intrinsically antimicrobial polymerisable monomer is of significance especially if it can be used with self-etching primers enabling resistance to degradation of the interface. MethodsExperimental adhesives were developed incorporating eugenyl methacrylate (EgMA) at concentrations of 0,10 or 20 wt%, designated as EgMA0, EgMA10 and EgMA20, respectively, for use as a two-step self-etch DBS with the functional monomer bis[2-(methacryloyloxy) ethyl] phosphate (BMEP) in the primer. The curing, thermal and wettability properties of the adhesives were determined, and hybrid layer formation was characterised by confocal laser scanning microscopy, microtensile bond strengths (µTBS) and nanoleakage by back-scattered SEM. In situ zymography was used to assess MMP inhibitory activity of the BMEP-EgMA DBS. ResultsEgMA in the adhesives lowered the polymerisation exotherm and resulted in higher Tg, without negatively affecting degree of conversion. Water sorption and solubility were significantly lower with higher concentrations of EgMA in the adhesive. The formation of a distinct hybrid layer was evident from confocal images with the different adhesives, whilst EgMA20 yielded the highest µTBS post water storage challenges and lowest nanoleakage after 6 months. The experimental DBS exhibited minimal to no MMP activity at 3 months. SignificanceThe hydrophobic nature of EgMA and high cross-link density exerts considerable benefits in lowering water uptake and polymerisation exotherm. The application of EgMA, adhesives in conjunction with BMEP in a multi-functional self-etching DBS can resist MMP activity, hence, enhance longevity of the dentine-resin composite interface.

Recent Advances in Direct Adhesive Restoration Resin-Based Dental Materials With Remineralizing Agents

Resin-based dental materials are popular restorative materials especially in direct adhesive restoration because of the excellent mechanical and esthetic properties. Toward the realization of minimally invasive dental procedures, direct composite resin adhesive restoration has become the main treatment for dental defects. In addition, for caries-affected dentin close to the pulp, conservation remineralization has been advocated to save the living pulp. However, the resin–dentin interface can be destabilized by various factors, especially the enzymatic degradation of collagen fibrils within the hybrid layer and polymer hydrolysis. Furthermore, for resin-based restorative materials, the marginal gap remains a major problem that can lead to the occurrence of secondary caries. To address these issues, research efforts have focused on the remineralization of mineral-depleted dental hard tissues using remineralizing bioactive substances. In this review, we first described various bioactive agents with remineralizing properties. Furthermore, we discussed recent advances in resin-based dental materials for enamel or dentin remineralization. Finally, we examined the current challenges and prospects of these emerging materials. This work aims to provide a theoretical foundation for the future development of resin-based dental materials in direct adhesive restoration with remineralizing agents.

Chlorhexidine-loaded poly (amido amine) dendrimer and a dental adhesive containing amorphous calcium phosphate nanofillers for enhancing bonding durability

ObjectiveA novel method of combining chlorhexidine (CHX) loaded poly (amido amine) (PAMAM) dendrimers with a dental adhesive containing amorphous calcium phosphate (ACP) nanofillers are proposed for etch-and-rinse bonding system to enhance resin-dentin bonding durability. MethodsThe CHX-loaded PAMAM and ACP nanofillers were synthesized and characterized. Their effects on the cytotoxicity were tested by MTT assay. Micro-tensile bond strength (μTBS) before and after thermomechanical challenges were used to evaluate the bonding durability. Anti-matrix metalloproteinase (MMPs) property was examined using in-situ zymography. A double-fluorescence technique was used to examine interfacial permeability after bonding. Dentin remineralization in Ca/P lacking solution was observed under scanning electron microscopy. ResultsCompared with a 0.2 wt% CHX solution, the PAMAM loaded CHX had less cytotoxicity, while the in situ zymography showed it could still inhibit MMPs activity within the hybrid layer after released from PAMAM. The application of the novel method maintained the μTBS better than the control group after thermomechanical challenges, and it did not negatively affect water permeability of the bonding interfaces. CHX-loaded PAMAM regulated the calcium (Ca) and phosphate (P) ions provided by the ACP-containing adhesives to remineralize the demineralized dentin surfaces without initial Ca/P in the environment. SignificanceThe novel method can reduce the cytotoxicity of CHX, inhibit MMPs activities, maintain μTBS, and induce dentin remineralization, which are crucial factors for enhancing bonding durability.

Potential of Epigallocatechin-3-gallate as Chelating Agent against Matrix Metalloproteinase Expression and as Cross-Linking Agent Towards Hybrid Layer in Dentin Collagen: A Review

Adhesive dentistry’s main assumption is to create a strong chemical bond between dental hard tissues and restorative composite material. One of the most important aspects of this interface is the hybrid layer. Unfortunately, due to physical and chemical causes, the hybrid layer wears away with time. Epigallocatechin-3-gallate (EGCG), a component extracted from green tea, has several roles in the medical and dentistry field including as a crosslinking agent and as a chelating agent. Although there are several negative results, EGCG was proven to be able to preserve resin-dentin bonds without harming the restoration. As a crosslinking agent and chelating agent, EGCG has the potential to enhance the physical properties of dentin collagen and resin-dentin adhesion. The purpose of this study was to see how EGCG, as a cross-linking agent, affected dentinal collagen and hybrid layers, as well as how chelating chemicals affected Matrix metalloproteinase (MMPs).