Bond Durability Research Articles

Influence of the thickening agent contained in a phosphoric acid etchant on bonding between feldspar porcelain and resin cement with a silane coupling agent.

Phosphoric acid (PA) etchants are widely used for the bonding pretreatment of teeth; however, their influences on the bonding between glass-ceramics and resin cement have not been clarified yet. This study investigated the effect of a thickening agent on the bonding strength between feldspar porcelain treated with a PA etchant and resin cement with a silane coupling agent. The experiments were performed using two PA etchants: commercial one and prepared one consisting a PA aqueous solution and poly(ethylene glycol) thickening agent. The samples were evaluated by shear bond strength testing, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The obtained results revealed that the thickening agent adhered to the porcelain surface and inhibited cement bonding. Meanwhile, PA remained on the surface due to the presence of the thickening agent and activated the silane coupling agent. Overall, the PA etchant did not improve the bond durability.

Designer Adhesives for Tough and Durable Interfaces in High‐Performance Ti‐Carbon PEKK Hybrid Joints

AbstractAdvanced high‐performance structural applications require the right materials in the right place and suitable interface engineering. However, poor adhesion in harsh environmental conditions frequently challenge material interfaces. An example is the moisture sensitivity of titanium‐poly ether ketone ketone (PEKK) interfaces. Here, this work offers a high‐performance composite adhesive system, which combines strong adhesion and high interfacial toughness, particularly when used in metal‐polymer bonding. This system includes aminopropyl triethoxy silane (APTES)–polydopamine (SiPDA) layers, which can be formed on the titanium surface before the joining process with carbon fiber‐reinforced PEKK (C/PEKK). Adhesion between PEKK and titanium is evaluated before and after hot/wet conditioning using mandrel peel tests. This work discovers that applying thin SiPDA layers not only results in a remarkable rise in the interfacial fracture toughness but also provides durable bond stability after hot/wet conditioning. These findings indicate that polydopamine‐based coatings show great potential to achieve stable interfaces for the next generation of high‐performance metal‐polymer hybrid materials.

Durability of bond between carbon/glass hybrid fiber-reinforced polymer (HFRP) bar and concrete in water

Glass-fiber-reinforced polymer (GFRP) bars have been widely used as a reinforcement in concrete, and glass fibers are susceptible to reacting with alkali ions in concrete pores. Thus, carbon fibers are wrapped around GFRP bars to produce carbon/glass hybrid fiber-reinforced polymer (HFRP) bars so as to promote the durability of the internal GFRP bars in concrete. This work studies the durability of the interfacial bond between GFRP bars/HFRP bars and concrete using pullout tests. The specimens are tested after immersion in distilled water for 0, 150, 255, and 544 days. The failure of the GFRP bar–concrete composite is due to damage to the GFRP bar, while the HFRP bar–concrete composite fails because of a combination of the scratching of the HFRP bar and the failure of the concrete. Both HFRP and GFRP bars are scratched as the immersion period extends. Further, the strength of the bond between the HFRP bar and concrete is lower than that of the bond between the GFRP bar and concrete, while the bond stiffness of the HFRP bar–concrete composite is higher than that of the GFRP bar–concrete composite. The bond strength of the HFRP bar–concrete and GFRP bar–concrete composites increases in the early immersion periods but decreases after 544 days of immersion in water. The retention of the bond strength of the HFRP bar–concrete composite is superior to that of the GFRP bar–concrete composite. The carbon fiber coat is proven to improve the durability of the bond between HFRP bars and concrete in water. A formula for predicting the bond strength of HFRP bar–concrete and GFRP bar–concrete composites in water is also developed. Finally, the modeling results demonstrate that the bond strength retention of the HFRP bar–concrete and GFRP bar–concrete composite is 76% and 46% after 50 years of service time, respectively.

Understanding the bond performance between BFRP bars and alkali-activated seawater coral aggregate concrete under marine environments

To improve the bond durability of fiber-reinforced polymer (FRP) bars with coral aggregate concrete (CAC), this study employed alkali-activated materials (AAMs) as an alternative to ordinary Portland cement for preparing alkali-activated slag CAC (AACAC) and investigated their bond behavior with FRP bars under seawater corrosion environments. The influences of various exposure times (0, 6, 9, and 12 months) and seawater environments (seawater immersion and drying-wetting cycles) on bond performance were considered. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were adopted to characterize the microstructural changes and mineralogical characteristics at the cross-section of BFRP bars and at paste matrix-aggregates interfaces of the concrete after seawater environment exposure. The tested results manifested that with the increase in exposure age, the bond strength for AACAC and CAC specimens gradually degraded, but their slope at the ascending stage of bond-stress curves (i.e., bond stiffness) tended to be enhanced. Compared with CAC specimens, AACAC specimens achieved a slightly lower rate of performance degradation. After being suffered from seawater conditions for 12 months, the compressive strength and bond strength of CAC specimens decreased by approximately 6.5% and 2.3%, respectively, while those of AACAC specimens only degraded by 2.5% and 1.5%, respectively.

EDTA-functionalized silica nanoparticles as a conditioning agent for dentin bonding using etch-and-rinse technique

ObjectiveThis study investigated the possibility of using ethylenediaminetetraacetic acid functionalized silica nanoparticles (EDTA-SiO2) as a dentin-conditioning agent using etch-and-rinse technique to promote the durability of dentin bonding. MethodsThe SiO2-EDTA were synthesized by N- [(3- trimethoxysilyl) propyl] ethylenediamine triacetic acid (EDTA-TMS) and SiO2 (50 nm), then characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The capacity of SiO2-EDTA to chelate calcium ions from dentin was examined by inductively coupled plasma-optic emission spectrometry (ICP-OES). The dentin surfaces conditioned with SiO2-EDTA were detected by field emission scanning electron microscopy (SEM), TEM and microhardness testing. For dentin bonding, dentin surfaces were adopted wet- or dry-bonding technique and bonded with adhesive (AdperTM Single Bond2) and applied composite resin (Filtek Z350) on them. The durability of dentin bonding was evaluated by mircotensile bond strength test, in-situ zymography and nanoleakage testing. ResultsFTIR, TGA and XPS results showed that SiO2-EDTA contained N element and carboxyl groups. SEM, TEM and microhardness results indicated that SiO2-EDTA group created extrafibrillar demineralization and retained more intrafibrillar minerals within dentin surface. In the dentin bonding experiment, SiO2-EDTA group achieved acceptable bond strength, and reduced the activity of matrix metalloproteinase and nanoleakage along bonding interface. ConclusionIt was possible to generate a feasible dentin conditioning agent (SiO2-EDTA), which could create dentin extrafibrillar demineralization and improve dentin bond durability. Clinical significanceThis study introduces a new dentin conditioning scheme based on SiO2-EDTA to create extrafibrillar demineralization for dentin bonding. This strategy has the potential to be used in clinic to promote the life of restoration bonding.

Comparison of dentin bond durability in different adhesive systems containing glycerol-phosphate dimethacrylate (GPDM) functional monomers under long-term water storage

Comparison of dentin bond durability in different adhesive systems containing glycerol-phosphate dimethacrylate (GPDM) functional monomers under long-term water storage

Bonding effect of a Zr/Si coating prepared on zirconia using a sol-gel method

Statement of problemZirconia has been widely used as a dental prosthetic material. However, bonding to zirconia is challenging, and whether a Zr/Si coating would improve bonding is unclear. PurposeThe purpose of this in vitro study was to prepare a Zr/Si coating on zirconia ceramics using a sol-gel method and to determine whether the bonding to resin is improved. Material and methodsPresintered zirconia specimens were prepared and divided into 5 groups: 4 experimental groups with ratios of the binary sol-gel precursor (zirconium oxychloride/tetraethoxysilane) set as 2:1 (Z2), 1:1 (Z1), 0.5:1 (Z0.5), and 0.25:1 (Z0.25) and Group C as the control group. In addition to surface roughness measurements, scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD) were carried out to characterize the surface. Each group was divided into 2 subgroups according to whether a silane coupling agent was applied. Half of the bond specimens were stored in deionized water for 24 hours; the remaining half were aged using 5000 thermocycles. The shear bond strength (SBS) of resin bonded to specimens was tested for the initial and durable bond strength, and the bonding interface was also observed by SEM after debonding. Data were subjected to 1-way ANOVA and the post hoc Tukey honestly significant difference test (α=.05). ResultsThe Zr/Si coating formed on zirconia ceramics. Z0.5 had the greatest mean ±standard deviation roughness (2.13 ±0.15 μm) and had the highest silicon content (21.7 ±0.21%). t-ZrO2, m-ZrO2, c-SiO2, and ZrSiO4 were detected by XRD in Z1. The SBS values were decreased by aging but were significantly increased by Zr/Si coating, especially for Z0.5, with the application of silane (initial: 22.92 ±2.79 MPa; aged: 9.91 ±0.92 MPa). ConclusionsThe Zr/Si coating significantly improved the initial and aged bond strength, and the optimal Zr/Si ratio of the sol-gel appeared to be 0.5:1.

Bond durability between BFRP bars and seawater coral aggregate concrete under seawater corrosion environments

The combination of fiber-reinforced polymer (FRP) composites with seawater coral aggregate concrete (CAC) in offshore construction contributes to reduced construction costs and avoids the corrosion problems related to steel-reinforced concrete structures. However, the durability for FRP-reinforced CAC members during service in marine environments is not well understood, which greatly hinders their application in offshore construction. In this paper, accelerated aging tests were employed for investigating the bond performance between the basalt-FRP (BFRP) bars and the CAC under seawater drying-wetting cycle and immersion environments. The effects of various exposure temperatures and exposure times on bond characteristics were considered, and scanning electron microscopy (SEM) was adopted to characterize microstructure changes at the cross-section of BFRP bars subjected to seawater exposure environments. The experimental results revealed that after being exposed to seawater corrosion conditions, the slope in the rising stage of the curves (i.e., initial bond stiffness) appeared to increase somewhat due to the hygroscopic expansion effect of the FRP bars, but the bond strength and its corresponding slip value demonstrated a gradual decrease. After being subjected to seawater drying-wetting cycle conditions at 45 °C and 60 °C for 12 months, the bond strength of BFRP bars in CAC declined by approximately 6.5 % and 12.0 %, respectively. This deterioration in the bond strength was related to the degradations in the mechanical properties of the FRP bars and the CAC, as well as the interfacial performance between the FRP bars and the CAC.

Bond durability between BFRP bars and recycled aggregate seawater sea-sand concrete in freezing-thawing environment

Fibre reinforced polymer (FRP) bar reinforced recycled aggregate seawater sea-sand concrete (RASSC) structures can reasonably solve the two key problems of reinforcement corrosion and resource shortage. In this paper, the bond durability between basalt fibre reinforced polymer (BFRP) bars and RASSC in freezing-thawing environment was studied by eccentric pull-out tests. The research parameters were freezing-thawing cyclic numbers and concrete cover thicknesses. The results revealed that the bond strength between BFRP bars and RASSC decreased significantly with the increase in freezing-thawing cyclic numbers. Additionally, the bond strength increased with concrete cover thicknesses. The variation laws of slip at bond strength and bond stiffness were similar to those of bond strength. Considering the effect of freezing-thawing cyclic numbers, the equations for relative compressive strength and relative dynamic elastic modulus of RASSC were established. Considering the effects of freezing-thawing cyclic numbers and concrete cover thicknesses, the equations for bond strength, slip at bond strength, and bond stiffness between BFRP bars and RASSC were given. Furthermore, mBPE model and CMR model were calibrated.

Bond durability between anchored GFRP bar and seawater concrete under offshore environmental conditions

The lower bond strength of FRP bars to concrete compared to steel bars has remained an unsolved barrier to the widespread use of FRP-reinforced concrete under extreme loading. Additionally, the degradation of the bond between FRP reinforcement and concretes in aggressive environments adds to the existing concern. In this study, an innovative anchorage system comprised of polypropylene pipe was used to strengthen the bond between seawater concrete and GFRP bars after 250 days of exposure to offshore environmental conditions. As material factors, two types of GFRP bars (sand-coated and ribbed) and two types of concrete (normal and seawater concrete) were evaluated. Four distinct environmental conditions were used to assess the samples: (i) ambient environment (control), (ii) tap water, (iii) seawater, and (iv) wet-dry cycles in seawater. According to the findings of the direct pull-out tests, the suggested anchor system strengthens the bond and shifts the failure mode from bond failure to bar rupture. Additionally, after exposure to 250 days of seawater wet-dry cycles, GFRP-reinforced seawater concrete lost 5% of its maximum bond strength (developed bar tensile stress). All other samples exposed to different environmental conditions either increased or decreased in bond strength by less than 5% after 250 days, compared to the control samples.

Durability of bond of EBR CFRP laminates to concrete under real-time field exposure and laboratory accelerated ageing

The durability of bond between carbon fibre-reinforced polymer (CFRP) laminates and concrete with the externally bonded reinforcement (EBR) technique was investigated under real-time field exposure (RTFE) and accelerated ageing. The experimental program, over two years, includes four outdoor environments inducing carbonation, freeze–thaw attack, extreme temperatures, and airborne chlorides from the ocean. A laboratory environment (20 °C/55% RH) was used as reference environment. Additionally, a water-immersion environment (20 °C) was also considered. Relatively low values of bond degradation were observed, where the maximum pullout force varied between −4 % and +16 % under RTFE, while on water–immersed specimens, the maximum pullout force decreased by ∼8 %.

Infiltrating fluorapatite glass-ceramics on the surface of dental 3 % yttria-stabilized zirconia to enhance bond strength

Zirconia is a material commonly used for denture repair due to its excellent mechanical properties. However, the low bond strength between zirconia dentures and natural teeth may cause the prosthesis to fall off, which is a major obstacle to its clinical success. Improving the bonding strength between dental zirconia and teeth and resisting the adhesive failure of zirconia prosthesis have been difficult problems in recent years. Thus, this study aims to infiltrate synthesized fluorapatite (Ca5(PO4)3F, FAp) glass-ceramics on an unsintered zirconia surface. The microstructure, phase characterization, surface morphology, mechanical properties, and bonding strength were comprehensively evaluated in this study. Scanning electron microscopy images of the cross-section of infiltrated zirconia revealed a residual FAp glass-ceramics coating on the surface, under which is the graded layer, demonstrating that the FAp glass-ceramics infiltrated the loose porous zirconia embryo to form a mechanical chimera. Energy dispersive spectroscopy results showed that silicon, which is the principal element of the FAp glass-ceramics, penetrated the zirconia to a depth of nearly 150 μm. These results verified the mechanical stability of the FAp glass-ceramics coating. Meanwhile, the shear strength test between the infiltrated zirconia and teeth showed that the bonding strength increased by approximately 3-fold, while the bond durability and flexural strength of the infiltrated zirconia also increased. As a new material for infiltrating zirconia, the application of the synthesized FAp glass-ceramics on the surface of unsintered zirconia with an appropriate coating time can ensure a high penetration depth and prevent stripping. Meanwhile, the bond strength and durability of the infiltrated zirconia can be significantly enhanced without reducing its mechanical properties.

Synergistic effect of collagen cross-linking and remineralization for improving resin-dentin bond durability.

In this study, the synergistic effect of glutaraldehyde-cross-linking and remineralization on the strength and durability of resin-dentin bonds was investigated. Dentin surfaces were etched with 35% phosphoric acid. The control specimens were bonded with Adper Single Bond 2 using wet bonding without pretreatment. The experimental specimens were pretreated with 5% (v/v) glutaraldehyde solution for 3min and placed in a remineralizing solution for 0, 12, and 24 h, followed by dry bonding. After performing composite build-ups on the specimens, they were longitudinally sectioned, immediately, and after aging for 3h with sodium hypochlorite (NaOCl), to evaluate microtensile bond strength (µTBS). The cross-linked specimens exhibited µTBS values comparable with those of the control group, but the µTBS decreased significantly after NaOCl aging. The cross-linked dentin remineralized for 24 h exhibited an increase in µTBS. After aging in NaOCl, the µTBS of the specimens remineralized for 24 h did not decrease and was significantly higher than for the other experimental groups. Cross-linking with dry bonding maintained µTBS in specimens before aging in NaOCl, but the bonding durability was compromised. Remineralization of cross-linked dentin for 24 h followed by dry bonding increased the immediate µTBS and improved bond durability. Therefore, combining cross-linking with remineralization of collagen fibrils progressively increased resistance to degradation, improving bond durability.

Bond behavior of recycled tyre steel fiber reinforced concrete and basalt fiber-reinforced polymer bars under static and fatigue loading conditions

Nowadays, there is a growing demand for the development of structures and construction materials from recycled or reused and renewable resources, in line with circular economy principles and the goal of sustainable development. The present study explores promising solutions for increasing the sustainability of concrete structures, through the application of basalt fibers reinforced polymer (BFRP) rebars, whose raw materials show an unlimited availability on earth, as well as recycled steel fibers from waste tyres (RTSF), for RTSF reinforced concrete structures with BFRP reinforcements. Three different types of self-compacting concretes with 1.1% fiber volume fractions of industrial and/or recycled steel fibers were developed, where 50% and 100% of the industrial steel fibers (ISF) weight was replaced by RTSF. Five different groups of pull-out specimens, with total number of 26 specimens, were fabricated to evaluate bond performance of BFRP rebar embedded in RTSF reinforced concrete. The understanding of the bond behaviour is critical to the effective design of reinforced concrete structures under both static and dynamic loadings. The influence of the type of reinforcement, dosage of the adopted RTSF, type of loading, and concrete flow direction on bond stress versus slip behavior, maximum bond stress, and failure mode are analysed and discussed. One of the main contributions of this research regards the understanding of the effect of RTSF orientation on bond performance obtained when BFRP rebars are pulled out from RTSF reinforced concrete. Compared to ISF, using RTSF for reinforcing concrete can increase the bond strength between BFRP rebars and fiber reinforced concrete up to 6.3% under static and 9.7% under fatigue loading regime. As the future research in this area, it is recommended to evaluate the long-term bond durability of BFRP reinforced FRC embedded in seawater, the environmental and economic feasibility of using BFRP and TRSF for reinforcing concrete structures, and fiber orientation and dispersion using image analysis and 3D visualization.

Effect of polyhydroxy-terminated PAMAM dendrimer on dentin matrix metalloproteinases within the hybrid layers

BackgroundIntrafibrillar remineralization within the hybrid layers (HLs) has recently attracted extensive attention in achieving durable resin-dentin bonds. The polyhydroxy-terminated poly(amidoamine) dendrimer (PAMAM-OH) at fourth generation becomes a desirable candidate to induce intrafibrillar remineralization to protect exposed collagen fibrils within HLs based on the size exclusion effect of fibrillar collagen. However, the remineralization process in vivo is time-consuming, during which the exposed collagen fibrils are vulnerable to enzymatic degradation, resulting in unsatisfactory remineralization. Thereby, if PAMAM-OH itself possesses concomitant anti-proteolytic activity during the induction of remineralization, it would be very beneficial to obtain satisfactory remineralization.MethodsBinding capacity tests using adsorption isotherm and confocal laser scanning microscopy (CLSM) were performed to assess if the PAMAM-OH had adsorption capacity on dentin. Anti-proteolytic testings were detected by MMPs assay kit, in-situ zymography and ICTP assay. Adhesive infiltration of resin-dentin interface and tensile bond strength before and after thermomechanical cycling were implemented to assess if the PAMAM-OH adversely affected resin-dentin bonds.ResultsAnti-proteolytic testings performed using MMPs assay kit, in-situ zymography and ICTP assay indicated that PAMAM-OH inhibited exogenous soluble MMP-9 as well as had inhibitory effect on the endogenous proteases. Adhesive infiltration of resin-dentin interface and tensile bond strength before and after thermomechanical cycling were implemented to indicate that the PAMAM-OH pretreatment had no adverse effects on immediate dentin bonding and prolonged the durability of resin-dentin bonds.ConclusionsPAMAM-OH possesses anti-proteolytic activity and prevents exposed collagen fibrils within HLs from degradation, which lays the foundation for the satisfactory intrafibrillar remineralization induced by PAMAM-OH within HLs to achieve durable resin-dentin bonds in the next work.

Polyphenols Can Improve Resin-Dentin Bond Durability by Promoting Amorphous Calcium Phosphate Nanoparticles to Backfill the Dentin Matrix.

To investigate the effects of proanthocyanidins (PA), myricetin, resveratrol, and kaempferol on the modification of dentin collagen and the inhibition of matrix metalloproteinase (MMP) activity, and to evaluate their contributions to the biomimetic remineralization and resin-dentin bonding performance. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and in situ zymography were applied to verify the collagen modification and MMP activity inhibition induced by these four polyphenols. Scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis, X-ray diffraction (XRD), ATR-FTIR, Vickers hardness numbers (VHN), and micro-computed tomography (micro-CT) were performed to characterize the remineralized dentin. Microtensile bond strength (μTBS) and nanoleakage were investigated to evaluate the effects of the four polyphenols on resin-dentin bonding durability. ATR-FTIR and in situ zymography confirmed that these four polyphenols could modify dentin collagen and inhibit MMP activity, respectively. Chemoanalytic characterization exhibited the efficacies of the four polyphenols in promoting dentin biomimetic remineralization. The surface hardness of PA-pretreated dentin was the greatest. Micro-CT results demonstrated that the PAs group possessed the highest amount of dentin surface minerals and the lowest amount of deep-layer minerals. The surface and deep-layer mineral contents of the Myr group were higher than Res and Kae groups. Treatment with these four polyphenols significantly increased the initial μTBS compared with the control group without primer conditioning. μTBS decreased significantly during aging, and the decrease was more severe in the PAs and Kae groups than in the Myr and Res groups. With or without aging, the polyphenol groups exhibited relatively less fluorescence. However, the Myr and Res groups showed less serious nanoleakage after aging. PA, myricetin, resveratrol, and kaempferol can modify dentin collagen, inhibit MMP activity, promote biomimetic remineralization, and improve resin-dentin bond durability. Compared with PA and kaempferol, myricetin and resveratrol are more effective in improving resin-dentin bonding.

A Comparison of Laser and Mechanical Surface Pretreatment Methods on Shear Bond Strength of Resin Composite to Resin-Modified Glass Ionomer.

Dentin margins have a higher microleakage than enamel in composite restorations due to weaker bond durability. Clinically, most margins are located apical to cementoenamel junction on the dentin or cementum. Different surface preparation methods may have dissimilar effects on the shear bond strength of resin-modified glass ionomer (RMGI) to composite resin, regarding the layering technique employed in restoration of these cavities. This study aimed to investigate the shear bond strength of RMGI to composite resin using different mechanical surface preparation methods. In this in vitro study, 72 RMGI samples were prepared in six groups (n=12): control, acid etching, air abrasion with aluminum oxide (Al2O3), bur, Er: YAG laser, and Er, Cr: YSGG laser groups. Two samples from each group were randomly examined under a scanning electron microscope (SEM). A bonding layer and composite resin were applied and cured. Then the samples were subjected to 5000-cycles thermocycling procedure. The shear bond strength was then evaluated using a universal testing machine. Finally, the failed surface of the samples was evaluated under a light microscope to examine the failure mode. For the statistical analysis, one-way ANOVA and Games-Howell post hoc test was used to compare quantitative variables and chi-squared test to investigate the relationship between the failure mode and the groups. The significant level was set at 0.05. The results showed significant differences between the mean of the strength variable in the groups (p< .001). The acid-etch and air abrasion groups exhibited significantly the lowest and highest values, respectively. The chi-squared test results also showed a significant relationship between the failure mode in the study groups (p= .008). Acid etching before completing RMGI polymerization could adversely affect shear bond strength. The air abrasion and bur methods are among the best methods to increase the shear bond strength between composite resin and RMGI. Using Er, Cr: YSGG and Er: YAG lasers could increase the bond strength results.

Improving epoxy adhesion with steel adherends using a tannic acid‐based additive: Impact on resin properties and interfacial bonding

AbstractTraditional adherend surface treatment techniques such as grit blasting, acid etching, phosphating and primer treatments alone are often inadequate for maintaining interfacial bond durability of adhesively bonded joints. Therefore, the existing interfacial bonds between epoxy adhesive and the adherend should be strengthened. Tannic acid (TA) is a plant‐based polyphenol that is inexpensive and easily available in nature. Its potential as an additive to improve the interfacial bond durability of epoxy adhesives has not been studied adequately. In the present study, an additive (TA‐AGE) was synthesized by grafting allyl glycidyl ether (AGE) onto phenolic hydroxyl groups of TA. With 1 wt% TA‐AGE additive in the epoxy, the single lap shear strength improved by 37%. Further, accelerated aging studies were performed to understand the impact of water uptake on the mechanical and viscoelastic properties and interfacial bond durability of the epoxy with 1 wt% TA‐AGE additive. TA‐AGE modification can increase hydrophilicity and enhance the water uptake characteristics of epoxy. This can negatively impact its mechanical properties and glass transition temperature (Tg) due to plasticization effects. Nevertheless, Boeing wedge test and single lap shear tests reveal that the strengthened interfacial bonds to steel adherends with the additive were robust and durable.

Effects of Adhesive Types and Structural Configurations on Shear Performance of Laminated Board from Two Gigantochloa Bamboos

Semantan (Gigantochloa scortechinii) and beting (Gigantochloa levis) bamboo are the two Malaysian bamboo that are suitable to be converted into laminated bamboo boards. One of the main criteria for laminated board is its good bondability, which is determined by shear performance. The shear performance of laminated board is influenced by several factors such as the species used, adhesive types and lamination configurations. Therefore, in this study, laminated bamboo boards were produced using Semantan and Beting bamboo bonded with phenol–resorcinol–formaldehyde (PRF) and polyurethane (PUR) adhesives. Different configurations (lay-up patterns and strip arrangements) were used during the consolidation of the laminated boards. The bamboo strips were arranged in three different arrangements, namely vertical, horizontal and mixed, and then assembled into a three-layered structure with two lay-up patterns, which are perpendicular and parallel. Shear performances, such as shear strength, bamboo failure and delamination of the boards, were evaluated. The results revealed that the adhesive type and lay-up pattern were the most influential factors on the shear performance. PRF-bonded laminated bamboo boards outperformed PUR-bonded laminated bamboo boards in terms of shear strength and bamboo failure but PUR bonding had better bond durability as indicated by its low delamination. Boards laminated parallelly significantly outperformed those bonded perpendicularly. As for strip arrangement, PRF-bonded laminated boards were less influenced by it compared to PUR-bonded laminated boards. The results suggested that PRF is a better adhesive for bamboo lamination due to its higher shear performance and more consistent performance across structural configurations (lay-up patterns and strip arrangements).

Effect of a primer containing Artemisinin on dentin endogenous MMPs and resin bond durability

ObjectivesThis study aims to investigate the potential effect of a primer containing Artemisinin (ART) or its derivative—dihydroartemisinin (DHA) on the dentin endogenous MMPs activity and resin bonding durability under etch-and-rinse mode. Materials and methodsMolecular docking was applied for evaluating the potential interactions of MMP-2 and MMP-9 with ART and DHA. Then human third molars were randomly assigned to six groups, after etch-and-rinse treatment, pretreated with the primers containing 0.25, 0.5 mg/mL ART, 0.25, 0.5 mg/mL DHA and 2% chlorhexidine (CHX) for 2 min, respectively, while one untreated group was served as the control group. The endogenous MMPs activity of demineralized dentin was tested with in situ zymography test and zymographic assay. Following the etch-and-rinse bonding process with a universal resin bond, the specimens of the microtensile bond strength (μTBS) and nanoleakage were tested with or without 10,000 °C thermocycling and 6-month storage in artificial saliva at 37 °C. ResultsMolecular docking showed that ART and DHA combined with MMP-2 and MMP-9 through forming covalent bonds with the zinc ion of MMPs. Compared with the control group, the ART, DHA and CHX groups showed less endogenous MMPs activity, and the MMPs activity of 0.5 mg/mL DHA group had no significant difference from that of 2% CHX group. Ageing condition reduced the μTBS values dramatically and also aggravated the nanoleakage of all the groups, specifically, the control group showed lower μTBS value and a broader, thicker and more consecutive silver deposition than other groups. ConclusionsThe primer containing ART or DHA could preserve bond durability and slow down the nanoleakage of resin-dentin interface over time through inhibiting the endogenous MMPs activity.